Segui questo link per vedere altri tipi di pubblicazioni sul tema: Aquifers.
Tesi sul tema "Aquifers"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Aquifers".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Chen, Yiming. "Aquifer storage and recovery in saline aquifers." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52266.
Testo completoAbstract (sommario):
Aquifer storage and recovery (ASR) is a particular scheme of artificial recharge of groundwater by injecting fresh water into aquifers and subsequently recovering the stored water during times of peak demand or extended drought. In the era of combating climate change, ASR, as an effective means for water reuse and sustainable management of water resources in concert with the natural environment, represents a huge opportunity for climate change adaptation to mitigate water availability stress.The success of an ASR scheme is quantified by the recovery efficiency (RE), defined as the volume of stored water that can be recovered for supply purposes divided by the total volume injected. It is not uncommon that RE may be significantly lower than 100% because of the water quality changes as a consequence of the mixing between the injected water and native groundwater and the interaction between injected water and soil. Thus, the key of a successful ASR scheme is (1) to select appropriate aquifers and (2) to design optimal operational processes to build up a bubble of injected water with minimized negative impact from such mixing and interaction.
To achieve this, this thesis develops an integrated knowledge base with sound interdisciplinary science and understanding of the mixing processes under operational ASR management in aquifers with various hydrogeological conditions. Analytical and numerical modeling are conducted to improve the scientific understanding of mixing processes involved in ASR schemes and to provide specific technical guidance for improving ASR efficiency under complex hydrogeological conditions. (1) An efficient approach is developed to analytically evaluate solute transport in a horizontal radial flow field with a multistep pumping and examine the ASR performance in homogeneous, isotropic aquifer with advective and dispersive transport processes. (2) Numerical and analytical studies are conducted to investigate the efficiency of an ASR system in dual-domain aquifers with mass transfer limitations under various hydrogeological and operational conditions. Simple and effective relationships between transport parameters and ASR operational parameters are derived to quantify the effectiveness and ascertain the potential of ASR systems with mass transfer limitations.(3) Effects of hydrogeological and operational parameters on ASR efficiency are assessed in homogeneous/stratified, isotropic/anisotropic coastal aquifers. Effects of transverse dispersion are particularly investigated in such aquifers.(4) Finally, we test and study an innovative ASR scheme for improving the RE in brackish aquifers: injection through a fully-penetrated well and recovery through a partially-penetrated well.
2
Artiola, Janick. "Arizona Aquifers." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2013. http://hdl.handle.net/10150/298168.
Testo completoAbstract (sommario):
Video is available on the UofAZCALS YouTube channel.<br>About 5% of Arizona's population depends on private wells for fresh water and more than 40% of our annual water use comes from Arizona's aquifers. Following a brief introduction to regulations, requirements and equipment used for drilling a private well in Arizona, this video presents the geologic origins of Arizona's aquifer materials with illustrations and pictures of AZ aquifers. Finally, aquifers are ranked by their ability to store and produce water.
3
Payne, Scott Marshall. "Classification of aquifers." Diss., [Missoula, Mont.] : The University of Montana, 2010. http://etd.lib.umt.edu/theses/available/etd-03082010-112041.
Testo completo
4
Sun, Xiaobin. "Testing and evaluation of artesian aquifers in Table Mountain Group aquifers." University of the Western Cape, 2014. http://hdl.handle.net/11394/4369.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhD<br>The Table Mountain Group (TMG) Aquifer is a huge aquifer system which may provide large bulk water supplies for local municipalities and irrigation water for agriculture in the Western Cape and Eastern Cape Provinces in South Africa. In many locations, water pressure in an aquifer may force groundwater out of ground surface so that the borehole drilled into the aquifer would produce overflow without a pump. Appropriate testing and evaluation of such artesian aquifers is very critical for sound evaluation and sustainable utilization of groundwater resources in the TMG area. However, study on this aspect of hydrogeology in TMG is limited. Although the flow and storage of TMG aquifer was conceptualised in previous studies, no specific study on artesian aquifer in TMG was made available. There are dozens of flowing artesian boreholes in TMG in which the pressure heads in the boreholes are above ground surface locally. A common approach to estimate hydraulic properties of the aquifers underneath is to make use of free-flowing and recovery tests conducted on a flowing artesian borehole. However, such testing approach was seldom carried out in TMG due to lack of an appropriate device readily available for data collection. A special hydraulic test device was developed for data collection in this context. The test device was successfully tested at a flowing artesian borehole in TMG. The device can not only be used to measure simultaneous flow rate and pressure head at the test borehole, but also be portable and flexible for capturing the data during aquifer tests in similar conditions like artesian holes in Karoo, dolomite or other sites in which pressure head is above ground surface. The straight-line method proposed by Jacob-Lohman is often adopted for data interpretation. However, the approach may not be able to analyse the test data from flowing artesian holes in TMG. The reason is that the TMG aquifers are often bounded by impermeable faults or folds at local or intermediate scale, which implies that some assumptions of infinite aquifer required for the straight-line method cannot be fulfilled. Boundary conditions based on the Jacob-Lohman method need to be considered during the simulation. In addition, the diagnostic plot analysis method using reciprocal rate derivative is adapted to cross-check the results from the straight-line method. The approach could help identify the flow regimes and discern the boundary conditions, of which results further provide useful information to conceptualize the aquifer and facilitate an appropriate analytical method to evaluate the aquifer properties. Two case studies in TMG were selected to evaluate the hydraulic properties of artesian aquifers using the above methods. The transmissivities of the artesian aquifer in TMG range from 0.6 to 46.7 m2/d based on calculations with recovery test data. Storativities range from 10-4 to 10-3 derived from free-flowing test data analysis. For the aquifer at each specific site, the transmissivity value of the artesian aquifer in Rawsonville is estimated to be 7.5–23 m2/d, with storativity value ranging from 2.0×10-4 to 5.5×10-4. The transmissivity value of the artesian aquifer in Oudtshoorn is approximately 37 m2/d, with S value of 1.16×10-3. The simulation results by straight-line and diagnostic plot analysis methods, not only imply the existence of negative skin zone in the vicinity of the test boreholes, but also highlight the fact that the TMG aquifers are often bounded by impermeable faults or folds at local or intermediate scale. With the storativity values of artesian aquifers derived from data interpretation, total groundwater storage capacity of aquifers at two case studies was calculated. The figures will provide valuable information for decision-makers to plan and develop sustainable groundwater utilization of artesian aquifers in local or intermediate scales. With the hydraulic test device readily available for data collection, more aquifer tests can be carried out in other overflow artesian boreholes in TMG. It becomes feasible to determine the hydraulic properties of artesian aquifers for the entire TMG. Thereof quantification of groundwater resources of artesian aquifers in TMG at a mega-scale becomes achievable. This would also contribute towards global research initiative for quantification of groundwater resources at a mega-scale.
5
Wendelborn, Anke. "Zinc and copper behaviour during stormwater aquifer storage and recovery in sandy aquifers." Monash University. Faculty of Engineering. Department of Civil Engineering, Institute for Sustainable Water Resources, 2008. http://arrow.monash.edu.au/hdl/1959.1/68715.
Testo completoAbstract (sommario):
In the light of increasing demand and diminishing supplies a sustainable urban water management for Melbourne and other cities will need to include water recycling and reuse of reclaimed water and stormwater. One key issue in stormwater reuse is the need for storage between times of collection until times of demand. Aquifer storage and recovery (ASR) would be a valuable option as it has limited space requirements and restricts loss from evaporation. However, stormwater commonly contains elevated levels of heavy metals, of which Zn and Cu are the most mobile. Stormwater also contains suspended solids, organic carbon, oxygen and nutrients, which influence the behaviour of injected metals and induce geochemical changes in the aquifer. While stormwater ASR has been practiced in limestone aquifers in South Australia, field data for sandy aquifers, which are more prevalent around Melbourne, are very limited. Risk assessment regarding the potential impact of stormwater ASR on the quality of the aquifer and groundwater resources in sandy aquifer is therefore necessary. After a characterisation of stormwater from different Melbourne catchments confirmed comparatively high concentrations of Zn and Cu in stormwater, three siliceous aquifer sediments were used in a series of batch sorption experiments as well as column experiments imitating one ASR cycle to assess the impact of different parameters on Zn and Cu behaviour. The reactive geochemical transport model PHT3D was then modified to simulate experimental results with the outlook that it could be used as a predictive tool for long term evaluation. The study showed that Zn adsorption was limited and desorption of large fractions occurred, indicating that injected amounts of Zn are mobile and would mainly be recovered. In contrast, Cu adsorption was higher and desorption was limited, indicating that injected amounts of Cu would mainly accumulate in the aquifer. The release of metals was triggered by reduction in pH, increase in ionic strength and particle mobilisation. Metal concentrations were also increased after storage phases, while minor sediment constituents, especially organic matter, significantly reduce metal mobility. The different role of dissolved and solid organic carbon is critical in understanding Cu behaviour during stormwater ASR. Pretreatment of stormwater to reduce the injection of colloids, organic carbon and metals are recommended to limit metal accumulation in the subsurface. Monitoring of water quality throughout the ASR cycle would be encouraged to validate the current findings with field data. Special attention should be paid to backflushed water quality to ensure correct disposal.
6
Shamsudduha, Mohammad. "Mineralogical and geochemical profiling of arsenic-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain, Minikganj, Bangladesh." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Spring%20Theses/SHAMSUDDUHA_MOHAMMAD_47.pdf.
Testo completo
7
Williams, David G. "Whole aquifer system management: the northeast floridan aquifer system under an interstate compact." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/30907.
Testo completo
8
Park, Chan-Hee. "Saltwater Intrusion in Coastal Aquifers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4857.
Testo completoAbstract (sommario):
Utilizing the analytical solution of the steady state sharp interface saltwater intrusion model in coastal aquifers, a multi-objective optimization formulation of pumping rates and well locations in a coastal aquifer is formulated to solve problems in water management practice. The proposed optimization problem uses progressive genetic algorithm technique and the method developed is applied to the previous work of Cheng et al. [2000]. Through this analysis, several other applications are provided to demonstrate the use of the model in practical applications. This work is the first to optimize pumping rates as well as well locations simultaneously in coastal aquifer management.
Known the limitation of the analytical solution, the work is expanded to cover the physics of saltwater intrusion in a more realistic way. This is variable density flow in a variably saturated porous medium. In this method, mixing between two fluids such as saltwater and freshwater can be described and the porous medium is also expanded to cover saturated and unsaturated zones together. One of the objectives is to develop a three dimensional physical model, verify the model, and apply to various applications in coastal aquifers.
The developed model, TechFlow, is used to investigate instability issues associated with the numerical solution of the Elder problem in the perspective that includes physical instability issues associated with density differences used in numerical solutions, sensitivity of the solution to idealization irregularity, and the importance of accurate estimation of the velocity field and its association to the grid density levels that is necessary to solve the problem accurately.
Saltwater intrusion hydrodynamics in a beach under the influence of tidal effects is also investigated using TechFlow. Based on the results of TechFlow with the use of various boundary conditions for the transport equation, the saltwater intrusion hydrodynamics in a beach under the influence of tidal effects shows unique dynamics. These solutions are primarily affected by density differences, tidal effects on a mild slope, variably saturated porous medium and finite domain solution condition. TechFlow is also used to investigate saltwater upconing beneath pumping wells both two- and three-dimensional applications.
9
Teo, Hhih-Ting, and h. teo@griffith edu au. "Tidal Dynamics in Coastal Aquifers." Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030729.155028.
Testo completoAbstract (sommario):
The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better prediction
10
Halihan, Todd. "Permeability structure in fractured aquifers /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
Testo completo
11
Teo, Hhih-Ting. "Tidal Dynamics in Coastal Aquifers." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365678.
Testo completoAbstract (sommario):
The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better prediction<br>Thesis (Masters)<br>Master of Philosophy (MPhil)<br>School of Engineering<br>Full Text
12
Sun, Dongmin. "Aquitard control of stream-aquifer interaction and flow to a horizontal well in coastal aquifers." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4740.
Testo completoAbstract (sommario):
This dissertation is composed of three parts of major contributions: In Chapter II, we developed a new conceptual model and derived a new semi-analytical model for flow to a horizontal well beneath a water reservoir. Instead of treating the leakage from aquitard as a source term inside the aquifer which is called HantushâÂÂs assumption (1964), we linked flows in aquitard and aquifer by the idea of continuity of flux and drawdown. The result in this chapter is compared with that of Zhan and Park in 2003 which HantushâÂÂs assumption is adopted at various hydraulic and well configurations. It shows that HantushâÂÂs assumption becomes inaccurate in regions where vertical velocity components are significant. In Chapter III, we deal with the interaction of an aquifer with two parallel surface water bodies such as two streams or canals. In this chapter, new closed-form analytical and semi-analytical solutions are acquired for the pumping induced dynamic interaction between two streams and ground water for two different cases. In the first case, the sediment layers separating the streams from the aquifer ground water do not exist. In the second case, the two low permeable layers are considered. The effect of aquitard and water right competition is addressed in this chapter. This model can be used for interpreting and deriving hydrologic parameters of aquitard and aquifer when pumping occurs between two channels. It can also be used to predict stream depletion which is essential for water management and ecology conservation. In Chapter IV, we investigated the three dimensional upconing due to a finite-length of horizontal well and its critical conditions. The results are compared with those of vertical wells. The critical condition which includes the critical rise and the critical time at a certain pumping rate depends on the well length, the initial interface location, the well location, and the pumping rate. Our results show that horizontal well might be a better tool for coastal groundwater resources development. In real field applications, installing long wells as shallow as possible is always desirable for sustaining long periods of pumping with significant rates.
13
Tremblay, Philippe. "Étude hydrogéologique de l'aquifère de Saint-Honoré avec emphase sur son bilan hydrique /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
Testo completo
14
Rotzoll, Kolja. "Hydraulic Parameter Estimation Using Aquifer Tests, Specific Capacity, Ocean Tides, and Wave Setup for Hawai'i Aquifers." Thesis, Water Resources Research Center, University of Hawaii at Manoa, 2007. http://hdl.handle.net/10125/22265.
Testo completoAbstract (sommario):
The islands of Hawaii face increasing ground-water demands due to population growth in the last decades. Analytical and numerical models are essential tools for managing sustainable ground-water resources. The models require estimates of hydraulic properties, such as hydraulic conductivity and storage parameters. Four methods were evaluated to estimate hydraulic properties for basalts on the island of Maui. First, unconventional step-drawdown tests were evaluated. The results compare favorably with those from classical aquifer tests with a correlation of 0.81. Hydraulic conductivity is log-normally distributed and ranges from 1 to 2,500 m/d with a geometric mean of 276 m/d and a median of 370 m/d. The second approach developed a simplified parameter-estimation scheme through an empirical relationship between specific capacity and hydraulic parameters that utilized Hawaii's state well database. For Maui's basalts, the analysis yields a geometric-mean and median hydraulic conductivity of 423 and 493 m/d, respectively. Results from aquifer tests and specific-capacity relationships were used to generate island-wide hydraulic-conductivity maps using kriging. The maps are expected to be of great benefit in absence of site-specific field assessments. In the third approach, ocean-tide responses in the central Maui aquifer were used to estimate an effective hydraulic diffusivity of 2.3 x 10^7 m^2/d. The position of the study area necessitated refining the existing analytical solution that considers asynchronous and asymmetric tidal influence from two sides in an aquifer. Finally, measured ground-water responses to wave setup were used to estimate hydraulic parameters. Setup responses were significant as far as 5 km inland and dominated barometric-pressure effects during times of energetic swell events. The effective diffusivity estimated from setup was 2.3 x 10^7 m^2/d, matching that based on tides. Additionally, simple numerical ground-water flow models were developed to assess the accuracy of results from analytical solutions for step-drawdown tests, dual-tides and wave setup, and to evaluate sediment-damping effects on tidal propagation. The estimated mean hydraulic conductivities of the four methods range between 300 and 500 m/d for basalts in Maui. The results of different methods are consistent among each other and match previous estimates for basalts.<br>USGS Pacific Island Water Science Center
15
Rotter, Ben E. G. "Modelling bioremediation of uranium contaminated aquifers." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2573.
Testo completoAbstract (sommario):
Radionuclide extraction, processing and storage have resulted in a legacy of radionuclide-contaminated groundwater aquifers worldwide. An emerging remediation technology for such sites is the in situ immobilisation of radionuclides via biostimulation of dissimilatory metal reducing bacteria. While this approach has been successfully demonstrated in experimental studies, advances in understanding and optimization of the technique are needed. Mass transfer processes in heterogeneous and structured porous media may significantly affect the geochemical and microbial processes taking place in contaminated sites, impacting remediation efficiency significantly. The objective of this work was to understand better how heterogeneous porous media may affect immobilisation efficiency through interactions with the dominant geochemical, microbial and transport processes. A biogeochemical reactive transport model was developed for uranium immobilisation by DMRB. Physical heterogeneity is conceptually represented by a two-region model. Simulations investigate the parameter sensitivities of the system over wide ranging geochemical, microbial and groundwater transport conditions. The simulations highlight the conditions under which optimal remediation occurs. The relative significance of regional microbial residence patterns, U(VI)-surface complexation, geochemical conditions such as mineralogy, and porous media characteristics such as porosity and regional mass transfer are identified. Additionally, low level radioactive waste disposal sites typically contain significant quantities of cellulose, whose hydrolysis can have a significant impact on the geochemical conditions in these sites. Those geochemical conditions, in turn, can affect radionuclide mobility and bioimmobilisation. To investigate the potentially critical role of cellulose, process-based predictive model was developed, which includes a novel approach to biomass transfer between a cellulose-bound biofilm and biomass in the bulk liquid. A sensitivity analysis of the system parameters revealed the significance of bacterial colonisation of cellulose particles by attachment through contact in solution. The thesis concludes that the processes involved in uranium bioimmobilisation are sensitive to regional residence characteristics, media porosity, surface complexation, microbial efficiency, and mass transfer under varying conditions. Careful characterisation of potential sites and use of a model that includes these processes in sufficient detail is therefore deemed necessary before the remediation effectiveness can be reliably predicted.
16
Mühlherr, Ingo H. "Nitrous oxide in British limestone aquifers." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389365.
Testo completo
17
Clarke, Alastair James. "Simulating gas leaks in shallow aquifers." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708469.
Testo completo
18
Rehfeldt, Kenneth Robert. "Prediction of macrodispersivity in heterogeneous aquifers." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/65014.
Testo completo
19
Forghani, Ali. "Simulation and Optimization Models to Evaluate Performance of Aquifer Storage and Recovery Wells in Fresh Water Aquifers." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6933.
Testo completoAbstract (sommario):
Aquifer storage and recovery (ASR) involves artificially recharging an aquifer through well(s) using surplus water for later recovery in high-demand months. The operators of the studied ASR system developed the system as a means of receiving additional water rights to supplement their pre-existing water rights for extraction in dry months. However, the region’s water regulators define the performance of this ASR system as the amount of the injected water that is recoverable from the same wells during extraction periods. The study proposes recovery effectiveness (REN) as the performance index of this ASR system. REN equals the injectate proportion that the same wells can recover. Quantifying the system's achievable REN is required to determine the amount of the additional water rights. Similarity between the injected water and native groundwater, however, prevents an accurate REN estimation using on-field techniques. This necessitates the use of computer modeling for estimating REN in this system. The study employs simulation, statistical, and optimization models to quantify and maximize REN in the studied ASR system in Utah.
20
Brakefield, Linzy Kay Clement Thangadurai Prabhakar. "Physical and numerical modeling of buoyant groundwater plumes." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Civil_Engineering/Thesis/Brakefield_Linzy_10.pdf.
Testo completo
21
Kustu, M. Deniz. "Optimal Storage Of Freshwater In Saline Aquifers." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606200/index.pdf.
Testo completoAbstract (sommario):
Storage of freshwater in saline aquifers has a strategic importance in water deficit countries. The freshwater stored in these aquifers may be the only source of water available during times of crisis. Coupled simulation and optimization type groundwater management models have been developed that will achieve the optimal control of the storage of freshwater in a stagnant manner for constant density and variable density flows in hypothetical single- and multi-layered saline aquifers.
The study is carried out in two stages. In the first stage, a transient model of five years is simulated that allows sufficient time for the freshwater mound to be created. In the second stage, an optimization model is formulated which minimizes the pumping/injection rates of a set of hydraulic gradient control wells subject to a set of constraints consisting of systems response equations, demand requirements, hydraulic gradient controls, pumping and injection limitations. The optimization models select which wells to be pumped and which ones to be injected and decide on their pumping/injection schedules to maintain the freshwater mound from migration. The results of the optimization models showed that the mound is successfully contained in its original location by controlling the hydraulic gradient via pumping/injection wells.
22
Duah, Anthony A. "Sustainable utilisation of Table Mountain Group aquifers." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_2705_1373463070.
Testo completoAbstract (sommario):
<p>The Table Mountain Group (TMG) Formation is the lowest member of the Cape Supergroup which consists of sediments deposited from early Ordovician to early Carboniferous times, approximately between 500 and 340 million years ago. The Table Mountain Group (TMG) aquifer system is <br>exposed along the west and south coasts of South Africa. It is a regional fractured rock aquifer that has become a major source of bulk water supply to <br>meet the agricultural and urban water requirements of the Western and Eastern Cape Provinces of South Africa. The TMG aquifer system comprises of an approximately 4000 m thick sequence of quartz arenite and minor shale layers deposited in a shallow, but extensive, predominantly eastwest striking <br>asin, changing to a northwest orientation at the west coast. The medium to coarse grain size and relative purity of some of the quartz arenites, <br>together with their well indurated nature and fracturing due to folding and faulting in the fold belt, enhance both the quality of the groundwater and its <br>exploitation potential for agricultural and domestic water supply purposes and its hot springs for recreation. The region is also home to some unique <br>and indigenous floral species (fynbos) of worldwide importance. These and other groundwater dependent vegetation are found on the series of <br>mountains, mountain slopes and valleys in the Cape Peninsula. The hydrogeology of the TMG consists of intermontane and coastal domains which <br>have different properties but are interconnected. The former is characterized by direct recharge from rain and snow melt, deep groundwater circulation with hot springs and low conductivity groundwater. The coastal domain is characterized by shallow groundwater occurrence usually with moderate to <br>poor quality, indirect recharge from rainfall of shallow circulation and where springs occur they are usually cold. The sustainable utilization of the TMG <br>aquifer addressed the issues of the groundwater flow dynamics, recharge and discharge to and from the aquifer<br>challenges of climate change and climate variability and their potential impact on the aquifer system. The concept of safe yield, recharge and the capture principle and the integration of <br>sustainable yield provided the basis for sustainable utilization with the adaptive management approach. Methodology used included the evaluation of <br>recharge methods and estimates in the TMG aquifer and a GIS based water balance recharge estimation. The evaluation of natural discharges and <br>artificial abstractions from the TMG aquifer system as well as its potential for future development. The Mann-Kendal trend analysis was used to test historical and present records of temperature and rainfall for significant trends as indication for climate variability and change. The determination of <br>variability index of rainfall and standard precipitation index were additional analyses to investigate variability. The use of a case study from the Klein <br>(Little) Karoo Rural Water Supply Scheme (KKRWSS) within the TMG study area was a test case to assess the sustainable utilization of TMG aquifers. <br>Results show that recharge varies in time and space between 1% and 55% of MAP as a result of different hydrostratigraphic units of the TMG based on <br>geology, hydrology, climate, soil, vegetation and landuse patterns however, the average recharge is from 1% to 5% of MAP. The TMG receives recharge <br>mainly through its 37,000 km2 of outcrop largely exposed on mountainous terrain. Natural discharges from the TMG include 11 thermal and numerous <br>cold spring discharges, baseflow to streams and reservoirs, and seepage to the ocean. Results from this study also show increasing temperature <br>trend over the years while rainfall trend generally <br>remain unchanged in the study area. Rainfall variability persists hence the potential for floodsand droughts in the region remain. Global and Regional Models predict about 10% to 25% reduction in rainfall and increase in variability in future. Impacts of <br>his change in climate will affect the different types of aquifers in various ways. Increase in temperature and reduction in rainfall will increase <br>evapotranspiration, reduce surface flows and eventually reduce shallow aquifer resources. Coastal aquifers risk upsurge in salinisation from sea level <br>rise and increase in abstractions from dwindling surface water resources. While floods increase the risk of contamination to shallow aquifers droughts <br>put pressure on all aquifers especially deep aquifers which are considered to be more reliable due to the fact that they are far removed from surface conditions. Future population growth and increase in freshwater demand will put more pressure on groundwater. Recharge to groundwater have been <br>over-estimated in certain areas in the past leading to high abstraction rates from boreholes causing extensive groundwater storage depletion evident by high decline in groundwater levels in these areas and hampering sustainable management of the aquifer resources. Over-abstraction have resulted in <br>loss of stream flow and baseflow reduction to streams during summer, complete loss of springs and reduction of flow to others. Flow to wetlands, <br>riparian vegetation, and sometimes loss and shifts in dependent ecosystems have also resulted from over-abstraction. Sustainability has spatial and <br>temporal implications due to changing climate and demand. The study recommends adaptive management practices in which several factors are <br>considered in managing groundwater together with surface water resources in order to maintain ecological and environmental integrity. The KKRWSS <br>and other groundwater supply schemes in the Western and Eastern Cape Provinces demonstrate the huge potential of the TMG to provide freshwatersupply for domestic and irrigation water needs however, the huge decline in groundwater levels due to over-abstraction in the KKRWSS and <br>other groundwater schemes underscores the need for sustainable utilization of the TMG groundwater resources for present and future generations with <br>minimal impacts on the quality, dependent hydrological and ecosystems as well as the environment.</p>
23
Mohd, Amin Sharidah. "Geochemical modelling of CO2 in saline aquifers." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24136.
Testo completoAbstract (sommario):
Carbon dioxide, CO2, disposal into saline aquifers could reduce emissions of anthropogenic greenhouse gases into the atmosphere. To ensure that the CO2 is trapped securely and will not escape to the surface, storage in such formations must be designed carefully. The geochemical reactions involved depend on the composition of the injected fluid introduced in the aquifer and the composition of the initial minerals assemblage and the aquifer brine. This thesis studies mineral dissolution/precipitation during CO2 storage, both in the cap rock and the storage aquifer itself. The overall objective is to propose an ideal storage design for long term, inexpensive and safe CO2 disposal in saline aquifers. The rate-limiting effects of CH4 impurities in gas streams on the CO2 reactivity in the cap rock and aquifer (carbonate and sandstone) at conditions representative of storage locations are studied. Representative geochemical data of formation water and mineralogy assemblages of cap rock (Nordland shale) overlying the Sleipner field, Dogger carbonate aquifer from Paris basin, France and Frio sandstone aquifer from Texas, US, are used. Kinetic batch and one-dimensional and two-dimensional reactive transport models are run to predict mineral alteration induced in the cap rock and in the aquifer. Cap rock models are run using PHREEQC for 10,000 years. The model considers both pure CO2 and mixtures of CO2 with CH4 (1-4 (w/w)%) in the injected gas stream. The simulations demonstrate that mixtures of CO2 with CH4 suppress the porosity increase in the cap rock, leading to more secure storage. The aquifers models incorporate 1 (w/w)% organic matter and are run using TOUGHREACT. CO2 was initially injected at constant rate of 30kg/s for 25 years and the models were subsequently run for 10,000 years to study long-term storage. The simulations demonstrate that injection of CO2 in microbial-mediated aquifers enhances the precipitation of secondary carbonates minerals and decreases the porosity of both sandstone and carbonate aquifers. Overall, this study proposes two main design criteria for safe and cost-effective CO2 storage: CO2 injection with CH4 (1-4 (w/w)%) and CO2 injection into microbial-mediated aquifers to enhance mineral precipitation, rendering storage secure.
24
Fazal, Md Abul. "MANAGING GROUNDWATER AQUIFERS WITH SIMULATION/OPTIMIZATION MODELS." Kyoto University, 1999. http://hdl.handle.net/2433/181889.
Testo completoAbstract (sommario):
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第7880号<br>農博第1038号<br>新制||農||777(附属図書館)<br>学位論文||H11||N3243(農学部図書室)<br>UT51-99-G474<br>京都大学大学院農学研究科地域環境科学専攻<br>(主査)教授 河地 利彦, 教授 青山 咸康, 教授 三野 徹<br>学位規則第4条第1項該当
25
Ronayne, Michael James. "Understanding groundwater dynamics in structurally heterogeneous aquifers /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Testo completo
26
Chavez, Rodriguez Adolfo 1951. "Modeling mountain-front recharge to regional aquifers." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/191124.
Testo completoAbstract (sommario):
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.
27
Khudaida, Kamal. "Modelling CO2 sequestration in deep saline aquifers." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21104.
Testo completoAbstract (sommario):
In spite of the large number of research works on carbon capture and sequestration (CCS), the migration and behaviour of CO2 in the subsurface (i. e. strata below the earth's surface) still needs further understanding and investigations with the aim of encouraging the governmental policy makers to adopt CCS technology as one of the most viable means to tackle the global warming threats. In this research work, a series of numerical simulations has been carried out using STOMP-CO2 simulation code to determine the flow behaviour and ultimate fate of the injected supercritical carbon dioxide (scCO2) into saline aquifers in medium terms of storage (i. e. few thousand years). The characteristics of the employed simulator, including the mathematical algorithm, governing equations, equations of states and phase equilibria calculations are explained in details.
28
Greskowiak, Janek Johannes. "Reactive transport processes in artificially recharged aquifers." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2006. http://dx.doi.org/10.18452/15582.
Testo completoAbstract (sommario):
In der vorliegenden Dissertation sollten die hydrogeochemischen Prozesse herausgearbeitet werden, die für die Wasserqualitätsänderung während eines ASR Experiments in Bolivar, Südaustralien und während der Versickerung in einem künstlichen Grundwasseranreicherungsbecken in Berlin von Bedeutung waren. Reaktive Stofftransportmodellierung des ASR Experiments in Bolivar, Südaustralien zeigte, dass die hydrochemischen Veränderungen in der direkten Umgebung des Injektionsbrunnens während der Speicherphase nur durch rapide Änderungen der Sauerstoff- und Nitrat reduzierenden Bakterienmasse erklärt werden können. Die hydrochemischen Veränderungen in größerer Distanz zum Injektionsbrunnen wurden überwiegend durch Ionenaustauschprozesse und Kalzitlösung verursacht. Geochemische und hydraulische Messungen unter einem Sickerbecken in Berlin zeigten, dass die beobachteten geochemischen Änderungen im Sickerwasser mit den periodisch auftretenden wassergesättigten/wasserungesättigen Bedingungen unter dem Becken einhergehen. Während der ungesättigten Periode wird Luft unter das Becken gezogen und führt zur plötzlichen Reoxidierung von bereits in der gesättigten Periode gebildeten Eisensulfiden und zur beschleunigten Mineralisation von sedimentärem organischem Kohlenstoff. Reaktive Stofftransportmodellierung auf größerer Skale zeigte, dass allein die saisonalen Temperaturunterschiede im Infiltrationswasser für die beobachtete zeitliche und räumliche Dynamik der Redoxzonen im weiteren Abstrom des Sickerbeckens verantwortlich sind. Das Abbauverhalten der Arzneimittelsubstanz Phenazon hängt ausschließlich von der Verfügbarkeit von gelöstem Sauerstoff und damit indirekt von der Wassertemperatur im Aquifer ab. In der vorliegenden Arbeit wird deutlich, dass ein adäquates Verständnis der wasserqualitätsändernden Prozesse in künstlichen Anreicherungsystemen nur dann erreicht werden kann wenn Strömung, Transport und reaktive Prozesse, im Feld als auch in der Modellierung, simultan betrachtet werden.<br>In this thesis, three major studies were carried out in order to understand the key factors controlling the water quality changes that occurred during a reclaimed water Aquifer Storage and Recovery (ASR) experiment at Bolivar, South Australia and during ponded infiltration in Berlin, Germany. Multi-component reactive transport modelling of the ASR experiment suggested that during the storage phase, dynamic changes in bacterial mass have a significant influence on the local geochemistry in the vicinity of the injection well. Water quality changes further away from the injection well were mainly driven by ion exchange and calcite dissolution. Geochemical and hydraulic measurements below an artificial recharge pond in Berlin, Germany, showed that the observed dynamic changes of the hydrochemistry within the seepage water are strongly linked to the periodic saturated/unsaturated hydraulic conditions below the pond. During unsaturated conditions, atmospheric oxygen penetrates from the pond margins to the centre below the pond, leading to (i) a sudden re-oxidation of sulphide minerals that have formed previously during saturated conditions and (ii) an enhanced mineralisation of sedimentary particulate organic carbon. Reactive transport modelling showed that at larger scale, seasonal temperature changes of the infiltration water are the key control for the observed temporal and spatial redox dynamics further downstream the recharge pond. Moreover, the degradation behaviour of the pharmaceutically residue phenazone solely depends on the availability of dissolved oxygen, and thus indirectly on the water temperature within the aquifer. Overall this thesis shows that a sound understanding and analysis of the key processes affecting the water quality changes during artificial recharge of groundwater could only be achieved when flow, transport and reactive processes are considered simultaneously, both in the field and during modelling.
29
Costall, Alexander Ross. "Hydro-geophysics in High-Quality Coastal Aquifers." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/82107.
Testo completoAbstract (sommario):
Electrical resistivity imaging (ERI) and groundwater solute transport modelling are developed for recovery of the hydrogeological architecture of coastal margins. ERI acquisition and processing parameters, along with the influence of hydraulic anisotropy and heterogeneity in karstic aquifers, are explored with examples selected along more than 100 km of coastline proximal to Perth Western Australia. The methods will contribute to accurate predictive groundwater modelling and sustainable management of high-quality coastal aquifers worldwide.
30
Batista, Filho Job Jesus. "A dinamica das aguas subterraneas no estuario do Rio Itanhaem, litoral sul do Estado de São Paulo." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287665.
Testo completoAbstract (sommario):
Orientador: Sueli Yoshinaga Pereira<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias<br>Made available in DSpace on 2018-08-07T09:50:38Z (GMT). No. of bitstreams: 1
BatistaFilho_JobJesus_M.pdf: 4294081 bytes, checksum: 28f487525ec460febd41ef1f05e36218 (MD5)
Previous issue date: 2006<br>Resumo: O presente trabalho estuda a interferência da maré nos aqüíferos costeiros, identificando alterações hidrodinâmicas e químicas em suas águas. A pesquisa foi realizada no estuário do rio Itanhaém, em duas localidades: no Sitio de Pesquisa, com 7 poços instalados, situados às margens do rio Acima, a 3,5 km do oceano, e no CePeRio - Centro de Pesquisa do Estuário do rio Itanhaém, com 1 poço, localizado a aproximadamente 1 km do oceano. O estudo foi executado em 3 etapas, buscando-se conhecer: a geologia dos aqüíferos, suas características físicas, químicas e geométricas. Para os aspectos hidrodinâmicos, englobaram-se o monitoramento do nível d'água superficial e subterrâneo e os cálculos dos parâmetros hidrodinâmicos, como: condutividade hidráulica, velocidade média linear e transmissividade. Para a hidroquímíca foram executadas coletas periódicas, a cada 45 minutos, análise dos parâmetros físicoquímicos: temperatura, pR, Eh, condutividade elétrica (CE), sólidos totais dissolvidos (STD) e salinidade. Foram coletadas amostras em cada etapa para se an$l.lisar a composição química das águas estudadas, quantificando-se os seguintes íons: Na, K, Si, Mg, Ca, Sr, Co, Mn, Cu, P, Zn, Pb, AI, Ba, Cd, N~, Fe, Cr, RC03-, F- ,cr ,Br- ,N ,S042- e PO/- . Os aqüíferos estudados, um livre e um confmado, são compostos de sedimentos arenosos de granulometria fina. O aqüífero confinado é composto de areia com lente df. conchas calcáreas, à profundidade de 20 metros. As águas superficiais monitoradas foram: as dos rios Acima, Itanhaém e do ribeirão Campininha, que margeiam as áreas estudadas. O aqüífero livre, formado por areia fina, e o rio Acima apresentam águas sulfatadas ou cloretadas sódicas. No aqüífero, o STD varia de 40 a 70 mg/L e o pH é ácido (entre 4 e 5); no rio, o STD varia de 90 a 5.900 mgIL e o pH de 6 a 7. O aqüífero confinado, com argila siltosa na sua base e conchas calcáreas na sua estrutura, apresenta águas bicarbonatadas sódicas, com STD variando de 310 a 2.000 mg/L e pH neutro (entre 6 e 7,5). O aqüífero livre, com condutividade hidráulica (10 de 10-4 m/s, possui influência direta das oscilações da maré, com uma variação de amplitude do nível d'água (NA) 5 vezes menor que a da maré; o aqüífero confinado, com K igual a 10-6 m/s, oscila 11 vezes menos que a maré, com maior variação de 1,4 m. A direção do fluxo hidrodinâmico no aqüífero livre é para NW e a do confinado é para WSW, ambos com descarga no rio Acima. O aqüífero livre tem velocidade média linear da ordem de 10-6 m/s e transmissividade de 205 m2/dia, e o confinado 10-8 m/s e 13 m2/dia. Apenas no aqüífero livre, durante subidas fortes da maré, o fluxo hidrodinâmico se altera, derivando para o norte. Hidroquimicamente, as águas subterrâneas variam pouco com a intrusão salina. No inverno, as águas superficiais são mais salobras que em outras épocas do ano, o que está associado a fatores como: a maré mafs alta e a pluviometria reduzida<br>Abstract: The present work studied the influence of the tide in the coastal aquifers by identifying hydrodynamic and chemical alterations in the aquifiers. The research was carried out in the Itanhaém river estuary in two localities: in the Sitio de Pesquisa with 7 installed wells situated on the banks of the Acima river, 3,5 km from the ocean, and in the CePeRio - Center of Research ofthe ltanhaém river estuary with 1 well located approximately 1 km from the oceano The study was executed in 3 stages that studied the geologic formations of the aquifers and their physical, chemical and geometric characteristics. The hydrodynamic aspects were studied by monitoring of the superficial and underground water leveI, and hydrodynamic parameters such as hydraulical condutivity, linear average velocity and transmissivity were determined. The hydrochemical part of the research was executed with periodic collections of samples every 45 minutes and analyzed for the physical chemical parameters of temperature, pH, Eh, electric condutivity (EC), total dissolved solids (TDS) and salinity. AIso, samples were collected for each stage of the study and analyzed for the following íons: Na, K; Si, Mg, Ca, Sr, Co, Mo, Cu, P, Zn, Pb, AI, Ba, Cd, Ni, Fe, Cr, HC03-, F- ,cr ,Br- ,N ,sot e P043- . The aquifers, one phreatic and one confined,rare both composites of fine sand sediments. The confined one is a sand layer with presences of limestone shells and has a depth of 20 meters. The surface waters were also monitored in the Acima river, the Campininha brook and the Itanhaém river, which border the study area. The phreatic aquifer is formed of fine sand and with the Acima river has sodium sulfated or chlorinated and sodium bicarbonated water. In the aquifer, the TDS varied between 40 and 70 mg/L and pH was acidic (between 4 and 5). In the river, the TDS varied from 90 to 5,900 mg/L and pH was 6 to 7. The confined aquifer, with silt clay and limestone shell, had sodic bicarbonated waters with the TDS varying from 310 to 2,000 mg/L and pH neutral (between 6 and 7,5). The phreatic aquifer with hydraulical condutivity (K) 10-4 m/s had a direct influence from tidal oscillations with a variation of phreatic leveI amplitude 5 times lesser than that of the tide. The confined aquifer with K of 10-6 m/s, oscillated 11 times less than the tide for variations of larger than 1,4 m. The hydrodynamic flow direction for the phreatic aquifer was to NW and for the confined one it was for WSW, both with discharges in the Acima river. The phreatic aquifer had linear average velocity of the order of 10-6 m/s with a transmissivity of 205 m2/day and for the confined the values were 10-8 m/s and 13 m2/day. In the phreatic aquifer the hydrodynamic flow was modified during strong flows of the tide northward. Hydrochemically, the groundwater varied slightly with saline intrusion. In the winter, the river had the biggest ionic concentrations in comparison to the other seasons which were associated with factors such as the tide being higher in and the low precipitation at that time of year<br>Mestrado<br>Geologia e Recursos Naturais<br>Mestre em Geociências
31
Walter, Martin. "Explaining the emergence of transboundary groundwater management : the cases of Guaraní aquifer system, the Hueco and Mesilla Bolsón aquifers, and the Génévois aquifer." Paris, Institut d'études politiques, 2012. https://spire.sciencespo.fr/notice/2441/5rkqqmvrn4tl22s9mc41lidr0.
Testo completoAbstract (sommario):
Malgré la diversité de contributions concernant l’analyse des ressources hydriques et la multiplicité d’expériences de gestion de ces ressources, les eaux souterraines n’ont été incorporées dans l’agenda politique des relations internationales que très récemment. En ligne avec les recherches dédiées à la compréhension des défis associés à la gestion des eaux et à l’émergence des mécanismes de régulation pour la gestion environnementale, ce travail examine la création de mécanismes pour la gestion conjointe des eaux souterraines transfrontalières. Pour ce faire, il essaye de répondre une question relativement simple : quels facteurs ont été déterminants pour l’émergence et la mise en œuvre de mécanismes de gestion conjointe des eaux souterraines ? A partir d’une révision de la littérature disponible et de l’étude comparée de trois cas, cette recherche a trouvé que dans la reconnaissance et la formulation des problèmes des eaux souterraines interagissent toujours trois types de facteur : les usages de l’eau souterraine, les caractéristiques hydrogéologiques des aquifères et la valeur sociale attribuée à la disponibilité éco-systémique des ressources. Cette recherche a trouvé d’ailleurs que la simple existence de problèmes associés à la disponibilité des ressources ne pousse pas automatiquement à la création des mécanismes de gestion. Ces derniers, qui peuvent être coordonnés ou unilatéraux, découlent d’une articulation d’éléments systémiques et socio-institutionnels<br>Despite the diversity of the contributions to the analysis of water resources and the myriad of water management experiences, transboundary groundwaters have only relatively recently entered the international political agenda. In line with research dedicated to understanding the challenges associated with the management of water resources and the creation of environmental regulatory frameworks, this dissertation examines the emergence of mechanisms for the management of transboundary groundwater resources. In doing so, it makes a seemingly straightforward inquiry. What are the factors that trigger the emergence and implementation of groundwater management mechanisms? Drawing from the review of the literature and the comparative analysis of three cases of transboundary groundwater management, this research finds that the recognition of groundwater problems is determined by the interplay of three factors: the uses of groundwater, the features of the hydrogeological resources, and the social valuation of the eco-system services provided by the resources. In addition, it suggests that groundwater problems are not sufficient to explain the nature of the mechanisms employed for the management of the resources. It argues that management mechanisms, which may be coordinated or unilateral, result from the configuration of both systemic and socio-institutional factors
32
Damico, James Ralph. "Geostatistical Characterization of Heterogeneity in the Aberjona River Aquifer, Woburn, Massachusetts." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1166544810.
Testo completo
33
McHugh, Kathleen M. "Western water law and the stream-aquifer system and how models are used to determine permitting and compliance of rules governing ground and surface water interaction." Thesis, The University of Arizona, 2003. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0234_sip1_w.pdf&type=application/pdf.
Testo completo
34
Murray, Eric Charles. "Guidelines for assessing single borehole yields in secondary aquifers." Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1005512.
Testo completoAbstract (sommario):
The motivation for this research project arose from the realisation that many South African rural water supply schemes fail due to the over abstraction of groundwater from single boreholes. The main reason for this mis-management of groundwater is a result of inappropriate borehole yield recommendation methods. This research project set out to review existing borehole yield assessment methods and establish new methods which take the shortcomings of existing methods into account. The study is concerned with borehole yield assessment methods applicable to secondary aquifers, since these aquifers are by far the most common in South Africa. The yield assessment methods have been grouped into those that are based on aquifer yield analyses, and on the analysis of single borehole test pump data. In order to assess which methods give suitable yield recommendations, it was necessary to compare the yields obtained using the various methods, with established yields from production boreholes. The focus of the aquifer yield component of the study, was to develop a method for estimating the proportion of recharge that can be abstracted from a single borehole located in a relatively small aquifer. The method was developed by computer simulations of aquifers with different hydraulic properties, and by establishing a formula which describes the relationship between recharge and the abstractable proportion of recharge. Under specific hydrogeological conditions, the recharge based method proved to be reliable in relation to established yields from production boreholes. Of the borehole yield assessment methods based on the analysis of test pump data, none of the existing methods proved to be reliable. However, the yields obtained using the two newly developed methods compared favourably to the established yield of existing production boreholes. Both of these methods are based on the application of the Cooper-Jacob approximation of the Theis equation. This study reviews existing methods and presents newly developed methods for recommending borehole abstraction rates in secondary aquifers. While existing borehole yield assessment methods were found to be unreliable, some of the newly developed methods, if correctly applied, give acceptable yield recommendations.
35
Biswas, Ashis. "Arsenic Geochemistry in the Alluvial Aquifers of West Bengal, India : Implications for targeting safe aquifers for sustainable drinking water supply." Doctoral thesis, KTH, Mark- och vattenteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128938.
Testo completoAbstract (sommario):
The natural occurrences of high (>10 μg/L) dissolved arsenic (As) in groundwater of Bengal Basin has put millions of people under the threat of chronic As exposure through drinking water. Present study has examined the processes that regulate As mobilization and its distribution in shallow aquifers and the potentiality of finding safe aquifers within shallow depth (<50 m) for drinking water supply. The results indicate that in terms of aquifer sediment colors and water quality two types of aquifer namely brown sand aquifer (BSA) and grey sand aquifer (GSA) can be distinguished within the depth, accessible by low-cost drilling. The redox condition in the BSA is delineated to be Mn oxyhydroxides reducing, not sufficiently lowered for As mobilization resulting in high Mn and low Fe and As in groundwater. While in GSA, currently the reductive dissolution of Fe oxyhydroxides is the prevailing redox process causing As mobilization into groundwater of this aquifer type. It is revealed that the vertical distribution of As and other aqueous redox parameters is related to the redox zonation within aquifer. The decoupling of As and Fe release into groundwater is evident in the shallowest part of aquifer because of Fe enrichment by weathering of silicate minerals especially of biotite, the precipitation of secondary mineral phases like siderite and vivianite and incomplete reduction of Fe oxyhydroxides. It is characterized that the seasonal variations of As and other aqueous solutes are limited within the upper portion of aquifer only (<30 m bgl) and can be related to seasonal cycling of redox status, aggregation and dispersion of As scavenging colloids, local groundwater abstraction and monsoonal recharge. The results of surface complexation modeling indicate that PO43- is the major competitor of As(III) and As(V) adsorption onto Fe oxyhydroxides. This study concludes that the reductive dissolution of Fe oxyhydroxides followed by competitive sorption reactions with the aquifer sediment is the process conducive for As enrichment in groundwater of Bengal Basin. Present study advocates that despite low concentration of As in groundwater, a rigorous assessment of attendant health risk for Mn is necessary prior to considering mass scale exploitation of the BSA for sustainable drinking water supply. This study also validates that TW platform colors can be used as a rapid screening tool for As and Mn in drinking water wells to prioritize As mitigation management.<br><p>QC 20130919</p><br>EURINDIA 2009-1665
36
Matengu, Brian Munihango. "Groundwater assessment and sustainable management of the coastal alluvial aquifers in Namib Desert, Namibia: Omdel Aquifer as case study." University of Western Cape, 2020. http://hdl.handle.net/11394/7852.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhD<br>The study addressed the groundwater assessment and sustainable management of the coastal alluvial aquifers in Namib Desert, the Omaruru River Delta Aquifer (Omdel Aquifer) was used as a case study. Sustainable utilization of groundwater in parts of hyper-arid Sub-Saharan Africa, like the Namib Desert, is always a challenge due to lack of resources and data. Understanding of hydrogeological characteristics of the Omaruru Delta Aquifer System is a pre-requisite for the management of groundwater supply in the Central Namib area (Namib Desert). For the Omdel Aquifer in the Omaruru catchment, Namibia, issues to investigate include the lack of information on the geology and hydrogeological setting, the hydraulic properties and geometry of the aquifer at the inflow and outflow sections, groundwater recharge conditions upstream of the aquifer, and the impact of artificial recharge.
37
Demirbas, Korkut. "Optimal Management Of Coastal Aquifers Using Heuristic Algorithms." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613135/index.pdf.
Testo completoAbstract (sommario):
Excessive pumping in coastal aquifers results in seawater intrusion where optimal and efficient planning is essential. In this study, numerical solution of single potential solution by Strack is combined with genetic algorithm (GA) to find the maximum extraction amount in a coastal aquifer. Seawater intrusion is tracked with the potential value at the extraction well locations. A code is developed by combining GA and a subroutine repeatedly calling MODFLOW as a numerical solver to calculate the potential distribution for different configurations of solution (trial solutions). Potential distributions are used to evaluate the fitness values for GA. The developed model is applied to a previous work by Mantoglou. Another heuristic method, simulated annealing (SA) is utilized to compare the results of GA. Different seawater prevention methods (i.e. injection wells, canals) and decision variables related to those methods (i.e. location of the injection wells or canals) are added to model to further prevent the seawater intrusion and improve the coastal aquifer benefit. A method called &ldquo<br>Alternating Constraints Method&rdquo<br>is introduced to improve the solution for the cases with variable location. The results show that both proposed method and the regular solution with GA or SA prove to be successful methods for the optimal management of coastal aquifers.
38
Strehlow, Karen. "Aquifers in volcanic regions : monitoring capabilities and hazards." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720850.
Testo completo
39
MacMinn, Christopher William. "Migration and trapping of CO₂ in saline aquifers." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70422.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 123-128).<br>Mitigation of climate change requires a reduction in atmospheric carbon dioxide (C0 2) emissions. One promising tool for achieving this is the large-scale injection of CO2 into deep saline aquifers. After injection, upward leakage of the CO2 is a primary concern because it will be buoyant relative to the ambient groundwater and, as a result, will rise toward the top of the aquifer and may migrate laterally away from the injection site. To assess leakage risks and estimate aquifer capacity requires an accurate understanding of the subsurface migration and trapping of the buoyant C0 2; however, many aspects of the fundamental physics of CO 2 migration and trapping are not fully understood, and traditional reservoir-simulation tools are currently unable to resolve the impact of small-scale trapping processes on these large-scale fluid flows. In this Thesis, we develop a simple gravity-current model for the post-injection migration and trapping of a buoyant plume of CO2 in a confined, sloping saline aquifer with a natural groundwater through-flow. We include both residual trapping, where small blobs of CO 2 are immobilized by capillarity along the trailing edge of the plume, and solubility trapping driven by convective dissolution, where CO2 dissolves into the groundwater and sinks downward in dense, C0 2-rich fingers. Although idealized, this model offers physical insight into the processes controlling CO 2 migration and trapping, and is not limited by computational resources. We derive solutions to the model in several limiting cases, and we use these solutions to study the interplay between slope and groundwater flow, and the competition between residual and solubility trapping. We validate the model against laboratory analog experiments, finding good agreement between the experimental results and the predictions of the model. We then use the experiments to study the small-scale dynamics of the convective-dissolution instability: the formation, descent, and coarsening of the fingers. Finally, we use the model to study the migration and trapping of CO 2 in the Mt. Simon Sandstone, a large deep saline aquifer in the Midwestern United States that is considered to be a promising candidate for geological CO 2 storage.<br>by Christopher William MacMinn.<br>Ph.D.
40
Karam, Hanan Nadim. "Seawater circulation in coastal aquifers : processes and impacts." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78141.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 150-154).<br>This thesis explores the subterranean domain of chemical cycling in coastal oceans abutting permeable aquifers, where transport through sediments is dominated by advection, rather than diffusion. We investigate the mechanisms by which seawater circulates in the subsurface over a range of spatio-temporal scales, and the chemical reactions to which this circulation is coupled. Seawater circulation in coastal aquifers is driven by salinity variations in pore water as well as by the effects of temporally variable forcings at both terrestrial (variable recharge) and marine (tides, waves and secular sea level changes) boundaries. It is coupled to the transport of biogeochemically reactive species through the subsurface and their exchange between the sediments and the water column. Our understanding of how different forcing mechanisms interact to determine spatial scales and residence times of subsurface seawater circulation, as well as temporal patterns and rates of aquifer-surface water exchange has thus far been very limited. The large range in the spatial and temporal scales of flow dynamics associated with different forcings challenges our ability to comprehensively observe and monitor their associated seafloor fluxes. In this thesis, we present a novel, homemade instrument for high-resolution, long-term monitoring of seafloor fluxes, designed to address this challenge. Two-year deployments of several such instruments at Waquoit Bay, MA, produced the most comprehensive datasets on seafloor fluxes available to date, multiplying the length of published time series by tenfold. The length and integrity of the datasets permit the use of spectral analysis to investigate distinct frequency components of seafloor fluxes and quantify their relationship to various forcing mechanisms. The temporal and areal coverage of the datasets allow us to distinguish the contributions of different forcings to observed fluxes, as a function of distance from shore and season. Furthermore, we discuss new insight derived from the data into the physics underlying observed seafloor fluxes and their associated subsurface circulation processes. Additionally, we describe results from an independent but related project to characterize chemical dynamics associated with seawater circulation in beach sand at Waquoit Bay. We present evidence for the important contribution of this circulation to the nitrogen budget of the Bay.<br>by Hanan Nadim Karam.<br>Ph.D.
41
Watson, Francesca Elizabeth. "Numerical simulation of CO2 storage in saline aquifers." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11189/.
Testo completoAbstract (sommario):
CO2 capture and storage (CCS) has been proposed as a climate change mitigation strategy. The basic principle is to prevent CO2 which would normally be emitted from large point sources, such as power stations, from entering the atmosphere. This is achieved by capturing the CO2 at source and storing it in a location where it will be trapped and unable to enter the atmosphere. This work looks specifically at geological storage of CO2 in deep saline formations. Dynamic simulations can be used to investigate the fundamental physical and chemical processes which occur when CO2 is injected into geological formations. They can also be used to determine the suitability of a particular site for CO2 storage. The scale of the processes being simulated is important when building a dynamic model. Here dynamic simulations have been used to explore three different aspects of geological CO2 storage in deep saline formations. The first model investigates large scale CO2 migration and pressure build up at a potential CCS site. The second model concentrates on the small scale processes of CO2 dissolution and convection. The third model attempts to accurately model both the large scale processes of CO2 injection and migration and the small scale processes of CO2 dissolution and convection. Dynamic simulations have been used to model storage capacity, CO2 migration and pressure buildup at a potential CO2 storage site in the UK North Sea. There are large uncertainties in the input data so various models have been run using a range of parameters. The primary control on pressure buildup at the site is the permeability of the unit directly beneath it. The plume diameter is primarily controlled by the porosity and permeability of the reservoir unit. Despite uncertainties in the input data, the use of a full three-dimensional (3D) numerical simulation has been extremely useful for identifying and prioritizing factors that need further investigation. Dissolution of CO2 into existing formation waters (brine) leads to an increase in brine density proportional to the amount of dissolved CO2. This can lead to gravitational instabilities and the formation of convection currents. Convection currents, in turn, will increase CO2 dissolution rates by removing CO2 saturated brine from the CO2-brine interface. The dissolution and subsequent convection of CO2 which has leaked through a fracture is investigated using dynamic simulations. The instigation of convection currents due to flow through a fracture increases dissolution rates. Comparison of our results with fracture flow rates shows that for typical fracture apertures dissolution from a fracture is small relative to the amount of CO2 flowing through the fracture. Two phase flow effects and the currents caused by an advancing plume of injected CO2 can affect patterns of CO2 dissolution and convection within a reservoir. Most existing models of CO2 dissolution and convection use a static boundary layer or do not involve two phase flow effects. A radial, two phase, two component model has been built to model the injection process along with convection enhanced dissolution. The model performs well compared to analytical solutions in terms of the large scale processes of CO2 migration and pressure buildup but modelled convection is highly dependent on grid resolution. Numerical instabilities are also present. Further work is needed to increase the accuracy of the model in order to allow higher resolution modelling to be carried out and modelling of the smaller scale processes to be improved.
42
Mary, Makokha. "Seawater intrusion and contaminant transport in coastal aquifers." Kyoto University, 2008. http://hdl.handle.net/2433/136601.
Testo completoAbstract (sommario):
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第13874号<br>農博第1689号<br>新制||農||953(附属図書館)<br>学位論文||H20||N4341(農学部図書室)<br>UT51-2008-C790<br>京都大学大学院農学研究科地域環境科学専攻<br>(主査)准教授 小林 晃, 教授 河地 利彦, 教授 川島茂人<br>学位規則第4条第1項該当
43
Mao, Deqiang. "Stochastic Analysis of Pumping Tests in Unconfined Aquifers." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/222873.
Testo completoAbstract (sommario):
The S shaped log log drawdown time curve typical of pumping tests in unconfined aquifers is reinvestigated via numerical experiments. We examine the temporal and spatial evolution of the rate of change in storage in an unconfined aquifer during pumping. This evolution is related to the transition of water release mechanisms from the expansion of water and compaction of the porous medium to the drainage of water from the unsaturated zone above the initial water table and initially saturated pores as the water table falls during the pumping of the aquifer. We conclude that the transition of the water release mechanisms and vertical flow are the cause of the S shaped drawdown time. Cross-correlation analysis is then employed to examine the relationship between hydraulic properties of an unconfined aquifer and pressure observations. The analysis reveals that head observed in the saturated zone at late times along a streamline is positively correlated with the conductivity (K(s)) of the region upstream of the observation location, and negatively correlated with the K(s) of the region downstream of the observation location along the same streamline. Besides, head observations in the saturated zone at the early time are positively correlated with specific storage (S(s)) in a narrow region between the observation and pumping locations. At intermediate and late times, the head positively correlates with the heterogeneity of α (pore-size distribution parameter) in a thin disk-shaped unsaturated region above the pumping and observation locations. Saturated water content θ(s) in the vadose zone directly above the pumping and monitoring locations is found positively correlated with the head observations during the intermediate times and late times.In the end, a stochastic inverse estimation is conducted to jointly interpret a sequential pumping test in a three dimensional unconfined aquifer. K(s), S(s), θ(s) and α are estimated at the same time. The estimated results capture the pattern of the heterogeneous parameters as well as the details with a smooth distribution. The estimated heterogeneous parameter fields produce better head predictions than the traditional homogeneous method.
44
Field, Graeme. "Particle Filters for State Estimation of Confined Aquifers." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/804.
Testo completoAbstract (sommario):
Mathematical models are used in engineering and the sciences to estimate properties of systems of interest, increasing our understanding of the surrounding world and driving technological innovation. Unfortunately, as the systems of interest grow in complexity, so to do the models necessary to accurately describe them. Analytic solutions for problems with such models are provably intractable, motivating the use of approximate yet still accurate estimation techniques. Particle filtering methods have emerged as a popular tool in the presence of such models, spreading from its origins in signal processing to a diverse set of fields throughout engineering and the sciences including medical research, economics, robotics, and geophysics.
In groundwater hydrology, a key component of aquifer assessment is the determination of the properties which permit water resource managers to estimate aquifer drawdown and safe yield. Presented is a particle filtering approach to estimate aquifer properties from transient data sets, leveraging recently published analytically-derived models for confined aquifers. The approach is examined experimentally through validation against three common aquifer testing problems: determination of (i) transmissivity and storage coefficient from non-leaky confined aquifer performance tests, (ii) transmissivity, storage coefficient, and vertical hydraulic conductivity of a confining unit from leaky confined aquifer performance tests, and (iii) transmissivity and storage coefficient from non-leaky confined aquifer performance tests with noisy data and boundary effects. The first two problems are well-addressed and the presented approach compares favorably to the results obtained from other published methods. The third problem, which the presented method can tackle more naturally than previously-published methods, underscores the flexibility of particle filtering and, in turn, the promise such methods offer for a myriad of other geoscience problems
45
Nguyen, Bach Thao. "Coupling geophysical and isotopic approaches to better simulate saltwater intrusion into coastal aquifers : a case study in the Crau aquifer." Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0052/document.
Testo completoAbstract (sommario):
La recherche a porté sur les contraintes reliées à la modélisation des écoulements des eaux souterraines en aquifère côtier. Dans ces aquifères, la présence concomitante d’eaux douces et d’eaux salées modifient les patrons d’écoulement classiquement représentés par l’équation de Darcy. L’influence de la salinité de l’eau sur ses propriétés (densité) et sur la perméabilité du milieu complexifie la représentation mathématique des équations d’écoulement et la résolution des systèmes d’équations. Par ailleurs, l’influence des hétérogénéités du milieu rend plus difficile et hasardeux le paramétrage des modèles et leur calibration. Pour ce faire, nous avons proposé d’utiliser les résultats d’investigations géophysiques et isotopiques des eaux. Une meilleure description du milieu souterrain et l’imagerie de l’interface eau douce/eau salée peut en effet aider à un meilleur paramétrage et à une validation accrue de la simulation des écoulements des nappes côtières. Les mesures géochimiques telles celles des isotopes du radium ont aidé à la validation des flux et concentrations simulés. Notre approche a été appliquée sur la partie aval de la nappe de la Crau. La comparaison des résultats simulés par le modèle aux données de terrain résultant des suivis réalisés ont montré l’intérêt et l’applicabilité et la validation de notre approche méthodologique<br>The research has focused on the constraints related to the modeling of groundwater in coastal aquifer. In these aquifers, the concomitant presence of freshwater and saltwater alters the flow patterns typically represented by the Darcy equation. The influence of salinity on density and permeability complex the mathematical resolution of flow equations. Moreover, the influence of heterogeneities of aquifer makes it more difficult and risky the model parameterization and its calibration. We propose to use fort that the results of both geophysical and isotopic investigations. Thus, we hypothesize that the description of the subsurface and the imaging of the freshwater/saltwater can help to setup and validate the simulation of groundwater in coastal aquifers. Also we have shown that geochemical measurements such as radon may help to validate the simulated flow. Our approach was applied on the downstream part of the Crau aquifer. The comparison of simulated results to data resulting from monitoring has shown the usefulness and applicability of our approach
46
Zhang, Zhihui. "Quantitative characterization of aquifer heterogeneity and simulation of contaminant transport in a solvent-contaminated aquifer." Diss., The University of Arizona, 1999. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1999_148_sip1_w.pdf&type=application/pdf.
Testo completo
47
Lin, Lixiang. "Hydraulic Properties of the Table Mountain Group (TMG) Aquifers." Thesis, University of Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5115_1262826953.
Testo completoAbstract (sommario):
<p><font face="TimesNewRoman">
<p align="left">Research findings in current study provide a new insight into the fractured rock aquifers in the TMG area. Some of the results will have wide implications on the groundwater management and forms a solid basis the further study of the TMG aquifers.</p>
</font></p>
48
Gervais, Francoise. "Fate and Transport of Naphthenic Acids in Glacial Aquifers." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/1229.
Testo completoAbstract (sommario):
Naphthenic acids (NAs) are carboxylated alkanes and cycloalkanes concentrated in wastewater during oil sands processing. The general chemical formula is C{n}H{n+Z}O{2}, where n represents the number of carbon atoms and Z specifies a homologous family with 0-6 rings (Z=0 to Z=-12). The wastewater is acutely toxic to surface water organisms and is stored in tailings ponds with over 230 million m³ of fines tailings and free water. The purpose of this thesis was to provide a preliminary evaluation of the potential attenuation of NAs during groundwater flow from the ponds. Laboratory studies were conducted to evaluate possible attenuation mechanisms. Aerobes from aquifer material degraded 60% of the NAs over 20 weeks in laboratory microcosms. The greatest decrease occurred in the low molecular weight bicyclic homologues with 12 to 16 carbons. The microbial activity confirms that aerobic naphthenate-degrading bacteria occur naturally in the glacial aquifer near Suncor's Pond 2/3. These results support the hypothesis that limited aerobic biodegradation of the smaller components of NAs could occur relatively rapidly under field conditions. There was no measurable decrease in NA concentration over six months in anaerobic microcosms, although microbial activity did lead to sulfate-reducing and methanogenic conditions. The theoretical retardation in glacio-fluvial sands was calculated using soil-water partitioning coefficients (K{d}) determined by batch equilibration experiments using a mixture of naturally occurring naphthenic acids as well as the nine surrogates. The retardation (porosity of 0. 3, bulk density of 1. 5 g/mL) ranged from 1. 2 to 2. 6. However, no measurable sorption was seen at the field sites. Detailed characterization allows us to examine how the proportions of homologue, or groups of molecules with the same molecular weight and number of cycloalkane rings, vary. Aerobic biodegradation favoured removal of low molecular weight NAs. A 15% mass loss attributed to sorption caused no changes in the 3D signature. Thus, changes in NA "signature" in groundwater systems were then attributed to aerobic biodegradation. Three plumes were examined for evidence of attenuation of NAs via biodegradation. First, the individual samples were classified as background, possibly process-affected or process-affected using a combination of Piper diagrams, the stable isotopes oxygen-18 and deuterium, dissolved chloride and sodium, as well as the total naphthenic acids concentration. Second, in order to estimate attenuation due to dispersive dilution, a linear correlation line was drawn between various conservative tracers and the naphthenic acids concentration. This allowed the identification of certain samples as possibly having a lower concentration of NAs than could be expected from simple dispersive dilution. Third, the 3D signature of certain samples were examined for the presence of the aerobic biodegradation 3D signature. One site showed good evidence for aerobic biodegradation of naphthenic acids. A second site showed some evidence for biodegradation under methanogenic conditions but the evidence was not definitive. The evidence at the third site was contradictory and no conclusions could be drawn from it. This research suggests some attenuation of NAs by biodegradation may be possible during groundwater flow.
49
Kolbe, Tamara. "Temporal and spatial structures of denitrification in crystalline aquifers." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S048/document.
Testo completoAbstract (sommario):
La contamination des aquifères de proche subsurface par les intrants d'origine agricole (nitrates) est un problème mondial.L'utilisation excessive d'engrais depuis plusieurs décennies a impacté la qualité des masses d'eau souterraines et soulève des enjeux pour la santé humaine comme pour celle des écosystèmes. Les nitrates dans les aquifères peuvent être réduits en diazote gazeux par l'activité microbienne hétérotrophique (la biomasse microbienne obtenant l'énergie nécessaire à ce processus via le carbone organique issu de la surface) et/ou par l'activité autotrophique (la biomasse microbienne obtenant cette fois ci son énergie depuis une source proche, lithologique). Les taux de dénitrification sont très variables spatialement, et sont régulés par l'interaction entre la structure des flux d'eau souterrains avec l'activité biogéochimique. Localiser l'activité biogéochimique dans les aquifères est difficilement réalisable à l'échelle des bassins versants, mais paraît crucial pour la gestion des masses d'eau souterraines. Bien que les processus de l'activité microbienne ne puissent pas être entièrement résolus à l'échelle locale, ce manuscrit de thèse propose une caractérisation des taux de dénitrification à l'échelle du bassin versant, basée sur l'analyse de données et sur une approche de modélisation intégrée. Cette thèse propose d'utiliser de manière extensive des traceurs conservatifs et réactifs associés aux flux d'eau souterraine et des modèles de transport afin d'identifier les contrôles géologiques et biogéochimiques sur les capacités de dénitrification dans les aquifères. Cette méthodologie a été appliquée à un aquifère libre cristallin de 76 km² situé en Bretagne. A partir des concentrations en CFC-12, O2, NO3- et N2 dissous mesurées dans 16 puits, il a été possible de reconstituer les chroniques d'apports de nitrate dans la zone saturée et de définir les variations spatio-temporelles de la dénitrification. Il est prouvé ici que la dénitrification est en premier lieu contrôlée par la position des donneurs d'électron. Ce travail propose un cadre d'interprétation général sur la base de l'utilisation combinée et complémentaire des traceurs et sur la modélisation semi-explicite pour estimer à l'échelle régionale les capacités de dénitrification et les stocks de nitrates dans les aquifères<br>Unconfined shallow aquifers in agricultural areas are contaminated by nitrates worldwide. Excessive fertilization over the last decades has affected groundwater quality as well as human and ecosystem wellbeing. Nitrate in groundwater can be microbially reduced to dinitrogen gas by heterotrophic (microbes obtaining their energy from surface-derived organic carbon) and autotrophic (microbes obtaining their energy from a lithological source) processes. However, denitrification rates are highly spatially variable, following involved interactions between groundwater flow structures and biogeochemical activity. The location of biogeochemical activity in the aquifer is difficult to access at the catchment scale, but of vast importance to gain predictive capabilities for groundwater management. Even though microbial processes cannot be resolved at the local scale, this dissertation proposes a catchment scale characterization of denitrification rates based on an integrated model- and data-driven approach. The dissertation proposes an extensive use of conservative and reactive tracers combined with groundwater flow and transport models to identify the geological and biogeochemical controls on aquifer denitrification capacities. The methodology is applied to a crystalline unconfined aquifer of 76 km2 size in Brittany, France. Based on CFC-12, O2, NO3-, and dissolved N2 concentrations measured in 16 wells, it is possible to reconstruct historical nitrate inputs to the saturated zone and to define spatiotemporal denitrification activity. It is shown that denitrification is primarily controlled by the location of electron donors. The dissertation proposes a general interpretation framework based on tracer information combined with complementary semi-explicit lumped parameter models to assess regional denitrification capacities and nitrate legacy
50
Jose, Surabhin Chackiath. "Experimental investigations on longitudinal dispersive mixing in heterogeneous aquifers." Stuttgart Inst. für Wasserbau, 2004. http://deposit.d-nb.de/cgi-bin/dokserv?idn=975731157.
Testo completo