Dissertations / Theses: 'Groundwater tracers Groundwater Aquifers' – Grafiati (2024)

Abstract:

Thesis (M.S.)--University of California, San Diego, 2009.
Title from first page of PDF file (viewed July 2, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 75-78).

Abstract:

The contamination of groundwater by naturally occurring arsenic (As) in South and South East Asia has resulted in the exposure of an estimated 100 million people to hazardously high concentrations of this known carcinogen. Whilst the biogeochemical processes and mechanisms responsible for releasing As to groundwater are now understood, the fundamental controls on these processes have yet to be resolved. In particular, the role of different sources of organic matter (OM) in controlling the rate and extent of As release and how the contributions of these different sources may be influenced by groundwater abstraction practices, remains poorly constrained. Indeed, it is the absence of such key information which currently limits our capability to accurately predict both where and when As will be released in to the groundwaters of this region. Elucidation of the controls of these processes is therefore of vital importance for aiding policy makers and those responsible for mitigating the effects of the current catastrophe in providing a sustainable source of As free drinking water to millions of people in the countries impacted.We conducted investigations at two known As hotspots in West Bengal and Cambodia to assess the impact of groundwater abstraction practices on the composition of dissolved organic carbon (DOC) and As release. The radiocarbon age of DOC at both sites requires a contribution of young surface or near surface derived OM as well as contributions from older, sedimentary sourced OM. Mixing profiles at the Cambodian study site suggest this subsurface OM end member to have an age of between 1000 and 6000 years. A clear association is observed between high As concentrations in shallow groundwaters containing young DOC, with lower concentrations of As being associated with older DOC in deeper groundwater. This provides the first direct confirmation that younger, more labile sources of OM are able to support more extensive As release in these aquifers. Perhaps more importantly, it is shown that modern surface derived OM can be drawn into As contaminated groundwaters. Comparison of the residence times of groundwaters suggests that the extent of ground-surface water interaction is more extensive and extends to greater depths in aquifers that have been subjected to massive groundwater abstraction. Indeed, it is suggested thatgroundwater abstraction practices may be responsible for driving the downward transport of As contaminated shallow groundwater into deeper groundwater, and may potentially be driving changes in the composition of organic carbon within the groundwater. This could give rise to a more reactive, bioavailable organic carbon pool which has the potential to further influence As mobility in these groundwaters. The potential for secular changes in the groundwater As hazard in these regions must therefore consider the impact that changes in the DOC composition may have on the biogeochemical evolution of these aquifers.

Abstract:

>Magister Scientiae - MSc
Extreme weather events in combination with geographical changes in groundwaterutilization, groundwater availability, aquifer recharge, and ultimately changes in the quality of water resources, are expected in the future. As a consequence of changing weather patterns and urbanization the demand for groundwater is likely to increase in certain areas. We know that most waterborne pathogenic health epidemics are associated with contamination of farm water and wastewater. There is however limited understanding of the nature and extent of chemical, physical and biological processes that control the fate and transport of the microorganismsin primary and secondary aquifers. In this thesis, transport results are reported, where E. coli and PDR1 were selected as the biological tracers transported through a primary aquifer at the University of the Western Cape. In conjunction with the microbes salt and Rhodamine (chemical tracers) were injected to compare their fate and transport mechanism in the primary aquifer medium. A series of controlled Darcy experiments under laboratory and field conditions were conducted. Each provided a different data and information. The results from laboratory studies were used to improve design of the field studies. In both cases, the data collected provided information on fate and transport of microbes in groundwater. The field design phase of the experiment was an up-scaling of the laboratory phase of this project. The amount of chemical tracers injected into the aquifer was increased in proportion to the size of the research site. Tracer tests using chemical and microbial tracers were conducted simultaneously. Results of laboratory tests demonstrate a 5 times slower transport of microbes, compared totests with salts during the laboratory phase. The salts at field scale show a breakthrough occurring after 2 days whereas the microbes –did not break through during the 28 days of the observation period. A new borehole was drilled closer to the pumping borehole to eliminate distance or travel time, but this had no effect on field results for the microbes.
National Research Foundation

Abstract:

Abstract Water resources management calls for methods to simultaneously manage groundwater (GW) and surface water (SW) systems. These have traditionally been considered separate units of the hydrological cycle, which has led to oversimplification of exchange processes at the GW-SW interface. This thesis studied GW hydrology and the previously unrecognised connection of the Rokua esker aquifer with lakes and streams in the area, with the aim of identifying reasons for lake water level variability and eutrophication in the Rokua esker. GW-SW interactions in the aquifer were first studied with field methods. Seepage meter measurements showed substantial spatial variability in GW-lake interaction, whereas transient variability was more modest, although present and related to the surrounding aquifer. Environmental tracers suggested that water exchange occurs in all lakes in the area, but is of varying magnitude in different lakes. Finally, GW-SW interaction was studied in peatland catchments, where drainage channels in the peat soil presumably increased groundwater outflow from the aquifer. Amount and rate of GW recharge were then estimated with a simulation approach developed explicitly to account for the physical characteristics of the Rokua esker aquifer. This produced a spatially and temporally distributed recharge estimate, which was validated by independent field techniques. The results highlighted the impact of canopy characteristics, and thereby forestry management, on GW recharge. The data collected and the new understanding of site hydrology obtained were refined into a fully integrated surface-subsurface flow model of the Rokua aquifer. Simulation results compared favourably to field observations of GW, lake levels and stream discharge. A major finding was of good agreement between simulated and observed GW inflow to lakes in terms of discharge locations and total influx. This thesis demonstrates the importance of using multiple methods to gain a comprehensive understanding of esker aquifer hydrology with interconnected lakes and streams. Importantly, site-specific information on the reasons for water table variability and the trophic status of Rokua lakes, which is causing local concern, is provided. As the main outcome, various field and modelling methods were tested, refined and shown to be suitable for integrated GW and SW resource management in esker aquifers
Tiivistelmä Vesivarojen hallinnassa tarvitaan menetelmiä pohja- ja pintaveden kokonaisvaltaiseen huomioimiseen. Pohja- ja pintavesiä tarkastellaan usein erillisinä osina hydrologista kiertoa, mikä on johtanut niiden välisten virtausprosessien yksinkertaistamiseen. Tässä työssä selvitettiin Rokuan pohjavesiesiintymän hydrologiaa ja hydraulista yhteyttä alueella oleviin järviin ja puroihin. Tutkimuksessa pyrittiin osaltaan selvittämään syitä harjualueen järvien pinnanvaihteluun ja veden laatuongelmiin. Kenttätutkimuksissa todettiin voimakasta alueellista vaihtelua järven ja pohjaveden vuorovaikutuksessa. Pohjaveden suotautumisen ajallinen vaihtelu puolestaan oli vähäisempää, mutta havaittavissa, ja kytköksissä järveä ympäröivän pohjavesipinnan vaihteluihin. Merkkiaineet vesinäytteistä viittasivat vastaavan vuorovaikutuksen olevan läsnä myös muissa alueen järvissä, mutta suotautuvan pohjaveden määrän vaihtelevan järvittäin. Turvemailla tehdyt mittaukset osoittivat pohjaveden purkautuvan ojaverkostoon ja ojituksen mahdollisesti lisäävän ulosvirtaamaa pohjavesiesiintymästä. Pohjaveden muodostumismäärää ja -nopeutta tutkittiin numeerisella mallinnuksella, joka kehitettiin huomioimaan harjualueelle ominaiset fysikaaliset tekijät. Mallinnus tuotti arvion ajallisesti ja alueellisesti vaihtelevasta pohjaveden muodostumisesta, joka varmennettiin kenttämittauksilla. Tuloksissa korostui kasvillisuuden, ja sitä kautta metsähakkuiden, vaikutus pohjaveden muodostumismääriin. Hydrologiasta kerätyn aineiston ja kehittyneen prosessiymmärryksen avulla Rokuan harjualueesta muodostettiin täysin integroitu numeerinen pohjavesi-pintavesi virtausmalli. Mallinnustulokset vastasivat mittauksia pohjaveden ja järvien pinnantasoista sekä purovirtaamista. Työn merkittävin tulos oli, että mallinnetut pohjaveden purkautumiskohdat ja purkautumismäärät alueen järviin vastasivat kenttähavaintoja. Tämä työ havainnollisti, että ymmärtääkseen pohjaveden ja siitä riippuvaisten järvien ja purojen vuorovaikutusta harjualueella on käytettävä monipuolisia tutkimusmenetelmiä. Työ toi lisätietoa Rokuan harjualueen vesiongelmien syihin selittäen järvien vedenpinnan vaihtelua ja vedenlaatua pohjavesihydrologialla. Väitöstyön tärkein anti oli erilaisten kenttä- ja mallinnus-menetelmien soveltaminen, kehittäminen ja hyödylliseksi havaitseminen harjualueiden kokonaisvaltaisessa pinta- ja pohjavesien hallinnassa

Abstract:

Multiple saline tracers were used to explore the role of geologic structure on groundwater recharge at the Fractured Rock Research Site in Floyd County, Virginia. Tracer migration was monitored through soil, saprolite, and fractured crystalline bedrock for a period of 3 months with chemical, physical, and geophysical techniques. Potassium chloride (KCl) and potassium bromide (KBr) tracers were applied at specific locations on the ground surface to directly test flow pathways in a shallow saprolite and deep fractured rock aquifer. Previous work at the Fractured Rock Research Site have identified an ancient thrust fault complex that is present in the otherwise competent metamorphic bedrock; fracturing along this fault plane has resulted in a highly transmissive aquifer that receives recharge along the vertically oriented portion of the fault zone. A shallow aquifer has been located above the thrust fault aquifer in a heterogeneous saprolite layer that rapidly transmits precipitation to a downgradient spring. Tracer monitoring was accomplished with differential electrical resistivity, chemical sampling, and physical monitoring of water levels and spring discharge. Tracer concentrations were monitored quantitatively with ion chromatography and qualitatively with differential resistivity surveys. KCl, applied at a concentration of 10,000 mg/L, traveled 160 meters downgradient through the thrust fault aquifer to a spring outlet in 24 days. KBr, applied at a concentration of 5,000 mg/L, traveled 90m downgradient through the saprolite aquifer in 19 days. KCl and KBr were present at the sampled springheads for 30 days and 33 days, respectively. Tracer breakthrough curves indicate diffuse flow through the saprolite aquifer and fracture flow through the crystalline thrust fault aquifer. Heterogeneities in the saprolite aquifer had a large effect on tracer transport, with breakthrough peaks varying several days over vertical distances of several meters. Monitoring saline tracer migration through soil, saprolite, and fractured rock provided data on groundwater recharge that would not have been available using other traditional hydrologic methods. Travel times and flowpaths observed during this study support preferential groundwater recharge controlled by geologic structure. Geologic structure, which is not currently considered an important factor in current models of Blue Ridge hydrogeology, should be evaluated on a local or regional scale for any water resources investigation, wellhead protection plan, or groundwater remediation project.
Master of Science

Abstract:

Groundwater is documented to flow through solution-widened fractures and bedding planes in limestone and dolostone units in low-relief topography. This enhancement, or karstification, is much harder to study in alpine environments like the Bear River Range of northern Utah. This is problematic, due to the fact that the Bear River Range karst aquifer system supplies the City of Logan with a large quantity of water at Dewitt Spring. Furthermore, the karst aquifer sustains the Logan River for much of the year, and may allow groundwater to flow directly in the subsurface to the Cache Valley principal aquifer system.Flow measurements along the Logan River constrain a minimum volume of 2.32x106 m3 /y (1.88x103 af/y) that could recharge the Cache Valley principal aquifer. Hydraulic characteristics of alpine karst were estimated by analysis of major ions, stable isotopes, and dissolved gases in spring waters. These data reflect quick groundwater flow through caverns, with no evidence for “diffuse” flow anticipated by some to occupy interstitial space. In fact, the oldest reasonable estimated recharge age for groundwater is 70 years. Young recharge, fast flow, and low storage capability indicate that alpine karst aquifers are very sensitive to droughts and that related water resources are vulnerable to longer-term changes in climate.

Abstract:

Thesis (MSc)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: This study was conducted to assess groundwater characteristics of geologically different fracturerock aquifers, at different depths, by means of chemical, isotope and 14C-dating results and to testfor a "deeper seated aquifer", with different characteristics.Jurassic dolerite dykes and sills, Cretaceous kimberlite fissures and pipes, as well as EWtrending sinusoidal megafolds, comprise the structural domains of the study area. Fluvialsandstone and mudstone of the Beaufort Group are the dominant lithology of the study area.The main water type found in the area is a water type not dominated by any anions or cations inparticular. The second is a water type in which Na-S04 is dominant, followed by a Na-HC03dominated water and to a lesser extend a Ca-S04 type water.The main cause of groundwater salinity is the infiltration of evaporated water to the subsurface,suggested by the isotopic enrichment of 0180 and 02H, indicating very slow recharge from pondedwater during excessive rainfall events.There is a fair difference in isotopic values between surface measurements and measurementstaken at depth, enforcing the possibility of a "second deeper seated aquifer". The water with thelower 180 values, for samples at depth suggest that this water has a source further inland, fromrainfall on the range to the NE, the Hex River Mountain or Pramberge, which has greatly depleted180 values relative to SMOW.Most of the groundwater samples taken at depth indicated a 14C~dating of century age (±200years), although in an evolutionary sequence the water is not such an old (evolved) water type,lending support to the theory about the migration of deeper seated water and thus a "seconddeeper seated aquifer system".The chemical character of the groundwater is predominantly controlled by the infiltration ofevaporated surface and subsurface water, the topographical nature of the catchments, geologicalinfluences (i.e. the process of dissolution, precipitation and ion exchange) and the influence ofman.Variability in water quality is caused by differences in rainfall, recharge, evaporation, topography,soil type and thickness, vegetation cover and antropogenic activities. Micro-scale differences occur due to the nature of groundwater flow in Karoo rocks, namely the resulting variations withinmatrix and fracture components of the groundwater flux. The residence times are often differentfor these two main components and give rise to the differences in mineralization and soluteproportion in passing groundwater.This project should be seen as a basis of continuing study to provide the concrete answersneeded to manage groundwater projects in the fractured rock aquifers of the Karoo.Enslin (1950) expresses the classical hydrological conceptualisation of Karoo dolerite dykes -lithe effect of induration and crushing of the sedimentary rock is that the permeability hasbeen increased and the contact zone has been changed into an aquifer lying between thesolid dyke and the saturated, low permeability country rock".
AFRIKAANSE OPSOMMING: Hierdie studie was onderneem met die doel. om grondwater eienskappe te ondersoek ingeologies verskillende gekraakte / genate aquifere en by verskillende dieptes met die hulp vanchemiese, isotopiese en 14C-datering resultate, om sodoende te toets vir 'n "tweede dieperliggende aqulfeer", met verskillende eienskappe.Doleriet gange en plate (Jura), kimberliet gange en pype (Kryt), sowel as OW lopendesinusvormige mega-verskuiwings en monoklienes van die Kaapse Plooi Gordel, Vorm diestrukturele omgewings in die studie gebied. Die dominante litologie in die studie gebied is fluviaalgedeponeerde sandsteen en moddersteen van die Beaufort Groep.Die opvallendste water-tipe wat in die studie gebied waargeneem word is 'n grondwater wat geendominante katione of anione toon nie, tweedens is daar 'n Na-S04 tipe grondwater wat gevolgword deur 'n Na-HC03 tipe water en daarna 'n Ca-S04 grondwater tipe.Die hoof oorsaak van saliniteit in the grondwater is die infiltrering van verdampte water na diegrondwater-tafel, deur die verryking in 01BOen 02H, wat stadige infiltrasie van water na hewigereënval episodes voorstel.Die verskil van isotoop waardes by vlak en diepper watervlakke, steun die moontlikheid van dieaanwesigheid van 'n "tweede dieper liggende aquifeer". Water met die lae 1BO-waardes (metdiepte) dui op 'n opvangsgebied meer na die noordoostelike binneland, soos byvoorbeeld die HexRivier Berge en die Pramberge.Meeste van die grondwater monsters wat geneem is by 'n redelike diepte toon 'n 14C-dateringwaarde van ongeveer 200 jaar, alhoewel die water uit 'n evolutionere oogpunt nie so oud is nieen sodoende ondersteuning bied aan die teorie van die beweging van dieper liggende water endie bestaan van 'n "tweede dieper liggende aquifeer".Die chemiese karakter van grondwater word hoofsaaklik beheer deur die infiltrering vanverdampte oppervlak water na die grondwater-tafel, die topografiese geaardheid van dieopvangsgebied, geologiese invloede (soos die prosesse van presipitering, oplossing en ioonuitruiling), sowel as die infloed van die mens. Wisselvalligheid in die kwaliteit van grondwater word veroorsaak deur verskille in reënval,infiltrasie, evaporasie, topografie, grond tipe en diepte, plantegroei en die aktiwiteite van diemens. Verskille op mikro-vlak word veroorsaak deur die aard van die grondwater vloei deur dieKaroo gesteentes, volgens die verskil in hidroliese geleiding tussen vloei in die matriks en vloei indie krake / nate. Daar is ook 'n verskil in die tydsbestek wat grondwater in die twee hoofstrukturelekomponente deurbring en so die verskil in mineralisasie en saliniteit in die dinamiesegrondwater veroorsaak.Die projek moet gesien word as die basis vir voortdurende studie om konkrete antwoorde teverseker vir die gebruik in grondwater bestuur projekte van die gekraakte / genate rots aquifere indie Karoo.Enslin (1950) konseptualiseer Karoo doleriet gange as volg: "die effek van indringing enverbrokkeling van sedimentêre gesteentes is dat die deurlaatbaarheid verhoog word endat die kontak sone verander is na 'n aquifeer wat lê tussen die soliede gang en dieversadigde, lae deurlaatbare wand-gesteentes".

Abstract:

Combining geochemical data with physical data produces a powerful method for understanding sources and fluxes of waters to river systems. This study highlights this for river systems in regions of complex hydrogeology, shown here through the identification and quantification of base-flow sources to the Verde River and its tributaries within the middle Verde River watershed. Specifically, geochemical tracers (major solutes, stable and radioactive isotopes) characterize the principal aquifers (C, Redwall-Muav, and Verde Formation) and provide a conceptual understanding of the hydrologic connection between them. For the surface-water system, PCA is utilized to identify potential base-flow sources to the Verde River on a several-kilometer scale. Solute mixing diagrams then provide relative inputs of these sources, and when combined with stream discharge, allow for quantification of water sources. The results of this study provide an improved conceptual model that reveals the complexity of groundwater-surface water exchanges in this river basin.

Abstract:

Environmental tracers can provide information on groundwater age, recharge conditions and flow processes. This information is useful for evaluating groundwater sustainability and vulnerability by identifying groundwater provenance and information for water budgets. Gibsons, British Columbia is a growing coastal community relying on groundwater to supply drinking water to two thirds of its 4,300 residents. The Town of Gibsons is proud of its untreated groundwater resource and proactive about keeping it protected and sustainable for future generations. Samples of noble gases, tritium, and stable isotopes of oxygen and hydrogen were collected from the aquifer. Tracer results improved the site conceptual model by identifying a previously unknown contribution of mountain block recharge (MBR) and by providing recharge elevation estimates using noble gas thermometry. The updated conceptual model including the mountain block was integrated into a regional three-dimensional numerical groundwater flow model calibrated to both hydraulic heads and to recharge elevation, a non-traditional approach to model calibration. This is the first study to use recharge elevation as a calibration target, which proved to be imperative for constraining bedrock geometry and minimizing model non-uniqueness. Tracer and modeling results indicate that groundwater in the Gibsons aquifer contains a mixture of approximately 45% MBR and 55% bench recharge. The MBR component is pre-modern (> 50 years) groundwater that recharged at elevation and cold temperatures (~5°C) and has evolved hydrogeochemistry and high concentrations of excess air (EA; >0.005 ccSTP/g) and ⁴Heterr (>10-⁹ ccSTP/g). Bench recharge is modern (< 10 years) groundwater recharged at low elevations and warm temperatures (~9°C), and has non-evolved hydrogeochemistry and low concentrations of EA (0.001-0.003 ccSTP/g) and ⁴Heterr (<10-⁹ ccSTP/g). Effects of increased pumping due to population growth and decreased recharge rates caused by climate change were assessed by conducting a sensitivity analysis of groundwater flow. Based on the study results, it is recommended to carry out long-term groundwater monitoring; sustainable groundwater use and community involvement are required to ensure groundwater sustainability.

Abstract:

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第7880号
農博第1038号
新制||農||777(附属図書館)
学位論文||H11||N3243(農学部図書室)
UT51-99-G474
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 河地 利彦, 教授 青山 咸康, 教授 三野 徹
学位規則第4条第1項該当

Abstract:

Regions of surface water and groundwater exchange are major sites for the transfer and transformation of solutes and nutrients between stream and subsurface environments. Conventional stream and groundwater exchange investigations are limited by methodologies that require intensive field investigations and/or the set-up of expensive infrastructure. These difficulties are exacerbated where hydraulic gradients are very low and stream discharge highly variable. This thesis uses a suite of environmental tracers (Cl-, Rn-222, H-2 & O-18, Sr-87/Sr-86) to characterise the extent of stream and groundwater exchange between a sand bed stream and adjacent alluvial aquifer in a subtropical catchment (the Wollombi Brook) of eastern Australia. The aims were to identify sources and relative contributions of different sources of groundwater to stream discharge and specifically to improve the methodology of using Rn-222 to obtain quantitative estimate of groundwater fluxes.The sensitivity of the Rn-222 technique for identifying groundwater discharge based on the Rn-222 concentration in stream water was improved via an iterative numerical approach to account for Rn-222 loss from stream water via turbulent gas exchange and radioactive decay. Optimal distances between stream sampling points for defining the magnitude of groundwater discharge to stream flow based on Rn-222 concentrations in stream water is a function of average stream velocity and water depth. The maximum allowable distance between sampling points for determining the magnitude of groundwater discharge to the Wollombi Brook was 2 km. This work showed that groundwater discharged to all reaches of the Wollombi Brook during baseflow and flood recession conditions. Alluvial groundwater contributed less than 30% of water to stream flow in the mid Wollombi Brook catchment.Dilution of steady-state Rn-222 concentrations measured in transects from the stream to the alluvial sediments showed that significant surface water and groundwater exchange occurs even when gradients between surface water and groundwater are low. Lateral stream water influx to the adjacent alluvial aquifer was more extensive in the lowland areas of the Wollombi Catchment during low flow than flood recession conditions. Extensive stream water influx to the adjacent alluvial aquifer occurs contrary to the net direction of surface water and groundwater flux (as indicated by hydraulic gradients toward the stream channel). The rate of stream and groundwater exchange within the adjacent alluvial aquifer appears to be greatest during baseflow conditions. Fresh alluvial groundwater appeared to provide a buffer against higher salinity regional groundwater discharge to the alluvial aquifer in some reaches of the Wollombi Brook catchment. Pumping of the alluvial aquifer and diversions of surface water may jeopardise the water quality and volume of the alluvial aquifer and induce water flow from the regional aquifer toward the stream, potentially salinising the fresh alluvial aquifer and subsequently the stream.The change in the Cl- concentration and the variation in slope of the deuterium � oxygen-18 line between consecutive stream sampling points could be used to differentiate between regional and alluvial groundwater discharge to stream flow. Incorporating this information with three-component end-member mixing using [Sr2+] and Sr-87/Sr-86 showed that stream and alluvial groundwater exchange within the stream channel was highest in the lowland floodplains during low flow conditions. The least stream and alluvial groundwater exchange occurred in the low streambed gradient mid reaches of the Wollombi Brook regardless of stream stage. The greatest difference in the degree of stream and alluvial groundwater exchange between high and low stream stages occurred in the lowland floodplains of the Wollombi Brook.

Abstract:

Groundwater is used worldwide as a major source for agricultural irrigation, industrial processes, mining, and drinking water. An accurate understanding of groundwater levels and trends is essential for decision makers to effectively manage groundwater resources throughout an aquifer, ensuring its sustainable development and usage. Unfortunately, groundwater is one of the most challenging and expensive water resources to characterize, quantify, and monitor on a regional basis. Data, though present, are often limited or sporadic, and are generally not used to their full potential to aid decision makers in their groundwater management.This thesis presents a solution to this under-utilization of available data through the creation of an open-source, Python-based web application used to characterize, visualize, and quantify groundwater resources on a regional basis. This application includes tools to extrapolate and interpolate time series observations of groundwater levels in monitoring wells through multi-linear regression, using correlated data from other wells. It is also possible to extrapolate time series observations using machine learning techniques with Earth observations as inputs. The app also performs spatial interpolation using GSLIB Kriging code. Combining the results of spatial and temporal interpolation, the app enables the user to calculate changes in aquifer storage, and to produce and view aquifer-wide maps and animations of groundwater levels over time. This tool will provide decision makers with an easy to use and easy to understand method for tracking groundwater resources. Thus far, this tool has been used to map groundwater in Texas, Utah, South Africa, Colombia, and the Dominican Republic.

Abstract:

The purpose of the study is to understand quantitatively the spatial distribution of groundwater recharge in the Sana'a Basin, Yemen i.e. irrigation recharge, wadi recharge and urban recharge and to assess the impact of these components on the groundwater quality. A combination of field measurements and modelling was used to determine the irrigation return for several crops and soil types. Over the basin, the total return flows, between 20 to 40 % of the water applied, are about 30 MCM/year. A method was developed to calculate recharge through ephemeral wadi beds using an indirect approach, requiring only daily rainfall data and geomorphological observations. The technique combines a rainfall-runoff model with calculation of daily water balance for the wadi channel. The method was applied to two wadis with sufficient subsurface data to estimate groundwater recharge independently from calibration of groundwater models for the shallow aquifer. The values of infiltration calculated by groundwater flow model were in good agreement with the results of the channel water balance model. Regression analysis was used to derive a generalised relationship between recharge and wadi flows. Application of this technique allows extension of wadi recharge estimates to numerous ungauged wadis over 20 years. Wadi recharge over the Sana'a basin is erratic and varies between 129 MCM and 3 MCM with an average of 38 MCM/year. An inventory of abstraction by private wells in Sana'a city, has allowed an improved estimation of urban recharge over the last 20 years, an average of 60% of the water abstracted (76% supplied). Water chemistry indicates that the shallow aquifer within the plain and lower reaches of major wadis has been polluted. However, dilution is taking place through mixing with the deep fresh water through the boreholes. Total annual recharge varies between 143 MCM and 21 MCM with an average of 66 MCM. This represents a significant amount of the annual average abstraction of 82 MCM. Previous estimate of recharge to aquifers of the basin has been less soundly based.

Abstract:

The Middle San Pedro Basin in southeastern Arizona is a typical alluvial basin in the semi-arid southwestern United States with a rapidly growing population that is dependent upon groundwater resources for water supply. This study investigated recharge areas, compartmentalization and potential mixing of water sources, and travel times of groundwater throughout the basin using variations in major ion chemistry (water type, Ca/Sr ratios, SO4/Cl ratios) and isotope ratios (18O, 2H, 3H, 34S, 13C, 14C) of groundwaters, surface waters and precipitation in conjunction with hydrogeologic data (e.g. hydraulic head and hydrostratigraphy). Recent recharge (<50 years) has occurred within mountain systems along the basin margins, and in shallow floodplain aquifers adjacent to the San Pedro River. Groundwaters in confined aquifers in the central basin were recharged at high elevation in the fractured bedrock and have been extensively modified by water-rock reactions over long timescales (up to 34,600 years). These results can be used to constrain physical assumptions of future groundwater flow models designed to help make improved water management decisions.

Abstract:

Abstract Groundwater-dependent ecosystems (GDEs) are aquatic or terrestrial ecosystems that rely directly or indirectly on groundwater (GW). Recent European and Finnish legislation requires better consideration of these systems in GW management. The main aim of this thesis was to develop new methods for GDE classification and management, by testing environmental tracer methods in different environments. New information about GW-surface water interactions was obtained and novel methods for GDE classification and management were developed for lakes, peatlands, streams, and springs. Stable water isotopes proved to be an efficient tool for determining the GW dependence of lakes. An iterative isotope mass balance method was applied for 67 lakes situated in the Rokua esker aquifer area. Stable water isotopes also showed potential in determining the GW dependence of a peatland surface horizon. A study conducted in peatlands adjacent to Viinivaara esker aquifer indicated that the GW dependence of peatlands can vary significantly and that GW-dependent areas can extend outside current GW protection areas. Thermal images proved useful in pinpointing clear GW seepage locations in peatlands. For streams, a novel stream tracer index method was developed to evaluate GW dependence based on GW volume in streams, thermal properties of streams, and stream water quality. The method was tested in three streams discharging from Viinivaara and Rokua aquifers and was found to efficiently capture spatial variations in GW dependence. In Oulanka region, hydrological and chemical characterization and statistical methods were used to classify springs into different types. Spring altitude and δ2H value were identified as useful proxies for spring water chemistry. The methods developed in this thesis can be helpful when classifying and studying GDEs and applying environmental tracer methods in various environments. Knowing the GW dependence of an ecosystem, the impacts of possible GW table decline caused by e.g., GW abstraction, drainage, and/or climate change can be evaluated. For large-scale applications, GDE classification methods have to be practical, effective, and low-cost. Combined use of stable water isotopes and other tracers can be especially effective for characterizing ecosystem hydrology on different temporal and spatial scales
Tiivistelmä Pohjavedestä riippuvat ekosysteemit (GDE) ovat vesi- tai maaekosysteemejä, jotka ovat suoraan tai epäsuorasti riippuvaisia pohjavedestä. Euroopan Unionin ja Suomen lainsäädännön mukaan pohjavesien hallinnassa tulisi ottaa paremmin huomioon GDEt. Tämän työn tavoitteena oli kehittää uusia menetelmiä näiden ekosysteemien luokitteluun ja hallintaan. Luonnollisia merkkiainemenetelmiä soveltaen saatiin uutta tietoa pohjavesi-pintavesi vuorovaikutuksesta ja kehitettiin uusia menetelmiä GDE-luokitteluun järville, soille, puroille ja lähteille. Veden stabiilit isotoopit osoittautuivat tehokkaaksi työkaluksi järvien pohjavesiriippuvuuden määrittämisessä. Iteratiivista isotooppimassatase-menetelmää käytettiin 67 Rokuan järven pohjavesiriippuvuuden selvittämiseen. Veden stabiileilla isotoopeilla pystyttiin myös määrittämään suon pinnan pohjavesiriippuvuus. Viinivaaran harjun viereisen suoalueen tutkimus näytti, että suon pohjavesiriippuvuus voi vaihdella merkittävästi ja pohjavedestä riippuvia alueita löytyy myös nykyisten pohjavesirajojen ulkopuolelta. Lisäksi soilla havaittiin selkeitä pohjavedenpurkupaikkoja lämpökamerakuvauksen avulla. Puroille kehitettiin uusi menetelmä, jolla niiden pohjavesiriippuvuutta voidaan arvioida perustuen pohjaveden määrään puroissa, puroveden lämpötilaominaisuuksiin ja puroveden laatuun. Menetelmää testattiin Viinivaaran ja Rokuan harjuista purkautuville puroille ja sillä havaittiin pohjavesiriippuvuuden vaihtelevan purojen eri osissa. Oulangan lähteitä luokiteltiin eri tyyppeihin hydrologisen ja kemiallisen karakterisoinnin ja tilastollisten menetelmien avulla. Lähteiden altitudin ja δ2H-arvon havaittiin ennustavan lähdeveden kemiallista koostumusta. Tässä tutkimuksessa kehitetyt menetelmät voivat olla hyödyllisiä GDE-luokittelussa, eri ekosysteemien tutkimisessa ja luonnollisten merkkiainemenetelmien soveltamisessa eri ympäristöissä. Kun ekosysteemin pohjavesiriippuvuus tiedetään, voidaan arvioida pohjavedenotosta, ojituksesta ja/tai ilmaston muutoksesta mahdollisesti aiheutuvan pohjavedenpinnan laskun vaikutuksia. Suuressa mittakaavassa, GDE-luokittelumenetelmien tulee olla käytännöllisiä, tehokkaita ja halpoja. Veden stabiilien isotooppien ja muiden merkkiaineiden yhdistetty käyttö vaikuttaa olevan tähän erityisen tehokas työkalu, jolla voidaan ymmärtää ekosysteemien hydrologiaa eri temporaalisissa ja spatiaalisissa mittakaavoissa

Abstract:

Hydraulic conductivity fields (K) and degradation rate constants (a) arecommonly used in predicting the fate and transport of reactive contaminants. Thenatural heterogeneity in aquifer porous materials and its effect on hydrologicalparameters such as K and a has to be accounted for by using an appropriate stochasticapproach.The spatial distribution of K and its correlation with a were examined. Randomfields of K having prescribed mean, variance, and correlation lengths were generatedusing the HYDRO_GEN method. Transport simulations were conducted for anensemble of two-dimensionally heterogeneous aquifers. Both positive and negativecorrelations of K and a were considered.The solute’s remaining mass in both the positive and negative correlationscenarios was found to be, on average, within a small range. Concentration profiles fora positive K-a correlation displayed a more uniform behavior of the contaminatedplume, compared to a more variable spreading in the negatively correlated cases.

Abstract:

Thesis (M.S.)--West Virginia University, 2005
Title from document title page. Document formatted into pages; contains xi, 105, [43] p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 96-104).