Seawater Intrusion Modeling

I also want to thank all people working at Chyn for creating such a pleasant and amusing working environment, which makes it almost the 'second home'. In particular, I would like to thank Daniel Hunkeler, Heinz Surbeck and Pierre Schnegg for their involvment in this project, leading to numerous results and very fruitful discussions. Without the close collaboration with the Cyprus Water Development Department, field work in Cyprus would not have been possible. Their interest and support and fruitful discussions were very much appreciated. Special thanks go to Dr. Andreas Christodoulides, whose personal involvement in helping us with anything we needed during the field campaigns in Cyprus will remain unforgettable. Special thanks go to the managements of the Lanitis and Phasouri plantations, who authorised the implementation of the monitoring wells and who provided a lot of logistical support. A very special thank goes to Fabien Cornaton for all the support and help he has given me throughout these years, with many discussions leading onto new tracks. Also, I want to thank him for all the long-distance trouble-shooting and debugging across the oceans and corrections he did for me in the last phase of the work. My parents and family I want to thank so much for all the unforgettable support I got from them, particularly in the very last and difficult phase of the work. My father's patience in correcting my 'awkward' english and his pertinent comments and advice kept me going.

For the extension of the harbour of Antwerp (Belgium), excavation is needed for a new dock. Appropriate measures need to be taken for the monitoring of the possible disturbance of the salt/fresh water distribution in the phreatic aquifer. The disruption can be caused by the deposition of the dredging sludge. In several piezometers, measurements have been carried out before the dredging started. In this way, the salt/fresh water distribution at time t 0 (March 2003) has been qualified. In March 2004, the first measurements to investigate the possible changes in groundwater quality have been carried out. There are no significant changes expected in the groundwater quality after one year. This is confirmed by the electromagnetic induction loggings.

Hydrogeochemical analyses were carried out to identify geochemical processes occurring in the low-lying coastal aquifer of Ravenna, North Adriatic Sea (Italy). The area is characterized by a complex coexistence of several environments: coastal dunes, paleodunes, pine forests, freshwater wetlands, rivers, brackish lagoons, gravel pit lakes, reclaimed lands, agricultural fields and industrial areas. Water quality is of primary importance for the sustainability of these, areas and a full understanding of geochemical processing is fundamental for their management. A total of 104 water samples was collected from groundwater wells and surface water bodies, and analyzed for the major and trace elements (TEs). Field measurements of chemical-physical parameters were carried out by a multiparameter device XS PCD650; major elements were analyzed following the Italian National Environmental Agency standards (APAT-IRSA 2003), while TEs were analyzed by ICP-AES/ICP-MS. The major findings include:...

Ground-and surface water chemistry and stable isotope data from the coastal zone near Ravenna (Italy) have been examined to determine the geochemical conditions and processes that occur and their implications for fresh water availability in the various brackish/saline coastal environments. Fresh water in shallow coastal aquifers is often not enough to provide drinking water but it may sustain agriculture and natural environments such as pine forests, dunes and lagoons. The hydrochemistry and stable O and H isotopes of the ground and surface water near Ravenna were investigated in relation to these particular environments: rivers, drainage channels, lagoons, coastal dunes, paleo dunes, agricultural fields, and gravel pit lakes. Emphasis was put on the spatial distribution of ground water bodies with similar hydrochemistry. Most water samples are of the brackish to saline NaClÀ type (NaCl concentration 300-20,000 mg/L) with a negative Base Exchange Index (BEX) that is indicative of cation-exchange reactions caused by water rock interactions during the infiltration of saline water in a fresh water aquifer. Calcium-dominated fresh water is found only in the rivers, in the irrigation and drainage channels, and in a few ground water samples. The analysis of stable isotopes and SO 2À 4 =Cl À and d 18 O/Cl À ratios shows that the major chemical and physical processes determining the salinity in the area are evaporation, mixing with saline water, cation exchange, oxidation of organic matter, migration and seepage of (hyper) saline water. The migration and upward seepage of (hyper) saline water driven by the hydraulic gradients induced by the drainage system causes the aquifer to become more saline over time. The areas where natural recharge occurs have always been small and this in combination with the Mediterranean climate results in very little natural recharge. Therefore, unless drastic changes to the hydraulic infrastructure are made, the coastal aquifer near Ravenna will become more saline and will threaten the ecology of current natural areas as well as the farmland.

Subsurface physical barriers have been effectively used to mitigate seawater intrusion (SWI). Traditionally, the primary emphasis in both numerical studies and practical implementations has been on vertical barriers. The current research aims to explore the dynamics of SWI under various cutoff-wall inclination angles and depths, as well as aquifer heterogeneity using both experimental and numerical simulations. The impact of aquifer characteristics was assessed by utilizing a low hydraulic conductivity (K) aquifer (case L), a high hydraulic conductivity aquifer (case H), and two stratified aquifers. The stratified aquifers were created by grouping different hydraulic conductivity layers into two cases: high K above low K (case H/L) and low K above high K (case L/H). The model simulations covered seven different cutoff-wall inclination angles: 45.0°, 63.4°, 76.0°, 90.0°, 104.0°, 116.6°, and 135.0°. The maximum repulsion ratio of SWI wedge length was observed at an inclination angle o...

Saltwater intrusion (SWI) is a widespread environmental problem that poses a threat to coastal aquifers. To address this issue, this research employs both numerical and experimental methods to study saltwater intrusion under the impact of sea level rise and varying freshwater boundary conditions in two homogeneous aquifers. The study compares transient numerical groundwater heads and salt concentrations to experimental results under receding-front and advancing front conditions. In the low permeability aquifer, the root mean square error is 0.33 cm and the R2 is greater than 0.9817. Similarly, in the high permeability aquifer, the root mean square error is 0.92 cm and the R2 is greater than 0.9335. The study also compares the results of ten experimental tests for steady-state saltwater intrusion wedge and toe length with seven different analytical solutions. The experimental results are then compared to these analytical solutions to find the most suitable equation. The Rumer and Har...

Groundwater field pumping out and tracer injection test had been carried out at Nghiem Xuyen commune, Thuong Tin district, Hanoi where salinized and fresh groundwater boundary exist in the Pleistocene aquifer. The test was executed with pumping out rate of 9l/sec and tracer injection rate of 0.7l/sec of water with the salt concentration of 5g/l. The interpretation and analysis of the groundwater solute transport parameters by the field pumping out and tracer injection test is a rather complicated and delicate task due to the variability of the temporal boundary conditions. The test results have shown that although the tracer injection time is rather long (up to 60 hours), the tracer breakthrough curve of the tracer concentration of the pumped out water has its very specific characteristic shape, however with some variation due to the test invisible variability of conditions. The results of the parameter identification based on the method of least squares have given effective porosity of 0.32 and longitudinal dispersivity of 2.5m (which give the hydrodynamic dispersion of from D=250m 2 /day right outside the pumping well screen to D=18m 2 /day right outside the injection well screen). The minimal sum of squares of the differences between the observed and model normalized tracer concentration is 0.00119, which is corresponding to the average absolute difference between observed and model normalized concentrations of 0.0355 (while 1 is the worse and 0 is the best). The results have also shown that the maximal tracer concentration right outside the pumping out well screen is 6.1 times greater than the tracer concentration of the pumped out water. The distortion flow coefficient αW (the ratio between the flow rate through the injection well section without its presence) and the groundwater flow into the tracer injection well is from 18.66 (at the early testing time) to 10.76 (at the later testing time).

This paper demonstrates the application of a recently developed free and open-source GIS-integrated hydrochemical-hydrogeological analysis tool (named AkvaGIS) for the management and interpretation of hydrogeological data with respect to a coastal aquifer system. The aforementioned tool is composed of a geospatial database implemented in Spatialite, complemented with a set of developed tools for the analysis, interpretation, and visualization of groundwater quality parameters and hydrogeological data. This ICT tool is part of the FREEWAT platform, an open-source and public domain GIS-integrated modelling environment based on groundwater flow and solute transport numerical models, including a water management and planning module. The case study that was used to perform a demonstration of the aforementioned tool, is a coastal aquifer system in Greece, suffering from both seawater intrusion and nitrate contamination as a result of extensive agricultural activities. It involves a complex hydrogeological environment incorporating karst and granular aquifer layers, subjected to different exploitation conditions. AkvaGIS was proved a useful ICT tool for the analysis and interpretation of the collected hydrogeological/hydrochemical data and results, which may be considered as a valuable tool for analyzing different aspects of aquifer systems.

In arid and semiarid zones, groundwater plays a key role in the ecology and availability of freshwater. Coastal lagoons in arid zones have great importance as a refuge for species of flora and fauna, as a source of freshwater, and for recreational purposes for local communities and tourism. In addition, as environments under natural stress, they are suffering pressure from anthropogenic activities and climate change, especially in zones with intense touristic development as in the case of the Baja California Peninsula in northwest Mexico. In this paper, we analyze the future of a coastal lagoon impacted by climate change and anthropogenic pressures. We constructed a groundwater MODFLOW-SWI2 model to predict changes in freshwater–saltwater inputs and correlated them with the geospatial analysis of the distribution and evolution of the water body and surrounding vegetation. The methodology was applied to the San Jose lagoon, one of the most important wetlands in the Baja California pe...

The island of Susak differs from other Croatian islands in its geological and hydrogeological properties, because it is, for the most part, covered with fine-grained loess-type sands. At the outset of the research it was unclear whether the main aquifer lies within the superficial deposits or within the underlying carbonate rocks. This gave rise to two alternative conceptual models, depending on whether the interface between the superficial cover and the carbonates occurs above or below sea level. Hydrogeological and geophysical investigations were conducted. The primary objective of the geophysical exploration was to determine optimum positions for exploratory boreholes. The results showed that the main aquifer is contained within the carbonate rocks, and that this carbonate aquifer is overlain by a second, confined, aquifer within the superficial sandy deposits. Groundwater within the carbonate aquifer is hydraulically connected to the sea by fault zones. Measurement of electrical conductivity in boreholes established that the mixing zone of fresh and salt water is at depths from 22 to 30 m below ground level. It is necessary to ensure constant control of pumping quantities and control of the brackish water lens by monitoring of the groundwater salinity. For inclusion in public water supply, the groundwater should be treated by desalination.

ABSTRACTGeophysical surveys are carried out in the coastal area of Petrosino (south‐western Sicily) to study the time evolution of seawater contamination of the coastal aquifer, probably increased due to human impact. The overexploitation of the aquifer, due to an intensive agricultural use has affected significantly the natural hydro‐geochemical state of the basin. The study is based on a processing and integrated analysis of hydrogeological, geochemical and geophysical data. In particular in the last two years seasonal time‐lapse electrical resistivity tomographies (ERT), new TDEM soundings and Multi‐Analysis Surface Wave soundings (MASW) have been carried out. The interpretation of the total set of previously existing and new geophysical data made it possible to reconstruct a three‐dimensional model of the electrical resistivity of the aquifer, aimed at defining the extent and geometry of the seawater intrusion. Furthermore, the execution of a series of high‐resolution time‐lapse...

This chapter describes the occurrence of saltwater/freshwater interface in coastal aquifers. It has a brief description of the physics, hydraulics, and mathematics behind the theory of saltwater intrusion and the saltwater/freshwater interface. It also includes a section on numerical modeling techniques and the available computer models for saltwater-intrusion problems in coastal aquifers. Anthropogenic effects on saltwater intrusion such as changes in land use and landscape vegetation cover, groundwater pumping patterns, and the amount of pumping are also discussed. Finally, remedies, control and management of saltwater intrusion such as implementation of recharge wells, creation of artifi cial recharge basins, and construction of barriers are discussed. This chapter is expected to be useful to agricultural communities of coastal plains whose irrigation water is solely dependent on groundwater resources. It may also be of interest to individuals working in coastal-watershed and land-management businesses and governmental or local decision makers by addressing the problem of saltwater intrusion into coastal aquifers and its possible remediation and control techniques.

Quaternary sea level fluctuations have led to the development of beach ridges on many South Atlantic coasts. The objective of this paper was to asses from lithological, hydrochemical, isotopic, and geophysical studies the salinization processes affecting groundwater stored in Pleistocene and Holocene beach ridges of the northern Patagonian coast. A hydrogeomorphological characterization of the area was performed using digital elevation models, the interpretation of satellite images, and field studies. Vertical electrical soundings were performed on transects running perpendicular to beach ridges in order to define variations in the freshwater-saltwater interface position. The salinity, chemistry, and stable isotopes of the groundwater were analyzed. The results demonstrated that the groundwater salinization of Pleistocene ridges responds to processes associated with the geological-geomorphological evolution of the area. The cementation of these surface sediments limits rainwater inf...

Managed aquifer recharge (MAR) is increasingly used to secure drinking water supply worldwide. The city of Amsterdam (The Netherlands) depends largely on the MAR in coastal dunes for water supply. A new MAR scheme is proposed for the production of 10 × 10 6 m 3 /year, as required in the next decade. The designed MAR system consists of 10 infiltration ponds in an artificially created sandbank, and 25 recovery wells placed beneath the ponds in a productive aquifer. Several criteria were met for the design, such as a minimum residence time of 60 days and maximum drawdown of 5 cm. Steady-state and transient flow models were calibrated. The flow model computed the infiltration capacity of the ponds and drawdowns caused by the MAR. A hypothetical tracer transport model was used to compute the travel times from the ponds to the wells and recovery efficiency of the wells. The results demonstrated that 98% of the infiltrated water was captured by the recovery wells which accounted for 65.3% of the total abstraction. Other sources include recharge from precipitation (6.7%), leakages from surface water (13.1%), and natural groundwater reserve (14.9%). Sensitivity analysis indicated that the pond conductance and hydraulic conductivity of the sand aquifer in between the ponds and wells are important for the infiltration capacity. The temperature simulation showed that the recovered water in the wells has a stable temperature of 9.8-12.5 °C which is beneficial for posttreatment processes. The numerical modelling approach is useful and helps to gain insights for implementation of the MAR.

With the growing population and the adverse effects of climate change, the pressure on coastal aquifers is increasing, leading to a larger risk of saltwater intrusion (SI). SI is often complex and difficult to characterize from well data only. In this context, electrical resistivity tomography (ERT) can provide high-resolution qualitative information on the lateral and vertical distribution of salinity. However, the quantitative interpretation of ERT remains difficult because of the uncertainty of petrophysical relationships, the limitations of inversion, and the heterogeneity of aquifers. In this contribution, we propose a methodology for the semiquantitative interpretation of ERT when colocated well data are not available. We first use existing wells to identify freshwater zones and characterize the resistivity response of clayey deposits. Then, we approximate the formation factor from water samples collected in the vicinity of ERT data to derive a resistivity threshold to interpr...

The research of saltwater upconing is crucial for the development and utilization of island freshwater resources. In this paper, a laboratory physical experiment device was developed, and the saltwater upconing and recovery of island freshwater lenses were investigated using rainfall simulations and single-well and multi-well pumping tests with various pumping intensities. The results of the experiment revealed that: (1) The thickness of the freshwater lens increased continuously and linearly during the early stages of rainfall. As the rainfall continued, the upward trend slowed and eventually leveled off. (2) Under the same pumping duration, when the pumping intensity was less than the critical pumping intensity, the increasing height rate of the saltwater upconing increased linearly at a small gradient, and when the pumping intensity was greater than the critical value, the rising height rate of the saltwater upconing increased linearly at a large gradient. (3) Under the same pump...

Patterns of Pore Water Chemistry which produced non-uniform groundwater flow conditions. We conclude that on mesotidal high energy beaches, the rapidly changing beach morphology produces zones with different approximations to steady-state conditions. Therefore, we suggest that zone-specific endmember sampling is the optimal strategy to reduce uncertainties of SGD-driven constituent fluxes.

We report first results from a study on water and element exchange across the land-ocean boundary at the southern Baltic Sea. The focus is set on ferruginous fresh ground waters escaping at the shore line, flowing in air contact before entering a subterranean mixing zone with brackish Baltic Sea water. The present study combines the results from multiple sampling campaigns that investigated the composition of several springs as well as the surface and subsurface development of fresh waters on the way to the Baltic Sea. This is achieved by a combination of hydroand solid-phase geochemical and stable isotope measurements with ground water dating. Results are compared to the composition of groundwaters recovered from wells in the catchment area and the local isotope meteoric water line developed for Warnemünde. The spring water is shown to be impacted by the dissolution of biogenic carbon dioxide and marine carbonate as well as the oxidation of pyrite in glacial sediments. Dating yield...

We report first results from a study on water and element exchange across the land-ocean boundary at the southern Baltic Sea. The focus is set on ferruginous fresh ground waters escaping at the shore line, flowing in air contact before entering a subterranean mixing zone with brackish Baltic Sea water. The present study combines the results from multiple sampling campaigns that investigated the composition of several springs as well as the surface and subsurface development of fresh waters on the way to the Baltic Sea. This is achieved by a combination of hydroand solid-phase geochemical and stable isotope measurements with ground water dating. Results are compared to the composition of groundwaters recovered from wells in the catchment area and the local isotope meteoric water line developed for Warnemünde. The spring water is shown to be impacted by the dissolution of biogenic carbon dioxide and marine carbonate as well as the oxidation of pyrite in glacial sediments. Dating yield...

In this note, the Water Budget Method (WBM) is applied to estimate local values of the specific yield of the deep karst aquifer of Salento peninsula. A selection in a period of two years of relevant short precipitation events has been considered and the related localized recharges have been compared to the water table fluctuations measured at two selected wells. The recharge amounts have been corrected by using data of evapotranspiration and soil water storage available from a micrometeorological base. The results are very similar for both the wells and more consistent when the corrections are applied. A discussion involving frequency and apertures of the fractures in the rock mass of the aquifer suggests the effect of the karst dissolution to be dominant in determining these values of the specific yield.

Most of the coastal ecosystems face double whammy problems in terms of excess water congestion during the monsoon period and non availability of freshwater during the post monsoon period. Ingression of saline water due to high tide is a challenge to humanity, in general, and agriculture, freshwater resource, fisheries and aquaculture in particular. Eastern part of India is highly populated with plenty of natural resources. But due to lack/poor irrigation infrastructure, maximum freshwater flows to the sea. Hence, this ecosystem requires adequate attention to develop and refine appropriate technological options to facilitate more freshwater availability throughout the year and check the saline water ingression in order to increase the overall land and water productivity of the area. Geographic, engineering, socioeconomic and environmental factors which are closely associated with the water management issues have been reviewed for proper water management options in the coastal ecosystem.

Water flow and solute transport through a fractured vadose zone underneath an industrial contaminated site in Belgium were studied with a new methodological concept. The Vadose Zone Experimental Setup (VZES) combines a vadose zone monitoring system (VMS) with cross-borehole geophysics. The VMS provides continuous chemical and hydraulic information at multiple depths in the vadose zone. When combining such information with multidirectional subsurface imaging from geophysical measurements, flow and transport can be characterized at a scale that covers the spatial variability of the subsurface. The setup was installed on site and monitoring was carried out under natural recharge conditions. Results reveal quick rises in water content as a response to rainfall events in the upper and intermediate part of the vadose zone (down to 3.65 m depth). Macropore, micropore, matrix and preferential flow mechanisms are identified at these depth ranges. At greater depths, flow dynamics is slower an...

Groundwater levels and water samples were collected from 20 drinking water pumping and piezometer wells in the urban area of Dakar coastal region in the year 2019. The pH-value, electrical conductivity, as well as calcium, magnesium, sodium, potassium, chloride, sulfate, bicarbonate, and nitrate concentrations were measured to assess the hydrochemical quality of the infrabasaltic aquifer in the area. The present work carried out a hydrochemical analysis to interpret the groundwater chemistry of the aquifer. The results of this chemical analysis indicate that Na + > Mg 2+ > Ca 2+ > K + was the most dominant cation sequence in the groundwater, while Cl − > 3 HCO − > 2 4 SO − > 3 NO − was the most dominant one for anions. The chemical analysis of our samples showed, that the Cl-Ca-Mg facies was dominant in the aquifer, while Cl-Na-K and HCO 3-Na-K facies represent 20% and 10% of the groundwater sampled, respectively. A comparison of the measured groundwater quality in relation to WHO drinking water quality standards revealed that 80% of the water samples are suitable for drinking purposes. Ca enrichment, Simpson ratio, ratio of sodium chloride, and calculating Base Exchange (BEX) indices for the samples revealed that the groundwater is mainly affected by three factors: seawater intrusion due to aquifer overexploitation on one hand, and freshening processes and nitrate pollution, on the other, mainly caused by the groundwater flow from the unconfined aquifer.

The temperature distribution of shallow sectors of coastal aquifers are highly influenced by the atmospheric temperature and recharge. However, geothermal heat or vertical fluxes due to the presence of the saline wedge have more influence at deeper locations. In this study, using numerical models that account for variable density, periodic oscillations of temperature have been detected, and their origin has been attributed to the influence exerted by recharge and tides. The combined analysis of field data and numerical models showed that the alternation of dry and wet periods modifies heat distribution in deep zones (>100 m) of the aquifer. Oscillations with diurnal and semidiurnal frequencies have been detected for groundwater temperature, but they show differences in terms of amplitudes and delay with electrical conductivity (EC). The main driver of the temperature oscillations is the forward and backward displacement of the freshwater–saltwater interface, and the associated th...

Coastal freshwater resources are commonly under high risk of being contaminated from seawater. The main processes that affect seawater intrusion are groundwater overexploitation, land use change, and climate change effects. In this context coastal lagoons represent the more sensitive environments prone to seawater intrusion. Numerical modelling is a useful tool to understand and predict seawater intrusion. In this study, a three-dimensional SEAWAT model is employed to simulate the seawater intrusion to coastal aquifers of Variconi Oasis (Italy). The present simulation was divided into a calibration and a validation model, then the model was used to predict the salinization trend up to 2050. Results show the role of the sea in salinizing the beach front, while the retrodunal environment is characterized by transitional environments. Future seawater intrusion scenarios considering only climate data showed no significative differences in respect to the actual situation. The same happens considering also a low sea level rise prediction. On the contrary, the worst scenario (high sea level rise prediction), depicts a quite different situation, with a saline intrusion in the Variconi oasis that will severely affect the fragile transitional ecosystem. This modelling framework can be used to quantify the effects of climate changes in similar coastal environments.

Introduction. A case study of heat transport modeling in the shallow aquifer of the Turin City (NW Italy) with finite-difference computer code is here reported. A detailed geological characterization of the subsoil and the estimation of hydrogeological and thermal features of the shallow aquifer are essential tools in support of heat transport simulations for the design of open-loop system. This modeling has the purpose of evaluate the thermal plume propagation connected to the re-injection of altered thermal water in the aquifer with temperature higher or lower than the average annual value. This research focuses on the following problems: a) to study the effects induced by the discharge of water in the shallow aquifer at temperature higher than the annual average value and the consequent rise of temperature induced downstream of the same. In this case, the thermal modeling of the shallow aquifer allows to estimate the alteration on the thermal groundwater state in order to predict phenomena of "groundwater's thermal pollution" with associated environmental problems; b) to study the effects related to the injection in the aquifer of water at lower temperature than the annual average value. The discharge of water at lower temperature causes a decrease of the water calorific power with a consequent loss of efficiency of the geothermal plant. From the practical point of view, the methodology here proposed can be applied in the preliminary stages of a geothermal system design, where it is convenient to assess the optimal distance between extraction and injection wells in order to avoid "thermal feedback phenomena" and, more generally, assessing the environmental impact related to the extension of the thermal anomaly in the subsurface. Morphological and geological setting of the Turin city. The Turin city is located in a narrow strip of the north western Po Plain, between the Alps and Turin Hill (Fig. 1A). In particular, it is placed in a marginal position, at the edge with the Turin Hill, where the current course of the Po River is located that separates a plain sector from a hill one. The plain area (altitude ranging from 200-350 m a.s.l.) shows a weak inclination towards east and NE (about 1‰). In detail, the morphology is slightly articulated by the presence of small embankments and depressions connected with ancient trends of Po River, characterized by small areal extension, height of few meters and mostly discontinuous areal development (Forno and Lucchesi, 2012). Nevertheless, the morphology of the plain is affected by a generalized anthropic reshaping that causes the modification of numerous natural forms and the creation of new anthropic forms. The plain does not have the typical structure of a subsiding plain, instead, it presents a sector with important recent uplift, connected to the Padane Thrust Front (TFP), that influences the geometry of the sedimentary bodies and created important variations of the hydrographic network during the Pleistocene up to the recent settling of the Po River to the north of the hill (Forno, 1982; Forno and Lucchesi, 2012). The shallow subsoil of Turin consists of Pleistocene fluvial and outwash sediments linked to Alpine watercourses forming wide fans, cut by the erosional scarps linked to the present course of the Po River and partly filled by its Holocene fluvial sediments. The distribution area of the deposits linked to Po River is restricted to the narrow band at the edge of the river bed. Overall, the fluvial and outwash deposits show a shallow thickness, comprised between 10 m, on the edge with the Turin Hills, up to 80 m towards the Alpine chain. These sediments are organized

A combination of geologic descriptions of cores, borehole geophysics, surfacegeophysical soundings and water-sample analyses was used to characterize flow in the surficial aquifer in the vicinity of Big Cypress National Preserve, Collier County, south Florida. The geophysical analysis augmented by aquifer tests and piezometer measurements showed that the surficial aquifer is under unconfined conditions, is in hydraulic connection with surface water bodies, and is underlain by a series of confining units and confined aquifers. Seawater intrusion appears as a simple wedge of saline water underneath the coastal region. The pattern of salinity in the underlying aquifers is variable and shows no relation to distance from the coast or from the surficial wedge of seawater intrusion. Borehole flow-log data document the existence of a strong vertical hydraulic-head gradient throughout the study area. The subsurface distribution of salinity in the study area apparently is determined by variations in the amount of seepage of saline water from underlying aquifers and not by lateral seawater intrusion except near the wedge of sea water imaged by the surface geophysics.

The study presents simulations of seawater intrusion (SWI) in the coastal aquifers of Amol-Ghaemshahr, Northern Iran in response to oscillations of sea level and groundwater extraction and incorporates the assessment of the impacts of future changes in sea level and withdrawals from the aquifers on groundwater salinization. A numerical model of variable-density groundwater flow and solute transport was developed to investigate the extent of SWI. The SEAWAT 4 was used to solve the variable-density groundwater flow and solute transport governing equations. Calibration of the model was carried out in three steps involving the dynamic steady-state and the transient mode of flow models as well as transient mode of solute transport model. Calibrated model run for the year 2010-2011 corroborated well with the field data wherein the seawater intrusion has taken place intermittently along the coastline in the eastern part and 9.7% of the land along the coastline (i.e., 6.96 km) was encroached by seawater. Predictions on the SWI for the year 2030 were made with all hydrogeological conditions assumed to remain the same as those in 2010-2011 by simulating the movement of the interface resulting from the changes in sea-level and groundwater withdrawals. The results show that Amol-Ghaemshahr aquifer is sensitive to groundwater withdrawal and sea-level rise. The studies established that various combinations of groundwater extraction and sea-level oscillations are predominant driver of SWI in the study area.

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The knowledge of the time to reach a new equilibrium after a hydraulic perturbation is crucial to model accurately the groundwater system. A hypothetical numerical model loosely based on the western margin of the Great Artesian Basin in Australia was used as a demonstration to estimate this time in large unconfined/confined aquifers. The time to reach a new steady state after a hydraulic perturbation, such as the cessation of the recharge in arid and semi-arid regions, is on the order of 50 ky. This time is longer than the present interglacial phase, i.e. 10ky since the last climate transition, and thus the hydrodynamic system is a transient one which is still responding to the paleo-perturbation due to recharge. Moreover, analytical solutions have been used to assess the time to reach a new equilibrium for several large aquifers in the world. The times obtained range between 0.4 and 5.8x10 10 years. These values suggest that large regional scale aquifer systems are rarely expected to be in steady state with respect to their hydraulic behaviour.

Saltwater intrusion (SWI) is a widespread environmental problem that poses a threat to coastal aquifers. To address this issue, this research employs both numerical and experimental methods to study saltwater intrusion under the impact of sea level rise and varying freshwater boundary conditions in two homogeneous aquifers. The study compares transient numerical groundwater heads and salt concentrations to experimental results under receding-front and advancing front conditions. In the low permeability aquifer, the root mean square error is 0.33 cm and the R2 is greater than 0.9817. Similarly, in the high permeability aquifer, the root mean square error is 0.92 cm and the R2 is greater than 0.9335. The study also compares the results of ten experimental tests for steady-state saltwater intrusion wedge and toe length with seven different analytical solutions. The experimental results are then compared to these analytical solutions to find the most suitable equation. The Rumer and Har...

Subsurface physical barriers have been effectively used to mitigate seawater intrusion (SWI). Traditionally, the primary emphasis in both numerical studies and practical implementations has been on vertical barriers. The current research aims to explore the dynamics of SWI under various cutoff-wall inclination angles and depths, as well as aquifer heterogeneity using both experimental and numerical simulations. The impact of aquifer characteristics was assessed by utilizing a low hydraulic conductivity (K) aquifer (case L), a high hydraulic conductivity aquifer (case H), and two stratified aquifers. The stratified aquifers were created by grouping different hydraulic conductivity layers into two cases: high K above low K (case H/L) and low K above high K (case L/H). The model simulations covered seven different cutoff-wall inclination angles: 45.0°, 63.4°, 76.0°, 90.0°, 104.0°, 116.6°, and 135.0°. The maximum repulsion ratio of SWI wedge length was observed at an inclination angle o...

Submarine groundwater discharge is an important part of the hydrological cycle, but remains under-investigated for confined aquifers with no surface outcrop at the beach. This paper considers the offshore directed flow of fresh groundwater in the unconfined and confined aquifers along the coast of the Western Netherlands. Salinity patterns based on hydrological, geological, and geophysical field data are presented in five shore-normal hydrogeological cross-sections, extending from the beach to 4 km inland. The offshore continuation of the fresh groundwater is discussed using analytical models and cone penetration tests (CPTs) performed at the beach. All CPTs taken around the low water line of the intertidal zone reveal that changes from saline to fresh groundwater are always associated with a low-permeable layer. Such a low-permeable layer, which can be as thin as a few decimetres, may form the confining layer between the unconfined and confined aquifers, or can occur within of the unconfined aquifer. Due to its high vertical resolution, a CPT is an effective method to detect these variations in salinity and lithology. At each of the investigated locations, freshwater was present in the confined aquifer. Assuming that this fresh groundwater is part of an active flow system, the submarine freshwater tongue is estimated to extend at least a few hundred meters offshore, based on analytical model calculations. Hydrochemical data from an old offshore borehole, however, suggest this may be an underestimate and that the submarine freshwater tongue originates from former times when the coastline was located further westward than nowadays.

Gravel pit lakes offer a variety of uses after excavation has ceased. One of those uses is the storage, infiltration, aquifer passage, and production of drinking water. We have investigated such a gravel pit lake in The Netherlands that is a state of the art drinking water production facility. The gravel pit lake is a flow-through lake, fed naturally by groundwater (~17%) and rainwater (~6%), and artificially with Meuse River water (~77%). The average concentrations of Cd, Cr, Cu, Ni, Pb and Zn in the lake's bottom sediments have increased over a 10 year period. Acidifying redox reactions caused by lowering of the water table and farmland fertilization upstream from the lake explain the mobilization of metals in the soil and subsequent transport with groundwater towards the lake. Dissolved metals (Al, Cd, Cr, Cu, Fe Mn, Ni and Zn) and PO 4 3− flow with the groundwater towards the lake, where they interact with oxygen-rich and alkaline water to (co)precipitate as Fe, Mn and Al oxides. The chemistry of the gravel pit lake water is determined by a complex interplay between the input of NO 3 − and PO 4 3− , soil composition up stream, biochemical processes in the lake that supply organic material, mixing processes (artificial and natural) that determine the amount of stratification and oxygen, and redox cycling processes in the bottom sediments that influence the concentration of metals and P in the lake water. Gravel pit lakes are young compared to natural lakes and the long term influence of these lakes is still largely unknown. This study confirms that they can form a sink for metals and thus influence the metal budget of a watershed. Compared to other artificial recharge methods, infiltration in a gravel pit lake along a river has certain advantages in that the lake already exists, the transport distance for the water to be infiltrated is short, the pretreatment of the infiltrated water is simple, and the long residence time of the water in the lake and the lake bank filtration attenuates quality variations of the infiltrated river water. For drinking water production or other usage of gravel pit lakes, an integrated monitoring and management of land use, ground-and surface water as well as lake bottom sediments are needed.

Multi-isotope composition of freshwater sources for the southern North and Baltic Sea Michael E. Böttcher-p. P-18 Airborne clay mapping at the East Frisian coast Bernhard Siemon-p. 371 P-19 Impact of tourism on groundwater extraction on the island of Langeoog, Germany Georg Houben-p. 180 P-20 Hydrogeological features of freshwater lenses on volcanic islandsphysical and numerical modeling Georg Houben-p. 176 P-21 Application of airborne electromagnetics for groundwater investigations in the vicinity of salt structures Florian Krause-p. 218 P-22 Groundwater flow analysis in variable-density formation waters-a comparison of common approximations Martina aus der Beek-p. 31 P-23 The salinization of useful Cenozoic aquifers by ascending Mesozoic brines-characterization on the basis of hydrochemical data from northern and central Poland Dorota Kaczor-Kurzawa-p. 200 P-24 Origins of groundwater salinity and implications for the groundwater management of Emborê Aquifer,

In most coastal areas in Mexico, there is an increase in housing development and facilities for tourism, consequently resulting in a negative impact on the environment. Due to this, an awareness of the critical role of groundwater in sustaining coastal populations, economies, and ecosystems is growing. The coastal zone of Sinaloa State is classified as an area with a high presence of saline groundwater in Mexico. The present work was performed in the Las Glorias Beach, Guasave, Sinaloa, Mexico. The results of the analysis of 19 soil and groundwater samples indicate the predominance of sandy soil and a wide range of water salinity, from slightly saline to brine. An electromagnetic profiling (EMP) survey was performed at the study site showing a low apparent electrical conductivity zone parallel to the coastline as indicative of the possible presence of fresh and/or slightly saline water. Apparent electrical conductivity values were compared with electrical conductivity values measured in groundwater samples collected in wells, resulting in a positive linear correlation (R = 0.97). This linear relation is explained by a φξ electromagnetic analytic model when 5.36 ≤ σ a ≤ 85.87 mS/cm. The linear relation was used to recalculate the apparent electrical conductivity values from EMP survey into electrical conductivity values of groundwater and, therefore, TDS values. The TDS map indicates the presence of a barrier of fresh/slightly saline groundwater parallel to the coastline that keeps a fragile balance that prevents the advance of saltwater intrusion from the sea of Cortés and from brine zones located in the northern part of the site. The advance of erosion in Las Glorias Beach exposes

With the growing population and the adverse effects of climate change, the pressure on coastal aquifers is increasing, leading to a larger risk of saltwater intrusion (SI). SI is often complex and difficult to characterize from well data only. In this context, electrical resistivity tomography (ERT) can provide high-resolution qualitative information on the lateral and vertical distribution of salinity. However, the quantitative interpretation of ERT remains difficult because of the uncertainty of petrophysical relationships, the limitations of inversion, and the heterogeneity of aquifers. In this contribution, we propose a methodology for the semiquantitative interpretation of ERT when colocated well data are not available. We first use existing wells to identify freshwater zones and characterize the resistivity response of clayey deposits. Then, we approximate the formation factor from water samples collected in the vicinity of ERT data to derive a resistivity threshold to interpr...

The Indus Delta is an endangered wetland on the Ramsar list due to a continued decrease of river flow toward the delta, resulting in seawater intrusion into the inland areas and deteriorating the potable patches of shallow groundwater and wetland areas. The groundwater in the lower Indus Basin is brackish, except for a few potable pockets, which are shrinking due to water extraction for drinking purposes. The gap thus occupied by saline water permanently degrades the potable groundwater. This paper correlates the potable patches with surface seepage due to either rainfall or river flows, to recommend a continuous flow of fresh water in the river system, and a revival of the ruined wetlands and lagoons. Twelve nested piezometers at various depths have been installed in the study area to monitor the groundwater quality temporally transformation. The water samples have been periodically collected to analyze physical and chemical properties for three years. The data trend indicates the rapid changes in shallow groundwater quality (up to the depth of 10 m) to the surface availability of freshwater. An area of 378 km 2 was turned from saline to fresh groundwater with only two spells of rainfall. The result confirms the positive impact on groundwater quality improvement due to rainfall and water in river tributaries. Based on this analysis, it is recommended to replenish the lagoons and shallow lakes with fresh water. Canals should run continuously to constantly recharge the shallow groundwater as the only source of drinking water in the study area.

Many coastal aquifers have experienced seawater intrusion (SWI) into fresh groundwater aquifers. The principal causes of SWI include over-pumping and events such as climate change (CC) and rising sea levels. In northern Morocco, the Rmel-Oulad Ogbane coastal aquifer (ROOCA) supplies high-quality groundwater for drinking water and agriculture. This favorable situation has led to increased pumping, resulting in environmental challenges such as dropping water table and SWI. Furthermore, the climate has resulted in less recharge, with an estimated annual precipitation of 602 mm and an average temperature of 18.5 °C. The goal of this study is to determine how CC, over-pumping, and sea-level rise (SLR) affect SWI. Computational groundwater and solute transport models are used to simulate the spatial and temporal evolution of hydraulic heads and groundwater solute concentrations. The calibration is based on steady and transient groundwater levels from 1962 to 2040. SWI simulations show tha...

With the growing population and the adverse effects of climate change, the pressure on coastal aquifers is increasing, leading to a larger risk of saltwater intrusion (SI). SI is often complex and difficult to characterize from well data only. In this context, electrical resistivity tomography (ERT) can provide high-resolution qualitative information on the lateral and vertical distribution of salinity. However, the quantitative interpretation of ERT remains difficult because of the uncertainty of petrophysical relationships, the limitations of inversion, and the heterogeneity of aquifers. In this contribution, we propose a methodology for the semiquantitative interpretation of ERT when colocated well data are not available. We first use existing wells to identify freshwater zones and characterize the resistivity response of clayey deposits. Then, we approximate the formation factor from water samples collected in the vicinity of ERT data to derive a resistivity threshold to interpr...

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