Groundwater Variations Research Articles

Evaluation of Hydraulic Properties of Aquitards Using Earthquake-Triggered Groundwater Variation.

The hydraulic properties of aquitards are not easily obtained because monitoring wells are usually installed in aquifers for groundwater resources management. Earthquake-induced crust stress (strain) triggers groundwater level variations over a short period of time in a large area. These groundwater anomalies can be used to investigate aquifer systems. This study uses a poroelastic model to fit the postseismic variations of groundwater level triggered by the Chi-Chi earthquake to evaluate the hydraulic properties of aquitards in the Jhoushuei River alluvial fan (JRAF), Taiwan. Six of the adopted eight wells with depths of 70 to 130 m showed good agreement with the recovery theory. The mean hydraulic conductivities (K) of the aquifers for the eight wells are 1.62 × 10-4 to 9.06 × 10-4 m/s, and the thicknesses are 18.8 to 46.1 m. The thicknesses of the aquitards are 11.3 to 42.0 m. Under the isotropic assumption for K, the estimated values of K for the aquitards are 3.0 × 10-8 to 2.1 × 10-6 m/s, corresponding to a silty medium. The results match the values obtained for the geological material of the drilling core and those reported in previous studies. The estimated values were combined with those given in previous studies to determine the distribution of K in the first two aquitards in the JRAF. The distribution patterns of the aquitards reflect the sedimentary environments and fit the geological material. The proposed technique can be used to evaluate the K value of aquitards using inverse methods. The inversion results can be used in hydrogeological analyses, contaminant modeling, and subsidence evaluation.

Isotopic analysis of water cycle elements in different land covers in a small headwater watershed

In this study, comparisons of isotopic variation of rainfall, throughfall, surface water, and groundwater were conducted in the Meilin watershed, which represents two different land uses, chestnut wood and bamboo. Also, isotopic differences between rainfall and throughfall were identified in these sub-watersheds. The results showed that the isotopic value of incremental rainfall, incremental throughfall and surface water exhibited a marked temporal variation in the selected sub-watersheds. The throughfall isotopic variation range was smaller than that of rainfall, which may result from the different production process between rainfall and throughfall. However, the isotopic composition difference between rainfall and throughfall resulting from different land uses was insignificant. The range of isotopic composition variation of surface water was not the same as that of rainfall, indicating that surface water came from a mix of precipitation and water stored before the rainfall event. The temporal variation of the isotopic composition of groundwater was small, implying that the influence of different land uses on groundwater isotopic composition was insignificant. The total variation range of δ2H and δ18O of groundwater was smaller than that of surface water and sequential incremental rainfall, which means the δ18O of groundwater can be replaced by that of base flow before the event in the hydrograph separation.

Controls on the chemical composition of saline surface crusts and emitted dust from a wet playa in the Mojave Desert (USA)

Saline-surface crusts and their compositions at ephemeral, dry, and drying lakes are important products of arid-land processes. Detailed understanding is lacking, however, about interactions among locally variable hydrogeologic conditions, compositional control of groundwater on vadose zone and surface salts, and dust composition. Chemical and physical data from groundwater, sediments, and salts reveal compositional controls on saline-surface crusts across a wet playa, Mojave Desert, with bearing on similar settings elsewhere. The compositions of chemically and isotopically distinctive shallow (<3 m) water masses are recorded in the composition of associated salts. In areas with deeper and more saline groundwater, however, not all ions are transported through the vadose zone. Retention of arsenic and other elements in the vadose zone diminishes the concentrations of potentially toxic elements in surface salts, but creates a reservoir of these elements that may be brought to the surface during wetter conditions or by human disturbance. Selective wind-erosion loss of sulfate salts was identified by the compositional contrast between surface salt crusts and underlying groundwater. At the sub-basin scale, compositional links exist among groundwater, salt crusts, and dust from wet playas. Across the study basin, however, lateral variations in groundwater and solid-salt compositions are produced by hydrogeologic heterogeneity.

Mapping of groundwater quality using Normalized Difference Dispersal Index of Dwarka sub-city at Delhi National Capital of India

In this study, geo-statistical tool was used to map groundwater quality parameters. Groundwater samples were collected from 30 wells. In order to quantify the site-specific variations, Normalized Difference Dispersal Index (NDDI) was used to map five parameters namely pH, EC, TH, Ca, and Mg. Maximum NDDI value enrichment was exhibited by EC (−0.01) and Mg (−0.009 ≈ −0.01) it reflects accretion. In addition, for pH (−0.012), TH (−0.027), and Ca (−0.025), it outlined by dilution or minor accretion, whereas median NDDI value for EC, Ca, Mg, TH and pH is −0.02, −0.02, −0.03, −0.029, and −0.04, respectively. NDDI mapping is a functional tool for evaluation and comparative assessment of spatio-temporal variations in groundwater. Further, frequency distribution and inter correlation analysis of the data-set has displayed coherence. The results of study will help in management of water resources.

Groundwater Level Declination in Bangladesh: System Dynamics Approach to Solve Irrigation Water Demand During Boro Season

Groundwater has been declining in Bangladesh since introduction of deep tube wells (DTWs) and shallow tube wells (STWs) in late 1970s. Seasonal variation of groundwater has been shifted upto 4 meters during last 33 years. During Boro seasons groundwater table dropped drastically than other seasons. This study hypothesized that groundwater extraction is much higher than the natural recharge plus percolated irrigated water. Farmer´s perception is that if they dig deeper the supply would not be a problem, which led uncontrolled use of shallow tube wells (STWs) to extract water from lowered zones. This study selected an area that is 20 km away from Dhaka city having intensive Boro production. Analyzing the interview data (to know about the practices by farmers at present and before) and Bangladesh Water Development Board groundwater table data, we tried to simulate the problematic scenario with the help of simulation software called iThink. To address the problem 3 different policies have been investigated to achieve sustainable solution of the problem. The chosen policies were - (1) Harnessing only groundwater; (2) Alternative cropping; and (3) Depending more to surface water. The simulation results show that alternative cropping and going for surface water could solve the problem as well as able to restore the groundwater to its previous condition. But moving to surface water is a passive solution independent to farmers´ decision. Alternative cropping through proper knowledge transfer mechanism is more sustainable solution considering present and future water crises.

The Geochemical Atlas of European ground water with emphasis on Hellas

A first impression of the geochemistry and quality of European ground water was obtained by using bottled mineral water as a sampling medium. In total, 1785 bottled waters were purchased from supermarkets of forty European countries, representing 1247 wells/drill holes/springs at 884 locations. All bottled waters were analysed for 72 parameters at the laboratories of the Federal Institute for Geosciences and Natural Resources (BGR) in Germany.The European geochemical maps give a first impression of the natural variation in ground water at the continental scale. The majority of European bottled waters are classified as of Ca-HCO3 type, because of the widespread carbonate lithologies, but there is considerable variation from Na-HCO3 type related to granitic rocks to Na-Cl type associated with deep saline brines. Since, the dominating lithology in Hellas comprises limestone, dolomitic limestone, marble, and maficultramafic rocks (ophiolites), the dominant major ions in Hellenic bottled waters are Ca2+, Mg2+, CO32- and HCO3-, and are, thus, classified in the Ca2+-Mg2+-HCO3- hydrochemical facies. The source aquifers of Hellenic bottled water are apparently continuously replenished by fresh water.Chromium, V and U are discussed, because of their importance in Hellenic ground water. In Europe, the former is clearly related to ophiolites, whereas V indicates the presence of recent volcanism and basaltic rocks, and U is associated with granitic intrusions and Bunter (central England) and Keuper (central Europe) sandstone of early and late Triassic, respectively. It can, therefore, be concluded that geology is one of the key factors influencing the observed element concentrations for a significant number of elements.

Factors controlling groundwater salinization and hydrogeochemical processes in coastal aquifers from southern Spain.

In detrital coastal aquifers, seawater and surface water may interact with groundwater in multiple ways. Understanding the interference of water fluxes in this type of environment is essential to effectively manage the groundwater resources in water-stressed regions, such as the Mediterranean coastal fringe. In this research, the characterization of the main hydrogeochemical processes and the interaction between surface water and groundwater in the Marbella-Estepona coastal aquifers (southern Spain) have been carried out by means of the combined use of different hydrogeochemical indicators along with isotope data. The results show that the diversity of source lithologies (peridotite, carbonate and/or metapelitic) substantially conditions the groundwater geochemistry. The analysis of ionic deltas made it possible a preliminary screening of the geochemical reactions that occur in the Marbella-Estepona aquifers, while the Discriminant Analysis allowed for a consistent classification of sampled groundwater types. The dissolution of calcite and dolomite determines the chemical composition of the groundwater from the eastern sector that are more conditioned by the rainwater infiltration. The dissolution of magnesium-bearing minerals (predominantly forming peridotite rocks) is observed in groundwater samples from the western and central sectors, whose chemical composition showed a greater influence of surface water. The spatial analysis of rCl-/Br- in groundwater has permitted to corroborate that saline intrusion is negligible, hardly affecting to its original water quality. The irregularly distributed recharge by precipitation (seasonal effect) and the atmospheric circulation of cloud fronts (coastal/continental effect) explains why most of groundwater sampled is isotopically impoverished with respect to the rainfall signature. The isotope approach also suggests the hydraulic relationship between surface water and groundwater in the study site. A deeper knowledge of spatial hydrogeochemical variations in coastal groundwater and the influence of water sources over them are crucial for a sustainable groundwater management and global change adaptation in equivalent Mediterranean water-stressed regions.

Spatio-temporal variability of groundwater storage in India

Groundwater level measurements from 3907 monitoring wells, distributed within 22 major river basins of India, are assessed to characterize their spatial and temporal variability. Groundwater storage (GWS) anomalies (relative to the long-term mean) exhibit strong seasonality, with annual maxima observed during the monsoon season and minima during pre-monsoon season. Spatial variability of GWS anomalies increases with the extent of measurements, following the power law relationship, i.e., log-(spatial variability) is linearly dependent on log-(spatial extent). In addition, the impact of well spacing on spatial variability and the power law relationship is investigated. We found that the mean GWS anomaly sampled at a 0.25 degree grid scale closes to unweighted average over all wells. The absolute error corresponding to each basin grows with increasing scale, i.e., from 0.25 degree to 1 degree. It was observed that small changes in extent could create very large changes in spatial variability at large grid scales. Spatial variability of GWS anomaly has been found to vary with climatic conditions. To our knowledge, this is the first study of the effects of well spacing on groundwater spatial variability. The results may be useful for interpreting large scale groundwater variations from unevenly spaced or sparse groundwater well observations or for siting and prioritizing wells in a network for groundwater management. The output of this study could be used to maintain a cost effective groundwater monitoring network in the study region and the approach can also be used in other parts of the globe.

Transient deformation of karst aquifers due to seasonal and multiyear groundwater variations observed by GPS in southern Apennines (Italy)

AbstractWe present GPS, hydrological, and GRACE (Gravity Recovery and Climate Experiment) observations in southern Apennines (Italy) pointing to a previously unnoticed response of the solid Earth to hydrological processes. Transient patterns in GPS horizontal time series near to large karst aquifers are controlled by seasonal and interannual phases of groundwater recharge/discharge of karst aquifers, modulating the extensional ∼3 mm/yr strain within the tectonically active Apennines. We suggest that transient signals are produced, below the saturation level of the aquifers and above a poorly constrained depth in the shallow crust, by time‐dependent opening of subvertical, fluid‐filled, conductive fractures. We ascribe this process to the immature karstification and intense tectonic fracturing, favoring slow groundwater circulation, and to multiyear variations of the water table elevation, influenced by variable seasonal recharge. The vertical component displays seasonal and multiyear signals more homogeneously distributed in space and closely correlated with estimates of total water storage from GRACE, reflecting the elastic response of the lithosphere to variations of surface water loads. The different sensitivities of vertical and horizontal components to the hydrologically induced deformation processes allow us to spatially and temporally resolve the different phases of the water cycle, from maximum hydrological loading at the surface to maximum hydrostatic pressure beneath karst aquifers. Finally, we suggest that transient deformation signals in the geodetic series of the Apennines are correlated to large‐scale climatic patterns (Northern Atlantic Oscillation) through their influence on precipitation variability and trends at the regional scale.

The chalk hyporheic zone: a true ecotone?

This review summarises the main ecotonal properties of chalk hyporheic zone (CHZ), using a holistic approach on both structure and functionality of this habitat. The corroborated results suggest that the CHZ represents a typically shallow habitat (approx. 40–50 cm deep), with a homogenous distribution of both fauna and chemistry between heads and tails of riffles (putative down and, respectively, upwelling zones). Despite being groundwater fed, the CHZ is equally influenced by surface waters, chemically and biologically. However, despite its shallowness, the CHZ plays a very important role in nutrients (re)cycling and in the energy flux towards river ecosystems, fuelling benthic food webs with surface-derived macronutrients and subsurface chemosynthetic C. Although groundwater variation influences strongly the river flow during winter, the effects on interstitial fauna dynamic are limited, suggesting the active role of CHZ played in the stochastic events of down/upward migration of fauna across habitats. Overall, the CHZ represents a confined, but critical habitat in the structure and functionality of chalk river ecosystems and fulfils most properties of a true ecotone.

Origin of Hexavalent Chromium in Drinking Water Wells from the Piedmont Aquifers of North Carolina

Hexavalent chromium [Cr(VI)] is a known pulmonary carcinogen. Recent detection of Cr(VI) in drinking water wells in North Carolina has raised public concern about contamination of drinking water wells by nearby coal ash ponds. Here we report, for the first time, the prevalence of Cr and Cr(VI) in drinking water wells from the Piedmont region of central North Carolina, combined with a geochemical analysis to determine the source of the elevated Cr(VI) levels. We show that Cr(VI) is the predominant species of dissolved Cr in groundwater and elevated levels of Cr and Cr(VI) are found in wells located both near and far (>30 km) from coal ash ponds. The geochemical characteristics, including the overall chemistry, boron to chromium ratios, and strontium isotope (87Sr/86Sr) variations in groundwater with elevated Cr(IV) levels, are different from those of coal ash leachates. Alternatively, the groundwater chemistry and Sr isotope variations are consistent with water–rock interactions as the major source for Cr(...

Establishing the range of background for radon variations in groundwater along the Serghaya fault in southwestern Syria

Long-term groundwater radon measurements were carried out in two selected karstic springs emerging from the Serghaya fault zone in southwestern Syria. The work is aimed at determining the range of radon background along the concerned fault, which represents a prominent branch segment of the Dead Sea Fault System in the region. The obtained data was statistically analyzed and the mean radon values have been standardized in terms of probability of magnitude in order to enable the separation between normal radon variations from other anomalous or geotectonic related values. The results revealed a general background range of radon concentration varying between 5000 and 13000 Bqm-3, and thus all radon values lying outside this range were considered anomalous. However, remarkable clusters of high radon concentrations with peak values more than twice times the background level, were observed in both monitoring springs through the period (1992-1994). These abnormal radon values were positively correlated with simultaneous time of high precipitations, while no significant earthquake activities were recorded in the region during that period. Therefore, such radon signals do not seem to be a reflection of regional changes in crustal strain, but rather they mostly indicate evidences of radon response to the groundwater table fluctuations due to high precipitations. These consequences may confirm the usefulness of radon application as an important natural tracer in hydrogeological investigations.

Isotopic signatures of precipitation, surface water, and groundwater interactions, Poyang Lake Basin, China

Poyang Lake, whose hydrological characteristics are impacted by the operation of the Three Gorges Dam, is the largest freshwater lake in China. However, water cycle mechanisms in the Poyang Lake Basin remain poorly understood. In this study, stable isotopes (δD and δ18O) of water samples (taken in April, July, and November 2013) and hydrological data are used to investigate the interactions between precipitation, river water, lake water, and shallow groundwater in the Poyang Lake region. The isotopic results show seasonal variations in precipitation, surface water, and groundwater, which provides a set of tools to identify waters that have different histories. The similar isotopic compositions of river water and groundwater suggest a close hydrological connection. Hydrological data present a positive correlation between river run-off and precipitation; however, isotopic results show that rivers in the Poyang Lake Basin in different seasons are primarily recharged by subsurface run-off with different proportion between base flow and near-surface quick flow, rather than by surface run-off directly formed by concurrent rainfall. Due to the geological characteristics of stratum in the Poyang Lake Basin, it is easier for precipitation to infiltrate into soil and recharge groundwater than to form direct surface flow that feeds rivers. The groundwater system is like a huge reservoir which can effectively impound rainfall water, playing an important role in restraining floodwater during the flood season and in ensuring river run-off supply during the dry season.

Dynamics and anthropogenic impacts of multiple karst flow systems in a mountainous area of South China

The Xiangxi River basin, South China, is a steep terrane with well-developed karst features and an important Cambrian-Ordovician aquifer. Meteoric water in this mountainous area features a mean δ18O elevation gradient of –2.4 ‰/km. This gradient was used to estimate mean recharge elevations of 760 m for Shuimoxi (SMX) spring, 1,060 m for Xiangshuidong (XSD) spring, and 1,430 m for drill hole ZK03, indicating multiple flow paths in the Cambrian-Ordovician karst aquifer. Mean residence times of 230 and 320 days and ∼2 years were estimated for these features, respectively, using the damped running average model that predicts the isotopic variations in groundwater from those in precipitation. Groundwater in the regional karst flow system has the longest residence time, the highest recharge elevation, the longest flow paths, the lowest addition of anthropogenic components, and the greatest amount of water–rock interaction as indicated by its higher dissolved solids, Mg2+ concentrations and Mg/Ca ratios than the springs. In contrast, the local and shallow karst flow systems respond rapidly to recharge events. Artificial tracer tests prove that these shallow karst systems can also quickly transmit anthropogenic contaminants, indicating that they are highly vulnerable to human impacts, which include the enrichment of NO3 –. The intensity of water–rock interaction and groundwater vulnerability are mainly determined by the structure and dynamics of the multiple karst flow systems.

Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer

Long-term groundwater recharge from rainfall in the Nile Delta is needed as an input for integrated groundwater modelling in the Nile Delta aquifer for more accurate simulation. The main objective is to estimate the spatial and temporal variation of groundwater recharge from rainfall in the Nile Delta aquifer. Water and Energy Transfer between Soil, Plants and Atmosphere under quasi-Steady State (WetSpass) model parameters were identified for the Nile Delta based on the available meteorological data for the area collected in 1991 and 2000. The collected data were rainfall, temperature, wind speed and evapotranspiration. Geomorphological characteristics, such as soil type, topography, groundwater depth and slope, were also collected as input data for the WetSpass model. ENVI software was used to come up with land use classification based on available land cover images of the Nile Delta for 1972, 1984, 1990, 2000 and 2009. The WetSpass model was calibrated by comparing the simulated groundwater recharge with the calculated one by using the water balance equation model. The results indicated close agreement in groundwater recharge between the two model outputs with R 2 of 0.99 and 0.94, while the root-mean-square errors (RMSEs) were 4.86 and 9.39 mm for 1991 and 2000, respectively. The WetSpass model was then applied in respect of 1970, 1980, 1990 and 2010 for the purpose of validation. The overall RMSE and R 2 for the 6 years were 8.83 mm and 0.88, respectively. The results of the WetSpass calibrated model provide information to support integrated groundwater modelling. The results reveal that WetSpass works well in simulating the components of the hydrological balance in the Nile Delta.

Assessing Groundwater Geospatial Variation Using Microgravity Investigation in the Arid Riyadh Metropolitan Area, Saudi Arabia: a Case Study

A combination of relative microgravity measurements at ground surface, and depth to water and water table measurements from adjacent wells were used to estimate geospatial variation of groundwater. A highly accurate portable Grav-Map gravimeter was used for gravimetric measurements at locations nearby a 42 well water table monitoring program. To efficiently correlate the two data sets, wells were clustered into five groups by geological unit and water saturation. Microgravity data was processed, interpreted, and correlated with both the depths to groundwater and the water table levels. Regression analyses revealed a strong negative correlation for microgravity and depth to groundwater in all five clusters; correlation coefficients varied between 0.70 and 0.97, and measured 0.78 over the entire study area. Microgravity values increased as groundwater depth decreased, likely because rising groundwater fills voids and fractures within soil and rocks, increasing rock density and therefore relative gravity. To validate the correlation, we superimposed a map of depths to water on the first derivative of microgravity measurements. The shallowest groundwater depths were positively related to the zero first derivatives, having intersection areas within a 75 % significance interval. Negative first derivatives covered the rest of the study area, with relative gravity decreasing with increasing groundwater depth. This technique can precisely and efficiently determine changes in subsurface geology and geospatial changes in depths to the groundwater table. Distances between microgravity stations should be small, to better detect small changes in gravity values, reflecting density contrasts underground.

Hydromorphology of the Unconfined Groundwater in the South of Klaten District (Data Before Earthquake Mei 27th 2006)

There are some characteristics and distributions of unconfined groundwater variation in the research area. Those are related to a system of water supply and consumptive use for drinking water. Variation of the groundwater characteristic depends on variation of morphology. Therefore, it is needed to delineate hydromorphology units of the regions as a base on groundwater resources management, especially for drinking water. The aims of the research are: (1) to study of the characteristic and distribution of unconfined groundwater variations base on landform units, (2) to study the factors that affect such variations, and (3) to establish the hydromorphology units of the regions for groundwater resources management, especially for drinking water. The method used in this research is landform approach and field survey. The sampling method is stratified sampling, based on landform as the analysis approach. Result of the research shows that there are some variations of groundwater characteristic at each landform. Landforms which have good groundwater characteristic are Hydromorphology Unit of Fluvio Volcanic Plain of Young Merapi (except Bayat region) and Hydromorphology Unit of Volcanic Foot Plain of Young Merapi. At those units, there are good quality of groundwater, bicarbonate water (hydrochemical type I), having low electric conductivity, shallow of water table, low in fluctuation, and middle to fast class in aquifer permeability. Those units are the most potential unconfined groundwater resources management for drinking water. The units which have poor groundwater characteristic are Hidromorphology Unit in Bayat Region, including Undulating Alluvial Plain, Fluvio Volcanic Plain of Young Merapi, and Swamp Alluvial Plain. Generally, the groundwater quality is medium to poor, the hydrochemical type is Va (initiation process of connate water) and type III (evaporate water), shallow up to medium of water table, and low to middle class of aquifer permeability. The taste of groundwater is brackish to saline with high concentration of chloride.

MONITORING GROUNDWATER STORAGE IN NORTHERN CHILE BASED ON SATELLITE OBSERVATIONS AND DATA SIMULATION

Groundwater is one of the most valuable sources of fresh water in many places worldwide, especially in regions with low pluviometric indices such as northern Chile. Thus, it is mandatory to monitor this precious resource in space and time domains. Currently, groundwater in Chile is monitored using sparse stations of water table observations. Although other indirect alternatives such as space-borne observations can contribute to regional understanding of groundwater variations, they have been poorly studied in Chile. In this study, groundwater monitoring is carried out based on 104 monthly solutions of the Gravity Recovery and Climate Experiment (GRACE) mission between 2004 and 2013. The extraction of the groundwater storage (GWS) signal obtained from GRACE was recovered once the effects of soil moisture and snow storage, retrieved from the Global Land Data Assimilation System (GLDAS), were removed. Analysis of the data was performed point-wise (six stations) and at regional scale (Northern Chile). Overall, the results are correlated with wells observations obtained by the General Directorate of Water Resources (DGA) of the Ministry of Public Works of Chile. Point-wise comparison shows root mean square error (RMSE) large than 30.0 mm while regional scale validation shows RMSE of 21.5 mm. Furthermore, regional groundwater variations obtained from GRACE/GLDAS are highly consistent in terms of trend with results obtained from well observations in the DGA network. The Empirical Orthogonal Function (EOF) analysis revealed higher annual groundwater variability in the metropolitan region and a higher inter-annual variability in the north. The methodology used may contribute to the regional study of spatial-temporal variations of groundwater in regions with sparse hydrometric network

식생/모래기반 자연해빈에서의 지하수위 변동특성

The variation of groundwater by wave, tide and precipitation conditions is closely related to the vegetation environment at the natural vegetation and sandy based beach, and it has a significant impact on the vegetation development and ground stabilization. In this study, the water temperature, electrical conductivity, and pressure were monitored at five observational stations normal to the Jinu-do(Island) shoreline of Nakdong river estuary from March 2012 to September 2014 (approximately 799 days) with the aim of measuring the variation in groundwater-table characteristics. The purpose of the study was to identify factors (tide, wave etc.) affecting groundwater-table variation using time series and correlation analysis, and to record spatial variations in the groundwater level and electrical conductivity as a result of storm events. The observational station in the intertidal zone was strongly affected by wave period and tide level. During the storm period, the groundwater-table and electrical conductivity were stabilized at the edge of sand dunes, vegetation, and areas of transition between freshwater and seawater.

Linking the morphology of fluvial fan systems to aquifer stratigraphy in the Sutlej‐Yamuna plain of northwest India

AbstractThe Indo‐Gangetic foreland basin has some of the highest rates of groundwater extraction in the world, focused in the states of Punjab and Haryana in northwest India. Any assessment of the effects of extraction on groundwater variation requires understanding of the geometry and sedimentary architecture of the alluvial aquifers, which in turn are set by their geomorphic and depositional setting. To assess the overall architecture of the aquifer system, we used satellite imagery and digital elevation models to map the geomorphology of the Sutlej and Yamuna fan systems, while aquifer geometry was assessed using 243 wells that extend to ∼200 m depth. Aquifers formed by sandy channel bodies in the subsurface of the Sutlej and Yamuna fans have a median thickness of 7 and 6 m, respectively, and follow heavy‐tailed thickness distributions. These distributions, along with evidence of persistence in aquifer fractions as determined from compensation analysis, indicate persistent reoccupation of channel positions and suggest that the major aquifers consist of stacked, multistoried channel bodies. The percentage of aquifer material in individual boreholes decreases down fan, although the exponent on the aquifer body thickness distribution remains similar, indicating that the total number of aquifer bodies decreases down fan but that individual bodies do not thin appreciably, particularly on the Yamuna fan. The interfan area and the fan marginal zone have thinner aquifers and a lower proportion of aquifer material, even in proximal locations. We conclude that geomorphic setting provides a first‐order control on the thickness, geometry, and stacking pattern of aquifer bodies across this critical region.