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1
Bailey, Mark A(Mark Alexander) 1970. « Improved techniques for the treatment of uncertainty in physically-based models of catchment water balance ». Monash University, Dept. of Civil Engineering, 2001. http://arrow.monash.edu.au/hdl/1959.1/8271.
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Mahanama, Sarith Prasad Panditha. « Distributed approach of coupling basin scale hydrology with atmospheric processes ». Thesis, Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22088817.
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3
Washburne, James Clarke. « A distributed surface temperature and energy balance model of a semi-arid watershed ». Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186800.
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A simple model of surface and sub-surface soil temperature was developed at the watershed scale (-100 km²) in a semi-arid rangeland environment. The model consisted of a linear combination of air temperature and net radiation and assumed: (1) topography controls the spatial distribution of net radiation, (2) near-surface air temperature and incoming solar radiation are relatively homogeneous at the watershed scale and are available from ground stations and (3) soil moisture dominates transient soil thermal property variability. Multiplicative constants were defined to account for clear sky diffuse radiation, soil thermal inertia, an initially fixed ratio between soil heat flux and net radiation and exponential attenuation of solar radiation through a partial canopy. The surface temperature can optionally be adjusted for temperature and emissivity differences between mixed bare soil and vegetation canopies. Model development stressed physical simplicity and commonly available spatial and temporal data sets. Slowly varying surface characteristics, such as albedo, vegetation density and topography were derived from a series of Landsat TM images and a 7.5" USGS digital elevation model at a spatial resolution of 30 m. Diurnally variable atmospheric parameters were derived from a pair of ground meteorological stations using 30-60 min averages. One site was used to drive the model, the other served as a control to estimate model error. Data collected as part of the Monsoon '90 and WG '92 field experiments over the ARS Walnut Gulch Experimental Watershed in SE Arizona were used to validate and test the model. Point, transect and spatially distributed values of modeled surface temperature were compared with synchronous ground, aircraft and satellite thermal measurements. There was little difference between ground and aircraft measurements of surface reflectance and temperature which makes aircraft transects the preferred method to "ground truth" satellite observations. Mid-morning modeled surface temperatures were within 2° C of observed values at all but satellite scales, where atmospheric water vapor corrections complicate the determination of accurate temperatures. The utility of satellite thermal measurements and models to study various ground phenomena (e.g. soil thermal inertia and surface energy balance) were investigated. Soil moisture anomalies were detectable, but were more likely associated with average near-surface soil moisture levels than individual storm footprints.
4
Oliver, Marcel 1963. « Mathematical investigation of models of shallow water with a varying bottom ». Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/191198.
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This dissertation is a mathematical investigation of the so-called lake and the great lake equations, which are shallow water equations that describe the long-time motion of an inviscid, incompressible fluid contained in a shallow basin with a slowly spatially varying bottom, a free upper surface and vertical side walls, under the influence of gravity and in the limit of small characteristic velocities and very small surface amplitude. It is shown that these equations are globally well-posed, i.e. that they possess unique global weak solutions that depend continuously on the initial data and on the bottom topography. Provided the initial data is in a class of sufficiently differentiable functions, it remains a member of that class for all times. In other words, the lake and great lake equations have global classical solutions. Moreover, if the equations are posed on a space-periodic domain and the initial data is real analytic, the solution remains real analytic for all times. The proof is based on a characterization of Gevrey classes in terms of decay of Fourier coefficients. Finally, a partial mathematical justification of the formal derivation of the lake equations is given. It is shown that solutions of the lake equation stay close to solutions of the rigid lid equations—the three dimensional Euler equations in the limit of small surface wave amplitude—in the following sense: For every error bound 6 there exists a time T = T(ε) such that for all times t ∈ [0, T] the difference between a solution to the lake equations and the solution to the rigid lid equation corresponding to the same initial data is less than E in a suitably chosen norm. Moreover, T tends to infinity as the aspect ratio of the basin tends to zero.
5
Goodrich, David Charles. « Basin Scale and Runoff Model Complexity ». Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 1990. http://hdl.handle.net/10150/614028.
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Distributed Rainfall-Runoff models are gaining widespread acceptance; yet, a
fundamental issue that must be addressed by all users of these models is definition
of an acceptable level of watershed discretization (geometric model complexity). The
level of geometric model complexity is a function of basin and climatic scales as well
as the availability of input and verification data. Equilibrium discharge storage is
employed to develop a quantitative methodology to define a level of geometric model
complexity commensurate with a specified level of model performance. Equilibrium
storage ratios are used to define the transition from overland to channel -dominated
flow response. The methodology is tested on four subcatchments in the USDA -ARS
Walnut Gulch Experimental Watershed in Southeastern Arizona. The catchments
cover a range of basins scales of over three orders of magnitude. This enabled a
unique assessment of watershed response behavior as a function of basin scale.
High quality, distributed, rainfall -runoff data was used to verify the model (KINEROSR). Excellent calibration and verification results provided confidence in
subsequent model interpretations regarding watershed response behavior. An
average elementary channel support area of roughly 15% of the total basin area is
shown to provide a watershed discretization level that maintains model performance
for basins ranging in size from 1.5 to 631 hectares. Detailed examination of
infiltration, including the role and impacts of incorporating small scale infiltration
variability in a distribution sense, into KINEROSR, over a range of soils and
climatic scales was also addressed. The impacts of infiltration and channel losses
on runoff response increase with increasing watershed scale as the relative influence
of storms is diminished in a semiarid environment such as Walnut Gulch. In this
semiarid environment, characterized by ephemeral streams, watershed runoff
response does not become more linear with increasing watershed scale but appears
to become more nonlinear.
6
El, Didy Sherif Mohamed Ahmed 1951. « Two-dimensional finite element programs for water flow and water quality in multi-aquifer systems ». Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191110.
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Multiple aquifer systems similar to those that exist at coal gasification sites are complicated groundwater situations. In these types of systems, the aquifers are separated by aquitards through which interaction between aquifers can occur. The movement of the products of combustion into the coal seam and adjacent aquifers is a serious problem of interest. This dissertation presents two-dimensional finite element models for water flow and water quality in multiple aquifer systems. These models can be applied for general problems as well as the problems associated with the burned cavities in coal gasification sites. The Galerkin weightedresidual method is used in both models. Eight-noded isoparametric elements are used. Spatial numerical integration is performed using Gaussian quadrature. A weighted finite difference scheme is used, in both of them, for time integration. The two models are written in FORTRAN V for the CDC CYBER 175. They are applicable to one- or two-dimensional problems involving steady-state or transient flow. Each aquifer can have different initial conditions and boundary conditions. Boundary conditions, pumping rates, and the recharge can be specified as a function of time. The output of the flow program-nodal heads and velocity components is used as an input to the quality program. The numerical models were validated for simple problems that have available analytical solutions.
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Tang, Philip Kwok Fan. « Stochastic Hydrologic Modeling in Real Time Using a Deterministic Model (Streamflow Synthesis and Reservoir Regulation Model), Time Series Model, and Kalman Filter ». PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/4580.
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The basic concepts of hydrologic forecasting using the Streamflow Synthesis And Reservoir Regulation Model of the U.S. Army Corps of Engineers, auto-regressive-moving-average time series models (including Greens' functions, inverse functions, auto covariance Functions, and model estimation algorithm), and the Kalman filter (including state space modeling, system uncertainty, and filter algorithm), were explored. A computational experiment was conducted in which the Kalman filter was applied to update Mehama local basin model (Mehama is a 227 sq. miles watershed located on the North Santiam River near Salem, Oregon.), a typical SSARR basin model, to streamflow measurements as they became available in simulated real time. Among the candidate AR and ARMA models, an ARMA(l,l) time series model was selected as the best-fit model to represent the residual of the basin model. It was used to augment the streamflow forecasts created by the local basin model in simulated real time. Despite the limitations imposed by the quality of the moisture input forecast and the design and calibration of the basin model, the experiment shows that the new stochastic methods are effective in significantly improving the flood forecast accuracy of the SSARR model.
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Fonley, Morgan Rae. « Effects of oscillatory forcing on hydrologic systems under extreme conditions : a mathematical modeling approach ». Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2075.
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At the large watershed scale, we emphasize the effects of flow through a river network on streamflow under dry conditions. An immediate consequence of assuming dry conditions is that evapotranspiration causes flow in the river network to exhibit oscillations. When all links in the river network combine their flow patterns, the oscillations interact in ways that change the timing and amplitude of the streamflow waves at the watershed outlet. The geometric shape of the river network is particularly important, so we develop an analytic solution for streamflow which emphasizes that importance.
Doing hydrology backward is a strategy recently developed by several researchers to deal with uncertainty in measurements of forcing terms applied to hydrologic models. The strategy has also been applied to resolve the assumption of homogeneity on realistic catchments that exhibit many heterogeneous properties. In this work, we demonstrate hydrology in the backward direction applied to two examples: using streamflow at the catchment scale to determine runoff at the hillslope scale and using the hillslope runoff to infer the applied evapotranspiration forcing under the assumption of dry conditions. In order to work across scales, we utilize the analytic solution for streamflow at the outlet of a river network. At the hillslope scale, we develop a soil model to create fluxes consistent with observed soil processes.
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Namde, Noubassem Nanas 1955. « Simulation of micro catchment water harvesting systems ». Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191121.
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A mathematical model for personal computers was prepared as a planning tool for development of micro catchment water harvesting systems. It computes runoff from natural or treated catchments, using estimated or actual parameters. The model also computes the water balance of the soil zone in the cultivated area and the water balance of the reservoir system which serves it. The model was calibrated with hydrolologic data and site characteristics for a location near Tucson, Arizona. Its prediction of cotton and grain sorghum yields was comparable to that of Morin (1977). An attempt was made to use weekly or monthly rainfall data for areas where daily data are unavailable. Lack of direct rainfall and runoff durations and infiltration characteristics made this attempt unsuccessful. This option cannot be used with the model in its current form.
10
Henry, Eric James. « Contaminant induced flow effects in variably-saturated porous media ». Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/191256.
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Dissolved organic contaminants that decrease the surface tension of water (surfactants) can have an effect on unsaturated flow through porous media due to the dependence of capillary pressure on surface tension. One and two-dimensional (1D, 2D) laboratory experiments and numerical simulations were conducted to study surfactant-induced unsaturated flow. The 1D experiments investigated differences in surfactant-induced flow as a function of contaminant mobility. The flow in a system contaminated with a high solubility, mobile surfactant, butanol, was much different than in a system contaminated with a sparingly soluble, relatively immobile surfactant, myristyl alcohol (MA). Because surface tension depression caused by MA was confined to the original source zone, the MA system was modeled using a standard unsaturated flow model (HYDRUS-1D) by assigning separate sets of hydraulic functions to the initially clean and source zones. To simulate the butanol system, HYDRUS-1D was modified to incorporate surfactant concentration-dependent changes to the moisture content-pressure head and unsaturated hydraulic conductivity functions. Following the 1D study, a two-dimensional flow cell (2.4 x 1.5 x 0.1 m) was used to investigate the infiltration of a surfactant contaminant plume from a point source on the soil surface, through the vadose zone, and toward a shallow aquifer. Above the top of the capillary fringe the advance of the surfactant solution caused a drainage front that radiated from the point source. Upon reaching the capillary fringe, the drainage front caused a localized depression of the capillary fringe and eventually a new capillary fringe height was established. Horizontal transport of surfactant in the depressed capillary fringe caused the propagation of a wedge-shaped drainage front in the downgradient direction. The numerical model HYDRUS-2D was modified to account for surfactant concentration-dependent effects on the unsaturated hydraulic functions and was successfully used to simulate the surfactant infiltration experiment. The extensive propagation of the drying front and the effect of vadose zone drainage on contaminant breakthrough time demonstrate the potential importance of considering surface tension effects on unsaturated flow and transport in systems containing surface-active organic contaminants or in systems where surfactants are used for remediation of the vadose zone or unconfined aquifers.
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Ropp, David L. « Numerical study of shallow water models with variable topography ». Diss., The University of Arizona, 2000. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2000_165_sip1_w.pdf&type=application/pdf.
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Lee, Haksu. « Development and performance analysis of a physically based hydrological model incorporating the effects of subgrid heterogeneity ». University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0129.
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[Truncated abstract] The balance equations of mass and momentum, defined at the scale of what has been defined as a Representative Elementary Watershed (REW) has been proposed by Reggiani et al. (1998, 1999). While it has been acknowledged that the REW approach and the associated balance equations can be the basis for the development of a new generation of distributed physically based hydrological models, four building blocks have been identified as necessary to transform the REW approach into, at the very least least, a workable modelling framework beyond the theoretical achievements. These are: 1) the development of reasonable closure relations for the mass exchange fluxes within and between various REW sub-regions that effectively parameterize the effects of sub-REW heterogeneity of climatic and landscape properties, 2) the design of numerical algorithms capable of generating numerical solutions of the REW-scale balance equations composed of a set of coupled ordinary differential and algebraic equations for the number of REWs constituting a study catchment and the sub-regions within the REWs, 3) applications of the resulting numerical model to real catchments to assess its performance in the prediction of any specified hydrological variables, and 4) the assessment of the model reliability through estimation of model predictive uncertainty and parameter uncertainty. This thesis is aimed at making substantial progress in developing each of these building blocks. Chapter 1 presents the background and motivation for the thesis, while Chapter 2 summarizes its main contributions. Chapter 3 presents a description of the closure problem that the REW approach faces, and presents and implements various approaches to develop closure relations needed for the completeness of balance equations of the REW approach. ... In addition, Chapter 4 also shows an initial application of CREW to a small catchment, Susannah Brook in the south-west of Western Australia. Chapter 5 presents the application of CREW to two meso-scale catchments in Australia, namely Collie and Howard Springs, located in contrasting climates. Chapter 6 presents results of the estimation of predictive uncertainty and parameter sensitivity through the application of CREW to two catchments in Australia, namely Susannah Brook and Howard Springs, by using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. Finally, Chapter 7 presents recommendations for future work for the further advancement of the REW approach. Through these exercises this PhD thesis has successfully transformed the REW-scale coupled balance equations derived by Reggiani et al. (1998, 1999) into a new, well tested numerical model blueprint for the development and implementation of distributed, physically based models applicable at the catchment, or REW scale.
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Sawunyama, Tendai. « Evaluating uncertainty in water resources estimation in Southern Africa : a case study of South Africa ». Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1006176.
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Hydrological models are widely used tools in water resources estimation, but they are simple representations of reality and are frequently based on inadequate input data and uncertainties in parameter values. Data observation networks are expensive to establish and maintain and often beyond the resources of most developing countries. Consequently, measurements are difficult to obtain and observation networks in many countries are shrinking, hence obtaining representative observations in space and time remains a challenge. This study presents some guidelines on the identification, quantification and reduction of sources of uncertainty in water resources estimation in southern Africa, a data scarce region. The analyses are based on example sub-basins drawn from South Africa and the application of the Pitman hydrological model. While it has always been recognised that estimates of water resources availability for the region are subject to possible errors, the quantification of these uncertainties has never been explicitly incorporated into the methods used in the region. The motivation for this study was therefore to contribute to the future development of a revised framework for water resources estimation that does include uncertainty. The focus was on uncertainties associated with climate input data, parameter estimation (and recognizing the uncertainty due model structure deficiencies) methods and water use data. In addition to variance based measures of uncertainty, this study also used a reservoir yield based statistic to evaluate model output uncertainty, which represents an integrated measure of flow regime variations and one that can be more easily understood by water resources managers. Through a sensitivity analysis approach, the results of the individual contribution of each source of uncertainty suggest regional differences and that clear statements about which source of uncertainty is likely to dominate are not generally possible. Parameter sensitivity analysis was used in identifying parameters which are important withinspecific sub-basins and therefore those to focus on in uncertainty analysis. The study used a simple framework for evaluating the combined contribution of uncertainty sources to model outputs that is consistent with the model limitations and data available, and that allows direct quantitative comparison between model outputs obtained by using different sources of information and methods within Spatial and Time Series Information Modelling (SPATSIM) software. The results from combining the sources of uncertainties showed that parameter uncertainty dominates the contribution to model output uncertainty. However, in some parts of the country especially those with complex topography, which tend to experience high rainfall spatial variability, rainfall uncertainty is equally dominant, while the contributions of evaporation and water use data uncertainty are relatively small. While the results of this study are encouraging, the weaknesses of the methods used to quantify uncertainty (especially subjectivity involved in evaluating parameter uncertainty) should not be neglected and require further evaluations. An effort to reduce data and parameter uncertainty shows that this can only be achieved if data access at appropriate scale and quality improves. Perhaps the focus should be on maintaining existing networks and concentrating research efforts on making the most out of the emerging data products derived from remote sensing platforms. While this study presents some initial guidelines for evaluating uncertainty in South Africa, there is need to overcome several constraints which are related to data availability and accuracy, the models used and the capacity or willingness to adopt new methods that incorporate uncertainty. The study has provided a starting point for the development of new approaches to modelling water resources in the region that include uncertain estimates.
14
Tecle, Aregai 1948. « Choice of multicriterion decision making techniques for watershed management ». Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/191145.
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The problem of selecting a multicriterion decision making (MCDM) technique for watershed resources management is investigated. Of explicit concern in this research is the matching of a watersned resources management problem with an appropriate MCDM technique. More than seventy techniques are recognized while reviewing the area of MCDM. A new classification scheme is developed to categorize these techniques into four groups on the bases of each algorithm's structural formulation and the possible results obtained by using the algorithm. Other standard classification schemes are also discussed to better understand the differences and similarities among the techniques and thereby demonstrate the importance of matching a particular multicriterion decision problem with an appropriate MCDM technique. The desire for selecting the most appropriate MCDM technique for watershed resources management lead to the development of 49 technique choice criteria and an algorithm for selecting a technique. The algorithm divides the technique choice criteria into four groups: (1) DM/analyst-related criteria, (2) technique-related criteria, (3) problem-related criteria and (4) solution-related criteria. To analyze the applicability of MCDM techniques to a particular problem, the levels of performance of the techniques in solving the problem are, at first, evaluated with respect to the choice criteria in each criterion group resulting in four sets of preference rankings. These four sets are then linearly combined using a set of trade-off parameters to determine the overall preference ranking of the techniques. The MUM technique selection process is itself modeled as a multiobjective problem. In this research, for example, a set of 15 techniques, the author is familiar with, are analyzed for their appropriateness to solve a watershed resources management problem. The performance levels of the 15 MCDM techniques in solving such a problem are evaluated with respect to a selected set of technique choice criteria in each criterion group leading to a set of four evaluation matrices of choice criteria versus alternative techniques. This technique choice problem is then analyzed using a two-stage evaluation procedure known as composite programming. The final product of the process resulted in a preference ranking of the alternative MCDM techniques.
15
Du, Jun 1962. « Short-range ensemble forecasting of an explosive cyclogenesis with a limited area model ». Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/191197.
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Since the atmosphere is a chaotic system, small errors in the initial condition of any numerical weather prediction (NWP) model amplify as the forecast evolves. To estimate and possibly reduce the uncertainty of NWP associated with initial-condition uncertainty (ICU), ensemble forecasting has been proposed which is a method of, differently from the traditional deterministic forecasting, running several model forecasts starting from slightly different initial states. In this dissertation, the impact of ICU and short-range ensemble forecasting (SREF) on quantitative precipitation forecasts (QPFs), as well as on sea-level cyclone position and central pressure, is examined for a case of explosive cyclogenesis that occurred over the contiguous United States. A limited-area model (the PSU/NCAR MM4) is run at 80-km horizontal resolution and 15 layers to produce a 25-member, 36-h forecast ensemble. Lateral boundary conditions for the MM4 model are provided by ensemble forecasts from a global spectral model (the NCAR CCM1). The initial perturbations of the ensemble members possess a magnitude and spatial decomposition which closely match estimates of global analysis error, but they were not dynamically-conditioned. Results for 80-km ensemble forecast are compared to forecasts from the then operational Nested Grid Model (NGM), a single 40-km MM4 forecast, and a second 25-member MM4 ensemble based on a different cumulus parameterization and slightly different initial conditions. Acute sensitivity to ICU marks ensemble QPF and the forecasts of cyclone position and central pressure. Ensemble averaging always reduces the rms error for QPF. Nearly 90% of the improvement is obtainable using ensemble sizes as small as 8-10. However, ensemble averaging can adversely affect the forecasts related to precipitation areal coverage because of its smoothing nature. Probabilistic forecasts for five mutually exclusive, completely exhaustive categories are found to be skillful relative to a climatological forecast. Ensemble sizes of --, 10 can account for 90% of improvement in probability density function. Our results indicate that SREF techniques can now provide useful QPF guidance and increase the accuracy of precipitation, cyclone position, and cyclone's central pressure forecasts. With current analysis/forecast systems, the benefit from simple ensemble averaging is comparable to or exceed that obtainable from improvement in the analysis/forecast system.
16
Fahy, Benjamin. « Evaluating the Impact and Distribution of Stormwater Green Infrastructure on Watershed Outflow ». PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/4732.
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Green Stormwater Infrastructure (GSI) has become a popular method for flood mitigation as it can prevent runoff from entering streams during heavy precipitation. In this study, a recently developed neighborhood in Gresham, Oregon hosts a comparison of various GSI projects on runoff dynamics. The study site includes dispersed GSI (rain gardens, retention chambers, green streets) and centralized GSI (bioswales, detention ponds, detention pipes). For the 2017-2018 water year, hourly rainfall and observed discharge data is used to calibrate the EPA's Stormwater Management Model to simulate rainfall-runoff dynamics, achieving a Nash-Sutcliffe efficiency of 0.75 and Probability Bias statistic of 3.3%. A synthetic scenario analysis quantifies the impact of the study site GSI and compares dispersed and centralized arrangements. Each test was performed under four precipitation scenarios (of differing intensity and duration) for four metrics: runoff ratio, peak discharge, lag time, and flashiness. Design structure has significant impacts, reducing runoff ratio 10 to 20%, reducing peak discharge 26 to 68%, and reducing flashiness index 56 to 70%. There was a reverse impact on lag time, increasing it to 50 to 80%. Distributed GSI outperform centralized structures for all metrics, reducing runoff ratio 22 to 32%, reducing peak discharge 67 to 69%, increasing lag time 133 to 500%, and reducing flashiness index between 32 and 62%. This research serves as a basis for researchers and stormwater managers to understand potential impact of GSI on reducing runoff and downstream flooding in small urban watersheds with frequent rain.
17
Thyer, Mark Andrew. « Modelling long-term persistence in hydrological time series ». Diss., 2000, 2000. http://www.newcastle.edu.au/services/library/adt/public/adt-NNCU20020531.035349/index.html.
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Shojaei, Nasim. « Automatic Calibration of Water Quality and Hydrodynamic Model (CE-QUAL-W2) ». PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1942.
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One of the most important purposes of surface water resource management is to develop predictive models to assist in identifying and evaluating operational and structural measures for improving water quality. To better understand the effects of external and internal nutrient and organic loading and the effects of reservoir operation, a model is often developed, calibrated, and used for sensitivity and management simulations. The importance of modeling and simulation in the scientific community has drawn interest towards methods for automated calibration. This study addresses using an automatic technique to calibrate the water quality model CE-QUAL-W2 (Cole and Wells, 2013). CE-QUAL-W2 is a two-dimensional (2D) longitudinal/vertical hydrodynamic and water quality model for surface water bodies, modeling eutrophication processes such as temperature-nutrient-algae-dissolved oxygen-organic matter and sediment relationships. The numerical method used for calibration in this study is the particle swarm optimization method developed by Kennedy and Eberhart (1995) and inspired by the paradigm of birds flocking. The objective of this calibration procedure is to choose model parameters and coefficients affecting temperature, chlorophyll a, dissolved oxygen, and nutrients (such as NH4, NO3, and PO4). A case study is presented for the Karkheh Reservoir in Iran with a capacity of more than 5 billion cubic meters that is the largest dam in Iran with both agricultural and drinking water usages. This algorithm is shown to perform very well for determining model parameters for the reservoir water quality and hydrodynamic model. Implications of the use of this procedure for other water quality models are also shown.
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Edelstein, Christopher. « Climatic conditions and storm hydrology of a small agricultural watershed ». Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1314224.
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Climatic conditions (precipitation, evapotranspiration, available soil moisture, and temperature) are important variables when considering cumulative storm streamflow for a watershed. The objective of this study was to determine what climatic conditions, if any, could be used to mathematically model cumulative storm streamflow for an extensively-drained small agricultural watershed in northwest Delaware County, Indiana. A water-level recorder was installed in Killbuck Creek during autumn 2002, spring, summer, and autumn 2003 and 2004. To determine discharge, velocity measurements were collected following US Geological Survey (USGS) methods and two rating curves (high and low flow) were constructed. Simple linear regressions were performed using cumulative streamflow as the dependent variable and precipitation, evapotranspiration, available soil moisture, temperature, and runoff as independent variables. Multiple linear regressions were used to examine combinations of the independent variables. Cumulative streamflow was most related to precipitation (r2 = 0.23 and p < 0.001) and least related to temperature (r2 = 0.03 and p < 0.5). The multiple linear regression from the combination of precipitation, runoff, and temperature provided the most accurate cumulative streamflow simulation (R2 = 0.53 and p < 0.001). Multiple linear regressions using climatic variables can be used to estimate cumulative streamflow for an agricultural watershed.Department of Natural Resources and Environmental Management
20
Zeng, Ning. « Climatic impact of Amazon deforestation : A study of underlying mechanism through simple modeling ». Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186999.
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An intermediate level model for tropical climatology including atmosphere-land-ocean interaction is developed. The model contains basically linearized steady state primitive equations with simplified thermodynamics. A simple hydrological cycle is also included. Special attention has been paid to land surface processes in attempting to study climate change caused by Amazon deforestation. In comparison with previous simple modeling work on tropical climatology or anomaly, the present model is more sophisticated in the sense that it predicts all the important meteorological variables with little input, while being computationally simple. The modeled tropical climatology appears to be realistic. The model generally better simulates the ENSO anomaly compared to many previous simple model simulations. We provide analysis of model results and discuss model deficiencies and possible improvements of the model. The climatic impact of Amazon deforestation is studied in the context of this model. Model results show a much weakened Atlantic Walker/Hadley circulation as a result of the existence of a strong positive feedback loop in the atmospheric circulation system and the hydrological cycle. The regional climate is very sensitive to albedo change and sensitive to evapotranspiration change. The pure dynamical effect of surface roughness on convergence is small, but the surface flow anomaly displays intriguing features. Analysis of the thermodynamic equation reveals the balance among convective heating, adiabatic cooling and radiation largely determines the deforestation response. The model provides a plausible mechanism for the common results of many GCM simulations. Studies of the consequences of hypothetical continuous deforestation suggest that the replacement of forest by desert may be able to sustain a desert-like climate. When a simple mixed layer ocean model is coupled with the atmospheric model, the results suggest a 1 °C decrease in SST gradient across the equatorial Atlantic ocean in response to Amazon deforestation. The magnitude of the decrease depends on the coupling strength.
21
Ritzi, Robert William. « The use of well response to natural forces in the estimation of hydraulic parameters ». Diss., The University of Arizona, 1989. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1989_119_sip1_w.pdf&type=application/pdf.
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Hyun, Yunjung. « Multiscale anaylses of permeability in porous and fractured media ». Diss., The University of Arizona, 2002. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2002_321_sip1_w.pdf&type=application/pdf.
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Schmid, Wolfgang. « A farm package for MODFLOW-2000 simulation of irrigation demand and conjunctively managed surface-water and ground-water supply / ». Diss., The University of Arizona, 2004. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2004_287_sip1_w.pdf&type=application/pdf.
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Vionnet, Leticia Beatriz, et Leticia Beatriz Vionnet. « Investigation of stream-aquifer interactions using a coupled surface water and groundwater flow model ». Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187414.
Texte intégralRésumé :
A finite element numerical model is developed for the modeling of coupled surface-water flow and ground-water flow. The mathematical treatment of subsurface flows follows the confined aquifer theory or the classical Dupuit approximation for unconfined aquifers whereas surface-water flows are treated with the kinematic wave approximation for open channel flow. A detailed discussion of the standard approaches to represent the coupling term is provided. In this work, a mathematical expression similar to Ohm's law is used to simulate the interacting term between the two major hydrological components. Contrary to the standard approach, the coupling term is incorporated through a boundary flux integral that arises naturally in the weak form of the governing equations rather than through a source term. It is found that in some cases, a branch cut needs to be introduced along the internal boundary representing the stream in order to define a simply connected domain, which is an essential requirement in the derivation of the weak form of the ground-water flow equation. The fast time scale characteristic of surface-water flows and the slow time scale characteristic of ground-water flows are clearly established, leading to the definition of three dimensionless parameters, namely, a Peclet number that inherits the disparity between both time scales, a flow number that relates the pumping rate and the streamflow, and a Biot number that relates the conductance at the river-aquifer interface to the aquifer conductance. The model, implemented in the Bill Williams River Basin, reproduces the observed streamflow patterns and the ground-water flow patterns. Fairly good results are obtained using multiple time steps in the simulation process.
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Samper, Calvete F. Javier(Francisco Javier) 1958. « Statistical methods of analyzing hydrochemical, isotopic, and hydrological data from regional aquifers ». Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191115.
Texte intégralRésumé :
This dissertation is concerned with the development of mathematical aquifer models that combine hydrological, hydrochemical and isotopic data. One prerequisite for the construction of such models is that prior information about the variables and parameters be quantified in space and time by appropriate statistical methods. Various techniques using multivariate statistical data analyses and geostatistical methods are examined in this context. The available geostatistical methods are extended to deal with the problem at hand. In particular, a three-dimensional interactive geostatistical package has been developed for the estimation of intrinsic and nonintrinsic variables. This package is especially designed for groundwater applications and incorporates a maximum likelihood cross-validation method for estimating the parameters of the covariance function. Unique features of this maximum likelihood cross-validation method include: the use of an adjoint state method to compute the gradient of the likelihood function, the computation of the covariance of the parameter estimates and the use of identification criteria for the selection of a covariance model. In addition, it can be applied to data containing measurement errors, data regularized over variable lengths, and to nonintrinsic variables. The above methods of analysis are applied to synthetic data as well as hydrochemical and isotopic data from the Tucson aquifer in Arizona and the Madrid Basin in Spain. The dissertation also includes a discussion of the processes affecting the transport of dissolved constituents in groundwater, the mathematical formulation of the inverse solute transport problem and a proposed numerical method for its solution.
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Chavez, Rodriguez Adolfo 1951. « Modeling mountain-front recharge to regional aquifers ». Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191124.
Texte intégralRésumé :
The estimation of mountain-front recharge to regional aquifers is approached from a hydroclimatic standpoint. Analytical models of the seasonal water yield and streamflow are developed in this dissertation. These models are specialized for hard-rock mountainous watersheds where deep percolation occurs through fractures exclusively. Input variables are considered to be stochastic, and a relationship between precipitation and surface runoff is derived by using a deterministic physical process. Streamflow models for the summer and winter rainy seasons are developed separately in terms of known parameters of the storm process and unknown parameters of the physical process. The winter model considers the generation of surface runoff from both rainfall and snowmelt. These models include the long-term effective subsurface outflow from the mountainous watershed, or mountain-front recharge, as one of the parameters to be identified. The parameter estimation problem is posed in the framework of maximum likelihood theory, where prior information about the model parameters and a suitable weighting scheme for the error terms in the estimation criterion are included. The issues of model and parameter identifiability, uniqueness and stability are addressed, and strategies to mitigate identifiability problems in our modeling are discussed. Finally, the seasonal streamflow models are applied to three mountainous watersheds in the Tucson basin, and maximum likelihood estimates of mountain-front recharge and other model and statistical parameters are obtained. The analysis of estimation errors is performed in both the eigenspace and the original space of the parameters.
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Kapangaziwiri, Evison. « Regional application of the Pitman monthly rainfall-runoff model in Southern Africa incorporating uncertainty ». Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1006178.
Texte intégralRésumé :
Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework.iText 1.4.6 (by lowagie.com)
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Mwelwa, Elenestina Mutekenya. « The application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin of Zambia ». Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1006171.
Texte intégralRésumé :
This thesis presents a discussion on the study undertaken in the application of the monthly time step Pitman rainfall-runoff model to the Kafue River basin. The study constituted one of the initial steps in the capacity building and expansion of the application of hydrologic models in the southern African region for water resources assessment, one of the core areas of the Southern African FRIEND project (Flow Regimes from International Experimental Network Data). The research process was undertaken in four major stages, each stage working towards achieving the research objectives. The first stage was the preparation of spatial data which included the selection and delineation of sub-catchments and inclusion of spatial features required to run the Pitman model and transferring the spatial data into SPATSIM. The second stage was the preparation of input data, mainly rainfall, streamflow, evaporation, and water abstraction data. This information was then imported into SPATSIM, which was able to assist in the further preparation of data by assessment of the input data quality, linking of observed flows and spatial interpolation of point rainfall data to average catchment rainfall in readiness for running and calibration of the model. The third stage was the running and calibration of the Pitman model. Use was made of both the automatic calibration facility, as well as manual calibration by means of the time series graph display and analysis facility of SPATSIM. Model calibration was used to obtain the best fit and an acceptable correlation between the simulated and the observed flows and to obtain simulation parameter sets for sub-catchments and regions within the Kafue catchment. The fourth stage was the analysis and evaluation of the model results. This included verification of results over different time periods and validation and testing of parameter transfers to other catchments. This stage also included the evaluation of SPATSIM as a tool for applying the model and as a database for the processing and storage of water resources data. The study’s output includes: A comprehensive database of hydrometeorological, physical catchment characteristics, landuse and water abstraction information for the Kafue basin; calibrated Pitman model parameters for the sub-catchments within the Kafue basin; recommendations for future work and data collection programmes for the application of the model. The study has also built capacity by facilitating training and exposure to rainfall-runoff models (specifically the Pitman model) and associated software, SPATSIM. In addition, the dissemination of the results of this study will serve as an effective way of raising awareness on the application of the Pitman model and the use of the SPATSIM software within Zambia and the region. The overall Pitman model results were found to be satisfactory and the calibrated model is able to reproduce the observed spatial and temporal variations in streamflow characteristics in the Kafue River basin.
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Keefer, Timothy Orrin, et Timothy Orrin Keefer. « Likelihood development for a probabilistic flash flood forecasting model ». Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/192077.
Texte intégralRésumé :
An empirical method is developed for constructing likelihood functions required in a Bayesian probabilistic flash flood forecasting model using data on objective quantitative precipitation forecasts and their verification. Likelihoods based on categorical and probabilistic forecast information for several forecast periods, seasons, and locations are shown and compared. Data record length, forecast information type and magnitude, grid area, and discretized interval size are shown to affect probabilistic differentiation of amounts of potential rainfall. Use of these likelihoods in Bayes' Theorem to update prior probability distributions of potential rainfall, based on preliminary data, to posterior probability distributions, reflecting the latest forecast information, demonstrates that an abbreviated version of the flash flood forecasting methodology is currently practicable. For this application, likelihoods based on the categorical forecast are indicated. Apart from flash flood forecasting, it is shown that likelihoods can provide detailed insight into the value of information contained in particular forecast products.
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Bosch, David Dean 1958. « Derivation and application of effective parameters for modeling moisture flow in heterogeneous unsaturated porous media ». Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/191158.
Texte intégralRésumé :
Spatial variability of porous media often prevents precise physical characterization of the system. In order to model moisture and solute transport through this media, certain sacrifices in precision must be made. Physical characteristics of the system must be averaged over large scales, lumping the small scale variability into the large scale characterization. Although this precludes a precise definition of the small scale flow characteristics, parameterization is much more attainable. This study addresses methods for determining effective hydraulic conductivity of unsaturated porous media. Effective conductivity is used to describe the large scale behavior of the system. Different methods for calculating the effective conductivity are presented and compared. Results indicate that the unit mean gradient method produces good estimates of the effective conductivity and can be applied using limited field data. The zone of correlation of the hydraulic parameters can be used in experimental design to minimize the errors associated with estimation of the mean pressure. An inverse method for evaluating the optimum effective hydraulic parameters is presented. Results indicate the optimization procedure is more sensitive to wetting than to drying conditions. Because of interaction between the hydraulic parameters, concurrent optimization of more than two of the parameters based on soil pressure data alone is not advised. Anisotropy in an unsaturated soil was found to be a function of the profile mean soil pressure. Results indicate the effective conductivity for flow parallel to soil layering can be estimated from the arithmetic mean of the unsaturated conductivity values for each of the layers and is between the harmonic and geometric means of these data for flow perpendicular to the layering. Estimates of the effective unsaturated hydraulic conductivity obtained through stochastic analysis agreed well with simulation results. Deviations between the stochastic predictions and simulation results are larger when the variability of the soil profile is greater and begin to deviate significantly when the variance of ln K(ψ₀) exceeds 5.0 and the variance of a exceeds 0.02 1/cm².
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Kapangaziwiri, Evison. « Revised parameter estimation methods for the Pitman monthly rainfall-runoff model ». Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1006172.
Texte intégralRésumé :
In recent years, increased demands have been placed on hydrologists to find the most effective methods of making predictions of hydrologic variables in ungauged basins. A huge part of the southern African region is ungauged and, in gauged basins, the extent to which observed flows represent natural flows is unknown, given unquantified upstream activities. The need to exploit water resources for social and economic development, considered in the light of water scarcity forecasts for the region, makes the reliable quantification of water resources a priority. Contemporary approaches to the problem of hydrological prediction in ungauged basins in the region have relied heavily on calibration against a limited gauged streamflow database and somewhat subjective parameter regionalizations using areas of assumed hydrological similarity. The reliance of these approaches on limited historical records, often of dubious quality, introduces uncertainty in water resources decisions. Thus, it is necessary to develop methods of estimating model parameters that are less reliant on calibration. This thesis addresses the question of whether physical basin properties and the role they play in runoff generation processes can be used directly in the estimation of parameter values of the Pitman monthly rainfall-runoff model. A physically-based approach to estimating the soil moisture accounting and runoff parameters of a conceptual, monthly time-step rainfall-runoff model is proposed. The study investigates the physical meaning of the model parameters, establishes linkages between parameter values and basin physical properties and develops relationships and equations for estimating the parameters taking into account the spatial and temporal scales used in typical model applications. The estimationmethods are then tested in selected gauged basins in southern Africa and the results of model simulations evaluated against historical observed flows. The results of 71 basins chosen from the southern African region suggest that it is possible to directly estimate hydrologically relevant parameters for the Pitman model from physical basin attributes. For South Africa, the statistical and visual fit of the simulations using the revised parameters were at least as good as the current regional sets, albeit the parameter sets being different. In the other countries where no regionalized parameter sets currently exist, simulations were equally good. The availability, within the southern African region, of the appropriate physical basin data and the disparities in the spatial scales and the levels of detail of the data currently available were identified as potential sources of uncertainty. GIS and remote sensing technologies and a widespread use of this revised approach are expected to facilitate access to these data.
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Khajehei, Sepideh. « A Multivariate Modeling Approach for Generating Ensemble Climatology Forcing for Hydrologic Applications ». PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2403.
Texte intégralRésumé :
Reliability and accuracy of the forcing data plays a vital role in the Hydrological Streamflow Prediction. Reliability of the forcing data leads to accurate predictions and ultimately reduction of uncertainty. Currently, Numerical Weather Prediction (NWP) models are developing ensemble forecasts for various temporal and spatial scales. However, it is proven that the raw products of the NWP models may be biased at the basin scale; unlike model grid scale, depending on the size of the catchment. Due to the large space-time variability of precipitation, bias-correcting the ensemble forecasts has proven to be a challenging task. In recent years, Ensemble Pre-Processing (EPP), a statistical approach, has proven to be helpful in reduction of bias and generation of reliable forecast. The procedure is based on the bivariate probability distribution between observation and single-value precipitation forecasts. In the current work, we have applied and evaluated a Bayesian approach, based on the Copula density functions, to develop an ensemble precipitation forecasts from the conditional distribution of the single-value precipitation. Copula functions are the multivariate joint distribution of univariate marginal distributions and are capable of modeling the joint distribution of two variables with any level of correlation and dependency. The advantage of using Copulas, amongst others, includes its capability of modeling the joint distribution independent of the type of marginal distribution. In the present study, we have evaluated the capability of copula-based functions in EPP and comparison is made against an existing and commonly used procedure for same i.e. meta-Gaussian distribution. Monthly precipitation forecast from Climate Forecast System (CFS) and gridded observation from Parameter-elevation Relationships on Independent Slopes Model (PRISM) have been utilized to create ensemble pre-processed precipitation over three sub-basins in the western USA at 0.5-degree spatial resolution. The comparison has been made using both deterministic and probabilistic frameworks of evaluation. Across all the sub-basins and evaluation techniques, copula-based technique shows more reliability and robustness as compared to the meta-Gaussian approach.
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Lopes, Vicente Lucio 1952. « A numerical model of watershed erosion and sediment yield ». Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191125.
Texte intégralRésumé :
A physically based, distributed parameter, event oriented, nonlinear, numerical model of watershed response is developed to accommodate the spatial changes in topography, surface roughness, soil properties, concentrated flow patterns and geometry, and land use conditions. The Green and Ampt equation with the ponding time calculation for an unsteady rain is used to compute rainfall excess rates. The kinematic wave equations are used to describe the unsteady one-dimensional overland and channel flow. The unsteady and spatially varying erosion/deposition process on hillslopes and channel systems is described dynamically using simultaneous rates of sediment entrainment and deposition rather than the conventional approach using steady state sediment transport functions. To apply the model the watershed is represented by a simplified geometry consisting of discrete overland flow planes and channel elements. Each plane or channel is characterized by a length, width, and a roughness parameter. For channel elements, a cross-section geometry is also needed. A modular computer program called WESP (Watershed Erosion Simulation Program) is developed to provide the vehicle for performing the computer simulations. Rainfall simulator plots are used to estimate infiltration parameters, hydraulic roughness, and soil erodibility parameters for raindrop impact and overland flow. The ability of the model to simulate watershed response (hydrograph and sedigraph) to a variety of rainfall inputs and antecedent soil moisture conditions is verified using data collected on two small watersheds. The good agreement between the simulated watershed response and the observed watershed response indicates that the governing equations, initial and upper boundary conditions, and structural framework of the model can describe satisfactorily the physical processes controlling watershed response.
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Allen, Roderick Lee. « The applicability of microcomputers to local water management ». PDXScholar, 1985. https://pdxscholar.library.pdx.edu/open_access_etds/3417.
Texte intégralRésumé :
Historically, hydrologic models have been available only on mainframe computers and have therefore not been used by local water managers to support daily decisions. The development of the microcomputer presents an opportunity for that to change.
Mathematical models of soil moisture and river routing are selected, developed and tested for use on a microcomputer as an aid to local water management. The models are then integrated with an appropriate data base in a computer program written for a microcomputer. The result is a Decision Support System for local water managers.
In order to evaluate the feasibility of using the Decision Support System, an application of the program to a small hypothetical river and irrigation system is carried out. The speed of execution indicates that the use of the Decision Support System on this class of computer under the present configuration may be possible if software or hardware changes can reduce data transfer times to and from disk.
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Koterba, Michael T. « Differential influences of storm and watershed characteristics on runoff from ephemeral streams in southeastern Arizona ». Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191126.
Texte intégralRésumé :
Relationships between thunderstorm and watershed variables and runoff from or within semiarid watersheds at Walnut Gulch, Arizona were examined. Variables showing greater sensitivity to basin and storm size were better flow predictors. Stepwise regression with three increasingly nonlinear algebraic models showed mean storm depth was the best simple predictor of runoff. Predictions improved using storm volume, a product of storm depth and areal extent. Initial runoff to streams was best described as a highly nonlinear function of storm and watershed variables. Runoff from a basin was a more linearized function of similar variables. The above differences were ascribed to channel transmission losses, reductions in runoff moving down initially dry channels. For a given basin and small storms, loss to runoff ratios exceeded 10:1 and were highly variable. Ratios were similar and less than 0.5:1 for storms centrally located over a basin and generating sufficient initial runoff to minimize flow variation due to losses. Losses increased disproportionately with basin size. Antecedent rainfall and first summer flows also affected rainfall runoff relationships in a differential manner. Wet conditions enhanced runoff more from larger versus smaller storms. First summer flows were less than expected probably because of higher soil infiltration and channel losses at the onset of summer storms. Overall, as storm size decreased or basin area increased, initial runoff was more often a localized phenomenon and downstream flow more dependent on storm depth, extent, location, and seasonal timing and basin channel losses, but less dependent on antecedent rainfall. Consequently, storm depth accounted for only 60% to 70% of the variation in flows while storm volume, antecedent rainfall, channel losses, and first summer flows explained 80% to 90%. Finally, oversimplifying storm or watershed variables or analytical methods led to errors in assessing their affect on runoff. It was also determined that current arguments supporting a recommendation to delete smaller, frequent annual floods to better fit remaining data to flood frequency curves were oversimplified. Distributed rainfall - runoff models with channel losses and regional storm depth - area - frequency data may be the way to develope flood curves for semiarid basins with short runoff records.
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Hameed, Maysoun Ayad. « Evaluating Global Sensitivity Analysis Methods for Hydrologic Modeling over the Columbia River Basin ». PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2398.
Texte intégralRésumé :
Global Sensitivity Analysis (GSA) approach helps to identify the effectiveness of model parameters or inputs and thus provides essential information about the model performance. The effects of 14 parameters and one input (forcing data) of the Sacramento Soil Moisture Accounting (SAC-SMA) model are analyzed by using two GSA methods: Sobol' and Fourier Amplitude Sensitivity Test (FAST). The simulations are carried out over five sub-basins within the Columbia River Basin (CRB) for three different periods: one-year, four-year, and seven-year. The main parameter sensitivities (first-order) and the interactions sensitivities (second-order) are evaluated in this study. Our results show that some hydrological processes are highly affected by the simulation length. In other words, some parameters reveal importance during the short period simulation (e.g. one-year) while other parameters are effective in the long period simulations (e.g. four-year and seven-year). Moreover, the reliability of the sensitivity analysis results is compared based on 1) the agreement between the two sensitivity analysis methods (Sobol' and FAST) in terms of highlighting the same parameters or input as the most influential parameters or input and 2) how the methods are cohered in ranking these sensitive parameters under the same conditions (sub-basins and simulation length). The results show that the coherence between the Sobol' and FAST sensitivity analysis methods. Additionally, it is found that FAST method is sufficient to evaluate the main effects of the model parameters and inputs. This study confirms that the Sobol' and FAST methods are reliable GSA methods that can be applied in different scientific applications. Finally, as a future work, we suggest to study the uncertainty associated with the sensitivity analysis approach regarding the reliability of evaluating different sensitivity analysis methods.
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Michaud, Jene Diane. « Distributed rainfall-runoff modeling of thunderstorm-generated floods a case study in a mid-sized, semi-arid watershed in Arizona / ». Diss., The University of Arizona, 1992. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1992_49_sip1_w.pdf&type=application/pdf.
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Wang, Maili. « Approximate method for solving two-stage stochastic programming and its application to the groundwater management ». Diss., The University of Arizona, 1999. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1999_068_sip1_w.pdf&type=application/pdf.
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Blue, Julie Elena. « Predicting tracer and contaminant transport with the stratified aquifer approach ». Diss., The University of Arizona, 1999. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1999_426_sip1_w.pdf&type=application/pdf.
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Oliveira, Greice Ximena Santos. « Relações entre medidas de evaporação de superfícies de água livre por evaporímetros e estimativas por métodos meteorológicos em duas regiões do Estado de São Paulo ». Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11131/tde-04082009-111344/.
Texte intégralRésumé :
Este trabalho objetivou estabelecer relações entre evaporação de tanques Classe A e de 20 m2, em Piracicaba, SP e testar o desempenho de métodos meteorológicos de estimativa da evaporação de superfícies de água livre nessa localidade e em Jaboticabal, SP. Utilizou-se dados meteorológicos coletados em ambiente de um pequeno lago artificial em Piracicaba para cálculos dos métodos de balanço de energia-razão de Bowen, Penman, Priestley-Taylor e Penman simplificado. Dados meteorológicos observados sobre gramado foram usados para estimativa pelos métodos de Penman, Penman modificado, Dalton adaptado, Linacre e tanque Classe ASnyder. Os métodos foram avaliados utilizando índices de concordância e desempenho a partir de análise de regressão e de desvios por comparação com medidas do evaporímetro de 20 m2. Foram observadas relações lineares significativas entre os valores da evaporação dos tanques Classe A e de 20 m2 em todos os meses do ano em Piracicaba. A razão mensal entre as medidas dos evaporímetros apresentou variação ao longo do ano, com superestimativa pequena (até 3%) de fevereiro a junho e em novembro, e grande (10% a 15%) nos outros meses, em relação aos dados de Oliveira (1971) para a mesma localidade. A maior consistência estatística e representatividade da série de medidas, com 3 repetições de tanque Classe A, indicam que os fatores mensais de relações entre os dois evaporímetros podem substituir os obtidos por Oliveira (1971). Todos os métodos utilizados nos dois ambientes apresentaram boa concordância em termos médios com os observados no tanque de 20 m2, sempre com grande dispersão dos dados, diminuindo com o aumento do número de dias de contabilização da evaporação. O método de balanço de energia apresentou bom desempenho com cálculos realizados em períodos de 24 horas, mostrando desvios acentuados com contabilização no período diurno. O método de Penman mostrou bom desempenho quando utilizado para períodos de 24 horas, com subestimativas médias entre -6,0% e -10,5%, mas com superestimativas de +7,2 e +12,4% no período diurno. Os métodos de Priestley-Taylor (1972) e de Penman simplificado mostraram desvios médios pequenos (+2,7 e +5,7%), sendo considerados de bom desempenho. Para os métodos que usaram observações no posto meteorológico, o do tanque Classe ASnyder mostrou os menores desvios médios em Piracicaba (+3,9% a + 4,6%), mas apresentou maiores superestimativas (+14,0% a +14,4%) em Jaboticabal. Outra discrepância entre localidades foi observada para o método de Penmam modificado, com subestimativas entre 5,5 e 14,1% em Piracicaba, mas desvio de +1,0%, em Jaboticabal. O método original de Penman mostrou desvios similares em ambas localidades (-8,9% a 12,3%), enquanto o de Dalton adaptado apresentou desvios de +2,1% a 8,1%, mas com alta dispersão em todos dias de contabilização. Os métodos de Penman simplificado e o de Priestley-Taylor, no caso do lago, e o tanque Classe ASnyder, no caso do posto meteorológico, foram os que no geral apresentaram resultados mais comparáveis com os do tanque de 20 m2, sendo que par ao último deve-se atentar para o desvio sistemático em Jaboticabal.This study aimed to establish relations between evaporation Class A pan and 20 m2 tank, in Piracicaba region, State of Sao Paulo, Brazil and to test the performance of meteorological methods to estimate open-water surfaces evaporation in this same region and also in Jaboticabal, SP. Computation of daily evaporation was performed by using weather data, collected in the environment of a small artificial lake in Piracicaba, and the following methods: energy balance-Bowen ratio, Penman, Priestley-Taylor and Penman simplified. The methods of Penman, Penman adapted, Dalton adapted, Linacre and of Class A pan-Snyder were evaluated by using weather station data in both regions. The results of the methods were compared with the measurements of the 20 m2 tank evaporation, in a daily basis, and also for two, three or for the mean values for all days of measurements in every month, using indexes of agreement and performance from the regression analysis and deviations from the estimated and measured values. The linear relations between evaporation measured by the two evaporimeters were significative for all months in Piracicaba. The ratio of the two measurements showed variation throughout the year, with a small overestimation (about 3%) from February to June and November, and greater (10% to 15%) in the other months, compared to results of Oliveira (1971) for the same region. Due to the statistical consistency and representativeness of the series of 9 years and 3 repetitions of Class A pan, it is indicated that the factors of monthly relations between the two evaporímeters observed in this study can advantageously replace those obtained by Oliveira (1971). All methods used in the two environments showed good agreement, in average basis, with measurements by 20 m2 tank, with large dispersion of data, which decreased with the increase of the time step. The energy balance method showed good performance when the calculations were performed in 24-h periods, but large deviations compared to the tank with data integrated over the daylight period. The Penman method showed good performance when used for periods of 24 h, with an average underestimation between - 6.0 and -10.5% when integrated over the 24-h period, but with overestimation of +7.2 and +12.4% for the daylight period. The methods of Priestley-Taylor (1972) and Penman simplified showed small deviations between +2.7 and + 5.7%, being considered as having good performance compared to the evaporimeter. Among the methods that used weather station data, the class A- Snyder was the one that showed the lowest average deviation in Piracicaba (+3.9 to + 4.6%), but the greatest overestimation (+14.0% to 14.4%) in Jaboticabal. Another discrepancy between locations was observed for the Penman method modified, with underestimation between 5.5% and 14.1% in Piracicaba, but deviation of +1.0% in Jaboticabal. The original Penman method showed similar deviations in the two regions (-8.9% to 12.3%), while Dalton adapted method showed deviations of +2.1% to 8.1%. The methods of Penman simplified and Priestley-Taylor, used in the lake environment, and the Class A pan-Snyder method, with the use of wheater station data, were those that showed most comparable results with the 20 m2 tank evaporation, but in Jaboticabal, it is necessary to take to account the observed systematic mean deviation.
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Price, Myra Ann. « Seasonal Variation in Runoff Curve Number ». Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/225411.
Texte intégralRésumé :
The seasonal variation in rainfall - runoff response is investigated for about 300 small watersheds throughout the United States. Data from USDA research watersheds were used to define runoff Curve Number for ordered data sets by months. Three major patterns of cyclic variation are found and investigated: 1) distinct and well - defined seasonal variations as typified by forested watersheds in heavy rainfall zones; 2) mildly cyclic variation found typically in meadows and grasslands, and 3) non - cyclic or unidentifiable patterns, including those with insufficient seasonal data. The only pattern that may be present is the well-defined seasonal variation found so far only in forested watersheds. Regional characteristics were found for individual crop types. For the watersheds studied there seemed to be no difference in the variation between crops except for meadow during the summer. Some associated background factors are explored, including long-term and short-term antecedent rainfall.
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Fernandes, Wescley de Sousa. « AvaliaÃÃo do Impacto das MudanÃas ClimÃticas na Oferta HÃdrica da Bacia HidrogrÃfica do ReservatÃrio Ãros usando os Modelos de MudanÃas ClimÃticas do IPCC-AR4, levando em ConsideraÃÃo as Diversas Incertezas Associadas ». Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8377.
Texte intégralRésumé :
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNo presente trabalho as projeÃÃes de vazÃes para a bacia do Ãros (CearÃ) foram obtidas usando as precipitaÃÃes dos modelos globais do quarto relatÃrio do Intergovernmental Panel on Climate Change (IPCC-AR4) para o perÃodo de 2010 a 2099 do cenÃrio A1B. As vazÃes foram geradas pelo modelo hidrolÃgico Soil Moisture Account Procedure (SMAP). Para a obtenÃÃo destas, as precipitaÃÃes foram corrigidas estatisticamente a partir dos dados observados, considerando as sÃries distribuiÃÃes do tipo gama. Quanto à evaporaÃÃo de entrada do modelo chuva-vazÃo foram feitas duas consideraÃÃes, a primeira consideraÃÃo utiliza vazÃes obtidas pelo modelo hidrolÃgico SMAP inicializado com evaporaÃÃo fornecidas pelo INMET e a segunda considera que a inicializaÃÃo foi feita por evaporaÃÃes estimadas pelo mÃtodo de Penann Mothieth. Para a anÃlise das variaÃÃes interanuais foram observadas as caracterÃsticas de tendÃncias das sÃries (usando mÃtodo clÃssico de Mann-Kendall-Sen) nos padrÃes de variaÃÃo (anÃlise da mÃdia e do coeficiente de variaÃÃo da sÃrie) e a anÃlise de extremos (comparaÃÃo das curvas de distribuiÃÃo acumulada do sÃculo XX e XXI). Para anÃlise sazonal considerou-se a anomalia na climatologia mÃdia dos modelos do sÃculo XXI em relaÃÃo ao sÃculo XX. Para a anÃlise interanual foi observado que a inicializaÃÃo do modelo hidrolÃgico SMAP com evaporaÃÃes estimadas pelo mÃtodo de Penann Motheith modificado pode surgir como implementaÃÃo para o teste de hipÃtese de Mann Kendall Sen. O calculo do coeficiente de variaÃÃo demonstrou que apesar da pouca divergÃncia quanto a ocorrÃncia de variabilidade, tratando-se de sÃries de vazÃes obtidas pelo SMAP inicializado com evaporaÃÃes estimadas, as rodadas dos modelos MIROC3_2_MEDRES relatou aumentos de variabilidade para o sÃculo XXI em relaÃÃo ao sÃculo XX. Quando a inicializaÃÃo no SMAP ocorre por meio de evaporaÃÃes fornecidas pelo INMET ocorre uma grande diversificaÃÃo nos valores de variabilidade. Ainda na anÃlise interanual, a curva de funÃÃo de distribuiÃÃo acumulada (CDF) demonstrou que dos 8 modelos analisados (modelos inicializados com evaporaÃÃes estimadas pelo mÃtodo de Penann-Motheith modificado) 3 apresentam maior freqÃÃncia de eventos secos, 3 apresentam uma freqÃÃncia de eventos mais Ãmidos e 2 modelos nÃo apresentando anÃlises significativas aproximando-se da curva gerada pela sÃrie de vazÃo observada. Quanto à anÃlise sazonal das vazÃes à observado que quando se utiliza o mÃtodo de Penann Motheith modificado para evaporaÃÃo (na inicializaÃÃo do SMAP) os valores de vazÃes tornam-se menores do que os valores obtidos por sÃries geradas pelo modelo hidrolÃgico inicializado com evaporaÃÃes fornecidas pelo INMET, relacionando o sÃculo XXI com o sÃculo XX.
In the present work flow projections for the basin Ãros (CearÃ) were obtained using the precipitation of global models of the fourth report of the Intergovernmental Panel on Climate Change (IPCC-AR4) for the period 2010 to 2099 the A1B scenario. The flows were generated by the hydrologic model Soil Moisture Account Procedure (SMAP). To obtain these, the precipitations were statistically corrected from the observed data, considering the distributions of the type series range. The evaporation model input rainfall-runoff were two considerations, the first consideration obtained by using flow hydrologic model initialized with SMAP evaporation provided by INMET and considers that the second boot occur by evaporation estimated by the method of Penann Mothieth. For the analysis of interannual variations were observed the characteristics of trends of the series (using the classical method of Mann-Kendall-Sen), the changing patterns of variation (analysis of the mean and coefficient of variation of the series) and the analysis of extremes (compared cumulative distribution curves of the twentieth century and XXI). For seasonal analysis considered the climate anomaly in the middle of the XXI century models over the twentieth century. For analysis it was observed that interannual hydrologic model initialization SMAP with evaporation estimated by the modified Penann Motheith can arise as an implementation for the hypothesis test of Mann Kendall Sen. The calculation of the coefficient of variation showed that despite the short confrontation over the occurrence of variability, in the case of streamflow series obtained by SMAP initialized with estimated evaporation, the rounds of the models MIROC3_2_MEDRES reported increases in variability for the XXI century in relation to the twentieth century. When booting into SMAP occurs through evaporation provided by INMET is a great diversification in the values of variability. Although the interannual analysis, the curve of cumulative distribution function (CDF) showed that eight of the analyzed models (models initialized with evaporation estimated by the method of Penann Motheith-modified) 3 have a higher frequency of dry events, have a third event frequency wet and two models showing no meaningful analyzes approaching the curve generated by the series of observed flows. As for seasonal analysis of the flow is observed that when using the method of Penann Motheith modified to evaporation (initialization SMAP) values of flow rates become smaller than the values obtained by series generated by the hydrologic model initialized with evaporation provided by INMET , relating the new century, the twentieth century.
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Mousavizadeh, Mohammad Hassan. « Integration of a geographic information system and a continuous nonpoint source pollution model to evaluate the hydrologic response of an agricultural watershed ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0015/NQ44524.pdf.
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Dressler, Kevin Andrew. « Estimating the Spatial Distribution of Snow Water Equivalent and Simulated Snowmelt Runoff Modeling in Headwater Basins of the Semi-arid Southwest ». Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1063%5F1%5Fm.pdf&type=application/pdf.
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Harter, Thomas. « Unconditional and conditional simulation of flow and transport in heterogeneous, variably saturated porous media ». Diss., The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1994_36_sip1_w.pdf&type=application/pdf.
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Orr, Shlomo. « Stochastic approach to steady state flow in nonuniform geologic media ». Diss., The University of Arizona, 1993. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1993_409_sip1_w.pdf&type=application/pdf.
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Hiester, Justin. « Investigations into the Regional and Local Timescale Variations of Subglacial Drainage Networks ». PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1022.
Texte intégralRésumé :
Subglacial water plays an important role in the regulation of an ice sheet's mass balance. It may be the dominant control on the velocities of ice streams and outlet glaciers on scales of months to millennia. Recent satellite observations of ice surface elevation changes have given researchers new insights into how subglacial water is stored and transported. Localized uplift and settling of the ice surface implies that lakes exist beneath the ice sheet that are being filled and drained on relatively short time scales. %At the base of an ice sheet water can be transported through a variety of drainage networks or stored in subglacial lakes.
Here, a numerical investigation of the mechanisms of transport and storage of subglacial water and the associated time scales is presented. Experiments are carried out using a finite element model of coupled ice and water flow. The first experiment seeks to understand the relationship between the depth of a basal depression and the area over which the feature affects basal water flow. It is found that as the perturbation to a topographic depression's depth is increased, water is rerouted in response to the perturbation. Additionally it is found that the relationship between perturbation depth and the extent upstream to which its effects reach is nonlinear. The second experiment examines how the aspect ratio of bed features (prolate, oblate, or equidimensional) influences basal water flow. It is found that the systems that develop and their interactions are mediated by both the topography and the feedbacks taken into account by the coupling of the systems in the model. Features oriented parallel to ice and water flow are associated with distributed fan systems that develop branches which migrate laterally across the domain and interact with one another on monthly and yearly timescales. Laterally oriented features develop laterally extensive ponds. As the ratio of longitudinal to lateral dimension of the topography is increased, a combination of these two water distributions is seen.
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Huth, Anne M. Kramer. « Geochemical and isotopic mixing models : two case studies in a snow-dominated and semi-arid environment ». Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/191260.
Texte intégralRésumé :
The influence of climate and antecedent moisture conditions on hydrological and biogeochemical fluxes was studied and contrasted in three nested, high-elevation, snowmelt-dominated catchments in the Sierra Nevada, California and one basin-floor, semi-arid catchment in southeastern Arizona. Investigations were completed within a different two-year period at each site, with the second year being climatically different (typically drier) than the first. Spring snowmelt, widespread winter frontal precipitation, and episodic summer rains induce surface water flow in these catchments, though the timing and magnitude of nutrient redistribution among soil and stream compartments varies in each. Surface water flow from spring snowmelt in high-elevation catchments travels through the subsurface or across the surface as direct runoff A more typical process producing surface water flow in semi-arid catchments is flooding during episodic or widespread rainfall. Hydrograph separations at Emerald Lake, Topaz Lake and Marble Fork catchments in Sequoia National Park, California, revealed that the majority of snowmelt flowed through soil before entering the stream in both average and highsnow years. The Emerald Lake watershed had a higher fraction of old water in its outflow in the average accumulation year because of the previous year's high accumulation and longer melt season. A mixing model analysis performed of the upper San Pedro River, Arizona, for wet and dry years showed that summer flood hydrographs were composed mainly of precipitation and surface runoff in both years, though a higher soil-water input occurred in the wetter year and in early season floods in the dry year. Stream and soil water nitrate concentrations were higher during floods in the dry year. Early season floods in the dry year exhibited more variability in stream water nitrate and sulfate, whereas late season flood concentrations reflected a well-mixed system and therefore less variation of these species during flood hydrographs. These data showed that periods of below average precipitation preceding major runoff periods result both in less soil water and solute export during summer floods in basin-floor catchments and less direct snowmelt in high-elevation catchments. Hydrologic and solute export in each catchment, despite their differing geographical locations, responds in similar ways to climate variability.
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Khajehei, Sepideh. « From Probabilistic Socio-Economic Vulnerability to an Integrated Framework for Flash Flood Prediction ». PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4666.
Texte intégralRésumé :
Flash flood is among the most hazardous natural disasters, and it can cause severe damages to the environment and human life. Flash floods are mainly caused by intense rainfall and due to their rapid onset (within six hours of rainfall), very limited opportunity can be left for effective response. Understanding the socio-economic characteristics involving natural hazards potential, vulnerability, and resilience is necessary to address the damages to economy and casualties from extreme natural hazards. The vulnerability to flash floods is dependent on both biophysical and socio-economic factors. This study provides a comprehensive assessment of socio-economic vulnerability to flash flood alongside a novel framework for flash flood early warning system. A socio-economic vulnerability index was developed for each state and county in the Contiguous United States (CONUS). For this purpose, extensive ensembles of social and economic variables from US Census and the Bureau of Economic Analysis were assessed. The coincidence of socio-economic vulnerability and flash flood events were investigated to diagnose the critical and non-critical regions. In addition, a data-analytic approach is developed to assess the interaction between flash flood characteristics and the hydroclimatic variables, which is then applied as the foundation of the flash flood warning system. A novel framework based on the D-vine copula quantile regression algorithm is developed to detect the most significant hydroclimatic variables that describe the flash flood magnitude and duration as response variables and estimate the conditional quantiles of the flash flood characteristics. This study can help mitigate flash flood risks and improve recovery planning, and it can be useful for reducing flash flood impacts on vulnerable regions and population.
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Tartakovsky, Daniel. « Prediction of transient flow in random porous media by conditional moments ». Diss., The University of Arizona, 1996. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1996_263_sip1_w.pdf&type=application/pdf.
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