Tesi sul tema "Hydrochemistry"

The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly understood, in terms of hydrology, water storage and biogeochemical processes. High temporal resolution biogeochemical sampling of bulk meltwaters at a typical, land-terminating outlet glacier of the GrIS was employed in order to infer processes at the ice sheet bed over three contrasting melt seasons. No high temporal resolution geochemical datasets previously existed for ice sheet environments, mainly due to inaccessibility. Bulk meltwaters comprised differing propOltions of waters originating from a widespread, distributed subglacial drainage system (these delayed flow waters being solute enriched due to prolonged residence times and high rock:water ratios in the contributing environments), and an efficient channelized system (dilute surface waters rapidly transmitted to the margin). Two-component chemical mixing models, in combination with MODIS satellite imagery, revealed that delayed flow was released continuously. However, higher volumes were released at times of subglacial outburst events when draining surface lakes interacted with the bed and expelled stored waters. Dissolution experiments and geochemical data indicated that these waters may have been stored at the bed over winter, or longer, and comprised one-third of delayed flow release in any given year (~O.02 km\ The geochemical data, in combination with 01 80 -H20 isotope data from bulk meltwaters and surface ice, were able to identify subglacial drainage system evolution and increasingly distant water sources contributing to bulk meltwaters. Enhanced silicate dissolution was observed compared to smaller valley glaciers, which may lead to enhanced CO2 sequestration compared to carbonate weathering' environments. Chemical weathering rates were lower than would be expected for a poly thermal ice mass, likely due to low reactivity bedrock. Ionic fluxes were higher in high melt years, which is a further indication of stored water release due to extensive basal flushing. Finally, isotopes of sulphate demonstrated that there are both oxic and anoxic conditions at the bed of the GrIS, with potential for highly anoxic sulphate reducing conditions in the interior.

This thesis investigates the inter-relationship between hydrological and water quality variations with reference to backwaters and dead zones in rivers. The examination of a series of controlled reservoir releases to an upland channel in Wales showed "in-channel" dead zones were important solute source and storage areas. Physico-chemical data have been presented to show the influence of main channel flow and quality variations on the hydrochemistry of a range of seven backwaters within the Trent basin. The hydrological regime of the mainstream seasonally modified backwater quality. The degree of main-flow influence declined with decreasing hydrological connectivity of the backwater environments with the mainstream. Furthermore other hydrological, biological and biogeochemical factors influenced backwater physico-chemistry. A generalised typology of permanent floodplain water bodies in the R. Trent catchment based upon water chemistry was established. An applied study examined the effect of reservoir cleaning/emptying operations and flood events on backwater hydrochemistry on the French Upper River Rhone. The simultaneous occurrence of decreasing mainstream discharge with the passage of the sediment laden release wave reduced its impact on backwater environments. Anthropogenic influences on riverine systems as a result of intensification of agriculture and urbanisation (e.g. nitrate pollution and river regulation) have influenced the hydrological and physico-chemical functioning of fluvial hydrosystems. In view of rising nitrate levels in many British rivers, trends within the Trent basin have been investigated. Rates of increase in concentration of 0.06 mg.l-1 N yr-1 were typical of rural catchments, whilst rates of up to 0.20 mg.l-1 N yr-1 were recorded in urbanised tributaries. Furthermore the impact of rising nitrate levels in the Trent catchment and river regulation on backwater hydrochemistry and ecology have been examined.

Human transformation of the Earth’s land surface has far-reaching and important consequences for the functioning of hydrological and hydrochemical processes in watersheds. In nowadays land-use change from forest to pasture is a major issue in particular in the tropics. A sustainable management of deforested areas requires an in-depth understanding of the water and nutrient cycle. On this basis we compared the involved hydrological pathways for rainfall to reach streams and the nutrient budgets of a tropical rainforest and a pasture. In addition we studied the links of hydrochemical differences to differences of the relative importance of flowpaths. This study was conducted in the southwestern part of the Brazilian Amazon basin. An intensive hydrological and hydrochemical sampling and monitoring network was set up. The results indicate that the hydrology was modified in many ways due to land-use change. The most important alteration was the increased importance of the fast flowpath overland flow. Solute exports were in particular linked to the increased volume of overland flow that resulted from the land-use change. An additional reason for the increased nutrient exports from the pasture are the high concentrations of these nutrients in pasture overland flow probably as a due to cattle excrements. Tight nutrient cycles with minimal nutrient losses could not be maintained after the land-use change. This study provides the first attempt to quantify the respective nutrient losses.
Die Zerstörung von natürlicher Vegetation kann weit reichende Folgen auf den Wasser- und Nährstoffhaushalt von Ökosystemen haben. Der Landnutzungswandel vom Wald zur Weide ist heute in den Tropen ein wichtiges Thema. Eine nachhaltige Nutzung abgeholzter Gebiete setzt ein fundiertes Wissen des Wasser- und Nährstoffhaushaltes voraus. Darauf aufbauend wurden in dieser Studie das Abflussverhalten und die Nährstoffbilanzen von einem tropischem Regenwald und einer Weide verglichen. Außerdem wurde untersucht inwieweit die Nährstoffbilanzen vom Abflussverhalten abhängen. Die Untersuchungsgebiete liegen im südwestlichen brasilianischen Amazonasgebiet. Ein umfangreiches System zur Aufnahme von hydrologischen Daten und zum Sammeln von Wasserproben wurde aufgebaut. Die Ergebnisse haben gezeigt, dass sich das Abflussverhalten durch die Landnutzung geändert hat. Die wichtigste Änderung vom Wald zur Weide war der gesteigerte Anteil des schnellen Wasserabflusses auf der Geländeoberfläche. Hieraus resultierten gesteigerte Nährstoffausträge aus der Weide gegenüber dem Wald. Ein weiterer Grund für die gesteigerten Nährstoffausträge sind die hohen Konzentrationen dieser Stoffe im Oberflächenabfluss der Weide, die vermutlich mit den Ausscheidungen des Viehs zusammenhängen. Es hat sich also gezeigt, dass der quasi-geschlossene Nährstoffkreislauf nach der Landnutzungsänderung nicht aufrecht erhalten werden konnte. Diese Arbeit liefert den ersten Versuch diese Nährstoffverluste zur quantifizieren.

Since their discovery, subglacial lakes beneath the Antarctic ice sheet have been a focus of scientific curiosity and study. It has been postulated that subglacial lakes present a viable habitat for microbial life and are underlain by sediments containing a record of changes in the ice sheet above. Subglacial Lake Ellsworth, West Antarctica, is the subject of a continued project aiming to achieve clean access in order to explore these hypotheses. One of the key outcomes of lake sampling is to establish the hydrochemistry, from which deductions about the limnology of the system can be made. A new theoretical insight into the hydrochemistry of subglacial lakes is achieved through reanalysis of the geochemical dataset published from meteoric and accretion ice from above Subglacial Lake Vostok, East Antarctica. It is shown that Subglacial Lake Vostok is a well-mixed system at steady-state. Of the flux of water to the lake, ~60% drains away from the lake and ~40% freezes at the ice-water interface. A downstream subglacial hydrological catchment is strongly indicated. An average cationic denudation rate of ~9meq∑+·m-2·yr-1 is inferred at the lake-sediment interface. The methods and outcomes of the Subglacial Lake Vostok model form the theoretical basis to scope the controls on the hydrochemistry of Subglacial Lake Ellsworth. A hydrologically open lake system leads to dilute, isotopically heavier water. A hydrologically more isolated lake system results in more concentrated waters with a stable water isotope composition that is removed from the local meteoric water line. Geochemical weathering reactions are expected to contribute the majority of dissolved ionic species and meteoric ice is shown to deliver oxygen and nitrogen to the lake. The model results provide a theoretical framework for the interpretation of analyses from lake water samples. The model results are also used to guide a sampling and analysis strategy which would optimise the scientific gains of subglacial lake sampling. The precise nature of the processes within Subglacial Lakes Ellsworth and Vostok remain untested, but this thesis provides a robust basis for interpreting the hydrochemistry of both lakes.

Earlier investigations at South Creek in northeastern Queensland established the importance of overland flow as a hydrologic pathway in this tropical rainforest environment. Since this pathway is ‘fast’, transmitting presumably ‘new’ water, its importance should be reflected in the stormflow chemistry of South Creek: the greater the volumentric contribution to the stormflow hydrograph, the more similarity between the chemical composition of streamwater and of overland flow is to be expected. Water samples were taken during two storm events in an ephemeral gully (gully A), an intermittent gully (gully B) and at the South Creek catchment outlet; additional spot checks were made in several poorly defined rills. The chemical composition of ‘old’ water was determined from 45 baseflow samples collected throughout February. The two events differed considerably in their magnitudes, intensities and antecedent moisture conditions. In both events, the stormflow chemistry in South Creek was characterized by a sharp decrease in Ca, Mg, Na, Si, Cl, EC, ANC, alkalinity and total inorganic carbon. pH remained nearly constant with discharge, whereas K increased sharply, as did sulfate in an ill-defined manner. In event 1, this South Creek stormflow pattern was closely matched by the pattern in gully A, implying a dominant contribution of ‘new’ water. This match was confirmed by the spot samples from rills. Gully B behaved like South Creek itself, but with a dampened ‘new’ water signal, indicating less overland flow generation in its subcatchment. In event 2, which occurred five days later, the initial ‘new’ water signal in gully A was rapidly overwhelmed by a different signal which is attributed to rapid drainage from a perched water table. This study shows that stormflow in this rainforest catchment consists predominantly of ‘new’ water which reaches the stream channel via ‘fast’ pathways. Where the ephemeral gullies delivering overland flow are incised deeply enough to intersect a perched water table, a delayed, ‘old’ water-like signal may be transmitted.

Boreal peatlands are substantial terrestrial carbon storages. They are also important for the function of several large-scale cycles and systems that humanity benefits from. Drainage affects peatlands by establishing a new, lower equilibrium for the groundwater table. As a consequence of a lowered groundwater table and physical disturbance from the ditch, a chain of events is triggered, causing a number of changes in the hydrology and hydrochemistry of peatlands. The review aimed at gathering the most relevant literature on how boreal peatlands are affected by drainage. This was carried out by searching for scientific articles on online databases and libraries. Besides reviewing hydrology and hydrochemistry, a compilation of boreal peatland characteristics and a background on the history of Swedish peatland drainage are handled in the report. The results show that concentrations and loads for a long range of water quality parameters are affected by drainage. The effects vary a lot depending on different peatland characteristics. Both runoff and chemical changes depends largely on whether ditches reach mineral soil beneath the peat. The most obvious and adverse effect on chemistry is a large increase in suspended solid concentration and export. Other changes include increases of mineralized nitrogen, decreased organic carbon transport, increased annual runoff and increased levels for a number of elements, such as Mg, Ca, K and Mn.

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 <1000 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 (< 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 "Toth" 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 (> 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.

Fens are increasingly recognised as important habitats in terms of biodiversity, and this has been formalised in recent legislation (EC Habitats Directive, 92/43/EEC). The influence of groundwater and surface water inputs on the fen habitat increases its vulnerability to water pollution, particularly from nutrients. Despite the conservation importance and potential vulnerability of the habitat, fens have not been widely studied in Scotland, in terms of extent, location, sensitivity to increased nutrient inputs, or in comparison to similar European sites. This study found that fens were widespread throughout mainland Scotland, and that basin fens were the most commonly occurring fen type, representing 43% of the 355 sites assessed. A survey of 18 basin fens found that 72% were potentially vulnerable to elevated nutrient inputs, being surrounded by improved/modified land. Despite this, only four sites showed greater nutrient concentrations in sub-surface water samples or water inputs. There was, however, a significant amount of variation in hydrochemistry between the sites. Detailed studies further assessed spatial and temporal variations in hydrochemistry, and associated hydrologic regimes on two similar basin fens, one in an agricultural catchment, the other surrounded by unimproved grassland. Spatial patterning of vegetation was associated with both base-richness and nutrient concentrations of subsurface water, and the frequency of water inundation. General relationships between the six fen vegetation types and the observed hydrological and hydrochemical variation were presented.

Hydrological pathways and episodic stream acidification were investigated by monitoring water quality in the Coalbum catchment during the later stage of canopy closure. Coalburn is a long-running experimental site, almost completely covered by a commercial coniferous plantation (part of the Kielder Forest in northern England). Regular sampling, event sampling and continuous monitoring were used to establish an extensive water quality data-base between 1993 and 1997. Cloud mist and precipitation at Coalburn are slightly acidic and the catchment can receive moderate levels of dry and wet acid deposition when the winds have tracked from an easterly direction. Coalburn streamwater chemistry displays well-buffered base-flows and acid episodes during high flows. Duration-frequency-magnitude analysis of the Coalburn acid episodes reveals they were less frequent than expected but had a longer duration. The acid events exceeded environment quality standards for freshwaters: pH and aluminium concentrations suggest a toxic impact on freshwater biota. However, the elevated calcium concentrations and presence of humic substances reduce the biological impact. The chemical signatures and variations in solutes were identified and used to postulate the causal mechanisms of the hydrochemical response and to produce the conceptual Coalburn runoff model. Mixing modelling was then applied to introduce a robust analysis into the process and produce the simplified Coalburn Model of acidification. Broadly, the Coalburn hydrochemical response can be explained by pre-event water sources and 'normal' catchment processes. However, during extreme events catchment conditioning and event-water can also influence the response. In improving knowledge of the likely water quality effects of coniferous plantation afforestation, the Coalburn study has contributed to calibrating the temporal and spatial variability of headwater acidification (and hence risks). This allows policy makers and environment managers to make informed decisions about land use/management and to apply the precautionary principle; the research findings were used to suggest a basic policy framework and protocols for catchment assessments to manage acidification issues through the cropping cycle within a headwater catchment.

This thesis reports the results obtained, and conclusions made regarding research into the hydrochemistry of a small impounded karst area in southeastern Australia. Water samples were collected from a variety of sites over a period of approximately six years and include samples that are representative of baseflow (drought conditions) and flood (high flow conditions) the two extremes of the flow regime. Four distinct water types were found to be associated with the karst spring and cave water sites sampled. In terms of physical, chemical and computed parameter values these have been classed as TYPE 1 water (median parameter values similar to those noted for the surface stream sites sampled with catchments of non-carbonate material); TYPE 2 water (catchment predominantly of limestone); TYPE 3 water (catchment predominantly of dolomite); TYPE 4 water (high median chemical concentrations). Spatial variation within the study area is considerable and intrinsic factors such as catchment lithology, the residence time of recharge, aspect and vegetation cover are the major natural controls in determining physical and chemical characteristics.

This thesis presents precipitation, streamwater and soil chemistry from three upland catchments in Scotland situated upon granite parent material and receiving different deposition loadings. Marine ions are identified as important components of precipitation and streamwater at the two coastal sites (Bealach and Cardoon) and lesser importance at the inland site (Allt a'Mharcaidh). Similar ratios of Na:Ca:Mg in precipitation and streamwater indicate the importance of catchment hydrology and organic soils in controlling streamwater chemistry. Input/output budgets indicate SO4-S and H+ loss from the Cardoon (a region of high acid deposition inputs) compared with the other two less polluted sites which exhibit SO4-S and H + retention. The SO4-S loss from the Cardoon is also associated with a high DOC flux in streamwater. In all three catchments differences were found between published critical load values and those calculated as part of this study. Seasonal and annual variations in critical loads for freshwaters at all sites indicate sampling for the national mapping exercise does not reflect the most acid-sensitive periods. Streamwater was also more sensitive than standing waters, with lower critical load values. Soil critical load values were lower than published soil critical load values as well as freshwater critical loads calculated in this study. Inclusion of marine-derived base-cations in PROFILE calculations of soil critical loads increased values markedly (1 keq ha-1yr -1) at the 2 coastal sites. Soil critical load varied little between horizons, suggesting that the identification of hydrologically important mineral horizon was not important. Lowest critical load values for freshwaters were controlled by the organic horizons which are not considered in PROFILE calculations. The implications of the omission of organic horizons from critical load calculations for soil in upland catchments are discussed and the use of critical loads at a catchment based level addressed.

This study uses high-resolution, long-term conductivity, temperature, discharge, pH, and laboratory data from 2001 through 2003 from an alpine karst spring located at 2,500 m amsl in Sequoia National Park, California to reveal detailed chemical parameters of this karst system. The data show a system with a pronounced spring run-off, extended periods of base flow quiescence, storm responses tied to precipitation as rain or as snowfall, and clear diurnal and seasonal patterns of discharge. pH and spC values show an inverse relationship to discharge and temperature, which are generally in phase. Total inorganic carbon (TIC) and the fraction of mineral-derived and biologically derived C were calculated using three methods. One provided values close to the theoretically likely ratio of 50:50 between the two C sources, while others showed ratios of greater biologically derived C, an unlikely possibility in groundwater chemistry. Saturation indices for the system vary seasonally, with base flow waters saturated at SI values between 0.2 and 0.5, and spring run-off (Q > 100 L/s) waters under saturated and chemically aggressive with SI values as low as -1.2. Late summer rain storm events can return the system to an under saturated state. The denudation rate for the marble bedrock, which makes up approximately 8% of the basin, was found to be high at 148.6 mm/1000 years. Ion and TIC flux are shown to be determined by discharge and not ion concentration.

Chemical and tritium analyses of groundwater, precipitation and discharge records, fracture orientations, lineaments, and structural, stratigraphic, and topographic relationships have been used to describe the groundwater systems of Mantua Valley, north-central Utah. Groundwater flows through fractured Paleozoic quartzites and carbonate rocks and discharges from eleven perennial springs in Mantua Valley. Permeability in quartzites is the result of intense faulting and jointing. Groundwater in carbonate aquifers flows through fractures and/or fractures modified by solution and discharges as relatively large springs (up to 227 liters per second). Neogene normal faulting, rather than extensive karst processes, has produced valleys which are closed or nearly closed to surface-water drainage. Groundwater in the area has relatively low total dissolved solids, is warmer than the mean annual air temperature, and is of the calcium-magnesium-bicarbonate type. Temperatures of the groundwater suggest circulation depths in excess of 10 to 185 meters. Intermittent turbidity and fluctuations in calcite and dolomite saturation indices and in groundwater temperatures suggest that springs may be supplied by mixtures of shallow and deeper groundwater flow. With the methods used here, a water budget analysis of the area indicates that recharge to the groundwater systems is approximately 49% of mean annual precipitation. Annual recharge and average discharge of the springs were used to calculate recharge areas, which range from 3.0 km2 to 18 km2. Tritium analyses of two of the springs suggest mean residence times of less than ten years.

Delta Wadi El-Arish, Sinai Peninsula, Egypt, forms one of the most important parts of Egypt for industrial and agricultural expansion projects. This study focuses on the hydrogeology and the hydrochemistry of the Quaternary aquifer in the delta Wadi El-Arish area. Accurate information about the groundwater characteristics of the Quaternary aquifer will allow implementation of a sound water management policy for the Wadi El-Arish area. The objectives of this study include: 1) determining the relationships between groundwater extraction and water levels and water quality using water-level measurements, total extraction of the wells, and chemical analyses of water samples; 2) determining the direction of groundwater flow using water-level measurements; 3) calculating the hydraulic parameters of the Quaternary aquifer using pumping test data; and 4) determining the hydrochemical characteristics of groundwater in the Quaternary aquifer. The results of this study indicate that: 1. Potentiometric surface elevations have decreased by an average of about 0.5 m. 2. Potentiometric surface elevations have decreased in response to an increase in extraction rates. 3. The transmissivity of the lower Pleistocene calcareous sandstone (kurkar) unit is higher than the transmissivity of the upper Pleistocene sand and gravel alluvial deposits. 4. Groundwater in the upper Pleistocene sand and gravel aquifer is augmented with groundwater leaking from the overlying Holocene sand deposits through the intervening sandy clay aquitard. 5. Total dissolved solids (TDS) concentrations have been increased by an average of about 1,500 ppm. 6. An increase in sea water intrusion in the northern part of the study area has occurred. 7. Groundwater in the calcareous sandstone kurkar is of lower quality than groundwater in the alluvium sand and gravel. Management of the groundwater resources should include the following recommendations: 1. No new pumping wells should be drilled in the area. 2. Accurate estimates for the total recharge should be determined using a more detailed water budget for the delta Wadi El-Arish area. 4. The operation of wells should be managed by an automatic control system.

For effective resource management and to establish groundwater and surface water interactions, an innovative range of hydrological tracers and hydrochemical techniques have been applied to a total catchment in southeast Queensland. Stable and radioisotopes, carbon-14, radon-222, noble gases and SF6 were analyzed to characterize and quantify recharge sources. Statistical methods were also combined with inverse geochemical and three-dimensional geological modelling techniques, to develop regional conceptual models of groundwater movement and interaction with rivers.

Groundwater salinity is widespread in Western Sydney; however, little is known about the processes which cause it. This thesis explored many features of the shallow groundwater system using a range of hydrogeological, geochemical and statistical techniques. Geostatistical analysis of historical data highlighted that 53.6% of the study region had shallow groundwater with an electrical conductivity exceeding 2,000µS/cm. Salinisation hazard mapping indicated that 0.66% of the region has a high salinisation hazard and 54.2% has a moderate salinisation hazard. The high-temporal-resolution dataset collected for this study, allowed the recharge and salt source (modern rainfall) to be identified, plus mechanisms of salt accumulation (cyclic process of evaporation and re-dissolution driven by high rates of evapotranspiration and clay-rich soils), and transport. From this, a geochemical model identifying the processes contributing to groundwater salinisation, and a conceptual model of the hydrogeological system were developed. Multivariate analysis identified seven water-types, their geographical distribution, and the causes of temporal variability for each water-type. Saline groundwater was found in many parts of the landscape, though temporal variability was generally limited. The monthly comparison approach, which analyses temporal variability, was developed for this study. This method increased our understanding of system variability and its causes, ultimately improving the conceptual model. The conceptual model generalises the geographical distribution of water-types based on landscape features, while temporal variability is related to water-types. The model significantly improves our understanding of the groundwater system, and our ability to manage it. Additionally, this study has illustrated that groundwater salinity arising from evaporative processes could be more wide-spread than currently thought, and may not be confined to arid or semi-arid environments.

Kentucky’s Upper Green River Basin has received significant attention due to the area’s high biodiversity and spectacular karst development. While carbonate bedrock is present throughout the watershed, it is more extensive and homogenous along the river between Greensburg and Munfordville than upstream from Greensburg where the geology is more heterogeneous. This research quantitatively evaluated how lithological differences between the two catchment areas impact hydrochemistry and inorganic carbon cycling. This first required correcting catchment boundaries on previous US Geological Survey Hydrologic Unit Maps to account for areas where the boundaries cross sinkhole plains. Basin boundaries using existing Kentucky Division of Water dye trace data differed from the earlier versions by as much as three kilometers. The river at the downstream site is more strongly influenced by carbonate mineral dissolution, reflected in higher specific conductance (SpC) and pH. The SpC at Munfordville ranges from 0.9 to 4.8 times that at Greensburg, averaging 2.0 times higher. Although rainfall is impacted by sulfuric acid from coal burning, river pH is buffered at both sites. The pH is higher at Munfordville 91% of the time, by an average of 0.28 units. Diurnal, photosynthetic pH variations are damped out downstream suggesting interactions between geologic and biological influences on river chemistry. River temperature differences between the two sites are at least 4oC higher at Greensburg under warm season conditions, but there is a clear trend of temperature differences diminishing as the river cools through the fall and winter. This results from a relatively stable temperature at Munfordville, impacted by large spring inputs of groundwater within the karst region downstream. Although weak statistical relationships between SpC and HCO3 - create uncertainties in high resolution carbon flux calculations, measurement of these fluxes is more highly impacted by discharge variations than concentration variations, which resulted in average daily atmospheric flux estimates within 34% between the two basins using weekly concentration data (3.3x108 vs. 2.2x108 gkm-2 d-1, where km2 is the outcrop area of carbonate rocks), and within only 12% using 15-minute concentration data from regressions (2.6x108 vs. 2.3x108 gkm-2 d-1) for Greensburg and Munfordville, respectively.

ROCHA, Ludmila Prazeres das Flores Oliveira. Hidroquímica do aquífero costeiro do município de Itarema - Ceará. 2015. 311 f. Tese (doutorado em geologia)- Universidade Federal do Ceará, Fortaleza-CE, 2015.
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The study area covers the coastal area of the county of Itarema, 230 km from Fortaleza, West coast of the State of Ceará. In this area, rare are the works aimed at the study of both surface water and groundwater. Although the exploitation of groundwater tends to increase in the area, due to the increase in population density, bringing with it potential risks of water contamination. Therefore it is important to assess the quality of the water and recharge mechanisms for the preservation and rational use of these resources. We collected samples of surface water and groundwater and carried out measurements of physical, chemical and bacteriological variables for all nine (9) sampling campaigns, using titrimetry, spectrophotometric, potenciometric and atomic absorption spectrometry methods. Groundwater is predominantly fresh water. And surface waters, according to the IQA-CETESB classification are good for public supply. Nitrate contamination in groundwaters, even at low concentrations, shows anthropic actions, not featuring seasonal effect. The study of trace elements sometimes presented some elements with higher levels than the VMP estipulated expected in the current legislation. However, these are not related to possible contamination by agrochemicals, according to the results of the analyses for quantification and qualification of organophosphates. Such results can be associated with the construction of the wells, their depth, waste deposition of various materials and even rock formations in the area. With respect to the study of isotopes, prevail lighter waters during the rainy periods than those collected during periods of drought, which characterizes the amount effect in rainfall. Through the water balance was estimated that, on average, about 31% of the total annual precipitation recharge the aquifers. Finally, the study of vulnerability to contamination of the aquifer, through the DRASTIC method, showed that in 79% of the area prevail moderate and high vulnerability. This requires great care with the use and occupation of the soil, in order to prevent damage to groundwater resources.
A área do estudo compreende a Zona Costeira do município de Itarema, distante 230 km de Fortaleza, Litoral Oeste do Estado do Ceará. Nesta área são raros os trabalhos que visam o estudo tanto das águas superficiais quanto subterrâneas. A explotação da água subterrânea tende a aumentar na área, devido ao aumento na densidade demográfica, trazendo com isso riscos potenciais de contaminação da água. Nesse sentido torna-se importante avaliar a qualidade da água e os mecanismos de recarga para a preservação e uso racional dessa. Foram coletadas amostras de águas superficiais e subterrâneas e realizadas medidas de variáveis físicas, químicas e bacteriológicas durante nove (9) campanhas de amostragem, empregando métodos titulométricos, espectrofotométricos e potenciométricos. As águas subterrâneas apresentam-se predominantemente como doce. E as águas superficiais, segundo classificação IQA-CETESB, encontram-se boas para abastecimento público. A contaminação por nitrato em águas subterrâneas, mesmo em baixas concentrações, evidencia ações antrópicas pontuais, não caracterizando efeito sazonal. O estudo dos elementos traço ora apresentou teores de alguns elementos mais elevados que os VMP previstos em legislação vigente, ora não. No entanto, estes não estão relacionados à possível contaminação por agrotóxicos, segundo os resultados das análises para quantificação e qualificação de organofosforados. Tais resultados podem estar associados ao tipo de construção dos poços, à profundidade destes, aos descartes de materiais diversos e até mesmo formação rochosa da área. Com relação ao estudo dos isótopos, prevalecem águas leves durante os períodos chuvosos às coletadas nos períodos de estiagem, o que caracteriza efeito quantidade de chuva. A recarga do aquífero (Ie) na área, foi estimada em 368,73 mm, representando 31% da PPT. E por fim, o estudo de vulnerabilidade à contaminação do aquífero através da aplicação do método DRASTIC apresentou que em 79% da área, predomina vulnerabilidade moderada e alta. Isso exige maiores cuidados com o uso e ocupação do solo, de forma a evitar danos aos mananciais subterrâneos.

Several thousand coastal perennially ice-covered oligotrophic lakes and ponds have been identified on the Antarctic continent. To date, most hydrochemical studies on Antarctica’s ice-covered lakes have been undertaken in the McMurdo Dry Valleys (more than 20 lakes/ponds studied since 1957) because of their proximity to the McMurdo research station and the New Zealand station Scott Base. Yet, little attention has been given to coastal ice-covered lakes situated in Antarctica’s central Queen Maud Land region, and more specifically in the Untersee Oasis: a polar Oasis that encompasses two large perennially ice-covered lakes (Lake Untersee & Lake Obersee), and numerous small ice-covered morainic ponds. Consequently, this PhD research project aims to describe and understand the distribution, ice cover phenology, and contemporary hydrochemistry of perennially ice-covered lakes and ponds located in the Untersee Oasis and their effect on the activity of the benthic microbial ecosystem. Lake Untersee, the largest freshwater coastal lake in central Queen Maud Land, was the main focus of this study. Its energy and water mass balance was initially investigated to understand its current equilibrium and how this perennially well-sealed ice-covered lake may evolve under changing climate conditions. Results suggest that Lake Untersee’s mass balance was in equilibrium between the late 1990s and 2018, and the lake is mainly fed by subglacial meltwater (55-60%) and by subaqueous melting of glacier ice (40-45%). A recursive stable water isotope (δD-δ18O) evolution model for well-sealed perennial ice-covered lakes that takes into account the effect of changing chemistry in residual waters on δD-δ18O values was then developed and determined that Lake Untersee is in isotopic steady-state. Modeling results also showed that Untersee most likely did not receive additional inputs from surface streams during the last 300–500 years at the time of sampling, in November-December 2017. However, in mid-January 2019, Untersee experienced a glacial lake outburst flood (GLOF) that increased the water level by 2 m (contributing 1.75×107 m3 of water), modifying its water chemistry and inorganic carbon load. High-resolution grain size and carbon isotope analyses of the benthic microbial mats suggest that GLOFs occurred periodically over the Holocene and that those events sporadically increased the primary productivity of its benthic microbial ecosystem. Finally, ice-covered ponds in the Oasis were identified and sampled to compare their morphometric properties, hydrochemical properties, and microbial mat activity with Lake Untersee. It was discovered that the Untersee Oasis ponds offer the full spectrum of ice cover types (i.e., perennial well-sealed, perennial and moat forming, and seasonally ice-covered) and that their hydrochemical properties depend on ice cover type. Empirical pond data was used to determine how Lake Untersee and the ponds themselves will evolve as they transition under a warming climate from well-sealed to moat forming and from moat forming to seasonally ice-covered.

This work describes an investigation into the impact of acid deposition on the hydrochemistry of the three main tributary catchments at Loch Dee in Southwest Scotland. The research covers two main objectives. First, the hydrochemical processes that determine the observed streamwater chemistry are examined empirically through the determination of the hydrochemical budgets for each sub-catchment. Second, the ability of the Integrated Lake Watershed Acidification Study model (ILWAS) to simulate the observed hydrochemical processes is evaluated. From the hydrochemical budgets two major factors are identified as responsible for the spatial variability in the streamwater chemistry at Loch Dee. These factors are the underlying geology and land-use management techniques. The role of afforestation is difficult to judge due to the immaturity of the forest. However, the budgets indicate that any influence is a result of the pre-afforestation ploughing and drainage rather than the presence of the trees. On a temporal basis the hydrochemical budgets show considerable variability on both a monthly and an annual timescale, with the variability in the streamwater outputs of bases and nutrients primarily related to the variability in precipitation quantity. The budgets also indicate that, particularly on an annual timescale, the dry deposition of sulphate and hence of acidity to the catchment varies considerably. Furthermore, on a monthly timescale, the temporal variation in the budgets indicates that the conservative ion chloride can be physically stored within the catchments. This finding has severe implications for the estimation of dry deposition inputs and for the utilisation of simple hydrochemical models. The ILWAS model is generally able to simulate the hydrological response of both catchments. However, the chemical simulations of both catchments are considerably smoothed and bear little resemblance to the observed data. This failure is ascribed to the large number of input variables for which site-specific data are not available, together with the use of monthly averaged precipitation quality to drive the model. Sensitivity analysis of the model indicates that the most critical input variables are the soil depth and soil solution chemistry, and that the majority of the input variables can be considered as calibration parameters. Given the subsequent large number of calibration parameters it is suggested that a unique calibration of the model will rarely be possible. Consequently, it is concluded that the primary use of the ILWAS model will be as an explanatory tool for examining conceptual ideas about the hydrochemical processes that determine acidification. The model's value as a management tool to help mitigate the effects of anthropogenically derived changes in surface water chemistry will be extremely limited.

Baseflow water chemistry between different septic system density groups was analyzed to understand how septic system usage impacts the water quality of the Yellow River Watershed located in Gwinnett County, Georgia. Seventy water samples were collected at baseflow conditions in the summer of 2006. The samples were analyzed for the abundance and distribution of chlorides, sulfates, nitrates, and specific conductance. Geographic Information Systems were used to determine sample collection sites, assign samples into density groups, and spatially analyze and display the results. Statistical methods were used to compare the results of each density group with all others,and to find any correlation of the anions with respect to specific conductance. Regression coefficient values between nitrate and specific conductance in all groups average 0.77 and the elevated nitrate concentrations in group four suggest a limited relationship between septic system density and baseflow water quality.

The Mt. Tom Price Mine, located in the Pilbara region of Western Australia, has been the site of major iron ore mining since the 1960s by Rio Tinto Iron Ore/Pilbara Iron. The thesis project area covers approximately 121 km², covering the Mt. Tom Price Mining area and the surrounding catchment boundary. The climate in the Pilbara region is arid, with rainfall driven by seasonal cyclonic events, producing 300 mm/year net rainfall on average. The geology of the Mt. Tom Price area consists of a series of banded iron formations (BIF) and shales that are generally low in hydraulic conductivity values. Iron ore in the region is produced through the process of supergene enrichment whereby gangue minerals are dissolved and replaced with haematite and goethite. Mining is focused in a series of open cast pits including, North Deposit, West Pits, Centre Pits, Southern Ridge, South East Prongs, Section Six, Section Seven, and the proposed Marra Mamba Pits. Due to the impermeable nature and complex geology of the BIF sequence, groundwater flow is dominated by bedrock aquifer flow, with compartmentalization occurring in several areas of the mine. Highly faulted and folded units can also have increased hydraulic conductivity values. Pit floor lowering began to encounter the regional water table in early 1994. A series of dewatering bores and depressurization measurements have been utilized to ensure dry mining practice. This data was used to help understand regional groundwater flow and create the Mt. Tom Price Groundwater Model (MTPGM). A 3D geological model of the project area was created to aid visualisation of semi-regional hydrogeology. From this model, accurate template files were created so that geological detail loss is kept to a minimal when entering hydrogeological parameters into the MTPGM. The MTPGM was setup using PMWIN Pro, a graphical user interface for use with MODFLOW. Stresses such as recharge and pumping were entered via software packages within MODFLOW. The model was run to simulate measured 1994-2007 responses to dewatering and high rainfall events. A Parameter Estimation (PEST) software package and trial and error calibration was used to lower stress response variances that were observed in the model output files. This was achieved by the adjustment of hydrogeological parameters such as hydraulic conductivity and specific yield values. A prediction simulation of final pit lake recovery was created Using the calibrated MTPGM. Recovery curves predicted that full recovery of the water table of the pit voids varied from 96 to 120 years, recovering to levels close to the initial heads measured in 1994 before large-scale pumping commenced. The hydrochemistry of the groundwater in the mining area is highly influenced by geological hosts, with clearly defined hydrochemical signatures approximated for each screened geological unit. Due to the sulphur rich, acid- forming Mt. McRae Shale, regular monitoring of pit and groundwater is essential. Final pit lake water quality was estimated using final pit levels and recovery rates approximated from the MTPGM, combined with historical data and previous groundwater quality reports. Pit lake water quality is dominantly driven by evaporation concentration, caused by high evaporation rates and low throughflow. Pit waters are expected to be brine waters (greater than 100,000 mg/L TDS), with high levels of acidity values occurring in the South East Prongs and Section Six pits due to the exposure of the acid forming Mt. McRae Shale above the pit lakes at these localities. Future studies should focus on more detailed modelling of the compartmentalised aquifer systems. This would produce much more accurate final pit lake levels. Further study of the Mt. McRae Shale formation and its implications on acidity should also be undertaken. Seasonal fluctuations in lake levels will affect acidity due to the continual re-exposure and oxidation of the Mt. McRae Shale. This could be studied to help understand short term pit lake quality conditions and help to predict long term acidity conditions in the pit lakes.

The links between hydrology, hydrochemistry and salmonid ecology were examined in an interdisciplinary study of the effects of hyporheic water quality on the survival and the development of salmonid ova. Three catchments located in the northeast of Scotland were examined. Work focussed on the Newmills Burn, a degraded agricultural catchment. Complementary studies were also undertaken on the Pow Burn, a comparative agricultural catchment, and the Girnock Burn, a contrasting semi-pristine upland catchment. The relative importance of sediment transport, groundwater-surface water (GW-SW) interactions and hydrochemistry, for the survival and development of salmonid ova, was assessed between spawning in autumn, and hatch in spring. Hydrochemical, hydrometric, isotopic and modelling techniques were applied to the problem in an evolving, serial approach to investigation. The infiltration of fine sediment to the streambed was not sufficient to explain observed fine scale spatial variability (<1m), nor complex spatial patterns of sub-surface hydrochemical change. Hydrochemical and piezometric data indicated that the observed spatial and temporal patterns could be explained by variable contributions of chemically reduced groundwater to the hyporheic zone. At the catchment scale, gross differences in land-use and channel characteristics substantially affected GW-SW interactions and consequently in-redd water quality. At the reach scale, local GW-SW interactions were controlled by geomorphology and riparian sedimentary stratigraphy. At the scale of individual redds, the influence of groundwater generally increased with depth into the hyporheic zone. Dissolved oxygen (DO) levels were implicated as the dominant control on in-redd mortality. Embryo survival and development correlated with mean DO concentrations. Mortality rates from samplers located within artificial redds ranged from 0-100% and showed a significant inverse relationship with mean DO concentrations (r2 = 0.85, P < 0.01). Where embryos survived, low DO affected rates of development. Embryos exposed to low DO concentrations retained a higher portion of the yolk sac mass near to hatch than those developing in more favourable conditions.

El comportament hidrodinàmic de les aigües subterrànies en conques intramuntanyoses ve condicionat principalment per la geologia, i especialment pel context estructural i els materials sedimentaris que reomplen la conca. L'estudi d'aquestes àrees requereix un enfocament a gran escala per poder determinar les zones de recàrrega i descàrrega dels diferents sistemes de flux que conformen els recursos hídrics de la zona. Aquestes zones solen estar afectades per un fort desenvolupament humà que pot donar lloc a una modificació de la quantitat i la qualitat de l'aigua subterrània de diferents formes. En aquest sentit, en conques intramuntanyoses és un aspecte clau entendre la importància de la geologia i de les pressions humanes en el flux d'aigua subterrània per arribar a assolir una gestió correcta dels recursos hídrics, així com per assegurar llur disponibilitat a llarg termini.
En aquesta tesi s'ha estudiat la depressió de la Selva com a un cas paradigmàtic on té lloc una important pressió sobre els recursos hídrics subterranis. Per tal d'estudiar el paper hidrogeològic que juguen les falles regionals en conques intramuntanyoses, en primer lloc, s'ha realitzat un model hidrogeològic conceptual a partir de la modelització del flux subterrani. Per fer‐ho, s'ha dut a terme una simulació d'una zona de falla subjacent a una formació al∙luvial, on la falla pot recarregar o drenar l'aqüífer al∙luvial. S'han considerat diferents valors de permeabilitat per la zona muntanyosa, la zona de falla i els materials sedimentaris, així com diferents gruixos de falla i condicions de contorn. Els resultats mostren que es poden produir fluxos verticals ascendents i descendents a la part superior de la zona de falla degut a l'acció de la formació al∙luvial, i fins i tot a través del sòcol, influenciant per tant la recàrrega dels materials sedimentaris de la depressió.
En segon lloc, s'ha caracteritzat el sistema hidrogeològic de la depressió de la Selva mitjançant mesures del nivell piezomètric i dades hidroquímiques e isotòpiques (δ18O, δD) al llarg de diverses campanyes de camp amb un doble objectiu: (i) caracteritzar un sistema hidrodinàmic on els elements tectònics juguen un paper important en la hidrodinàmica subterrània, i (ii) descriure la influència de l'explotació d'aigües subterrànies en la hidrodinàmica del sistema. Els resultats piezomètrics han posat de manifest la relació existent entre les formacions situades a les zones de muntanya que envolten la depressió i els materials sedimentaris que rebleixen aquesta. Les zones de falla tenen un efecte directe en la recarrega, permetent l'existència de fluxos verticals ascendents des del sòcol cap a diferents aqüífers sedimentaris. Les dades hidroquímiques i isotòpiques han validat aquestes observacions. En aquest sentit l'ió fluor (< 15 mg/l) i nitrat (< 217 mg/l) han estat usats com a traçadors dels fluxos profunds i superficials respectivament i han permès posar de manifest l'efecte dels bombejos en la distribució de les línies de flux. La composició isotòpica de la molècula de l'aigua (18OH2O, D) ha evidenciat canvis estacionals en les aigües captades pels pous posant de manifest l'existència de dos sistemes de flux: un sistema de flux regional amb llargs temps de trànsit i originat a les zones circumdants més elevades, i un sistema de flux local recarregat a la zona de la depressió. Els dos sistemes contribueixen de manera diferent als recursos hídrics que s'estan explotant, i la seva aportació específica defineix el potencial de la depressió per una explotació sostenible a llarg termini.
S'han caracteritzat les aigües des d'un punt de vista hidroquímic a partir de la composició en elements majoritaris, minoritats i traça (fluor, brom, liti, TOC) i de dades isotòpiques (18OH2O, D, triti, 34SSO4, 18OSO4). Aquesta caracterització ha permès una descripció acurada dels processos geoquímics que defineixen les fàcies hidroquímiques de l'aigua subterrània al llarg de la depressió de la Selva. Així, s'han definit dos sistemes de flux regional i diferents qualitats de l'aigua associada a la recarrega local, i alhora s'ha corroborat el model hidrogeològic conceptual de la depressió de la Selva.
Des d'un punt de vista regional, a la depressió de la Selva el control estructural defineix sistemes de flux locals, intermitjos i regionals, els quals son responsables de la hidrodinàmica a gran escala, fins al punt que aquests son responsables de la recuperació dels descensos del nivell piezomètric després del període de màxima extracció (estiu). A la zona d'estudi, l'origen de la recarrega, a escala regional, és atribuïda a la serralada Transversal, a la zona més septentrional de la conca, i a les Guilleries, especialment a la zona oest. Aquests sistemes hidrogeològics impliquen un flux vertical ascendent des del sòcol que recarrega els nivells aqüífers neògens de la depressió. Els sistemes de flux locals i intermitjos s'originen a la pròpia depressió o a les zones circumdants més properes, els quals estan menys afectats per les zones de falla. La pressió antròpica crea una barreja entre els diferents sistemes de flux modificant la qualitat de l'aigua al llarg de l'any.
Els resultats d'aquest estudi mostren que en conques intramuntanyoses per obtenir una caracterització integrada del sistema hidrogeològic i el coneixement necessari per formular estratègies específiques cap a una gestió sostenible dels recursos hídrics, i en concret a la depressió de la Selva, és necessari:
i) la utilització de diferents metodologies per abordar l'estudi d'aquests tipus de sistemes hidrogeològics. Així, en el present treball primerament s'aborda des de la caracterització de camp fins a la modelització numèrica passant per l'estudi de nivell piezomètrics i dades hidroquímiques e isotòpiques;
ii) caracteritzar l'evolució piezomètrica de les diferents formacions geològiques juntament amb les característiques hidroquímiques/isotòpiques i els processos geoquímics relacionats que defineixen les mostres d'aigua, i per tant, cada un dels extrems de barreja de la recarrega (local, intermitja i regional) que participen en el conjunt del sistema de flux;
iii) finalment, identificar les pressions humanes, fins i tot en els sistemes a més gran escala, com una verdadera alteració al comportament natural.
Aquesta tesi defineix els sistema hidrogeològic de la depressió de la Selva com a exemple de funcionament hidrodinàmic sota pressions antròpiques aplicable a altres conques intramuntanyoses. Aquest coneixement és necessari per formular estratègies de gestió dels recursos hídrics des d'un punt de vista quantitatiu i qualitatiu, com a eina indispensable per satisfer la demanda lligada a una millora socioeconòmica sense produir un empitjorament de la qualitat ambiental a llarg termini.
Groundwater hydrodynamics in range‐and‐basin areas are essentially determined by their geology, including the tectonic structure and the basin sedimentary infilling. Their study requires a large‐scale approach to determining the location of the recharge and discharge areas of each flow system providing the basin with water resources. Furthermore, most of these areas have undergone heavy human development that can modify groundwater quantity and/or quality in different ways. Understanding geological and human influences on groundwater flow in these areas is a key aspect in achieving an adequate water resources management and therefore its future availability.
In this dissertation, the Selva Basin has been studied as a paradigmatic case of a range‐and¬basin area with severe human pressure on its groundwater resources.A conceptual hydrogeological model emphasizing the role of the main fault zones has been developed and tested using numerical flow modeling as a first step. Groundwater flow has been simulated in a range‐and‐basin area affected by a significant fault zone, which may drain or recharge an overlying alluvial aquifer. Various hydraulic conductivity values for the range rocks, the fault¬zone, and the sedimentary infilling of the basin are considered, as well as different fault‐zone widths and boundary conditions. The results show that upward and downward fluxes develop in the upper part of the fault zone controlled by the action of the alluvial aquifer, and even through the basement floor, which influence the recharge of the sedimentary infilling of the basin.
Second, the Selva range‐and‐basin hydrogeological system is described using potentiometric, hydrochemical, and isotopic data (δ18O, δD) taken from different field surveys, in order to achieve a twofold objective: (i) to describe a hydrogeological system in which tectonic elements play a significant role in the flow dynamics, and (ii) to show the influence of groundwater exploitation on the hydrodynamics of the system. Hydraulic head data indicate the relationships between the geological formations in the range areas and the sedimentary infill of the basin. In this context, fault zones and a fracture network have a direct effect on the recharge, and allow an upward vertical flow from the basement to the sedimentary aquifers. Hydrochemical and isotopic data support this observation. The use of fluoride (up to 15 mg/l) and nitrate (up to 217 mg/l) as tracers for the contribution of deep and shallow flow systems respectively provides a detailed portrait of the effects of pumping on the flowpath distribution. Isotopic data depict seasonal trends in groundwater captured by wells. Two distinct flow systems are differentiated: a regional, large‐scale, long residence time system, originating in the surrounding ranges, and a local flow system constituted by infiltration in the lower areas of the basin. The two systems contribute differently to the resources that are withdrawn, and their specific contributions define the potential for sustainable future water exploitation in the basin.
The final part of this hydrogeological study is a more specific description of the geochemical processes that determine the hydrochemical characteristics of groundwater across the Selva basin, based on the interpretation of major, minor and trace elements (such as fluoride, bromide, lithium, TOC, and their ratios to some major elements), and isotope data (18OH2O, D, tritium,34SSO4,18OSO4). It defines two different regional flow systems and different water qualities of local recharge anduses this specific data to corroborates the overall hydrogeologic conceptual model for the Selva range‐and‐basin area. From a methodological perspective, this chapter explores the use of minor elements and isotopes in the interpretation of regional scale system hydrodynamics. It also discusses their use as tracers of the distinct ground water flows originating in distinct recharge areas and influenced by an intricate tectonic setting.
The results of this dissertation describe the flow system of the Selva basin. In this basin, structural control defines the local, intermediate and regional flow systems responsible for the large‐scale hydrodynamics of the basin and, more importantly, the recovery of drawdown after the main withdrawal period (summer). The origin of the recharge of the large‐scale, regional flow systems is assigned to the Transversal range on the northern side and to the Guilleries range, especially in the western part. These hydrogeological systems include a groundwater flow within the basement and an upward vertical recharge from the basement to the overlying Neogene sedimentary layers. The local and intermediate flow systems originate in the basin itself or in the less‐elevated surrounding ranges, and the fault system has a minor effect on their flowpaths. Human development modifies the flow paths mixing the different flow systems and changing the water quality along the year seasons.
From a broader point of view, this highlights the value of using different methodological insights in the study of these hydrogeological systems, as well as addressing the problem of water management in complex geological environments. First, it presents the outcome of various methodologies ranging from field work to numerical modeling, together with the analysis of hydraulic head, hydrochemical and isotopical data. Second, it shows the relevance of potentiometric evolution in different geological settings, and the treatment of the hydrochemical/isotopic features and related geochemical processes that define groundwater samples and therefore each of the recharge end‐members (local, intermediate, and regional) that participate in the overall flow systems. Finally, it identifies the effect of human pressures even on large‐scale flow systems, as true alterations of natural behavior. The recognition of these effects, together with an integrated characterization of the hydrogeological system, provides the necessary knowledge for formulating specific strategies for assessment focusing on sustainability of water resources management in these geological contexts.
In specific terms, these strategies must be based on the importance of the groundwater flow terms in the water balance for a given hydrological basin. These terms are usually overlooked, yet they play an important role, especially when groundwater resources from deep confined (or leaky) aquifers are exploited. In the case of the Selva basin, identifying this contribution is fundamental in establishing potential future exploitation rates that further socio‐economic developments may generate. This dissertation shows the scope of several approaches to describing this term in the water budget in range‐and‐basin areas in order to determine the availability of water resources therein, as a first essential step towards sustainability.

>Magister Scientiae - MSc
The present study investigated the application of a multi-method approach to determine groundwater-surface water (GW-SW) interactions to quantify and characterize the quality of water resources in a fractured rock aquifer system in upper catchment of the Berg River (G10A). Demonstrating methods for improved understanding of groundwater and surface water interactions is important for informing development of strategies that ensure effective utilization and management of water resources. Applying a single method to inform innovative strategies for water resources has proved futile. The current study shows how the use of several methods can provide the basis for devising practical strategies for water resource utilization and management. The three methods were applied as follows: First, the base flow separation was used whereby the Chapman and Lynne & Hollick digital filter algorithms were applied to time-series streamflow data from four stream gauging stations in the catchment. The computation from algorithms on three sites (gauging stations) showed that the mean Base Flow Index (BFI) value ranged between 7%-8% for the 2012-2014 periods. This means that discharges from subsurface water storages dominate stream flows throughout the study period. Secondly, the quality of groundwater and surface water was sampled using standard methods. Piper Diagrams generated on Aquachem™ software and radial charts were used to identify the predominant hydrochemical facies. Results showed that Na-Cl was the predominant GW and SW water-type. This means that both GW and SW are mainly influenced by recharging surface water as well as interaction occurring between the rock matrices and infiltrating water. Multivariate statistical analyses were used to evaluate the factors controlling GW and SW chemistry in the upper Berg River catchment and the results showed that GW and SW are influenced by natural processes. Two main factors (a. & b.) were extracted which explained 71.8% of the variation in both GW and SW physicochemical parameters. These factors include water-rock interactions and the recharge of surface water. Cluster Analysis extracted four major clusters that grouped sites with similar physicochemical characteristics together. Finally, differential stream gauging was applied to a 600m reach above the Berg River Dam. Three 200m sub-reaches were used to compute differences in flows between sub-reaches. Stream flow at each sub-reach was estimated using mass balance equations with electrical conductivity measurements during instant salt tracer injection tests. Results indicated that during both the wet season (high flow) dry season (low flow), the river continuously lost water to the subsurface. This was demonstrated by the 0.91m³/s and 2.24m³/s decrease in stream flow along the 600m reach. Dry season flow decreases were less than wet season flow decreases, indicated by markedly lower flow loss in respect to the wet season. This confirms results of the analysis of base flow separation, which indicated that discharges from subsurface storages dominate stream flows during low flow periods. The differential stream gauging approach did not provide distinct points along the selected stream reach where GW-SW interaction occurred; rather it provided a holistic representation of seasonal flow variations along the selected reach. This study showed that upper Berg River catchment is dependent on discharges from subsurface water storages to maintain dry season flows. Furthermore, this study showed that infiltration of surface water and discharge of subsurface water transfers the respective chemical signature of the contributor, meaning that the transfer of water of suitable quality will reduce contamination in the receiving water body (i.e. surface water). Transfer of water between subsurface and surface water contributed an average of 8% of the gauged flows in the catchment between 2012 and 2014, suggesting that the groundwater recharge process dominates this catchment.

Projections of population growth, urban expansion and decreasing water resources in arid and semi-arid regions have increased the importance of urban runoff as a potential renewable water resource that, through enhanced recharge, can augment groundwater supplies. However, it is unclear how urbanization alters hydrologic and hydrochemical responses of small catchments ( < 5 km²) in these regions. This body of work identified controls on the spatial and temporal variability of hydrologic and hydrochemical responses of urbanized catchments in the Tucson Metropolitan area of semi-arid southern Arizona. The temporal distribution and characteristics of rainfall did not control urban catchment hydrology where overall, there was no evidence of significant seasonal catchment wetting. Land use did not control hydrologic responses although runoff was more frequent and of longer duration in urbanized than in non-urban catchments. Runoff depth and runoff ratios were controlled by the combined effect of imperviousness, the characteristics of the stormwater drainage system and rainfall depth. Runoff hydrochemistry did not vary in response to land cover or imperviousness. Rapid increases in solute stores between rainfall-runoff vents resulted in invariant seasonal runoff solute concentrations. Four major factors controlling runoff hydrochemistry were identified: 1) landscape heterogeneity and catchment connectivity, 2) the spatial extent of pervious and biogeochemically active areas, 3) the efficiency of overland flow and runoff routing mobilization and 4) the extent of catchment wetting. The stormwater drainage system, and specifically the characteristics of the stream channel substrate, emerged as significant controls of runoff responses. Conservative transport of biogeochemically active solutes during runoff was observed in piped, concrete and gravel lined waterways, whereas solute sourcing and retention was more dynamic in grass lined reaches. Biogeochemical processing in the stream channel substrate between runoff events indicates that pervious waterways alter soil solute pools available for subsequent solute transport, and that stream channel biogeochemical processes are tightly linked to the characteristics of the channel substrate and cyclical channel wetting and drying. This body of work indicates that successful stormwater management strategies in the semi-arid Southwest should focus on the stormwater drainage network and the presence, density and characteristics of pervious channels.

An assessment of the hydrochemistry of groundwaters in the Murray and Otway Basins along the Victorian - South Australian border has been conducted. This area is known as the Victorian Designated Area (VDA) and contains three main aquifers, the Tertiary Limestone Aquifer, Tertiary Confined Sand Aquifer, and Pliocene Sands Aquifer. The area extends from the Murray River in the north to the Bass Strait coastline in the south. Agricultural development and increasing reliance on groundwater resources in the region have prompted the need for an investigation into the processes affecting groundwater chemistry. Particular emphasis has been placed on the causes of groundwater salinisation. Data sourced from the Victorian Department of Natural Resources and Environment Statewide Groundwater Database were used to assess temporal and spatial groundwater salinity trends in these aquifers. Groundwater salinity in all aquifers generally increases northwards, and corresponds to generally decreasing recharge northwards in the VDA. Groundwater salinity also increases along inferred flow paths for all aquifers. Both increasing and decreasing temporal groundwater salinity trends are observed within parts of the study area. The overall groundwater composition of the Tertiary Limestone Aquifer was also considered, as this aquifer is the most extensively exploited in the VDA. The groundwater type varies from generally Ca,Mg-HC03 type waters in the south, to NaCl, S04 type waters in the north. Examination of the major ions showed several systematic associations; there is a strong linear relationship between sodium, chloride and electrical conductivity; a charge balance between cations and anions exists for some groundwaters; there is increased bicarbonate with respect to chloride concentrations, and increased calcium with respect to magnesium, when compared with theoretical mixing concentrations between rain water and sea water. Generally low sulphate to chloride ratios exist throughout the study area, and sodium adsorption ratios generally increase northwards. Tertiary Limestone Aquifer groundwaters are undersaturated with respect to gypsum, supersaturated with respect to calcite and dolomite, and close to equilibrium or supersaturated with respect to aragonite. The factors affecting groundwater composition vary throughout the study area, and between aquifers. They include: a) concentration of salts by evapotranspiration, b) water-rock reactions such as de-dolomitization, and water-soil interactions through cation-exchange processes, c) changes in land use, and d) possible movement of groundwater of variable quality between aquifers through low-permeability layers. Rainfall, evaporation and evapotranspiration rates, soil type, groundwater flow direction, length of groundwater residence time, hydraulic conductivity, flow velocity, geology and subsurface structural barriers to regional groundwater flow, all contribute to the processes controlling groundwater composition in this region.

Isotopes and hydrochemistry were used to define groundwater flow systems and better understand the hydrogeological setting of the Karijini National Park within the Central Pilbara region, this study was initiated because of the near proximity of the Marandoo iron ore mine to the National Park. Based on the stable isotope composition of the water samples, two main groups of water can be identified. Groundwater is characterised by depleted δD and δ¹⁸O, suggesting no significant evaporation effect. Surface water on the other hand is more enriched in δD and δ¹⁸O due to evaporation. The relatively high concentration of Cl- compared to rainfall and depleted δD and δ¹⁸O values of groundwater indicate that recharge of the aquifers is occurring during intense rainfall events when rapid infiltration occurs. Evapotranspiration then acts to concentrate ionic species prior to recharge. The presence of CFCs in the groundwater indicates the presence of modern recharge water. Relationships between various ionic species has shown that infiltration through the Tertiary sequence and subsquent dissolution of carbonate minerals is main influence on increasing concentrations of Ca²⁺ , Mg²⁺ , HCO₃⁻ . The TDS concentration of the groundwater in the Marra-Mamba Iron Formation that hosts the Marandoo ore body is higher than most of the water bodies surrounding the mining area. This suggests that either significant chemical modification is occuring or it is recharged by different mechanisms to that of the Karijini groundwater. Relationships between the major ion concentration and catchment area, surficial Tertiary cover and distance between recharge and discharge were identified. The results show that the hydrochemistry of the water discharging at each location within the National Park can be justified by groundwater evolution within it’s own catchment.