Dissertations / Theses: 'Land Surface Water'

1

Elbag, Mark A. "Impact of surrounding land uses on surface water quality." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-050306-155834/.

Full text

Abstract:

Thesis (M.S.)--Worcester Polytechnic Institute. Keywords: Conductivity, pH, Dissolved Oxygen, UV absorbance, Source Water, Surface Water, Dissolved Organic Carbon, Total Organic Carbon, Particle Counts, Turbidity, E. coli, Fecal Coliforms, West Boylston Brook, Wachusett Reservoir, source water protection, surface water protection Includes bibliographical references (p.73-77).

APA, Harvard, Vancouver, ISO, and other styles

2

Elbag, Jr Mark A. "Impact of Surrounding Land Uses on Surface Water Quality." Digital WPI, 2006. https://digitalcommons.wpi.edu/etd-theses/665.

Full text

Abstract:

Source water protection is important to maintain public health by keeping harmful pathogens out of drinking water. Non-point source pollution is often times a major contributor of pollution to surface waters, and this form of pollution can be difficult to quantify. This study examined physical, chemical, and microbiological water quality parameters that may indicate pollution and may help to identify sources of pollution. These included measures of organic matter, particles, and indicator organisms (fecal coliforms and E. coli). The parameters were quantified in the West Boylston Brook, which serves as a tributary to the Wachusett Reservoir and is part of the drinking water supply for the Metropolitan Boston area. Water quality was determined over four seasons at seven locations in the brook that were selected to isolate specific land uses. The water quality parameters were first analyzed for trends by site and by season. Then, a correlation analysis was performed to determine relationships among the water quality parameters. Lastly, ANOVA analyses were used to determine statistically significant variations in water quality along the tributary.

APA, Harvard, Vancouver, ISO, and other styles

3

Decker, Mark Ryan. "IMPROVING THE HYDROLOGICAL CYCLE IN LAND SURFACE CLIMATE MODELS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195627.

Full text

Abstract:

The hydrological components of land surface climate models have increased greatly in complexity over the past decade, from simple bucket models to multilayer models including separate and distinct soil water and ground water components. While the parameterizations included in these models have also increased in complexity, the fundamental ability of the numerical solution for the vertical movement of soil water in the Community Land Model (or other land surface models) to simply maintain the hydrostatic solution of the original partial differential equation has yet to be determined.Also, the ability of current generation reanalysis products to simulate near surface quantities as gauged by flux tower measurements has yet to be determined.This study demonstrates that the numerical solution as used in CLM3.5 cannot maintain the hydrostatic state. An alternate form of the equation, titled the Modified Richards equation is presented so that the numerical solution maintains steady statesolutions. Also, an improved and simple bottom boundary condition is derived that itself doesn't destroy hydrostatic initial conditions. The new solution is demonstrated to be as accurate as proven numerical solutions while being one to three orders more computationally efficient. The Modified Richards equation together with the new bottom boundary condition is shown to improve the ability of CLM to simulate soil water, water table depth, and near surface turbulent fluxes.Comparison with flux tower observations shows that ERA-Interim better simulates near surface temperature and wind speed than other current generation reanalysis products. Reanalysis products are able to reproduce the flux tower observations on monthly timescales, and the errors between the products and the measurements are primarily due to biases. However, at six hourly timescales the errors are not only larger but also caused primarily by a lack of correlation with the observations.

APA, Harvard, Vancouver, ISO, and other styles

4

Chingombe, Wisemen. "Effects of land-cover - land-use on water quality within the Kuils - Eerste River catchment." Thesis, University of Western Cape, 2012. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5893_1373463134.

Full text

Abstract:

line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">The most significant human impacts on the hydrological system are due to land-use change. The conversion of land to agricultural, mining, industrial, or residential uses significantly alters the hydrological characteristics of the land surface and modifies pathways and rates of water flow. If this occurs over large or critical areas of a catchment, it can have significant short and long-term impacts, on the quality of water. While there are methods available to quantify the pollutants in surface water, methods of linking non-point source pollution to water quality at catchment scale are lacking. Therefore, the research presented in this thesis investigated modelling techniques to estimate the effect of land-cover type on water quality. The main goal of the study was to contribute towards improving the understanding of how different land-covers in an urbanizing catchment affect surface water quality. The aim of the research presented in this thesis was to explain how the quality of surface runoff varies on different land-cover types and to provide guidelines for minimizing water pollution that may be occurring in the Kuils-Eerste River catchment. The research objectives were (1) to establish types and spatial distribution of land-cover types within the Kuils-Eerste River catchment, (2) to establish water quality characteristics of surface runoff from specific land-cover types at the experimental plot level, (3) to establish the contribution of each land-cover type to pollutant loads at the catchment scale. line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">Land-cover characteristics and water quality were investigated using GIS and Remote Sensing tools. The application of these tools resulted in the development of a land-cover map with 36 land classifications covering the whole catchment. Land-cover in the catchment is predominantly agricultural with vineyards and grassland covering the northern section of the catchment. Vineyards occupy over 35% of the total area followed by fynbos (indigenous vegetation) (12.5 %), open hard rock area (5.8 %), riparian forest (5.2 %), mountain forest&nbsp &nbsp (5 %), dense scrub (4.4 %), and improved grassland (3.6 %). The residential area covers about 14 %. Roads cover 3.4 % of the total area. line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">Surface runoff is responsible for the transportation of large quantities of pollutants that affect the quality of water in the Kuils-Eerste River catchment. The different land-cover types and the distribution and concentration levels of the pollutants are not uniform. Experimental work was conducted at plot scale to understand whether land-cover types differed in their contributions to the concentration of water quality attributes emerging from them. Four plots each with a length of 10 m to 12 m and 5 m width were set up. Plot I was set up on open grassland, Plot II represented the vineyards, Plot III covered the mountain forests, and Plot IV represented the fynbos land-cover. Soil samples analyzed from the experimental plots fell in the category of sandy soil (Sa) with the top layer of Plot IV (fynbos) having loamy sand (LmSa). The soil particle sizes range between fine sand (59.1 % and 78.9 %) to coarse sand (between 7 % and 22 %). The content of clay and silt was between 0.2 % and 2.4 %. Medium sand was between 10.7 % and 17.6 %. In terms of vertical distribution of the particle sizes, a general decrease with respect to the size of particles was noted from the top layer (15 cm) to the bottom layer (30 cm) for all categories of the particle sizes. There was variation in particle size with depth and location within the experimental plots.line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">Two primary methods of collecting water samples were used grab sampling and composite sampling. The quality of water as represented by the samples collected during storm events during the rainfall season of 2006 and 2007 was&nbsp used to establish &nbsp water quality characteristics for the different land-cover types. The concentration of total average suspended solids was highest in the following land-cover types, cemeteries (5.06 mg L-1), arterial roads/main roads (3.94 mg L-1), low density residential informal squatter camps (3.21 mg L-1) and medium density residential informal townships (3.21 mg L-1). Chloride concentrations were high on the following land-cover types, recreation grass/ golf course (2.61 mg L-1), open area/barren land (1.59 mg L-1), and improved grassland/vegetation crop (1.57 mg L-1). The event mean concentration (EMC) values for NO3-N were high on commercial mercantile (6 mg L-1) and water channel (5 mg L-1). The total phosphorus concentration mean values recorded high values on improved grassland/vegetation crop (3.78 mg L-1), medium density residential informal townships (3mgL-1) and low density residential informal squatter camps (3 mg L-1). Surface runoff may also contribute soil particles into rivers during rainfall events, particularly from areas of disturbed soil, for example areas where market gardening is taking place. The study found that different land cover types contributed differently to nonpoint source pollution. line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">A GIS model was used to estimate the diffuse pollution of five pollutants (chloride, phosphorus, TSS, nitrogen and NO3-N) in response to land cover variation using water quality data. The GIS model linked land cover information to diffuse nutrient signatures in response to surface runoff using the Curve Number method and EMC data were developed. Two models (RINSPE and N-SPECT) were used to estimate nonpoint source pollution using various GIS databases. The outputs from the GIS-based model were compared with recommended water quality standards. It was found that the RINSPE model gave accurate results in cases where NPS pollution dominate the total pollutant inputs over a given land cover type. However, the N-SPECT model simulations were too uncertain in cases where there were large numbers of land cover types with diverse NPS pollution load. All land-cover types with concentration values above the recommended national water quality standard were considered as areas that needed measures to mitigate the adverse effects of nonpoint pollution. line-height:150% font-family:&quot Times New Roman&quot ,&quot serif&quot ">The expansion of urban areas and agricultural land has a direct effect on land cover types within the catchment. The land cover changes have adverse effect which has a potential to contribute to pollution.

APA, Harvard, Vancouver, ISO, and other styles

5

De, Chiara Giovanna. "Satellite remote sensing for surface soil water content estimation." Doctoral thesis, Universita degli studi di Salerno, 2010. http://hdl.handle.net/10556/125.

Full text

Abstract:

2008 - 2009 Satellite remote sensing is a useful source of observations of land surface hydrologic variables and processes and could be a practical substitution of conventional in-situ monitoring. Most of hydrological dynamic processes change not only throughout the years but also within weeks or months and their monitoring requires frequent observations. The most prominent advantage of the remote sensing technologies is that they offer a synoptic view of the dynamics and spatial distribution of phenomena and parameters, often difficult to monitor with traditional ground survey, with a frequent temporal coverage. Many of the variables in the land surface water balance can now be observed with satellite techniques thanks to an extensive development over the last decades. Often the problem connected to the use of remotely sensed data is their accuracy that, according to the sensor used and to the application considered, can ranges from moderate to excellent. The objective of this thesis has been to evaluate the use of satellite remote sensing techniques for the monitoring of two variables useful for hydrology applications: water body extension and soil moisture monitoring. The capability to map water surface is important in many hydrological applications, in particular accurate information on the extent of water boundary is essential for flood monitoring and water reservoir management. Often, this information is difficult to retrieve using traditional survey techniques because water boundaries can be fast moving as in floods or may be inaccessible. In this PhD thesis, an artificial basin for which in-situ information about the water extension are available is used as case study. The area extension recorded daily by the dam owner is compared to the one retrieved by using satellite images acquired from SAR and TM/ETM+ sensors. The outcomes of the analysis show that satellite images are able to map water body surfaces with a good accuracy. The analysis also highlighted the factor to be taken into account while using types of sensors. Soil moisture is recognized as a key variable in different hydrological and ecological processes as it controls the exchange of water and heat energy between land surface and the atmosphere. Despite the high spatial variability of this parameter it has been demonstrated that many satellite sensors are able to retrieve soil moisture information of the surface layer at catchment scale. Among other sensors, the Scatterometer is very useful for climatic studies and modelling analysis thanks, respectively, to the temporal frequency, global coverage and to the long time series availability. Even though the ERS Scatterometer has been designed to measure the wind over the ocean surface, in recent years it has been pointed out that backscattering measurements have high potentiality for soil moisture retrieval. The second task of this PhD thesis, concerning the use of satellite data for soil moisture monitoring, has been developed at Serco S.p.A. in the framework of the Advanced Scatterometer Processing System (ASPS) project developed by ESA (European Space Agency) to reprocess the entire ERS Scatterometer mission. Since the beginning of the ERS-1 Scatterometer mission in 1991 a long dataset of C-band backscattering signal from the Earth surface is available for studies and researches. This is a very consistent dataset, but in particular for climatology studies it is important to have high quality and homogeneous long term observation as also stated in the key guidelines included in the Global Climate Observing System (GCOS) from the World Meteorological Organization (WMO). The main goal of this task has been the generation of the new Scatterometer ASPS products with improved data quality and spatial resolution. This achievement required a long preparation activity but represents an important contribution to the C-band Scatterometer dataset available to the scientific community. In order to evaluate the usage of the re-processed Scatterometer data for soil moisture estimation, the backscattering measurements derived in the new ASPS products have been then compared to in-situ volumetric soil moisture data and the relationship between radar backscattering and soil moisture measurements has been investigated under different conditions: angle of incidence, angle of azimuth, data measurements resolution, season of the year. Analysis results show that a relationship between the C-band backscattering coefficient and the in-situ volumetric soil moisture exists and takes into account the incidence and azimuth angles and the vegetation cover. [edited by author] VIII n. s.

APA, Harvard, Vancouver, ISO, and other styles

6

Wang, Shusen. "Modelling water, carbon, and nitrogen dynamics in CLASS, Canadian Land Surface Scheme." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0008/NQ59692.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Tediosi, A. "HERBICIDE TRANSPORT FROM LAND TO SURFACE WATER IN AN ARTIFICIALLY DRAINED CATCHMENT." Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150206.

Full text

Abstract:

Pesticide use is often associated with a number of negative impacts on the environment and on water quality. In this thesis the processes contributing to herbicide transport from land to surface water were examined, using a combination of existing data analysis, modelling, and monitoring. Field investigations of herbicide transport were conducted on an artificially drained field dominated by heavy clay soil (Denchworth soil association), in the Upper Cherwell catchment (UK). The main drain was monitored over five months during November 2009 to March 2010, when the field was in oilseed rape (OSR) and was treated with propyzamide and carbetamide. In the UK recent attention has focused on these two herbicides, which are used to control black grass in OSR. Both chemicals were detected at very high concentrations (up to 55.7 μg l-1 and 694 μg l-1 for propyzamide and carbetamide, respectively). The concentration pattern clearly followed drain discharge, with rapid increase on the rising hydrograph limb and a quasi-exponential decline on the recession limb. The MACRO pesticide fate model, which was applied to represent field observations, supported the hypothesis that herbicide transport to drains is a very quick process and suggested that preferential flow is a major transport mechanism. This analysis has contributed to the development of a preliminary model of catchment-scale pesticide transfers, which integrates hillslope responses through the river network to simulate flow and herbicide losses at the catchment outlet. The application of this model tends to corroborate the hypothesis that rapid transport to drains play a major role in herbicide contamination of surface water at the catchment outlet. Herbicides seem to peak about one day after rainfall events. The results also suggest that the first few rain events following herbicide application are very critical in terms of chemical losses.

APA, Harvard, Vancouver, ISO, and other styles

8

James, Tosin. "Changes in Land Use Land Cover (LULC), Surface Water Quality and Modelling Surface Discharge in Beaver Creek Watershed, Northeast Tennessee and Southwest Virginia." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3747.

Full text

Abstract:

Beaver Creek is an impaired streams that is not supporting its designated use for recreation due to Escherichia coli (E.coli), and sediment. To address this problem, this thesis was divided into two studies. The first study explored changes in Land Use Land Cover (LULC), and its impact on surface water quality. Changes in E.coli load between 1997-2001 and 2014-2018 were analyzed. Also, Landsat data of 2001, and 2018 were examined in Terrset 18.31. Mann-Whitney test only showed a significant reduction in E.coli for one site. Negative correlation was established between E.coli load, and Developed LULC, Forest LULC, and Cultivated LULC. The second study modelled discharge for Beaver Creek watershed using HEC-HMS. This study simulated discharge in an upstream sub-watershed of Beaver Creek, and the full Beaver Creek with a Nash-Sutcliffe of 0.007, and R2 0.20. Sub-basins with high discharge were identified for further examination for possible high sediment load.

APA, Harvard, Vancouver, ISO, and other styles

9

Bourgeois-Calvin, Andrea. "Relationship between Land Use and Surface Water Quality in a Rapidly Developing Watershed in Southeast Louisiana." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/714.

Full text

Abstract:

The Tangipahoa River and Natalbany River watersheds (Tangipahoa Parish/County) in the Lake Pontchartrain Basin (southeastern Louisiana) are experiencing rapid urbanization, particularly in the wake of the 2005 hurricane season. To document the impact of land use on water quality, thirty sites were monitored for surface water physiochemical, geochemical, and bacteriological parameters. Water quality data was compared to land use within four sub-watersheds of the Tangipahoa Watershed and three sub-watersheds of the Natalbany Watershed. Urbanization had the most profound impact on water quality of all land uses. In watersheds with little urban land cover (< 7% with the sub-watershed) waterbodies had low dissolved salt, nutrient, and fecal coliform concentrations and high dissolved oxygen levels. Waterbodies within the urban region (> 28% urban land cover within the sub-watershed) of the parish had significantly greater dissolved salt, nutrient, and fecal coliform concentrations and decreased dissolved oxygen concentrations. Specifically, nutrient and fecal coliform concentrations increased as streams flowed through urban areas. The specific conductance, fecal coliform counts, concentrations of sulfate, HCO3-C, sodium, and nutrients (NO3-N, NO2-N, NH4-N, and PO4-P), and the ratios of Na:Cl, Cl:Br, and SO4:Cl were shown to be the parameters most indicative of urban impacts. Many of the geochemical parameters correlated significantly with each other, particularly within the urban streams (the streams with the greatest concentrations). While fecal coliform counts were high within the urban streams, programs to address malfunctioning wastewater treatment plants (WWTP) appear to be working, with fecal coliform counts declining and dissolved oxygen levels rising during the course of the data collection. In contrast, sites undergoing rapid development showed an increase in turbidity levels and a decrease on dissolved oxygen levels (both going from healthy to unhealthy levels) during the 18-month course of the data collection. By understanding the impacts of urbanization on streams of the Gulf Coast, local and regional municipalities may be able to reduce the impacts in already urbanized areas or mitigate the impacts at the outset of development.

APA, Harvard, Vancouver, ISO, and other styles

10

Gustafsson, David. "Boreal land surface water and heat balance : Modelling soil-snow-vegetation-atmosphere behaviour." Doctoral thesis, KTH, Mark- och vattenteknik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3406.

Full text

Abstract:

The water and heat exchange in thesoil-snow-vegetation-atmosphere system was studied in order toimprove the quantitative knowledge of land surface processes.In this study, numerical simulation models and availabledatasets representing arable land, sub-alpine snowpack, andboreal forest were evaluated at both diurnal and seasonaltimescales. Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden during three winters and two summersfrom 1997 to 2000 within the WINTEX project. A one-dimensionalsimulation model (COUP) was used to simulate the water and heatbalance of the field. Comparison of simulated and measured heatfluxes in winter showed that parameter values governing theupper boundary condition were more important for explainingmeasured fluxes than the formulation of the internal mass andheat balance of the snow cover. The assumption of steady stateheat exchange between the surface and the reference height wasinadequate during stable atmospheric conditions. Independentestimates of the soil heat and water balance together with thecomparison of simulated and measured surface heat fluxes showedthat the eddy-correlation estimates of latent heat fluxes fromthe arable field were on average 40 % too low. The ability of a multi-layered snowpack model (SNTHERM) tosimulate the layered nature of a sub-alpine snowpack wasevaluated based on a dataset from Switzerland. The modelsimulated the seasonal development of snow depth and densitywith high accuracy. However, the models ability to reproducethe strong observed snowpack layering was limited by theneglection of the effect of snow microstructure on snowsettling, and a poor representation of water redistributionwithin the snowpack. The representation of boreal forest in the land surfacescheme used within a weather forecast (ECMWF) model was testedwith a three-year dataset from the NOPEX forest site in centralSweden. The new formulation with separate energy balances forvegetation and the soil/snow beneath the tree cover improvedthe simulation of seasonal and diurnal variations in latent andsensible heat flux. Further improvements of simulated latentheat fluxes were obtained when seasonal variation in vegetationproperties was introduced. Application of the COUP model withthe same dataset showed that simulation of evaporation fromintercepted snow contributed to a better agreement with themeasured sensible heat flux above forests, but also indicatedthat the measurements might have underestimated latent heatflux. The winter sensible heat flux above the forest wasfurther improved if an upper limit of the aerodynamicresistance of 500 s m-1 was applied for stable conditions. A comparison of the water and heat balance of arable landand forest confirmed the general knowledge of the differencesbetween these two surface types. The forest contributed withconsiderably more sensible heat flux to the atmosphere than thearable land in spring and summer due to the lower albedo andrelatively less latent heat flux. Latent heat flux from theforest was higher in winter due to the evaporation ofintercepted snow and rain. The net radiation absorbed by theforest was 60 % higher than that absorbed by the arable land,due to the lower surface albedo in winter. Key words:soil; snow; land surface heat exchange;forest; arable land; eddy-correlation. QC 20100614

APA, Harvard, Vancouver, ISO, and other styles

11

Valayamkunnath, Prasanth. "Understanding the Role of Vegetation Dynamics and Anthropogenic induced Changes on the Terrestrial Water Cycle." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/105061.

Full text

Abstract:

The land surface and atmosphere interact through complex feedback loops that link energy and water cycles. Effectively characterizing these linkages is critical to modeling weather and climate extremes accurately. Seasonal variability in vegetation growth and human-driven land cover changes (LCC) can alter the biophysical properties of the land surface, which can in turn influence the water cycle. We quantified the impacts of seasonal variability in vegetation growth on land surface energy and water balances using ecosystem-scale eddy covariance and large aperture scintillometer observations. Our results indicated that the monthly precipitation and seasonal vegetation characteristics such as leaf area index, root length, and stomatal resistance are the main factors influencing ecosystem land surface energy and water balances when soil moisture and available energy are not limited. Using a regional-scale climate model, we examined the effect of LCC and irrigation on summer water cycle characteristics. Changes in biophysical properties due to LCC reducing the evapotranspiration, atmospheric moisture, and summer precipitation over the contiguous United States (CONUS). The combined effects of LCC and irrigation indicated a significant drying over the CONUS, with increased duration and decreased intensity of dry spells, and reduced duration, frequency, and intensity of wet spells. Irrigated cropland areas will become drier due to the added effect of low-precipitation wet spells and long periods (3-4% increase) of dry days, whereas rainfed croplands are characterized by intense (1-5% increase), short-duration wet spells and long periods of dry days. An analysis based on future climate change projections indicated that 3–4 °C of warming and an intensified water cycle will occur over the CONUS by the end of the 21st century. The results of this study highlighted the importance of the accurate representation of seasonal vegetation changes and LCC while forecasting present and future climate. Doctor of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

12

Yeh, Pat Jen-Feng 1969. "Representation of water table dynamics in a land surface scheme : observations, models, and analyses." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29617.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003. Includes bibliographical references (leaves 198-207). A recent regional-scale water balance analysis has indicated that the groundwater storage and groundwater runoff are significant terms in the monthly and annual water balance for areas with a shallow water table. However, most of the current land surface parameterization schemes lack any representation of regional groundwater aquifers. Such a simplified representation of subsurface hydrological processes would result in significant errors in the predicted land-surface states and fluxes especially for the shallow water table areas in humid regions. This study attempts to address this deficiency. To incorporate the water table dynamics into a land surface scheme LSX, a lumped aquifer model is developed to represent the regional unconfined aquifer as a nonlinear reservoir, in which the aquifer simultaneously receives the recharge from the overlying soils, and discharges runoff into streams. The dependence of groundwater runoff on the water table depth (WTD), i.e., groundwater rating-curve, is parameterized empirically based on the observations in Illinois. The unconfined aquifer model is linked to the soil model in a land surface scheme LSX through the groundwater recharge flux (i.e., soil drainage flux). The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively couples the aquifer model with the soil model. The second issue to be addressed in this thesis is the representation of the sub-grid variability of water table depths (WTD) in the coupled model LSXGW. A statistical-dynamical (SD) approach is used to account for the effects of the unresolved sub-grid variability of WTD in the grid-scale groundwater runoff. The probability distribution function (PDF) of WTD is specified as a two-parameter Gamma distribution based on observations. (cont.) The scale of this PDF is dynamic according to the varying grid-mean WTD at each time step. The shape parameter of the PDF describing the WTD is kept constant. The grid-scale groundwater rating-curve (i.e., aquifer storage-discharge relationship) is derived statistically by integrating a point groundwater runoff model with respect to the PDF of WTD. Next, a mosaic approach is utilized to account for the effects of sub-grid variability of WTD in the grid-scale groundwater recharge. According to the time-varying PDF, a grid-cell is categorized into different sub-grids based on WTD. The fraction describing each sub-grid can be determined from the WTD PDF; hence it varies with time. The grid-scale hydrologic fluxes are computed by averaging all the sub-grid fluxes weighted by their fractions. This new methodology combines the strengths of the SD approach and the mosaic approach. The developed model has been successfully tested in Illinois for an 11-year period (1984-1994). The results indicate that the simulated hydrologic variables (soil saturation and WTD) and fluxes (evaporation, runoff, and groundwater recharge) agree well with the observations in Illinois. Nevertheless, it is recognized that the excellent performance of LSXGW in the Illinois simulation is significantly attributed to the reliable estimation of the macro-scale groundwater rating-curve ... by Pat Jen-Feng Yeh. Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

13

Naugler, Trudy Lynn. "Groundwater - surface water interactions in the Salmon River Watershed, BC : integrating spectroscopy, isotopes, water quality, and land use analyses." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31782.

Full text

Abstract:

Understanding the sources and pathways of water pollutants is critical for protecting freshwater resources. Relationships between water quality and land use can be obscured by variable land use, seasonal variability, and interactions between surface water and groundwater. This research combines the tools of fluorescence spectroscopy, nitrate stable isotopes and water chemistry to better understand land use impacts on water quality. The Hopington aquifer, one of the most vulnerable aquifers in the Lower Fraser Valley, is a source of drinking water for the Township of Langley. This aquifer is also responsible for maintaining the summer stream flow in the Salmon River, a productive Coho salmon stream. Elevated nitrates in both ground and stream water are a concern. Twelve stream sites and eleven groundwater wells were sampled during 2006 to try and "fingerprint" different water sources. Samples were analyzed for: uv-visible absorbance, fluorescence, DOC, nutrients (ammonium, nitrate, ortho-phosphate), chloride, trace elements, and nitrate-isotopes (δ¹⁸0 and δ¹⁵N). The combination of these tools provided a more detailed look at the groundwater - surface water interactions and helped track pollutants within the system. Nitrate concentrations in the Salmon River increase where it cuts through the Hopington aquifer; concentrations peak in August when groundwater makes up the greatest proportion of the stream flow. Humic-like fluorescence was able to measure this groundwater influence because groundwater has much lower fluorescence. Nitrate isotopes showed that inorganic fertilizers were not a dominant source, but that soil N, septic tank leakage, and manure were possible sources. Stream sites influenced by groundwater had an isotopic fingerprint similar to nearby wells, showing that the nitrate source(s) were the same. A GIS-based land use analysis suggested that agricultural land use was having the greatest impact on local water quality, especially on surface waters in the wet season. Protein-like fluorescence showed potential as a tool for pollution monitoring and should be explored further. Science, Faculty of Resources, Environment and Sustainability (IRES), Institute for Graduate

APA, Harvard, Vancouver, ISO, and other styles

14

LIU, ZHONGWEI. "WATER QUALITY SIMULATION AND ECONOMIC VALUATION OF RIPARIAN LAND-USE CHANGES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1153507620.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Widén-Nilsson, Elin. "Global-Scale Modelling of the Land-Surface Water Balance : Development and Analysis of WASMOD-M." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8352.

Full text

Abstract:

Water is essential for all life on earth. Global population increase and climate change are projected to increase the water stress, which already today is very high in many areas of the world. The differences between the largest and smallest global runoff estimates exceed the highest continental runoff estimates. These differences, which are caused by different modelling and measurement techniques together with large natural variabilities need to be further addressed. This thesis focuses on global water balance models that calculate global runoff, evaporation and water storage from precipitation and other climate data.A new global water balance model, WASMOD-M was developed. Already when tuned against the volume error it reasonable produced within-year runoff patterns, but the volume error was not enough to confine the model parameter space. The parameter space and the simulated hydrograph could be better confined with, e.g., the Nash criterion. Calibration against snow-cover data confined the snow parameters better, although some equifinality still persisted. Thus, even the simple WASMOD-M showed signs of being overparameterised. A simple regionalisation procedure that only utilised proximity contributed to calculate a global runoff estimate in line with earlier estimations. The need for better specifications of global runoff estimates was highlighted. Global modellers depend on global data-sets that can have low quality in many areas. Major sources of uncertainty are precipitation and river regulation. A new routing method that utilises high-resolution flow network information in low-resolution calculations was developed and shown to perform well over all spatial scales, while the standard linear reservoir routing decreased in performance with decreasing resolution. This algorithm, called aggregated time-delay-histogram routing, is intended for inclusion in WASMOD-M.

APA, Harvard, Vancouver, ISO, and other styles

16

Browning, Drew. "Modeling non-point source pollution in surface water under non-stationary climates and land uses." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408983669.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Mölders, Nicole, and Armin Raabe. "On the influence of grid resolution and land surface heterogeneity on hydrologically relevant quantities." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212321.

Full text

Abstract:

Numerische Experimente wurden durchgeführt, um den Einfluß von Gittermaschenweite und subskaliger Heterogenität auf die Vorhersage der am Wasserkreislauf beteiligten Größen zu untersuchen. Die Modellergebnisse zeigen, daß die Evapotranspiration, Bewölkung und der Niederschlag von der Gittermaschenweite und der Heterogenität beeinflußt werden. Es zeigte sich, daß bei Verwendung gröberer Maschenweiten unter Einbezug der verschiedenen Landnutzungstypen innerhalb der Gittermasche die Obertlächenprozesse und Phänomene (z.B. Wärmeinseleffekt) realistischer beschrieben werden, als wenn nur ein Landnutzungstyp für das gesamte Gitterelement angenommen wird Numerical experiments were performed to investigate the influence of grid resolution and subgrid heterogeneity on the prediction of the quantities of the water cycle. The results were compared with each other and with those provided by a simulation using the same surface parameterization scheme but taking subgrid scale surface heterogeneity into account. The model results substantiate that the evapotranspiration, cloudiness and precipitation are affected by the grid resolution and the heterogeneity. lt was found that increasing the grid size but including the heterogeneity describes more realistically the surface processes and phenomena (e.g„ heat island effect) than assuming one land use type for the whole grid element

APA, Harvard, Vancouver, ISO, and other styles

18

Farhadi, Leila. "Estimation of land surface water and energy balance flux components and closure relation using conditional sampling." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70757.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012. Cataloged from PDF version of thesis. Includes bibliographical references (p. 348-364). Models of terrestrial water and energy balance include numerical treatment of heat and moisture diffusion in the soil-vegetation-atmosphere continuum. These two diffusion and exchange processes are linked only at a few critical points. The performance and sensitivity of models are highly dependent on the nature of these linkages that are expressed as the closure function between heat and moisture dynamics. Land response to radiative forcing and partitioning of available energy into sensible and latent heat fluxes are dependant on the functional form. Since the function affects the surface fluxes, the influence reaches through the boundary layer and affects the lower atmosphere weather. As important as these closure functions are, they remain essentially empirical and untested across diverse conditions. It is critically important to develop observation-driven estimation procedures for the terrestrial water and energy closure problem, especially at the scale of modeling and with global coverage. In this dissertation a new approach to the estimation of key unknown parameters of water and energy balance equation and their closure relationship is introduced. This approach is based on averaging of heat and moisture diffusion equations conditioned on land surface temperature and moisture states respectively. The method is derived only from statistical stationarity and conservation statements of water and energy and thus it is scale free. The aim of this dissertation is to establish the theoretical basis for the approach and perform a global test using multi-platform remote sensing measurements. The feasibility of this approach is demonstrated at point-scale using synthetic data and flux-tower field site data. The method is applied to the mesoscale region of Gourma (West Africa) using multi-platform remote sensing data. The retrievals were verified against tower-flux field site data and physiographic characteristics of the region. The approach is used to find the functional form of the Evaporative Fraction (ratio of latent heat flux to sum of latent and sensible heat fluxes) dependence on soil moisture. Evaporative Fraction is a key closure function for surface and subsurface heat and moisture dynamics. With remote sensing data the dependence of this function on governing soil and vegetation characteristics is established. by Leila Farhadi. Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

19

Mölders, Nicole, and Armin Raabe. "On the influence of grid resolution and land surface heterogeneity on hydrologically relevant quantities." Universität Leipzig, 1995. https://ul.qucosa.de/id/qucosa%3A15016.

Full text

Abstract:

Numerische Experimente wurden durchgeführt, um den Einfluß von Gittermaschenweite und subskaliger Heterogenität auf die Vorhersage der am Wasserkreislauf beteiligten Größen zu untersuchen. Die Modellergebnisse zeigen, daß die Evapotranspiration, Bewölkung und der Niederschlag von der Gittermaschenweite und der Heterogenität beeinflußt werden. Es zeigte sich, daß bei Verwendung gröberer Maschenweiten unter Einbezug der verschiedenen Landnutzungstypen innerhalb der Gittermasche die Obertlächenprozesse und Phänomene (z.B. Wärmeinseleffekt) realistischer beschrieben werden, als wenn nur ein Landnutzungstyp für das gesamte Gitterelement angenommen wird. Numerical experiments were performed to investigate the influence of grid resolution and subgrid heterogeneity on the prediction of the quantities of the water cycle. The results were compared with each other and with those provided by a simulation using the same surface parameterization scheme but taking subgrid scale surface heterogeneity into account. The model results substantiate that the evapotranspiration, cloudiness and precipitation are affected by the grid resolution and the heterogeneity. lt was found that increasing the grid size but including the heterogeneity describes more realistically the surface processes and phenomena (e.g„ heat island effect) than assuming one land use type for the whole grid element.

APA, Harvard, Vancouver, ISO, and other styles

20

Martinez, Agudelo John Alejandro. "On the Hydroclimate of Southern South America: Water Vapor Transport and the Role of Shallow Groundwater on Land-Atmosphere Interactions." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/595679.

Full text

Abstract:

The present work focuses on the sources and transport of water vapor to the La Plata Basin (LPB), and the role of groundwater dynamics on the simulation of hydrometeorological conditions over the basin. In the first part of the study an extension to the Dynamic Recycling Model (DRM) is developed to estimate the water vapor transported to the LPB from different regions in South America and the nearby oceans, and the corresponding contribution to precipitation over the LPB. It is found that more than 23% of the precipitation over the LPB is from local origin, while nearly 20% originates from evapotranspiration from the southern Amazon. Most of the moisture comes from terrestrial sources, with the South American continent contributing more than 62% of the moisture for precipitation over the LPB. The Amazonian contribution increases during the positive phase of El Niño and the negative phase of the Antarctic Oscillation. In the second part of the study the effect of a groundwater scheme on the simulation of terrestrial water storage, soil moisture and evapotranspiration (ET) over the LPB is investigated. It is found that the groundwater scheme improves the simulation of fluctuations in the terrestrial water storage over parts of the southern Amazon. There is also an increase in the soil moisture in the root zone over those regions where the water table is closer to the surface, including parts of the western and southern Amazon, and of the central and southern LPB. ET increases in the central and southern LPB, where it is water limited. Over parts of the southeastern Amazon the effects of the groundwater scheme are only observed at higher resolution, when the convergence of lateral groundwater flow in local topographical depressions is resolved by the model. Finally, the effects of the groundwater scheme on near surface conditions and precipitation are explored. It is found that the increase in ET induced by the groundwater scheme over parts of the LPB induces an increase in near surface specific humidity, accompanied by a decrease in near surface temperature. During the dry season, downstream of the regions where ET increases, there is also a slight increase in precipitation, over a region where the model has a dry bias compared with observations. During the early rainy season, there is also an increase in the local convective available potential energy. Over the southern LPB, groundwater induces an increase in ET and precipitation of 13 and 10%, respectively. Over the LPB, the groundwater scheme tends to improve the warm and dry biases of the model. It is suggested that a more realistic simulation of the water table depth could further increase the simulated precipitation during the early rainy season.

APA, Harvard, Vancouver, ISO, and other styles

21

Evans, Jason Peter, and jason evans@yale edu. "Modelling Climate - Surface Hydrology Interactions in Data Sparse Areas." The Australian National University. Centre for Resource and Environmental Studies, 2000. http://thesis.anu.edu.au./public/adt-ANU20020313.032142.

Full text

Abstract:

The interaction between climate and land-surface hydrology is extremely important in relation to long term water resource planning. This is especially so in the presence of global warming and massive land use change, issues which seem likely to have a disproportionate impact on developing countries. This thesis develops tools aimed at the study and prediction of climate effects on land-surface hydrology (in particular streamflow), which require a minimum amount of site specific data. This minimum data requirement allows studies to be performed in areas that are data sparse, such as the developing world. ¶ A simple lumped dynamics-encapsulating conceptual rainfall-runoff model, which explicitly calculates the evaporative feedback to the atmosphere, was developed. It uses the linear streamflow routing module of the rainfall-runoff model IHACRES, with a new non-linear loss module based on the Catchment Moisture Deficit accounting scheme, and is referred to as CMD-IHACRES. In this model, evaporation can be calculated using a number of techniques depending on the data available, as a minimum, one to two years of precipitation, temperature and streamflow data are required. The model was tested on catchments covering a large range of hydroclimatologies and shown to estimate streamflow well. When tested against evaporation data the simplest technique was found to capture the medium to long term average well but had difficulty reproducing the short-term variations. ¶ A comparison of the performance of three limited area climate models (MM5/BATS, MM5/SHEELS and RegCM2) was conducted in order to quantify their ability to reproduce near surface variables. Components of the energy and water balance over the land surface display considerable variation among the models, with no model performing consistently better than the other two. However, several conclusions can be made. The MM5 longwave radiation scheme performed worse than the scheme implemented in RegCM2. Estimates of runoff displayed the largest variations and differed from observations by as much as 100%. The climate models exhibited greater variance than the observations for almost all the energy and water related fluxes investigated. ¶ An investigation into improving these streamflow predictions by utilizing CMD-IHACRES was conducted. Using CMD-IHACRES in an 'offline' mode greatly improved the streamflow estimates while the simplest evaporation technique reproduced the evaporative time series to an accuracy comparable to that obtained from the limited area models alone. The ability to conduct a climate change impact study using CMD-IHACRES and a stochastic weather generator is also demonstrated. These results warrant further investigation into incorporating the rainfall-runoff model CMD-IHACRES in a fully coupled 'online' approach.

APA, Harvard, Vancouver, ISO, and other styles

22

Tanaka, Kenji. "Development of the new land surface scheme SiBUC commonly applicable to basin water management and numerical weather prediction model." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145376.

Full text

Abstract:

Kyoto University (京都大学) 0048 新制・論文博士 博士(工学) 乙第11576号 論工博第3817号 新制||工||1329(附属図書館) 22875 UT51-2004-U473 京都大学大学院工学研究科環境地球工学専攻 (主査)教授池淵周一, 教授椎葉充晴, 教授中北英一 学位規則第4条第2項該当

APA, Harvard, Vancouver, ISO, and other styles

23

Kgomotso, Phemo Karen. "Global environmental agreements and local livelihoods : how the internationalisation of environmental resources shapes access to and control over wetland resources in the Okavango Delta, Botswana." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/38451/.

Full text

Abstract:

This thesis examines how global environmental crisis narratives and discourses have influenced environmental policy and practice in conservation programmes for the Okavango Delta, Botswana. In particular, it highlights the contested nature of biodiversity conservation and the embedded power relations in the framing, definition and crafting of solutions to the problem of biodiversity degradation at local, national and international levels. The thesis therefore examines, based on these framings, the consequences of global environmental agreements, such as the Ramsar Convention and the UN Convention on Biological Diversity, for local livelihoods in terms of access to and control over local environmental resources in the Okavango Delta. Using a political ecological conceptual lens and related literature on common pool resource management and community-based natural resource management, this thesis traces the changing perceptions, narratives and discourses relating to the Okavango Delta over time, and assesses how these have shaped changes in policy for the Delta's use and management. It specifically analyses the implementation of international programmes and their role in facilitating these changes. Through an in-depth study of dynamic human-environment interactions around fisheries and other wetland resources, this thesis shows how international interventions have not only increased conflicts but also facilitated the strict regulation of these resources. The thesis therefore analyses how framing these and other common pool resources as being of ‘international significance' alters control over them and affects the livelihood security of the local people that depend on these resources. It concludes that such restrictive conservation policies and management approaches have led to a transfer of control over wetland resources from local subsistence users to other, more powerful, commercial interests, especially those in the international tourism industry.

APA, Harvard, Vancouver, ISO, and other styles

24

Moutahir, Hassane. "Likely effects of climate change on water resources and vegetation growth period in the province of Alicante, southeastern Spain." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/70649.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Mölders, Nicole, Thomas Beckmann, and Armin Raabe. "A module to couple an atmospheric and a hydrologic model." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212867.

Full text

Abstract:

A land-surface module to couple a meteorological and a hydrologic model is described. lt was implemented and tested in the Leipzig\'s version of GESIMA. Preliminary results of a coupling with NASMO are presented, although this article mainly focuses on the description of the module and its effect on the atmospheric water cycle. One positive impact of the module is that it allows to produce subgrid-scale evapotranspiration in more details and to heterogenize precipitation. This strongly affects soil wetness, cloudiness and the thermal regime of the atmospheric boundary layer Ein Bodenmodul zur Kopplung eines meteorologischen mit einem hydrologischen Modell wird vorgestellt. Er wurde implementiert und getestet in der Leipziger Version von GESIMA. Obgleich der Schwerpunkt des Artikels auf der Beschreibung des Moduls und seiner Auswirkung auf den atmosphärischen Wasserkreislauf liegt, werden auch vorläufige Ergebnisse einer Kopplung mit NASMO präsentiert. Ein positiver Effekt des Moduls ist, daß er ermöglicht, detaillierter die subskalige Evapotranspiration zu beschreiben und den Niederschlag zu heterogenisieren. Dies wirkt sich stark auf die Bodenfeuchte, die Bewölkung und das thermische Regime der atmosphärischen Grenzschicht aus

APA, Harvard, Vancouver, ISO, and other styles

26

Nagai, Haruyasu. "Development of a New Atmosphere-Soil-Vegetation Model to Study Heat, Water, and CO2 Exchanges between the Atmosphere and Land-surface." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147889.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Ma, Ning, Guo-Yue Niu, Youlong Xia, et al. "A Systematic Evaluation of Noah-MP in Simulating Land-Atmosphere Energy, Water, and Carbon Exchanges Over the Continental United States." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626444.

Full text

Abstract:

Accurate simulation of energy, water, and carbon fluxes exchanging between the land surface and the atmosphere is beneficial for improving terrestrial ecohydrological and climate predictions. We systematically assessed the Noah land surface model (LSM) with mutiparameterization options (Noah-MP) in simulating these fluxes and associated variations in terrestrial water storage (TWS) and snow cover fraction (SCF) against various reference products over 18 United States Geological Survey two-digital hydrological unit code regions of the continental United States (CONUS). In general, Noah-MP captures better the observed seasonal and interregional variability of net radiation, SCF, and runoff than other variables. With a dynamic vegetation model, it overestimates gross primary productivity by 40% and evapotranspiration (ET) by 22% over the whole CONUS domain; however, with a prescribed climatology of leaf area index, it greatly improves ET simulation with relative bias dropping to 4%. It accurately simulates regional TWS dynamics in most regions except those with large lakes or severely affected by irrigation and/or impoundments. Incorporating the lake water storage variations into the modeled TWS variations largely reduces the TWS simulation bias more obviously over the Great Lakes with model efficiency increasing from 0.18 to 0.76. Noah-MP simulates runoff well in most regions except an obvious overestimation (underestimation) in the Rio Grande and Lower Colorado (New England). Compared with North American Land Data Assimilation System Phase 2 (NLDAS-2) LSMs, Noah-MP shows a better ability to simulate runoff and a comparable skill in simulating R-n but a worse skill in simulating ET over most regions. This study suggests that future model developments should focus on improving the representations of vegetation dynamics, lake water storage dynamics, and human activities including irrigation and impoundments.

APA, Harvard, Vancouver, ISO, and other styles

28

Brunke, Michael A., Patrick Broxton, Jon Pelletier, et al. "Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)." AMER METEOROLOGICAL SOC, 2016. http://hdl.handle.net/10150/612995.

Full text

Abstract:

One of the recognized weaknesses of land surface models as used in weather and climate models is the assumption of constant soil thickness because of the lack of global estimates of bedrock depth. Using a 30-arc-s global dataset for the thickness of relatively porous, unconsolidated sediments over bedrock, spatial variation in soil thickness is included here in version 4.5 of the Community Land Model (CLM4.5). The number of soil layers for each grid cell is determined from the average soil depth for each 0.9 degrees latitude x 1.25 degrees longitude grid cell. The greatest changes in the simulation with variable soil thickness are to baseflow, with the annual minimum generally occurring earlier. Smaller changes are seen in latent heat flux and surface runoff primarily as a result of an increase in the annual cycle amplitude. These changes are related to soil moisture changes that are most substantial in locations with shallow bedrock. Total water storage (TWS) anomalies are not strongly affected over most river basins since most basins contain mostly deep soils, but TWS anomalies are substantially different for a river basin with more mountainous terrain. Additionally, the annual cycle in soil temperature is partially affected by including realistic soil thicknesses resulting from changes in the vertical profile of heat capacity and thermal conductivity. However, the largest changes to soil temperature are introduced by the soil moisture changes in the variable soil thickness simulation. This implementation of variable soil thickness represents a step forward in land surface model development.

APA, Harvard, Vancouver, ISO, and other styles

29

Ohta, Takeshi, Tetsuya Hiyama, Hiroki Tanaka, et al. "Seasonal variation in the energy and water exchanges above and below a larch forest in eastern Siberia." Wiley, 2001. http://hdl.handle.net/2237/7756.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Törnqvist, Rebecka. "Basin-scale change in water availability and water quality under intensified irrigated agriculture." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-93214.

Full text

Abstract:

Changes in land use and water use can greatly impact the cycling of water and water-borne substances. Increased redistribution of river water to irrigated fields can cause enhanced evapotranspiration and decreased river discharge. Additionally, the water quality can be affected by the external input of fertilisers and pesticides, and by changed pollutant transport pathways in expansive irrigation canal systems. This thesis examines basin-scale changes in water use, river discharge, water quality and nitrogen (N) loading under conditions of intensified irrigated agriculture, using the Aral Sea drainage basin (ASDB) with its two large rivers Syr Darya and Amu Darya in Central Asia as study area. Results show that more efficient irrigation techniques could reduce outtake of river water to the cotton fields in the ASDB by about 10 km3/year, while the corresponding river water saving at the outlet would be 60% lower. The result illustrates the importance of accounting for return flows of irrigation water in basin-scale water saving assessments. Moreover, a decrease in riverine N concentrations at the outlet of the Amu Darya River Basin (ADRB) was observed during a 40-year period of increasing N fertiliser input. The decrease was identified to be primarily caused by increased recirculation of river water in the irrigation system, leading to increased flow-path lengths and enhanced N attenuation. Decreasing N loads were shown to be primarily related to reduced discharge. N export from the basin may further decrease due to projected discharge reductions related to climate change. Furthermore, nutrients and metals were occasionally found at concentrations above drinking water guideline values in surface waters in the ADRB. However, metal concentrations in groundwater in the lower ADRB were subject to orders of magnitude higher health hazards. Projected decrease in downstream surface water availability would thus imply decreased access to water suitable for drinking. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript.

APA, Harvard, Vancouver, ISO, and other styles

31

Redfearn, Howard Daniel. "Rainfall-runoff changes due to urbanization: a comparison of different spatial resolutions for lumped surface water hydrology models using HEC-HMS." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4939/.

Full text

Abstract:

Hydrologic models were used to examine the effects of land cover change on the flow regime of a watershed located in North-Central Texas. Additionally, the effect of spatial resolution was examined by conducting the simulations using sub-watersheds of different sizes to account for the watershed. Using the Army Corps of Engineers, Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS), two different modeling methods were evaluated at the different sub-watershed resolutions for four rainfall events. Calibration results indicate using the smaller spatial resolutions improves the model results. Different scenarios for land cover change were evaluated for all resolutions using both models. As land cover change increased, the amount of flow from the watershed increased.

APA, Harvard, Vancouver, ISO, and other styles

32

Lemon, Michelle M. "The effects of land use and regional hydrology on surface water quality in the upper San Pedro River, Arizona, United States of America." Thesis, The University of Arizona, 2004. http://hdl.handle.net/10150/292075.

Full text

Abstract:

The purpose of this study is to examine the effects of land use and hydrology on surface water quality in a semi-arid watershed. Six synoptic sampling events were performed along the upper San Pedro River, AZ, USA before, during, and after the 2002 monsoon season. Water samples were analyzed for conservative solutes, nutrients, and organic matter. During non-monsoon baseflow periods, conservative solutes indicated limited hydrologic connection between regions. Protected reaches had significantly higher DOC concentrations and agricultural reaches had significantly higher DON and NO₃-N levels. In contrast, solute concentrations during the monsoon season indicated all regions were hydrologically linked. DOM and NO₃-N concentrations increased as terrestrially derived solutes were flushed into the stream. Nutrient loads were variable suggesting that changes in nutrient concentrations were related to individual reaches. This research demonstrates that hydrologic flowpaths and land cover are important controls on surface water quality at the reach and river scales.

APA, Harvard, Vancouver, ISO, and other styles

33

GHIRARDINI, Andrea. "Main sources and emission pathways of micropollutants released in surface water at a catchment scale: from a theoretical approach to a practical application on a case-study." Doctoral thesis, Università degli studi di Ferrara, 2021. http://hdl.handle.net/11392/2488226.

Full text

Abstract:

Due to the rising global population and the steady growth of the health care sector, the consumption of pharmaceuticals increased consistently in the last decades. Although modern medicine significantly developed, this brought to the possibility that residues of these compounds reach surface water, soil, and plants through several routes during their manufacture, use, and disposal. Considering a rural or peri-urban areas, pharmaceutical compounds may enter in the water environment via wastewater treatment plant efflluent, combined sewer overflow, and soil water flows originated from arable lands in which sewage sludge or animal manure have been amended as fertilizers. This thesis takes place in this background, aiming to, firstly, characterize the content of PPCPs in sewage sludge and zootechnical wastes originated from different animals and with various characteristics. Afterwards, the remobilization of these micropollutants was studied in order to have an overall view of their potential occurrence in the soil water flows and of the main factors influencing it (such as soil characteristics, physico-chemical properties of the compounds, sludge application rate and method, and so forth). These two first steps were carried out through a comprehensive and exhaustive literature review and were essential to prepare a general overview of the state-of-the-art on the topic. Then, all the elements were on the table to try to estimate the contribution of different sources (among them WWTP effluent, CSO, and surface runoff from manure or sewage sludge-amended soils) to the occurrence of selected pharmaceuticals in surface water, on a catchment scale. This last task was conducted in collaboration with the Institute for Water Quality, Resources and Waste Management of the TU Wien, and focused on a specific case-study regarding an Austrian peri-urban watershed. The result was the development of a modelling approach in order to identify the most relevant sources and emission pathways of pharmaceuticals, with particular attention to the significance of agricultural land runoff. The strength and weaknesses related to this model are discussed in this thesis, in order to lay the groundwork for moving from a case-study to an overall discussion of the topic. Finally, as a consequence of the work done, one last task was performed investigating the potential toxic effects on edible crops due to their irrigation with surface water contaminated by residues of PPCPs. The subject was explored in collaboration with the Department of Environment and Geography of the University of York, through a laboratory experiment in which garden cress plants – an edible crop commonly cultivated in northern Europe – were treated with mixtures of PPCPs simulating the irrigation with surface water similar to those that can be sampled worldwide. The results of this work showed that residues of micropollutants might cause visible effects on plant biomass even when occurring at very low concentrations (ng L-1 level), due to the synergistic and additive effects between the compounds. In conclusion, the findings of this thesis highlighted that the effects of the occurrence of PPCPs in the agricultural agroecosystem (soil, water, and plants), and mutatis mutandis in the receiving water environment, are measurable. This thesis pinpoints some issue related to this complex phenomenon, and the necessity to further investigate in this field to exhaustively deepen the problem.

APA, Harvard, Vancouver, ISO, and other styles

34

Christoffersen, Bradley. "The Ecohydrological Mechanisms of Resilience and Vulnerability of Amazonian Tropical Forests to Water Stress." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293566.

Full text

Abstract:

Predicting the interactions between climate change and ecosystems remains a core problem in global change research; tropical forest ecosystems are of particular importance because of their disproportionate role in global carbon and water cycling. Amazonia is unique among tropical forest ecosystems, exhibiting a high degree of coupling with its regional hydrometeorology, such that the stability of the entire forest-climate system is dependent on the functioning of its component parts. Belowground ecohydrological interactions between soil moisture environments and the roots which permeate them initiate the water transport pathway to leaf stomata, yet despite the disproportionate role they play in vegetation-atmosphere coupling in Amazonian forest ecosystems, the impacts of climate variability on the belowground environment remain understudied. The research which follows is designed to address critical knowledge gaps in our understanding of root functioning in Amazonian tropical forests as it relates to seasonality and extremes in belowground moisture regime as well as discerning which ecohydrological mechanisms govern ecosystem-level processes of carbon and water flux. A secondary research theme is the evaluation and use of models of ecosystem function as applied to Amazonia - these models are the "knowledge boxes" which build in the ecohydrological hypotheses (some testable than others) deemed to be most important for the forest ecosystems of Amazonia. In what follows, I investigate (i) which mechanisms of water supply (from the soil environment) and water demand (by vegetation) regulate the magnitude and seasonality of evapotranspiration across broad environmental gradients of Amazonia, (ii) how specific hypotheses of root function are or are not corroborated by soil moisture measurements conducted under normal seasonal and experimentally-induced extreme drought conditions, and (iii) the linkage between an extreme drought event with associated impacts on root zone soil moisture, the inferred response of root water uptake, and the observed impacts on ecosystem carbon and water flux in an east central Amazonian forest.

APA, Harvard, Vancouver, ISO, and other styles

35

Labadz, Martin. "A catchment modelling approach integrating surface and groundwater processes, land use and distribution of nutrients : Elimbah Creek, southeast Queensland." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/60017/1/Martin_Labadz_Thesis.pdf.

Full text

Abstract:

As the world’s population is growing, so is the demand for agricultural products. However, natural nitrogen (N) fixation and phosphorus (P) availability cannot sustain the rising agricultural production, thus, the application of N and P fertilisers as additional nutrient sources is common. It is those anthropogenic activities that can contribute high amounts of organic and inorganic nutrients to both surface and groundwaters resulting in degradation of water quality and a possible reduction of aquatic life. In addition, runoff and sewage from urban and residential areas can contain high amounts of inorganic and organic nutrients which may also affect water quality. For example, blooms of the cyanobacterium Lyngbya majuscula along the coastline of southeast Queensland are an indicator of at least short term decreases of water quality. Although Australian catchments, including those with intensive forms of land use, show in general a low export of nutrients compared to North American and European catchments, certain land use practices may still have a detrimental effect on the coastal environment. Numerous studies are reported on nutrient cycling and associated processes on a catchment scale in the Northern Hemisphere. Comparable studies in Australia, in particular in subtropical regions are, however, limited and there is a paucity in the data, in particular for inorganic and organic forms of nitrogen and phosphorus; these nutrients are important limiting factors in surface waters to promote algal blooms. Therefore, the monitoring of N and P and understanding the sources and pathways of these nutrients within a catchment is important in coastal zone management. Although Australia is the driest continent, in subtropical regions such as southeast Queensland, rainfall patterns have a significant effect on runoff and thus the nutrient cycle at a catchment scale. Increasingly, these rainfall patterns are becoming variable. The monitoring of these climatic conditions and the hydrological response of agricultural catchments is therefore also important to reduce the anthropogenic effects on surface and groundwater quality. This study consists of an integrated hydrological–hydrochemical approach that assesses N and P in an environment with multiple land uses. The main aim is to determine the nutrient cycle within a representative coastal catchment in southeast Queensland, the Elimbah Creek catchment. In particular, the investigation confirms the influence associated with forestry and agriculture on N and P forms, sources, distribution and fate in the surface and groundwaters of this subtropical setting. In addition, the study determines whether N and P are subject to transport into the adjacent estuary and thus into the marine environment; also considered is the effect of local topography, soils and geology on N and P sources and distribution. The thesis is structured on four components individually reported. The first paper determines the controls of catchment settings and processes on stream water, riverbank sediment, and shallow groundwater N and P concentrations, in particular during the extended dry conditions that were encountered during the study. Temporal and spatial factors such as seasonal changes, soil character, land use and catchment morphology are considered as well as their effect on controls over distributions of N and P in surface waters and associated groundwater. A total number of 30 surface and 13 shallow groundwater sampling sites were established throughout the catchment to represent dominant soil types and the land use upstream of each sampling location. Sampling comprises five rounds and was conducted over one year between October 2008 and November 2009. Surface water and groundwater samples were analysed for all major dissolved inorganic forms of N and for total N. Phosphorus was determined in the form of dissolved reactive P (predominantly orthophosphate) and total P. In addition, extracts of stream bank sediments and soil grab samples were analysed for these N and P species. Findings show that major storm events, in particular after long periods of drought conditions, are the driving force of N cycling. This is expressed by higher inorganic N concentrations in the agricultural subcatchment compared to the forested subcatchment. Nitrate N is the dominant inorganic form of N in both the surface and groundwaters and values are significantly higher in the groundwaters. Concentrations in the surface water range from 0.03 to 0.34 mg N L..1; organic N concentrations are considerably higher (average range: 0.33 to 0.85 mg N L..1), in particular in the forested subcatchment. Average NO3-N in the groundwater has a range of 0.39 to 2.08 mg N L..1, and organic N averages between 0.07 and 0.3 mg N L..1. The stream bank sediments are dominated by organic N (range: 0.53 to 0.65 mg N L..1), and the dominant inorganic form of N is NH4-N with values ranging between 0.38 and 0.41 mg N L..1. Topography and soils, however, were not to have a significant effect on N and P concentrations in waters. Detectable phosphorus in the surface and groundwaters of the catchment is limited to several locations typically in the proximity of areas with intensive animal use; in soil and sediments, P is negligible. In the second paper, the stable isotopes of N (14N/15N) and H2O (16O/18O and 2H/H) in surface and groundwaters are used to identify sources of dissolved inorganic and organic N in these waters, and to determine their pathways within the catchment; specific emphasis is placed on the relation of forestry and agriculture. Forestry is predominantly concentrated in the northern subcatchment (Beerburrum Creek) while agriculture is mainly found in the southern subcatchment (Six Mile Creek). Results show that agriculture (horticulture, crops, grazing) is the main source of inorganic N in the surface waters of the agricultural subcatchment, and their isotopic signature shows a close link to evaporation processes that may occur during water storage in farm dams that are used for irrigation. Groundwaters are subject to denitrification processes that may result in reduced dissolved inorganic N concentrations. Soil organic matter delivers most of the inorganic N to the surface water in the forested subcatchment. Here, precipitation and subsequently runoff is the main source of the surface waters. Groundwater in this area is affected by agricultural processes. The findings also show that the catchment can attenuate the effects of anthropogenic land use on surface water quality. Riparian strips of natural remnant vegetation, commonly 50 to 100 m in width, act as buffer zones along the drainage lines in the catchment and remove inorganic N from the soil water before it enters the creek. These riparian buffer zones are common in most agricultural catchments of southeast Queensland and are indicated to reduce the impact of agriculture on stream water quality and subsequently on the estuary and marine environments. This reduction is expressed by a significant decrease in DIN concentrations from 1.6 mg N L..1 to 0.09 mg N L..1, and a decrease in the �15N signatures from upstream surface water locations downstream to the outlet of the agricultural subcatchment. Further testing is, however, necessary to confirm these processes. Most importantly, the amount of N that is transported to the adjacent estuary is shown to be negligible. The third and fourth components of the thesis use a hydrological catchment model approach to determine the water balance of the Elimbah Creek catchment. The model is then used to simulate the effects of land use on the water balance and nutrient loads of the study area. The tool that is used is the internationally widely applied Soil and Water Assessment Tool (SWAT). Knowledge about the water cycle of a catchment is imperative in nutrient studies as processes such as rainfall, surface runoff, soil infiltration and routing of water through the drainage system are the driving forces of the catchment nutrient cycle. Long-term information about discharge volumes of the creeks and rivers do, however, not exist for a number of agricultural catchments in southeast Queensland, and such information is necessary to calibrate and validate numerical models. Therefore, a two-step modelling approach was used to calibrate and validate parameters values from a near-by gauged reference catchment as starting values for the ungauged Elimbah Creek catchment. Transposing monthly calibrated and validated parameter values from the reference catchment to the ungauged catchment significantly improved model performance showing that the hydrological model of the catchment of interest is a strong predictor of the water water balance. The model efficiency coefficient EF shows that 94% of the simulated discharge matches the observed flow whereas only 54% of the observed streamflow was simulated by the SWAT model prior to using the validated values from the reference catchment. In addition, the hydrological model confirmed that total surface runoff contributes the majority of flow to the surface water in the catchment (65%). Only a small proportion of the water in the creek is contributed by total base-flow (35%). This finding supports the results of the stable isotopes 16O/18O and 2H/H, which show the main source of water in the creeks is either from local precipitation or irrigation waters delivered by surface runoff; a contribution from the groundwater (baseflow) to the creeks could not be identified using 16O/18O and 2H/H. In addition, the SWAT model calculated that around 68% of the rainfall occurring in the catchment is lost through evapotranspiration reflecting the prevailing long-term drought conditions that were observed prior and during the study. Stream discharge from the forested subcatchment was an order of magnitude lower than discharge from the agricultural Six Mile Creek subcatchment. A change in land use from forestry to agriculture did not significantly change the catchment water balance, however, nutrient loads increased considerably. Conversely, a simulated change from agriculture to forestry resulted in a significant decrease of nitrogen loads. The findings of the thesis and the approach used are shown to be of value to catchment water quality monitoring on a wider scale, in particular the implications of mixed land use on nutrient forms, distributions and concentrations. The study confirms that in the tropics and subtropics the water balance is affected by extended dry periods and seasonal rainfall with intensive storm events. In particular, the comprehensive data set of inorganic and organic N and P forms in the surface and groundwaters of this subtropical setting acquired during the one year sampling program may be used in similar catchment hydrological studies where these detailed information is missing. Also, the study concludes that riparian buffer zones along the catchment drainage system attenuate the transport of nitrogen from agricultural sources in the surface water. Concentrations of N decreased from upstream to downstream locations and were negligible at the outlet of the catchment.

APA, Harvard, Vancouver, ISO, and other styles

36

Fox, John Tyler. "Spatiotemporal Patterns and Drivers of Surface Water Quality and Landscape Change in a Semi-Arid, Southern African Savanna." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81462.

Full text

Abstract:

The savannas of southern Africa are a highly variable and globally-important biome supporting rapidly-expanding human populations, along with one of the greatest concentrations of wildlife on the continent. Savannas occupy a fifth of the earth's land surface, yet despite their ecological and economic significance, understanding of the complex couplings and feedbacks that drive spatiotemporal patterns of change are lacking. In Chapter 1 of my dissertation, I discuss some of the different theoretical frameworks used to understand complex and dynamic changes in savanna structure and composition. In Chapter 2, I evaluate spatial drivers of water quality declines in the Chobe River using spatiotemporal and geostatistical modeling of time series data collected along a transect spanning a mosaic of protected, urban, and developing urban land use. Chapter 3 explores the complex couplings and feedbacks that drive spatiotemporal patterns of land cover (LC) change across the Chobe District, with a particular focus on climate, fire, herbivory, and anthropogenic disturbance. In Chapter 4, I evaluated the utility of Distance sampling methods to: 1) derive seasonal fecal loading estimates in national park and unprotected land; 2) provide a simple, standardized method to estimate riparian fecal loading for use in distributed hydrological water quality models; 3) answer questions about complex drivers and patterns of water quality variability in a semi-arid southern African river system. Together, these findings have important implications to land use planning and water conservation in southern Africa's dryland savanna ecosystems. Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

37

Milašaitė, Indrė. "Raseinių rajono nuotekų valyklų efektyvumo analizė." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20090114_160431-07549.

Full text

Abstract:

Vandenų apsauga yra viena iš svarbiausių aplinkosaugos sričių. Europos Sąjungos direktyvos griežtai reglamentuoja išleidžiamų į paviršinius vandenis miestų nuotekų kokybę. Ne mažiau kaip 80 procentų išleidžiamų nuotekų neturi viršyti didžiausios leidžiamos koncentracijos. Darbo tikslas ištirti nuotekų valyklų Raseinių rajono savivaldybėje darbo efektyvumą ir numatyti priemones jų darbui pagerinti. Darbe analizuojama Raseinių rajono (Raseinių, Ariogalos, Kaulakių gyvenviečių) nuotekų valyklų darbo efektyvumas. Analizei naudoti 2005-2007 metais atliktų tyrimų duomenys. Duomenų analizė parodė, kad visoms valykloms reikalinga rekonstrukcija, visose gyvenvietėse reikia didinti prie centrinės nuotekų šalinimo sistemos prisijungusių gyventojų skaičių. The protection of water is one of the most important spheres in the environment control. The quality of cities‘ sewage, that is drained to surface water, is strictly regulated by the directives of European Union. Not less than 80 per cent of drained sewage must not exceed the maximum allowable concentration. The purpose of this research is to analyse the effectiveness of sewage works in Raseiniai district and to provide the plant improvement scheme. In the article there is discussed the effectiveness of sewage works in Raseiniai district (Raseiniai, Ariogala, Kaulakiai). The data of 2007 is used in the analysis. The results show that the reconstruction is necessary for all the sewage works. Moreover, in all the places of residence it is a must to increase the number of residents who are linked to the central sewage removal system.

APA, Harvard, Vancouver, ISO, and other styles

38

Mölders, Nicole, Thomas Beckmann, and Armin Raabe. "A module to couple an atmospheric and a hydrologic model." Universität Leipzig, 1996. https://ul.qucosa.de/id/qucosa%3A15045.

Full text

Abstract:

A land-surface module to couple a meteorological and a hydrologic model is described. lt was implemented and tested in the Leipzig\''s version of GESIMA. Preliminary results of a coupling with NASMO are presented, although this article mainly focuses on the description of the module and its effect on the atmospheric water cycle. One positive impact of the module is that it allows to produce subgrid-scale evapotranspiration in more details and to heterogenize precipitation. This strongly affects soil wetness, cloudiness and the thermal regime of the atmospheric boundary layer. Ein Bodenmodul zur Kopplung eines meteorologischen mit einem hydrologischen Modell wird vorgestellt. Er wurde implementiert und getestet in der Leipziger Version von GESIMA. Obgleich der Schwerpunkt des Artikels auf der Beschreibung des Moduls und seiner Auswirkung auf den atmosphärischen Wasserkreislauf liegt, werden auch vorläufige Ergebnisse einer Kopplung mit NASMO präsentiert. Ein positiver Effekt des Moduls ist, daß er ermöglicht, detaillierter die subskalige Evapotranspiration zu beschreiben und den Niederschlag zu heterogenisieren. Dies wirkt sich stark auf die Bodenfeuchte, die Bewölkung und das thermische Regime der atmosphärischen Grenzschicht aus.

APA, Harvard, Vancouver, ISO, and other styles

39

Persson, Tony. "Evaporation and Heat-flux Aggregation in Heterogeneous Boreal Landscapes." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4326.

Full text

Abstract:

The boreal forests represent 8 % of all forested areas on the earth and have a significant role in the control of greenhouse gases and an impact on global climate change. The main objective of this thesis is to increase the understanding of how evaporation and heat-flux processes in the boreal forest zone are affecting the regional and global climate.A meteorological mesoscale model with an advanced land-surface parameterization has been utilized to study aggregation of fluxes of water vapour and heat. The model has been compared against four other methods for flux estimation in a southern boreal landscape. The results show that the mesoscale model is successfully reproducing 24-hour averages of fractionally weighted mast measurements of sensible and latent heat flux.The model was also evaluated against in-situ observations of surface fluxes and other meteorological variables. The results reveal that a correct initialization of soil moisture is crucial to simulate a realistic partitioning of the sensible and latent heat fluxes. Significant differences in surface fluxes and friction velocities between two apparently similar forest sites indicate the need for careful assessment of areal representativity when comparing mesoscale model results with in-situ observations.A parameterization for the absorption of solar radiation of high-latitude sparse forests was implemented and tested in the model that significantly improved the simulation of high wintertime midday sensible heat fluxes. A scheme for heat storage in vegetation was also implemented which improved the results, but the scheme needs further evaluation for high latitude forests.Two commonly used strategies for the description of land-surface heterogeneity, the effective parameter approach and the mosaic approach, were tested in the mesoscale model against airborne observations of sensible and latent heat fluxes. The results show that the mosaic approach produces better results especially when small lakes are present in model grid-squares. Norra halvklotets barrskogsbälte representerar 8 % av all skogsbeklädd mark på jorden och har stor betydelse för kontrollen av växthusgaser och påverkan på globala klimatförändringar. Syftet med denna avhandling är att öka förståelsen av hur avdunstning och värmeflöden i den boreala skogszonen påverkar klimatet regionalt och globalt.En meteorologisk mesoskalemodell med en avancerad landyteparameterisering har använts för att studera aggregering av avdunstning och värmeflöden. Modellen jämfördes med fyra andra metoder för uppskattning av värmeflöden i den boreala skogszonens södra delar. Resultaten visade att mesoskalemodellen reproducerar 24-timmarsmedelvärden av sensibelt och latent värmeflöde från areellt viktade mastmätningar med bra resultat.Modellen utvärderades även mot markbaserade mätningar av sensibelt och latent värme och andra meteorologiska variabler. Resultaten visar att en korrekt initialisering av markvatteninnehållet är avgörande för att simulera en realistisk uppdelning av de sensibla och latenta värmeflödena. Markanta skillnader i markyteflöden och friktionshastigheter mellan två liknande skogsmätstationer påvisar nödvändigheten av en noggrann bedömning av den areella representativiteten när man jämför resultat från mesoskalemodellen med markbaserade mätningar.En parameterisering för absorption av solstrålning i glesa skogsbestånd på höga breddgrader infördes och testades i modellen vilket markant förbättrade simuleringen av de höga sensibla värmeflöden som observerats vid middagstid på vintern. Ett uttryck för att beskriva värmelagring i vegetationen infördes också vilket förbättrade resultaten, men uttrycket behöver vidare utvärdering för skogsbestånd på höga breddgrader.Två ofta använda strategier för att beskriva markytans heterogenitet, effektiva parametermetoden och mosaikmetoden, testades i mesoskalemodellen mot flygburna observationer av sensibla och latenta värmeflöden. Resultaten visar att mosaikmetoden ger bättre resultat särskilt när mindre sjöar förekommer i modellrutorna.

APA, Harvard, Vancouver, ISO, and other styles

40

Amazirh, Abdelhakim. "Monitoring crops water needs at high spatio-temporal resolution by synergy of optical/thermal and radar observations." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30101.

Full text

Abstract:

L'optimisation de la gestion de l'eau en agriculture est essentielle dans les zones semi-arides afin de préserver les ressources en eau qui sont déjà faibles et erratiques dues à des actions humaines et au changement climatique. Cette thèse vise à utiliser la synergie des observations de télédétection multispectrales (données radar, optiques et thermiques) pour un suivi à haute résolution spatio-temporelle des besoins en eau des cultures. Dans ce contexte, différentes approches utilisant divers capteurs (Landsat-7/8, Sentinel-1 et MODIS) ont été developpées pour apporter une information sur l'humidité du sol (SM) et le stress hydrique des cultures à une échelle spatio-temporelle pertinente pour la gestion de l'irrigation. Ce travail va parfaitement dans le sens des objectifs du projet REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) qui visent à estimer l'humidité du sol dans la zone racinaire (RZSM) afin d'optimiser la gestion de l'eau d'irrigation. Des approches innovantes et prometteuses sont mises en place pour estimer l'évapotranspiration (ET), RZSM, la température de surface du sol (LST) et le stress hydrique de la végétation à travers des indices de SM dérivés des observations multispectrales à haute résolution spatio-temporelle. Les méthodologies proposées reposent sur des méthodes basées sur l'imagerie, la modélisation du transfert radiatif et la modélisation du bilan hydrique et d'énergie et sont appliquées dans une région à climat semi-aride (centre du Maroc). Dans le cadre de ma thèse, trois axes ont été explorés. Dans le premier axe, un indice de RZSM dérivé de LST-Landsat est utilisé pour estimer l'ET sur des parcelles de blé et des sols nus. L'estimation par modélisation de ET a été explorée en utilisant l'équation de Penman-monteith modifiée obtenue en introduisant une relation empirique simple entre la résistance de surface (rc) et l'indice de RZSM. Ce dernier est estimé à partir de la température de surface (LST) dérivée de Landsat, combinée avec les températures extrêmes (en conditions humides et sèches) simulée par un modèle de bilan d'énergie de surface piloté par le forçage météorologique et la fraction de couverture végétale dérivée de Landsat. La méthode utilisée est calibrée et validée sur deux parcelles de blé situées dans la même zone près de Marrakech au Maroc. Dans l'axe suivant, une méthode permettant de récupérer la SM de la surface (0-5 cm) à une résolution spatiale et temporelle élevée est développée à partir d'une synergie entre données radar (Sentinel-1) et thermique (Landsat) et en utilisant un modèle de bilan d'énergie du sol. L'approche développée a été validée sur des parcelles agricoles en sol nu et elle donne une estimation précise de la SM avec une différence quadratique moyenne en comparant à la SM in situ, égale à 0,03 m3 m-3. Dans le dernier axe, une nouvelle méthode est développée pour désagréger la MODIS LST de 1 km à 100 m de résolution en intégrant le SM proche de la surface dérivée des données radar Sentinel-1 et l'indice de végétation optique dérivé des observations Landsat. Le nouvel algorithme, qui inclut la rétrodiffusion S-1 en tant qu'entrée dans la désagrégation, produit des résultats plus stables et robustes au cours de l'année sélectionnée. Dont, 3,35 °C était le RMSE le plus bas et 0,75 le coefficient de corrélation le plus élevé évalués en utilisant le nouvel algorithme Optimizing water management in agriculture is essential over semi-arid areas in order to preserve water resources which are already low and erratic due to human actions and climate change. This thesis aims to use the synergy of multispectral remote sensing observations (radar, optical and thermal data) for high spatio-temporal resolution monitoring of crops water needs. In this context, different approaches using various sensors (Landsat-7/8, Sentinel-1 and MODIS) have been developed to provide information on the crop Soil Moisture (SM) and water stress at a spatio-temporal scale relevant to irrigation management. This work fits well the REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) project objectives, which aim to estimate the Root Zone Soil Moisture (RZSM) for optimizing the management of irrigation water. Innovative and promising approaches are set up to estimate evapotranspiration (ET), RZSM, land surface temperature (LST) and vegetation water stress through SM indices derived from multispectral observations with high spatio-temporal resolution. The proposed methodologies rely on image-based methods, radiative transfer modelling and water and energy balance modelling and are applied in a semi-arid climate region (central Morocco). In the frame of my PhD thesis, three axes have been investigated. In the first axis, a Landsat LST-derived RZSM index is used to estimate the ET over wheat parcels and bare soil. The ET modelling estimation is explored using a modified Penman-Monteith equation obtained by introducing a simple empirical relationship between surface resistance (rc) and a RZSM index. The later is estimated from Landsat-derived land surface temperature (LST) combined with the LST endmembers (in wet and dry conditions) simulated by a surface energy balance model driven by meteorological forcing and Landsat-derived fractional vegetation cover. The investigated method is calibrated and validated over two wheat parcels located in the same area near Marrakech City in Morocco. In the next axis, a method to retrieve near surface (0-5 cm) SM at high spatial and temporal resolution is developed from a synergy between radar (Sentinel-1) and thermal (Landsat) data and by using a soil energy balance model. The developed approach is validated over bare soil agricultural fields and gives an accurate estimates of near surface SM with a root mean square difference compared to in situ SM equal to 0.03 m3 m-3. In the final axis a new method is developed to disaggregate the 1 km resolution MODIS LST at 100 m resolution by integrating the near surface SM derived from Sentinel-1 radar data and the optical-vegetation index derived from Landsat observations. The new algorithm including the S-1 backscatter as input to the disaggregation, produces more stable and robust results during the selected year. Where, 3.35 °C and 0.75 were the lowest RMSE and the highest correlation coefficient assessed using the new algorithm

APA, Harvard, Vancouver, ISO, and other styles

41

Santos, Leila Tha?se Santana de Oliveira. "An?lise da qualidade da ?gua superficial do Rio Suba?, Bahia e influ?ncia do uso e ocupa??o do solo em seu entorno." Universidade Estadual de Feira de Santana, 2013. http://localhost:8080/tede/handle/tede/172.

Full text

Abstract:

Submitted by Verena Bastos (verena@uefs.br) on 2015-08-05T22:27:36Z No. of bitstreams: 1 Dissertacao_FINAL.pdf: 10730676 bytes, checksum: 8d2235818b9b2636a1d0590bbb36fe1a (MD5) Made available in DSpace on 2015-08-05T22:27:36Z (GMT). No. of bitstreams: 1 Dissertacao_FINAL.pdf: 10730676 bytes, checksum: 8d2235818b9b2636a1d0590bbb36fe1a (MD5) Previous issue date: 2013-03-15 Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES The Suba? river basin (BRS), whose source is located in Feira de Santana-BA and its mouth in the Bay of All Saints, poses serious environmental impacts in its main watercourses arising from dumping of domestic and industrial effluents, agricultural and extractive activities. This study aims to perform analysis of physicochemical processes and microbial surface water has not been studied in the stretch along the main river channel Suba? and analysis of processes for use and occupation of the soil surrounding the BRS. Use map and land use was generated from the RapidEye satellite image, 2010, together with field surveys and through the software ArcGis 9.3, Global Mapper 11 and Envi 4.0, identified five main classes: urban area, bodies water, bare soil, vegetation and agriculture, of which agriculture accounts for 77.6% of the entire basin area, bordering the main river from its source to its mouth. 13 points were defined water collection, geo-referenced throughout the course of the river and Suba? samples were collected in December 2011, April 2012 and November 2012. The results were analyzed based on CONAMA Resolution 357/05 and 430/12 for Class 2 waters sweet, consistent with the proposed framework for the spring and held Pearson correlation to unify the possible relationships of heavy metals and physico- Chemical. The results demonstrate the analyzed parameters, dissolved oxygen (DO), biochemical oxygen demand (BOD), turbidity and phosphate are above the maximum allowable values in most monitoring points, compared with the values of legislation and total coliforms and thermotolerant at all collection points and in all samples had values above that indicated by the legislation. Heavy metals, only Cd and Cr were not detected in any of the monitoring points and none of the collections. The highest concentrations of metals found in descending order were Zn> Mn> Cu> Pb> Ni. The Pearson correlation demonstrated a strong relationship between the physico-chemical parameters and metals. These results are related to the fact that water bodies receiving domestic and industrial effluents from various activities in the area of BRS. By the results it is concluded that the river Suba? presents a high level of degradation in the quality of its waters and represents a health risk for the population living around it. This research will provide subsidy for implementation of actions aimed at the rational use of water resources of BRS, and contribute to scientific studies that allow a better understanding of the real situation of this important and strategic industrial region of Bahia state. A bacia do rio Suba? (BRS), cuja nascente localiza-se em Feira de Santana-BA e sua foz na Ba?a de Todos os Santos, apresenta s?rios impactos ambientais nos seus principais cursos d??gua decorrentes do despejo de efluentes dom?sticos e industriais, atividades agropecu?ria e extrativista. O presente estudo teve como objetivo realizar an?lise dos processos f?sico-qu?micos e microbiol?gico da ?gua superficial no trecho ainda n?o estudado ao longo do canal principal do rio Suba? e an?lise dos processos de uso e ocupa??o do solo no entorno da BRS. O mapa de uso e ocupa??o do solo foi gerado a partir da imagem do sat?lite RapidEye, 2010, aliado com os levantamentos de campo e atrav?s dos softwares ArcGis 9.3, Global Mapper 11 e Envi 4.0, sendo identificados cinco classes principais: ?rea urbana, corpos d??gua, solo exposto, vegeta??o e agropecu?ria, das quais a agropecu?ria corresponde a 77,6% de toda ?rea da bacia, margeando o rio principal desde sua nascente at? a sua foz. Foram definidos 13 pontos de coleta de ?gua, georeferenciados ao longo do curso do rio Suba? e as coletas foram realizadas em dezembro de 2011, abril de 2012 e novembro de 2012. Os resultados foram analisados com base na resolu??o CONAMA 357/05 e 430/12 para ?guas doce Classe 2, condizentes com o enquadramento proposto para o manancial e realizou-se correla??o de Pearson para unificar as poss?veis rela??es dos metais pesados e dos par?metros f?sico - qu?micos. Os resultados dos par?metros analisados demonstraram que oxig?nio dissolvido (OD), demanda bioqu?mica de oxig?nio (DBO), turbidez e fosfato est?o acima dos valores estabelecidos pela legisla??o, na maioria dos pontos de monitoramento, e os coliformes totais e termotolerantes, em todos os pontos e em todas as coletas apresentaram valores acima dos indicados pela legisla??o vigente. Dos metais pesados, apenas Cd e Cr n?o foram detectados em nenhum dos pontos de monitoramento e em nenhuma das coletas. As maiores concentra??es de metais encontrados em ordem decrescente foram Zn>Mn>Cu>Pb>Ni. A correla??o de Pearson demonstrou forte rela??o entre os par?metros f?sico-qu?micos e os metais. Estes resultados est?o relacionados ao fato dos corpos d??gua receberem efluentes dom?sticos e industriais de diversas atividades desenvolvidas na ?rea da BRS. Pelos resultados encontrados conclui-se que o rio Suba? apresenta um alto n?vel de degrada??o da qualidade de suas ?guas e representa um risco de sa?de para popula??o residente em seu entorno. Esta pesquisa dar? subs?dio para implementa??o de a??es que visem o uso racional dos recursos h?dricos da BRS, al?m de contribuir com estudos cient?ficos que permitam um melhor conhecimento da real situa??o dessa importante e estrat?gica regi?o industrial do estado da Bahia.

APA, Harvard, Vancouver, ISO, and other styles

42

Matheny, Ashley Michelle. "Development of a Novel Plant-Hydrodynamic Approach for Modeling of Forest Transpiration during Drought and Disturbance." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468595149.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Muche, Muluken Eyayu. "Surface water hydrologic modeling using remote sensing data for natural and disturbed lands." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32609.

Full text

Abstract:

Doctor of Philosophy Department of Biological & Agricultural Engineering Stacy L. Hutchinson The Soil Conservation Service-Curve Number (SCS-CN) method is widely used to estimate direct runoff from rainfall events; however, the method does not account for the dynamic rainfall-runoff relationship. This study used back-calculated curve numbers (CNs) and Normalized Difference Vegetation Index (NDVI) to develop NDVI-based CNs (CN[subscript]NDV) using four small northeastern Kansas grassland watersheds with average areas of 1 km² and twelve years (2001–2012) of daily precipitation and runoff data. Analysis indicated that the CN[subscript]NDVI model improved runoff predictions compared to the SCS-CN method. The CN[subscript]NDVI also showed greater variability in CNs, especially during growing season, thereby increasing the model’s ability to estimate relatively accurate runoff from rainfall events since most rainfall occurs during the growing season. The CN[subscript]NDVI model was applied to small, disturbed grassland watersheds to assess the model’s ability to detect land cover change impact for military maneuver damage and large, diverse land use/cover watersheds to assess the impact of scaling up the model. CN[subscript]NDVI application was assessed using a paired watershed study at Fort Riley, Kansas. Paired watersheds were identified through k-means and hierarchical-agglomerative clustering techniques. At the large watershed scale, Daymet precipitation was used to estimate runoff, which was compared to direct runoff extracted from stream flow at gauging points for Chapman (grassland dominated) and Upper Delaware (agriculture dominated) watersheds. In large, diverse watersheds, CN[subscript]NDVI performed better in moderate and overall flow years. Overall, CN[subscript]NDVI more accurately simulated runoff compared to SCS-CN results: The calibrated model increased by 0.91 for every unit increase in observed flow (r = 0.83), while standard CN-based flow increased by 0.506 for every unit increase in observed flow (r = 0.404). Therefore, CN[subscript]NDVI could help identify land use/cover changes and disturbances and spatiotemporal changes in runoff at various scales. CN[subscript]NDVI could also be used to accurately estimate runoff from precipitation events in order to instigate more timely land management decisions.

APA, Harvard, Vancouver, ISO, and other styles

44

孝鎮, 金. "Effects of surface modification and water absorption on the mechanical properties of bamboo fiber reinforced composites." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10304675/?lang=0, 2009. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10304675/?lang=0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Pollock, Matthew John. "Geomorphic Differences between Unmined and Surface Mined Lands in Southeastern Ohio." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429613137.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Blackburn-Lynch, Whitney Cole. "DEVELOPMENT OF TECHNIQUES FOR ASSESSING AND RESTORING STREAMS ON SURFACE MINED LANDS." UKnowledge, 2015. http://uknowledge.uky.edu/bae_etds/37.

Full text

Abstract:

Surface mining is a commonly used method for extracting coal in the Appalachian Coalfields of the U.S. This mining practice produces excess spoil or overburden, which is often placed in adjacent valleys resulting in the creation of valley fills. These valley fills bury headwater streams, which in turn can negatively impact downstream ecosystems. In 2008, the University of Kentucky designed and constructed 1,020 m of ephemeral, intermittent and headwater streams on an existing valley fill (Guy Cove) as a proof-of-concept. The goal of the project was to evaluate whether or not a stream recreation could occur on mined lands, particularly a valley fill. The hydrograph characteristics discharge volume, peak discharge, discharge duration, peak time, lag time, and response time were evaluated from three watersheds: (1) unmined, forested watershed (control), (2) partially restored watershed with the intermittent stream (Guy Cove), and (3) a mined watershed with an unrestored stream (valley fill with traditional mined land reclamation practices). Results from four years of monitoring indicate that the created intermittent stream at Guy Cove is hydrologically similar to the control during storm events; however, differences were noted for base flow. A new stream restoration design technique, which combines natural channel design and furrow irrigation design protocols, was investigated.

APA, Harvard, Vancouver, ISO, and other styles

47

Ross, James Donald. "Influence of climate and land use on nutrient and bacterial dynamics in surface waters of the Lower Fraser Valley, British Columbia." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/31057.

Full text

Abstract:

It is understood that intensive agricultural activities can adversely impact surface-water quality resulting in risks to ecosystem and human health. What is less clear are the links between agricultural land use (type and intensity), environmental conditions and surface-water quality at varying spatial and temporal scales. There are also challenges with detecting agricultural influence on surface waters in a timely and accurate manner. This is of concern in the Lower Fraser Valley as this region has experienced significant agricultural intensification and population growth in recent years. This study examined influences of agricultural land use, climate and hydrology on water quality in three watersheds to identify land-use practices and environmental conditions producing the greatest risk of contamination. This was accomplished through an intensive surface-water sampling program to assess nutrient and bacterial dynamics in the Hatzic, Elk Creek and Salmon watersheds, combined with hydrometric and meteorological monitoring from 2002-2005. Spectroscopic techniques (absorption and fluorescence) were also evaluated as tools to detect and quantify agricultural influence. Consistent correlations between agricultural land use and contamination (nutrient and bacterial concentrations) were observed across all watersheds. Seasonal trends were consistent, with nutrient concentrations peaking during winter months (illustrating strong hydrological control over mobilisation and transport) and bacterial concentrations peaking during summer months (illustrating the supply-constrained nature of bacterial stores). Contaminant concentrations correlated with measures of agricultural intensity. Livestock operations represented the highest-risk land use for contamination, with even small operations producing observable impacts on water quality. Temporally, the greatest risk of bacterial contamination was associated with storm events preceded by periods of dry weather during summer months. Absorption and fluorescence were effective measures of agricultural influence as they quantify and characterize agriculturally-derived dissolved organic matter. Advantages of these techniques include rapid sample processing, minimal requirements for sample treatment and volume. Further, they provide qualitative information regarding water quality, water source and land use that is not available from nutrient or bacterial analyses alone. These techniques do not accurately detect contaminants in areas with minimal agricultural influence and therefore are limited as direct indicators of bacterial or nutrient concentrations. Science, Faculty of Resources, Environment and Sustainability (IRES), Institute for Graduate

APA, Harvard, Vancouver, ISO, and other styles

48

Watson, Eliza. "Surface Water Chemistry in White Oak Creek, North-East Texas: Effect of Land Use." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10687.

Full text

Abstract:

Over the last few decades increasing attention has been paid to the effects of land use activities and land management on stream water quality. Recent research has largely focused on dominant land uses such as urban development and agricultural cropland. The relative effect of land use activities and management on stream chemistry in sub-tropical rangeland ecosystems, where much of the land use is converted to pasture and agriculture is largely unknown. This study examined stream water quality and land use in a sub-tropical watershed in Northeast Texas largely dominated by rangeland. The study site, White Oak Creek Watershed located in the Sulphur River Basin, has been identified as an impaired stream due to low dissolved oxygen concentrations and subsequently listed on the Texas Commission for Environmental Quality's 303d list (TCEQ). In an attempt to determine potential sources of the low dissolved oxygen concentrations, twenty different chemical constituents were analyzed at 18 different sample sites in the tributaries of White Oak Creek and also along the main stem from April 2010 to March 2011. Dissolved oxygen concentrations over the study period were consistently above the minimum standard required by TCEQ and showed no indication of impairment. Correlation analysis did not show any clear correlation between dissolved oxygen and any specific land use, or any chemical constituent. Some nutrients and suspended sediment concentrations were significantly different among the sub-catchments of White Oak Creek. Urban land uses were significantly and positively correlated to electrical conductivity, ammonium-N, magnesium, calcium, and dissolved organic carbon. Agricultural land use was significantly and positively correlated to orthophosphate-P, dissolved organic nitrogen, total suspended solids, and turbidity. Forests were inversely and significantly related to nitrate-N, orthophosphate-P, sulfate, dissolved organic carbon, total suspended solids, and turbidity. The study suggested that by maintaining a relatively high proportion of forested land in a watershed that water quality can be improved.

APA, Harvard, Vancouver, ISO, and other styles

49

Lopez, Valencia Oliver Miguel. "Monitoring arid-land groundwater abstraction through optimization of a land surface model with remote sensing-based evaporation." Diss., 2018. http://hdl.handle.net/10754/627141.

Full text

Abstract:

The increase in irrigated agriculture in Saudi Arabia is having a large impact on its limited groundwater resources. While large-scale water storage changes can be estimated using satellite data, monitoring groundwater abstraction rates is largely non-existent at either farm or regional level, so water management decisions remain ill-informed. Although determining water use from space at high spatiotemporal resolutions remains challenging, a number of approaches have shown promise, particularly in the retrieval of crop water use via evaporation. Apart from satellite-based estimates, land surface models offer a continuous spatial-temporal evolution of full land-atmosphere water and energy exchanges. In this study, we first examine recent trends in terrestrial water storage depletion within the Arabian Peninsula and explore its relation to increased agricultural activity in the region using satellite data. Next, we evaluate a number of large-scale remote sensing-based evaporation models, giving insight into the challenges of evaporation retrieval in arid environments. Finally, we present a novel method aimed to retrieve groundwater abstraction rates used in irrigated fields by constraining a land surface model with remote sensing-based evaporation observations. The approach is used to reproduce reported irrigation rates over 41 center-pivot irrigation fields presenting a range of crop dynamics over the course of one year. The results of this application are promising, with mean absolute errors below 3 mm:day-1, bias of -1.6 mm:day-1, and a first rough estimate of total annual abstractions of 65.8 Mm3 (close to the estimated value using reported farm data, 69.42 Mm3). However, further efforts to address the overestimation of bare soil evaporation in the model are required. The uneven coverage of satellite data within the study site allowed us to evaluate its impact on the optimization, with a better match between observed and obtained irrigation rates on fields with higher frequency of available data. The inclusion of novel remote sensing sources (e.g. CubeSats) that offer higher frequencies and higher resolution can also be explored to improve the methodology, although further validation of these systems is needed. The developed framework has the potential to be used as a water management tool to monitor groundwater losses over large remote regions.

APA, Harvard, Vancouver, ISO, and other styles

50

Green, Julia. "The role of the land surface in the global carbon and water cycles." Thesis, 2019. https://doi.org/10.7916/d8-sfek-mh50.

Full text

Abstract:

The global continental carbon and water cycles are intimately linked through stomatal regulation during vegetation photosynthesis and biosphere-atmosphere interactions. Therefore, to have a complete understanding of both present and future climate, these cycles must be studied as an interconnected system. This thesis presents three studies that aim to better explain these interactions and provide a direction forward for improved model projections of climate. The first study shows that biosphere-atmosphere feedbacks can contribute up to 30% of climate and weather variability in certain regions that help determine the net CO2 balance of the biosphere. It demonstrates that Earth System Models are under-estimating these contributions, mainly due to the underestimation of the biosphere response to radiation and water availability. It emphasizes the importance of correctly capturing these feedbacks in models for accurate subseasonal to seasonal climate predictions. The second demonstrates that changes in soil moisture (both short-term variability and long-term trends) strongly limit the ability of the continents to act as a carbon sink, with overall effects on the same order of magnitude as the land sink itself. Photosynthesis rates tend to be reduced when soil moisture is depleted, leading to decreased carbon uptake. Additionally, respiration rates increase due to increased temperature through land-atmosphere feedbacks. These carbon losses are not compensated for during wet anomalies due to the nonlinear response of vegetation activity (both respiration and photosynthesis) to soil moisture. This suggests that the increasing trend in carbon uptake rate may not be sustained past the middle of the century and could result in accelerated atmospheric CO2 growth. The third decouples the effects of atmospheric dryness (vapor pressure deficit) and soil dryness on vegetation activity in the largest terrestrial carbon sink: the tropics. Understanding vegetation response to environmental drivers and stressors in the tropics is essential to accurately modeling these ecosystems and predicting whether they will remain carbon sinks in the future. The study finds that in regions that are water limited, vegetation is driven by precipitation and radiation while being limited by high vapor pressure deficit. Conversely, in the wettest regions that are light limited, increases in vapor pressure deficit accompany increasing rates of photosynthesis. These three studies contribute to our understanding of land-atmosphere and biosphere-atmosphere feedbacks and the coupling of the continental carbon and water cycles. They identify model process representations, such as soil moisture and vegetation water-stress, that are hindering our ability to make accurate forecasts. By improving our knowledge of these mechanisms and evaluating the ability of models to reproduce them, we pave the way forward for improved climate and weather projections. Better predictions can be used not only to protect society in the present, but also to appropriately shape climate policy to protect society in the future.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Land Surface Water'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles