Les aquifères karstiques constituent l'essentiel des ressources en eau du pourtour Méditerranéen. Au delà de la zone saturée de ces systèmes, la zone non saturée constitue une entité importante quant au transfert et au stockage temporaire de l'eau. La structure et le fonctionnement de cette entité du karst sont complexes et mal connus à cause du processus de karstification qui hiérarchise la circulation hydrodynamique en son sein. Dans cette étude nous utilisons des méthodes géodésiques et hydrogéologiques afin d'observer de façon directe et de quantifier les processus de transfert et de stockage de la zone non saturée. Les mesures gravimétriques en surface et profondeur sur différents systèmes karstiques ont permis de quantifier les variations du stockage en eau saisonnier dans la zone non saturée. La gravimétrie différentielle montre que ces variations sont réparties dans les quelques premiers mètres de la zone non saturée. Il semble, de plus, que la capacité de stockage de la zone non saturée soit fonction de la lithologie de l'encaissant (calcaire et dolomie). Enfin, des observations directes du flux d'eau en zone non saturée ont été effectuées par le biais de mesures dans différentes cavités. Nous montrons que certaines caractéristiques du flux d'eau en zone non saturée, comme la présence d'un flux bipolaire lent-rapide, peuvent être généralisées quelques soit la profondeur de mesure et la surface d'impluvium. La modélisation de ce flux, à partir d'un schéma simple, a montré la complexité des processus de transfert engendrés au sein de la zone non saturée. / Karst systems are the most important groundwater reservoirs in Mediterranean area. Beyond saturated zone, unsaturated zone constitute an entity where water storage and transfer play a major role in a global behavior of spring water. This structure and functioning are complex and not well known because of the high heterogeneity created and organized by groundwater flow. In this study, we used gravimetric and hydrogeologic method to directly observe and quantify water storage and transfer processes in unsaturated zone of karst system. Surface to depth gravity measurements on several karst system allow quantifying seasonal water storage changes in unsaturated zone. We show that these variations occur in the first tens meters of unsaturated zone. Furthermore, water storage capacity of unsaturated zone seems to be influenced by lithology (limestone or dolomite). Finally, direct observations of water flow in unsaturated zone are done using caves access. We show that some characteristics of unsaturated water flow such as bipolar slow-fast flow can be widespread for whatever depth of measurement and recharge area. Model of this flow, using a simple modeling scheme, show the complexity of water transfer processes in unsaturated zone of karst system.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / ABSTRACT This study was an investigation of the impact of recharge water with respect to quality and quantity into the Rehabilitated Block I opencast operation, a former opencast coal mine in Mpumalanga, Witbank Coalfields western complex. The rehabilitated areas consisted of three mined mini-pit areas known as Block I, Block I Extension A and B. The area has been rehabilitated by backfilling and leveling of spoil material, subsoil material, placement of approximately 400-mm topsoil layer and grassing. As part of the vegetation maintenance lime is added per annum, in an effort to neutralize the soil cover and further assist in neutralizing the potential acid mine drainage. Additional monitoring boreholes were drilled to increase the monitoring of the water quantity and qualities. Ground and surface water samples were taken, analysed for pH, conductivity, redox potential, sulphates, carbonates and trace metals. The pH of the ground and surface water ranged from moderately acidic to alkaline. One of the monitoring boreholes located on the lowest elevation of the Block I area was observed to be filled up to the collar level of the borehole with water samples showing elevated Fe and Mn concentrations of 216 and 46.2 mg l-1 respectively. The water classification revealed the following facies: Ca-Mg sulphate type for the borehole water and Ca-Mg sulphate-bicarbonate type for the surface waters. Acid base accounting studies on the soil samples showed a negative net neutralising potential of up to -9.8 kg t-1 CaCO3 which indicated the potential of acid mine drainage in the area. The total metal analyses showed that the area was contaminated with heavy metals such as Fe, Cr, Mn, Ni and Zn and the metalloid As was also detected. The highest recorded concentrations of total metals were 78 252; 2 402; 1 959; 1 360 and 15 109 mg kg-1 respectively. The highest concentration of Arsenic was detected at 824 mg kg-1 respectively. The transmissivity of the boreholes in the spoil material was highly variable and ranges from 100 to 5 000 m2 day-1. Pump testing suggests that borehole yields of between 23 and 4 l s-1 can be expected in the spoil areas. The specific yield or the drainage porosity of the spoil material was in the range of 25 to 30 %.

A hydrogeologic investigation was completed of the alluvial aquifer near the Osceola County Rural Water System (OCRWS) H-Series well-field, located in Osceola County, Iowa. The primary purpose of the investigation was to quantify drought resiliency benefits of engineered systems on a well-field scale through the use of a groundwater model. Specifically, a groundwater flow model was developed for the OCRWS H-Series well-field to quantify groundwater withdrawal and storage benefits of: • One rock riffle structure placed within the well-field • Two rock riffle structures placed within the well-field • An excavated, historic river channel system combined with one rock riffle structure The objective of these engineered systems is to increase the groundwater storage within the aquifer. Riffles and channel systems provide additional groundwater storage during periods of normal or above normal precipitation by raising the stage of the river. This additional storage, reflected in groundwater heads, is then available to maintain water production during a drought. Groundwater model results showed that all three of the engineered systems quantified substantially improved groundwater storage and induced recharge during the drought simulations. While each system was shown to influence the aquifer, benefits to groundwater storage and induced recharge from the two riffle system was shown to provide the greatest amount of drought resiliency benefit. Through the use of a cost-benefit analysis, the two riffle system was also shown to be the most cost-effective method in this study in terms of achieving additional groundwater storage and induced recharge to the aquifer.

The solid phase of an aquifer has an effect on the aqueous phase; if groundwater quality is degraded by the solid phase of an aquifer this is referred to as geogenic pollution. In this study, the Piney Point aquifer in the Virginia Coastal Plain was assessed for mechanisms that may release anions from the solid to aqueous phases and effect water quality. This was done by conducting leaching experiments modified from Balintova et al. (2013). Piney Point aquifer sediments and groundwaters were also analyzed to give a baseline for these experiments. Sedimentary analysis was found to be consistent with McFarland (2017) and groundwater anion concentrations were found to be less than the U.S. Environmental Protection Agency’s (EPA) established Maximum Contaminant Levels (MCL). Leaching experiments found that low pH environments may lead to the release of fluoride in association with phosphorus in sediments and general release of chloride. Nitrate release mechanisms in confined aquifers require further study, but it appeared as total inorganic carbon was dissolved, sedimentary total nitrogen concentrations increased. Sulfate concentrations in leaching experiments were found to be associated with sulfur concentrations in the solid phases. Furthermore, leaching experiments showed that when sediments are exposed to oxic environments then re-exposed to groundwater, higher concentrations of anions were released to the aqueous phases. This could be a particular issue with sulfate concentrations, which were above the EPA MCL in the majority of sediment samples in all leachate treatments.

In this thesis, we examine the equation describing fluid flow through saturated porous medium in order to develop a new method for approximating hydraulic head values in the subsurface. In particular, we show that under reasonable assumptions, the local explicit equation (LEE) method, an accurate, finite-difference based method that is highly sensitive to changes in the assumed location of hydraulic flow parameters, can be used to approximate hydraulic head values throughout a subsurface domain of interest. This forward solution of the fluid flow equation is solved using an altered finite difference scheme, designed to account for discontinuous jumps often encountered between subsurface material types. While the method is able to handle complicated discontinuities arising from the intermingling of various underground materials, the method determines values at nodes on an easy-to-use uniform Cartesian grid and only requires information from immediately adjacent points. The results of this research directly support the development of more accurate subsurface fluid flow models for use in a wide variety of real-world situations in areas such as water management, contaminant remediation and waste storage. Furthermore, the general development of the LEE method allows it to be used as an approximation technique for any equation where the media of interest encounters a jump.

This project addresses the topic of evaluating water movement inside a hillslope using a combination of conventional and advanced geophysical techniques. While slope dynamics have been widely studied, ground water movement in hills is still poorly understood. A combination of piezometers, ground-penetrating radar (GPR), and electrical resistivity (ER) surveys were used in an effort to monitor fluctuations in the subsurface water level in a reengineered slope near Keokuk, Iowa. This information, integrated with rainfall data, formed a picture of rainfall-groundwater response dynamics. There were two hypotheses: 1) that the depth and fluctuation of the water table could be accurately sensed using a combination of monitoring wells, ground-penetrating radar and resistivity surveys; and 2) that the integration of data from the instrumentation array and the geophysical surveys would enable the characterization of water movement in the slope in response to rainfall events. This project also sought to evaluate the utility and limitations of using these techniques in landslide and hydrology studies, advance our understanding of hillslope hydrology, and improve our capacity to better determine when slope failure may occur. Results from monitoring wells, stratigraphy, and resistivity surveys at the study site indicated the presence of a buried swale, channelizing subsurface storm flow and creating variations in groundwater. Although there was some success in defining hydrologic characteristics and response of the slope using this integrated approach, it was determined that GPR was ultimately not well suited to this site. However, the use of GPR as part of an integrated approach to study hillslope hydrology still appears to hold potential, and future work to further evaluate the applicability and potential of this approach would be warranted.

The Palm Valley oasis in arid central Australia is characterised by stands of palm trees (Livistona mariae). How these unique plants, separated by nearly a 1000 kilometres of arid country from their nearest relatives persist, has long fascinated visitors. Defining the hydrogeology of the Hermannsburg Sandstone, a regionally extensive and thick Devonian sequence of the Amadeus Basin that underlies Palm Valley, is the major thrust of investigation. Appraisal of drilling data shows this aquifer to be a dual porosity fractured rock aquifer which, on a regional scale, behaves as a low permeability, hydraulically continuous resource. Groundwater is low salinity (TDS &lt1000 mg/L) and bicarbonate rich. Slight variations in cation chemistry indicate different flow paths with separate geochemical histories have been sampled. Stable isotope (????H, ???????O) results from Palm Valley show groundwater to have a uniform composition that plots on or near a local meteoric water line. Radiocarbon results are observed to vary from effectively dead (&lt 4%) to 87 % modern carbon. To resolve groundwater age beyond the radiocarbon window the long lived radioisotope 36Cl was also used. Ratios of 36Cl/Cl range from 130 to 290 x 10-15. In this region atmospheric 36Cl/Cl ratio is around 300 x 10-15. Thus an age range of around 300 ka is indicated if, as is apparent, radioactive decay is the only significant cause of 36Cl/Cl variation within the aquifer. A review of previous, often controversial, 36Cl decay studies shows results are usually ambiguous due to lack of certainty when factoring subsurface Cl- addition into decay calculations. Apparently, due to the thickness of the Hermannsburg Sandstone, no subsurface sources of Cl- such as aquitards or halites, are encountered along groundwater flow paths, hence the clear 36Cl decay trend seen. The classic homogenous aquifer with varying surface topography, the &quotToth&quot flow model, is the simplest conceptual model that need be invoked to explain these isotope data. Complexities, associated with local topography flow cells superimposed on the regional gradient, signify groundwater with markedly different flow path lengths has been sampled. The long travel times (&gt 100 ka) indicate groundwater discharge would endure through arid phases associated with Quaternary climate oscillations. Such a flow system can explain the persistence of this arid zone groundwater-dependent ecosystem and highlight the possibility that Palm Valley has acted as a flora refuge since at least the mid- Pleistocene.

Thesis (M.S.)--University of Montana, 2006. / Title from title screen. Description based on contents viewed Mar. 23, 2007. Includes bibliographical references (p. 94-96).

Thesis (M.S.)--Baylor University, 2005. / Includes bibliographical references (p. 48-50).

The Grand River Watershed, in southern Ontario, is home to approximately 900,000 people and one of the fastest growing regions in Canada; specifically, in the urban areas of Guelph, Cambridge, Kitchener, and Waterloo. This growth strains the watershed’s capacity to supply adequate water resources to these municipalities, as well as manage the waste-water treatment effluent discharged from them. Nowhere in the watershed is this juxtaposition in water resource function more apparent than at the city of Brantford, with a population of approximately 100,000 people. Located forty-two kilometers downstream from the major urban areas, Brantford is unique in the watershed in that it obtains its entire municipal water supply directly from the Grand River, into which the upstream municipalities discharge 77% of the total waste-water treatment plant effluent emitted to the watershed. One contaminant of concern is nitrate, which, for decades, has been linked to numerous human and aquatic health complications. The input of nitrate from these upstream WWTP’s is considerable; the WWTP’s have a combined flow rate of 2.3 m3s-1, and a mean nitrate concentration of 10.4 mg N·L-1 (data from Anderson, 2012). As a comparison, the Nith River, the largest tributary to the Grand River between Cambridge and Brantford, has a summer baseflow of 2.9 m3s-1 and, from 2000 to 2004, had a mean nitrate concentration of 4.4 mg N·L-1 (Cooke, 2006). Brantford, in addition to treating their water supply, relies on the dilution of in-stream nitrate from groundwater that is thought to discharge along the Grand between Cambridge and the Brantford municipal water intake. This 40-km reach of the Grand River is colloquially referred to as either the discharge reach or the recovery reach. Recent data from various authors indicate that groundwater may not always act to dilute in-stream nitrate from upstream WWTPs (Encalata, 2008; Pastora, 2009; Rosamond 2009). The main objective of the research completed in this thesis was to refine the conceptual model of groundwater/surface water interaction along the Grand River between Cambridge and Brantford. Refinement of this conceptual model was accomplished in two parts. First, groundwater discharge, from bank seepage and direct discharge through the riverbed, was located using a variety of methods; a simple reconnaissance survey by canoe, a FLIR thermography survey, drag probe surveys, and a temperature profiling method. Then domestic wells, seeps, tributaries, riverbed discharge, and WWTP effluent were sampled to geochemically characterize inputs to the Grand River.