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1.
《水文科学杂志》2013,58(1):206-220
Abstract

The Asmari limestone formation is the major aquifer system at the Khersan 3 Dam site, Zagros, Iran. Characterization of the aquifer system and study of karst development are essential for forecasting leakage potential and to plan remediation works. The aquifer functioning and karst structure were evaluated by geology, well hydrodynamics and natural tracing studies, showing one unconfined and three artesian sub-aquifers, the last being characterized by rapid flow, with contributing old recharge water, and a recharge at higher elevation than the unconfined sub-aquifer. The anticline structure outcrops the artesian sub-aquifers downstream of the site. The confining layers disappear and the aquifer system discharges as a mix of all groundwater. Artesian groundwater is estimated to contribute about 80% (dry season) and 50% (wet season) of flow in the mixing zone. Very few karst features are observed in cores and galleries at the site, despite some karst landforms in the reservoir area. However the aquifer exhibits fast flow of karst type in the artesian sub-aquifers.  相似文献   

2.
Abstract

In order to evaluate groundwater quality and geochemical reactions arising from mixing between seawater and dilute groundwater, we performed a hydrochemical investigation of alluvial groundwater in a limestone-rich coastal area of eastern South Korea. Two sites were chosen for comparison: an upstream site and a downstream site. Data of major ion chemistry and ratios of oxygen–hydrogen isotopes (δ18O, δD) revealed different major sources of groundwater salinity: recharge by sea-spray-affected precipitation in the upstream site, and seawater intrusion and diffusion zone fluctuation in the downstream site. The results of geochemical modelling showed that Ca2+ enrichment in the downstream area is caused by calcite dissolution enhanced by the ionic strength increase, as a result of seawater–groundwater mixing under open system conditions with a constant PCO2 value (about 10?1.5 atm). The results show that, for coastal alluvial groundwater residing on limestone, significant hydrochemical change (especially increased hardness) due to calcite dissolution enhanced by seawater mixing should be taken into account for better groundwater management. This process can be effectively evaluated using geochemical modelling.

Editor D. Koutsoyiannis; Associate editor Y. Guttman

Citation Chae, G.-T., Yun, S.-T., Yun, S.-M., Kim, K.-H., and So, C.-S., 2012. Seawater–freshwater mixing and resulting calcite dissolution: an example from a coastal alluvial aquifer in eastern South Korea. Hydrological Sciences Journal, 57 (8),1–12.  相似文献   

3.
Abstract

This study proposes an empirical approach that can lead to the sustainable management of groundwater resources. This approach enables a comprehensive understanding of an aquifer, delineates distinct hydrological scenarios, and recommends a set of operational activities for each sub-region of the aquifer. The paper focuses on the Coastal aquifer of the Gaza Strip region which has been divided into three sub-regions. The southern sub-region (WSW) is classified as scenario “+a2”, which indicates that it can be used as a multi-annual groundwater reservoir. The northern sub-region (NW-E) is designated scenario “-a2”, where the recommended operational measures include injection of freshwater in wells and cleaning of the surface environment. The third sub-region (CSE), is classified as scenario “-b2”, which requires severe management measures to correct both a negative hydrological and environmental situation. The approach also involves on-going monitoring of the aquifer, and can be considered as an empirical tool to provide preliminary guidelines for long-term groundwater management.  相似文献   

4.
ABSTRACT

An innovative methodology that combines an indirect physiography-based method for determining the runoff coefficient at a sub-basin scale and a water balance model applied on a daily time scale was developed to calculate the natural groundwater recharge in three watersheds within the Oum Zessar arid area, Tunisia. The effective infiltration was calculated as part of the water surplus by considering the average available water content (AWC) of soil and an average runoff coefficient for each sub-basin. The model indicates that the sub-basins covered mainly by the “artificial” soils of tabias and jessour, characterized by average AWC values greater than 150 mm, did not contribute to natural groundwater recharge over the 10-year period (2003–2012) considered. The estimated volume for the Triassic aquifer amounted to about 4.5 hm3 year?1, which is consistent with previous studies. For the Jurassic and Cretaceous aquifers, the estimated volumes amounted to about 200 dm3 year?1.  相似文献   

5.
Spatial heterogeneity in the subsurface of karst environments is high, as evidenced by the multiphase porosity of carbonate rocks and complex landform features that result in marked variability of hydrological processes in space and time. This includes complex exchange of various flows (e.g., fast conduit flows and slow fracture flows) in different locations. Here, we integrate various “state‐of‐the‐art” methods to understand the structure and function of this poorly constrained critical zone environment. Geophysical, hydrometric, and tracer tools are used to characterize the hydrological functions of the cockpit karst critical zone in the small catchment of Chenqi, Guizhou Province, China. Geophysical surveys, using electrical resistivity tomography (ERT), inferred the spatial heterogeneity of permeability in the epikarst and underlying aquifer. Water tables in depression wells in valley bottom areas, as well as discharge from springs on steeper hillslopes and at the catchment outlet, showed different hydrodynamic responses to storm event rainwater recharge and hillslope flows. Tracer studies using water temperatures and stable water isotopes (δD and δ18O) could be used alongside insights into aquifer permeability from ERT surveys to explain site‐ and depth‐dependent variability in the groundwater response in terms of the degree to which “new” water from storm rainfall recharges and mixes with “old” pre‐event water in karst aquifers. This integrated approach reveals spatial structure in the karst critical zone and provides a conceptual framework of hydrological functions across spatial and temporal scales.  相似文献   

6.
Hydrogeological investigations were carried out in an arid area of Inner-Mongolia to determine the locations of future water supply resources. The first geophysical survey was conducted near Baiqi to identify favorable boreholes using magnetic resonance sounding (MRS). The yield capacities of 43 sites were investigated, and the extent of the potential groundwater storage was determined. Previous studies have indicated that a major tectonic structure may have a significant impact on the groundwater flow and well yield in the study area. Therefore, high-resolution seismic surveys were applied in the second stage of the investigation to determine the fault locations. After the regional identification, a major structure was investigated in detail to map the fracture patterns. Based on the assumption that the hydraulic conductivity of this formation is similar along the entire strike of the fracture, we proposed drilling a borehole (BQ3) in the zone. However, this well has a yield of only 0.8 L/s, falling short of the required flow rate of 3.0 L/s. Therefore, the objective of the final stage of exploration was to accurately define the attitude and extension of the aquifer and to select a more favorable borehole site that would meet the required water flow rate. The geophysical exploration was carried out using time-domain electromagnetic (TDEM) and MRS methods. The MRS results suggest optimal locations for water supply boreholes within the subsurface structures mapped by the TDEM inversion method. The data obtained by drilling and coring are in agreement with the predicted aquifer thickness from the TDEM data. Pumping tests indicate that the water discharge of borehole BQ4 was 3.5 L/s. Our results demonstrate that the delineation of the groundwater body using a combined application of three geophysical methods (the MRS, TDEM and 2D seismic methods) was successful.  相似文献   

7.
Abstract

This study evaluates an over-exploited aquifer (Balasor, India) and also explores the possibilities of sustainable management using several statistical approaches. First, bootstrap analysis indicates that groundwater pumping has resulted in the reduction of mean cultivated area as the average irrigation capacity per bore well dropped from 3.74 ha to 1.5 ha within a period of 10 years of operation. However, modelling the groundwater levels using the seasonal autoregressive integrated moving average (SARIMA) procedure showed no evidence of large-scale groundwater withdrawals. The derived models can be used for water table forecasting and also for infilling the missing observations. The empirical relationship among pumping test results indicated that well depth and aquifer thickness significantly influence the discharge from the aquifer. This discharge may have encouraged the resource-rich farmers to exploit the lower aquifer. Based on a contour plot, the zone of groundwater exploitation was estimated to vary from 25 to 60 m below the surface. Therefore, a uniform aquifer exploitation policy needs to be implemented to curb the vertical competition in exploiting the aquifer and to develop sustainable management of the groundwater.

Citation Panda, D. K. & Kumar, A. (2011) Evaluation of an over-used coastal aquifer (Orissa, India) using statistical approaches. Hydrol. Sci. J. 56(3), 486–497.  相似文献   

8.
Abstract

The Complex Terminal (CT) and Plio-Quaternary (P-Q) aquifers in the Chott Gharsa plain in southwestern Tunisia have been investigated with the aid of chemical and isotopic tools. It has been demonstrated that groundwater from the CT is mainly of palaeo-origin, especially in the western and central parts of the plain where the most negative values of δ18O and δ2H were observed (between??8.1 and??7.6‰ for δ18O, and??60 to??57‰ for δ2H), combined with low concentrations of radiocarbon (6.8–7.5 pmc) and absence of tritium. Modern recharge of the aquifer occurs only in the eastern part of the system where younger waters were observed, as indicated by their stable isotope composition, relatively high radiocarbon content and presence of tritium. Groundwater from the P-Q multi-layer aquifer represents mixtures of ascending deep CT waters and modern water recharging the P-Q aquifer system. Isotope mass balance was used to quantify mixing proportions. The calculations showed that the contribution of deep CT groundwater to the P-Q aquifer system reaches about 75% in the western and central parts of the plain where the CT aquifer remains strongly artesian. This contribution decreases to about 15% towards the eastern part of the plain, as a consequence of significant reduction of artesian pressure in this area of the CT aquifer. Chemical data suggest that mineralization of the studied groundwater systems is controlled mainly by dissolution of evaporative minerals (halite, anhydrite and gypsum) and cation exchange reactions with the matrix, possibly enhanced by recent anthropogenic disturbance of the system caused by lowering of the water table due to heavy exploitation and return flow of saline irrigation water into the P-Q aquifer.

Editor D. Koutsoyiannis; Associate editor E. Custodio

Citation Yangui, H., Abidi, I., Zouari, K., and Rozanski, K., 2012. Deciphering groundwater flow between the Complex Terminal and Plio-Quaternary aquifers in Chott Gharsa plain (southwestern Tunisia) using isotopic and chemical tools. Hydrological Sciences Journal, 57 (5), 967–984.  相似文献   

9.
The impacts of long-term pumping on groundwater chemistry remain unclear in the Manas River Basin, Northwest China. In this study, major ions within five surface water and 105 groundwater samples were analyzed to identify hydrogeochemical processes affecting groundwater composition and evolution along the regional-scale groundwater flow paths using the multivariate techniques of hierarchical cluster analysis (HCA) and principal components analysis (PCA) and traditional graphical methods for analyzing groundwater geochemistry. HCA classified the groundwater samples into four clusters (C1 to C4). PCA reduced the dimensionality of geochemical data into three PCs, which explained 86% of the total variance. The results of HCA and PCA were used to identify three zones: “recharge,” “transition,” and “discharge.” In the recharge zone the groundwater type is Ca-HCO3-SO4 and is primarily impacted by the dissolution of calcite and silicate weathering. In the transition zone the groundwater type is Ca-HCO3-SO4-Cl and is impacted by rock dissolution and reverse ion exchange. In the discharge zone the groundwater type is Na-Cl and is impacted by evaporation and reverse ion exchange. In addition, anthropogenic activities impact the groundwater chemistry in the study area. The groundwater type generally changes from Ca-HCO3-SO4 in the recharge area to Na-Cl in the discharge area along the regional-scale groundwater flow paths. This study provides a process-based knowledge for understanding the interaction of groundwater flow patterns and geochemical evolution within the Manas River Basin.  相似文献   

10.
Abstract

Chemical and isotopic data of groundwater of the Upper Cretaceous aquifer in the Orontes basin, Syria, have been used to assess the groundwater geochemistry, the origin of groundwater recharge and groundwater residence time. The chemical data indicate that dissolution of evaporite minerals is the main process controlling groundwater mineralization. The composition of stable isotopes δ18O and δ2H, together with 14C activity, reflect the existence of three different groups: (a) groundwater in the Coastal Mountains with δ18O of –6.65‰, quite similar to modern-day precipitation, and high 14C (>50 pmC); (b) groundwater in the unconfined aquifer of the Hama Uplift, which has δ18O of –5.52‰ and 14C near 20 pmC, and is recharged locally; and (c) groundwater from the confined aquifer of the Homs Depression, which is characterized by more depleted δ18O,, –8.01‰, and low 14C (<7 pmC), and might be recharged in the northern piedmont of the Anti-Lebanon Mountains. The distinctive isotope signatures of the latter two groups indicate different recharge elevations and palaeoclimatic effects. The low recharge rate of the groundwater in the Hama Uplift aquifer, and the even slower recharge rate in the Homs Depression aquifer, are reflected by groundwater 14C residence times of 5 and over 22 Ka BP, respectively.

Editor D. Koutsoyiannis

Citation Al-Charideh, A., 2013. Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin (Syria). Hydrological Sciences Journal, 58 (2), 452–467.  相似文献   

11.
Few studies have investigated large reaches of rivers in which multiple sources of groundwater are responsible for maintaining baseflow. This paper builds upon previous work undertaken along the Fitzroy River, one of the largest perennial river systems in north‐western Australia. Synoptic regional‐scale sampling of both river water and groundwater for a suite of environmental tracers (4He, 87Sr/86Sr, 222Rn and major ions), and subsequent modeling of tracer behavior in the river, has enabled definition and quantification of groundwater input from at least three different sources. We show unambiguous evidence of both shallow “local” groundwater, possibly recharged to alluvial aquifers beneath the adjacent floodplain during recent high‐flow events, and old “regional” groundwater introduced via artesian flow from deep confined aquifers. We also invoke hyporheic exchange and either bank return flow or parafluvial flow to account for background 222Rn activities and anomalous chloride trends along river reaches where there is no evidence of the local or regional groundwater inputs. Vertical conductivity sections acquired through an airborne electromagnetic (AEM) survey provide insights to the architecture of the aquifers associated with these sources and general groundwater quality characteristics. These data indicate fresh groundwater from about 300 m below ground preferentially discharging to the river, at locations consistent with those inferred from tracer data. The results demonstrate how sampling rivers for multiple environmental tracers of different types—including stable and radioactive isotopes, dissolved gases and major ions—can significantly improve conceptualization of groundwater—surface water interaction processes, particularly when coupled with geophysical techniques in complex hydrogeological settings.  相似文献   

12.
Rapid urbanization in the Jakarta area has become a severe subsurface environmental issue as it entails groundwater level decline and land subsidence caused by excessive groundwater pumping. In this study, apparent groundwater age rejuvenation in the deep aquifer under DKI Jakarta was found by comparing 14C activities between 1985 and 2008. We discussed the use of a numerical groundwater flow model to evaluate the rejuvenation process in this urbanized area. When considering the deep aquifer in the DKI Jakarta area, we can assume six direction fluxes toward the aquifer: two vertical fluxes (downward and upward flux) and four horizontal fluxes (northern, southern, western, and eastern flux). Results of model calculations show that the greatest groundwater flux among six flux directions became ‘vertical downward flux’, which means that shallower groundwater intrudes into the deep one because of excessive groundwater pumping from the mid‐1980s. This flux grows about 50% during the 2000s. This result is consistent with the detection of CFC‐12 and SF6, which functions as an indicator of young groundwater even in the deep groundwater. The rejuvenation ratio ‘R’ was determined using 14C activity in the groundwater; R increases with the CFC‐12 concentration and both show good correlation. Furthermore, we estimated the ‘vertical downward flux’ at each well's screen depth using model estimation. Results show that this flux is greater in the urban groundwater depression area and especially at shallower parts of the deep aquifer, and that it affects the magnitude of the shallow groundwater intrusion. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

13.
ABSTRACT

Integrated two-dimensional electrical resistivity imaging (ERI) and hydrochemical surveys were used to investigate the groundwater alluvial aquifer in Kuala Langat, Malaysia. The study in the Langat basin considered the thickness of the aquifer, the depth of the bedrock, the regions influenced by seawater intrusion, and the monitoring of water levels. The resistivity imaging results show that the upper layer consists of clay, while the second layer is an aquifer whose thickness varies mostly in the range of 10–30 m, and in some cases extends to 40 m. The bedrock depth varies from 30 to 65 m. The chemical analyses were carried out on groundwater samples from nine boreholes collected between 2008 and 2012. The analyses indicate that the total dissolved solids (TDS) exceed 1000 mg L-1 near the coastal area and are often less than 500 mg L-1 further inland. The ERI and hydrochemical analyses reveal that groundwater in the study area, especially towards the coast, is a mixture of brackish and fresh waters.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR M.D. Fidelibus  相似文献   

14.
The objective of this study was to investigate whether 222Rn in groundwater can be used as a tracer for light non‐aqueous phase liquid (LNAPL) quantification at a field site treated by dual‐phase LNAPL removal. After the break of a pipeline, 5 ha of soil in the nature reserve Coussouls de Crau in southern France was contaminated by 5100 m3 of crude oil. Part of this oil seeped into the underlying gravel aquifer and formed a floating oil body of about 3.9 ha. The remediation consists of plume management by hydraulic groundwater barriers and LNAPL extraction in the source zone. 222Rn measurements were performed in 21 wells in and outside the source zone during 15 months. In uncontaminated groundwater, the radon activity was relatively constant and remained always >11 Bq/L. The variability of radon activity measurements in wells affected by the pump‐and‐skim system was consistent with the measurements in wells that were not impacted by the system. The mean activities in wells in the source zone were, in general, significantly lower than in wells upgradient of the source zone, owing to partitioning of 222Rn into the oil phase. The lowest activities were found in zones with high non‐aqueous phase liquid (NAPL) recovery. LNAPL saturations around each recovery well were furthermore calculated during a period of high groundwater level, using a laboratory‐determined crude oil–water partitioning coefficient of 38.5 ± 2.9. This yielded an estimated volume of residual crude oil of 309 ± 93 m3 below the capillary fringe. We find that 222Rn is a useful and cheap groundwater tracer for finding zones of good LNAPL recovery in an aquifer treated by dual‐phase LNAPL removal, but that quantification of NAPL saturation using Rn is highly uncertain.  相似文献   

15.
In situ bioremediation is being considered to optimize an existing pump‐and‐treat remedy for treatment of explosives‐contaminated groundwater at the Umatilla Chemical Depot. Push‐pull tests were conducted using a phased approach to measure in situ hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and 2,4,6‐trinitrotoluene (TNT) degradation rates associated with various carbon substrates. Phase I included short‐duration transport tests conducted in each well to determine dilution rates and retardation factors for RDX and TNT. Phase II included aquifer “feedings” conducted by injecting 150 gallons of treated site groundwater amended with ethanol, corn syrup, lactose or emulsified oil (concentrations 10, 25 and 27 mM, respectively; 12% by volume for emulsified oil). Wells received up to 6 substrate “feedings” over the course of 3 months followed by monitoring dissolved oxygen, nitrate, Fe(II), and sulfate to gauge in situ redox conditions as indicators of anaerobic microbial activity. Phase III included push‐pull tests conducted by injecting 150 gallons of site groundwater amended with approximately 1000 µg/L RDX, 350 µg/L TNT, carbon substrate and a conservative tracer, followed by sampling over 8 d. Corn syrup resulted in the best RDX removal (82% on average) and the largest RDX degradation rate coefficient (1.4 ± 1.1 d?1). Emulsified oil resulted in the best TNT removal (99%) and largest TNT degradation rate coefficient (5.7 × 10?2 d?1). These results will be used to simulate full‐scale in situ bioremediation scenarios at Umatilla and will support a go/no‐go decision to initiate full‐scale bioremediation remedy optimization.  相似文献   

16.
We evaluated sources and pathways of groundwater recharge for a heterogeneous alluvial aquifer beneath an agricultural field, based on multi‐level monitoring of hydrochemistry and environmental isotopes of a riverside groundwater system at Buyeo, Korea. Two distinct groundwater zones were identified with depth: (1) a shallow oxic groundwater zone, characterized by elevated concentrations of NO3? and (2) a deeper (>10–14 m from the ground surface) sub‐oxic groundwater zone with high concentrations of dissolved Fe, silica, and HCO3?, but little nitrate. The change of redox zones occurred at a depth where the aquifer sediments change from an upper sandy stratum to a silty stratum with mud caps. The δ18O and δ2H values of groundwater were also different between the two zones. Hydrochemical and δ18O? δ2H data of oxic groundwater are similar to those of soil water. This illustrates that recharge of oxic groundwater mainly occurs through direct infiltration of rain and irrigation water in the sandy soil area where vegetable cropping with abundant fertilizer use is predominant. Oxic groundwater is therefore severely contaminated by agrochemical pollutants such as nitrate. In contrast, deeper sub‐oxic groundwater contains only small amounts of dissolved oxygen (DO) and NO3?. The 3H contents and elevated silica concentrations in sub‐oxic groundwater indicate a somewhat longer mean residence time of groundwater within this part of the aquifer. Sub‐oxic groundwater was also characterized by higher δ18O and δ2H values and lower d‐excess values, indicating significant evaporation during recharge. We suggest that recharge of sub‐oxic groundwater occurs in the areas of paddy rice fields where standing irrigation and rain water are affected by strong evaporation, and that reducing conditions develop during subsequent sub‐surface infiltration. This study illustrates the existence of two groundwater bodies with different recharge processes within an alluvial aquifer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

17.
The quaternary coastal Collo aquifer in northeast Algeria (NE Algeria) marks an important local water resource supporting domestic, industrial and agricultural activities. The aquifer shows signs of contamination due to the existence of various pollution sources, especially nitrogen compounds. Focusing the local identification of key vulnerable zones and related main hazard types for wise future water management, the present study highlights results from a coupled analysis of the well-established Geographical Information System (GIS)-based GOD (groundwater occurrence, overall aquifer class, depth to groundwater) hazard index analysis and the COST Action 620 plan. Most prevalent hazard types in the study area were identified as the urban/residential areas without public sewage systems, landfill and agricultural/pasturing areas. Regarding the vulnerability analysis particularly the northern aquifer region is endangered, dominated by high (22.4%) and moderate (27.4%) vulnerability classes. Central, western and southern aquifer regions are characterized by low (23.3%) and very low (26.9%) vulnerability classes. Overall, these GOD-derived results are in good agreement with earlier results obtained by the more complex DRASTIC approach. Final risk assessment and validation related to 2014/2015 nitrate sampling campaigns indicate that “high risk” and “very high risk” classes only apply to a small part of the study area in the northern sector (8%), whereas the main part (>60%) broadly affecting the central, western and southern sector only bears a low to very low risk of water pollution. Apart from a future-oriented groundwater abstraction strategy it is recommended to update the evaluation regularly to effectively consider dynamic changes of local anthropogenic activities and hazards.  相似文献   

18.
《水文科学杂志》2013,58(6):1241-1252
Abstract

Major ion geochemistry, and water molecule isotopes (18O, 2H) and radiogenic carbon (14C) of dissolved inorganic carbon (DIC) were used to investigate the hydrodynamic functioning of the multilayer aquifer system in the Moulares-Redayef basin, southern Tunisia. The groundwater of different aquifer levels is characterized by sulphate to calcium sulphate water type. The major geochemical processes in the aquifer system are evaporite mineral dissolution and mixing. The isotopic study allows two groundwater types to be identified: an old palaeoclimatic groundwater, marked by low 14C activity and relatively depleted stable isotope (18O and 2H) content characterizes the shallowest aquifers of the Plio-Quaternary and Miocene formations; however, a recent groundwater, distinguished by relatively high 14C activity and slightly enriched 18O and 2H content, characterizes the deep Upper Cretaceous artesian aquifer. In addition to these two water groups, other groundwaters are identified, indicating a mixing effect.  相似文献   

19.
Groundwater contributions to baseflow in Minnehaha Creek, a creek located in a highly developed watershed in the Minneapolis-St. Paul metropolitan area, from the watershed's Quaternary aquifer were quantified as part of an effort to manage low flow conditions in the creek. Considerable uncertainty exists with any single method used to quantify groundwater contributions to baseflow; therefore, a “weight of evidence” approach in which methods spanning multiple spatial scales was utilized. Analyses conducted at the watershed-scale (streamflow separation and stable isotope analyses) were corroborated with site-scale measurements (piezometer, seepage meter, and streambed temperature profiles) over a multi-year period to understand processes and conditions controlling connectivity between the stream, its shallow aquifer system and other flow sources. In the case of Minnehaha Creek, groundwater discharge was found to range from 6.2 to 23 mm year−1, which represented only 5 to 11% of annual streamflow during the study period. From the weight of evidence, it is conjectured that regional-scale hydrogeological conditions control groundwater discharge in Minnehaha Creek. Implications of these results with regard to possible augmentation of baseflow by increasing groundwater recharge with infiltration of stormwater are discussed.  相似文献   

20.
An innovative approach for regionalizing the 3‐D effective porosity field is presented and applied to two large, overexploited, and deeply weathered crystalline aquifers located in southern India. The method derives from earlier work on regionalizing a 2‐D effective porosity field in that part of an aquifer where the water table fluctuates, which is now extended over the entire aquifer using a 3‐D approach. A method based on geological and geophysical surveys has also been developed for mapping the weathering profile layers (saprolite and fractured layers). The method for regionalizing 3‐D effective porosity combines water table fluctuation and groundwater budget techniques at various cell sizes with the use of satellite‐based data (for groundwater abstraction), the structure of the weathering profile, and geostatistical techniques. The approach is presented in detail for the Kudaliar watershed (983 km2) and tested on the 730 km2 Anantapur watershed. At watershed scale, the effective porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that (a) depending on the geology and on the structure of the weathering profile, the vertical distribution of effective porosity can be very different and that the fractured layers in crystalline aquifers are not necessarily characterized by a rapid decrease in effective porosity and (b) that the lateral variations in effective porosity can be larger than the vertical ones. These variations suggest that within a same weathering profile, the density of open fractures and/or degree of weathering in the fractured zone may significantly vary from a place to another. The proposed method provides information on the spatial distribution of effective porosity that is of prime interest in terms of flux and contaminant transport in crystalline aquifers. Implications for mapping groundwater storage and scarcity are also discussed, which should help in improving groundwater resource management strategies.  相似文献   

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