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1.
It is important to understand the link between land surface/soil properties and shallow groundwater quality. To that end, soil properties and near‐water‐table groundwater chemistry of a shallow, unconfined aquifer were measured on a 100‐m grid on a 64‐ha irrigated field in southeastern North Dakota. Soil properties and hydrochemistry were compared via multivariate analysis that included product‐moment correlations and factor analysis/principal component analysis. Topographic low areas where the water table was in close proximity to the soil surface generally had higher apparent electrical conductivity (ECa) and higher percent silt and clay than higher positions on the landscape. The majority of the groundwater was characterized by Ca‐ and Mg‐HCO3 type water and was associated with topographic high areas with lower ECa and net groundwater recharge. Small topographic depressions were areas of higher ECa (net groundwater discharge) where salts that precipitated via evapotranspiration and evaporative discharge dissolved and leached to the groundwater during short‐term depression‐focused recharge events. At this site, groundwater quality and soil ECa were related to surface topography. High‐resolution topography and ECa measurements are necessary to characterize the land surface/soil properties and surficial groundwater quality at the field‐scale and to delineate areas where the shallow groundwater is most susceptible to contamination.  相似文献   

2.
In recent years, the water demand has been increasing considerably in Bojnourd, capital of Northern Khorasan province in NE of Iran, and the extracted water from Bojnourd alluvial aquifer, with an area of 65 km2, is not sufficient for residents. The required water is going to be supplied from Shirindare dam, located out of Bojnourd aquifer’s catchment area; therefore, the groundwater levels will rise in some parts of the aquifer, due to the return flow of supplied water, which will cause serious problems for the city. In this paper, the groundwater flow system of Bojnourd aquifer has been numerically simulated using MODFLOW code in GMS interface. The model, primarily, was calibrated for a steady state condition for the mean values of oneyear period (Sep. 2009 to Sep. 2010) which has a steady condition with low stresses on the aquifer. Then the model was run/calibrated for transient conditions for a two year period (Sep. 2007 to Sep. 2009). After determining the hydraulic properties of the aquifer and confirming their validity, different management scenarios, were applied to the model. Results reveal that groundwater levels in the urban area will rise by over 3 m, by infiltrating 40% of supplied water from the Shirindare dam into the aquifer. To manage the rising water levels, two different management scenarios were applied to the aquifer model. In doing so and with proper management of aquifer exploitation during critical situations, not only will the groundwater level drop; also the city of Bojnourd can develop urban landscaping by constructing sports/cultural camping area using the extra pumped water.  相似文献   

3.
The interaction between surface and groundwater plays a key role in a riparian ecosystem while the size of riparian groundwater has not been typically incorporated into hydrological modelling systems. An extensive geophysical survey composed of 25 individual DC electrical resistivity profiles was conducted at the Blair–Wallis site in Wyoming. The observed resistivity images show a near‐surface aquifer interpreted as the saturated alluvium deposit along the channel, rather than the geological bedrock. Based on the electrical resistivity images, it can be inferred that only the near‐surface portion of the groundwater actively interacts with the stream flow in the mountainous and hilly watershed. This study attempted the spatial extrapolation of the measured riparian aquifer depths by means of fitting functions based on the surface topography. The analysis indicated that the boundary of the riparian aquifer well corresponds to the topographical inflexion point of the hill slope profile. It was also demonstrated that the extent of alluvium deposit, where the area of riparian aquifer is indicated, can be delineated using the slope and curvature maps in the geographic information system. Then, the parabolic and biharmonic functions were tested for the groundwater depth estimation using the developed alluvium deposit map. The proposed methodology was effective if geological diffusion processes by wind and water dominated the topography. The spatial map of the active aquifer will be useful in hydrological drought analysis because it is considered to be a main source of baseflow during dry seasons.  相似文献   

4.
The strategic project of economic development in the Dornogobi Province in Mongolia is dependent on water supply. Thus a comprehensive hydrogeological characterization was focused on the Upper Cretaceous multi-aquifer system north of Sainshand city. A conceptual model was developed to discover the groundwater flow pattern essential to correct the setting of the numerical model of groundwater flow created using MODFLOW to assess the natural recharge of the aquifer. The conceptualization was based on geological and hydrogeological characterization. However, the evaluation of hydrochemistry proved to be the key factor revealing the principal feature of the groundwater flow pattern, which is the presence of preferential flow zones. These zones allow for intensive transfer of relatively fresh Na(Mg,Ca)?HCO3-dominated groundwater into discharge areas, where it leaks into the Quaternary aquifer. The numerical model suggested an enormous natural recharge of 22 100 m3/d, originating in 64% of the preferential flow zones.  相似文献   

5.
The effects of anthropogenic water use play a significant role in determining the hydrological cycle of north India. This paper explores anthropogenic impacts within the region's hydrological regime by explicitly including observed human water use behaviour, irrigation infrastructure and the natural environment in the CHANSE (Coupled Human And Natural Systems Environment) socio-hydrological modelling framework. The model is constrained by observed qualitative and quantitative information collected in the study area, along with climate and socio-economic variables from additional sources. Four separate scenarios, including business as usual (BAU, representing observed irrigation practices), groundwater irrigation only (where the influence of the canal network is removed), canal irrigation only (where all irrigation water is supplied by diverted surface water) and rainfed only (where all human interventions are removed) are used. Under BAU conditions the modelling framework closely matched observed groundwater levels. Following the removal of the canal network, which forces farmers to rely completely on groundwater for irrigation, water levels decrease, while under a canal-only scenario flooding occurs. Under the rainfed-only scenario, groundwater levels similar to current business-as-usual conditions are observed, despite much larger volumes of recharge and discharge entering and leaving the system under BAU practices. While groundwater abstraction alone may lead to aquifer depletion, the conjunctive use of surface and groundwater resources, which includes unintended contributions of canal leakage, create conditions similar to those where no human interventions are present. Here, the importance of suitable water management practices, in maintaining sustainable water resources, is shown. This may include augmenting groundwater resources through managed aquifer recharge and reducing the impacts on aquifer resources through occasional canal water use where possible. The importance of optimal water management practices that highlight trade-offs between environmental impact and human wellbeing are shown, providing useful information for policy makers, water managers and users. © 2019 John Wiley & Sons, Ltd.  相似文献   

6.
The concentrations of chlorofluorocarbons (CFC‐11, CFC‐12 and CFC‐113) and tritium (3H) content in groundwater were used to date groundwater age, delineate groundwater flow systems and estimate flow velocity in the Hohhot basin. The estimated young groundwater age is fallen in the bracket of 21 ~ 50 a and indicates the presence of two different age profiles and flow systems in the shallow groundwater system. Older age waters occur under the topographically low areas, where the aquifer is double‐layer aquifer system consisting of shallow unconfined‐semi‐confined aquifer and deep confined aquifer. This reflects long flow paths associated with regional flow. Groundwater (range from 21 to 34 years) in the north piedmont and east hilly areas, where the aquifer is a single‐layer aquifer consisting of alluvial fans, are typically younger than those in the low areas. The combination of CFCs dating with hydrogeological information indicates that both local and regional flow systems are present at the basin. The regional groundwater flow mainly flows from the north and east to the southwest, the local groundwater flow system occurs nearby the Hohhot city. The mean regional groundwater flow velocity of the shallow groundwater is estimated about 0.73 km/a. These findings can aid in refining hydrogeological conceptual model of the study area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

7.
The soil and water assessment tool (SWAT) has been widely used and thoroughly tested in many places in the world. The application of the SWAT model has pointed out that 2 of the major weaknesses of SWAT are related to the nonspatial reference of the hydrologic response unit concept and to the simplified groundwater concept, which contribute to its low performance in baseflow simulation and its inability to simulate regional groundwater flow. This study modified the groundwater module of SWAT to overcome the above limitations. The modified groundwater module has 2 aquifers. The local aquifer, which is the shallow aquifer in the original SWAT, represents a local groundwater flow system. The regional aquifer, which replaces the deep aquifer of the original SWAT, represents intermediate and regional groundwater flow systems. Groundwater recharge is partitioned into local and regional aquifer recharges. The regional aquifer is represented by a multicell aquifer (MCA) model. The regional aquifer is discretized into cells using the Thiessen polygon method, where centres of the cells are locations of groundwater observation wells. Groundwater flow between cells is modelled using Darcy's law. Return flow from cell to stream is conceptualized using a non‐linear storage–discharge relationship. The SWAT model with the modified aquifer module, the so‐called SWAT‐MCA, was tested in 2 basins (Wipperau and Neetze) with porous aquifers in a lowland area in Lower Saxony, Germany. Results from the Wipperau basin show that the SWAT‐MCA model is able (a) to simulate baseflow in a lowland area (where baseflow is a dominant source of streamflow) better than the original model and (b) to simulate regional groundwater flow, shown by the simulated groundwater levels in cells, quite well.  相似文献   

8.
Humans have strongly impacted the global water cycle, not only water flows but also water storage. We have performed a first global-scale analysis of the impact of water withdrawals on water storage variations, using the global water resources and use model WaterGAP. This required estimation of fractions of total water withdrawals from groundwater, considering five water use sectors. According to our assessment, the source of 35% of the water withdrawn worldwide (4300 km3/year during 1998–2002) is groundwater. Groundwater contributes 42%, 36% and 27% of water used for irrigation, households and manufacturing, respectively, while we assume that only surface water is used for livestock and for cooling of thermal power plants. Consumptive water use was 1400 km3/year during 1998–2002. It is the sum of the net abstraction of 250 km3/year of groundwater (taking into account evapotranspiration and return flows of withdrawn surface water and groundwater) and the net abstraction of 1150 km3/year of surface water. Computed net abstractions indicate, for the first time at the global scale, where and when human water withdrawals decrease or increase groundwater or surface water storage. In regions with extensive surface water irrigation, such as Southern China, net abstractions from groundwater are negative, i.e. groundwater is recharged by irrigation. The opposite is true for areas dominated by groundwater irrigation, such as in the High Plains aquifer of the central USA, where net abstraction of surface water is negative because return flow of withdrawn groundwater recharges the surface water compartments. In intensively irrigated areas, the amplitude of seasonal total water storage variations is generally increased due to human water use; however, in some areas, it is decreased. For the High Plains aquifer and the whole Mississippi basin, modeled groundwater and total water storage variations were compared with estimates of groundwater storage variations based on groundwater table observations, and with estimates of total water storage variations from the GRACE satellites mission. Due to the difficulty in estimating area-averaged seasonal groundwater storage variations from point observations of groundwater levels, it is uncertain whether WaterGAP underestimates actual variations or not. We conclude that WaterGAP possibly overestimates water withdrawals in the High Plains aquifer where impact of human water use on water storage is readily discernible based on WaterGAP calculations and groundwater observations. No final conclusion can be drawn regarding the possibility of monitoring water withdrawals in the High Plains aquifer using GRACE. For the less intensively irrigated Mississippi basin, observed and modeled seasonal groundwater storage reveals a discernible impact of water withdrawals in the basin, but this is not the case for total water storage such that water withdrawals at the scale of the whole Mississippi basin cannot be monitored by GRACE.  相似文献   

9.
In eastern England the Chalk aquifer is covered by extensive Pleistocene deposits which influence the hydraulic conditions and hydrochemical nature of the underlying aquifer. In this study, the results of geophysical borehole logging of groundwater temperature and electrical conductivity and depth sampling for major ion concentrations and stable isotope compositions (δ18O and δ2H) are interpreted to reveal the extent and nature of the effective Chalk aquifer of north Norfolk. It is found that the Chalk aquifer can be divided into an upper region of fresh groundwater, with a Cl concentration of typically less than 100 mg l−1, and a lower region of increasingly saline water. The transition between the two regions is approximately 50 m below sea-level, and results in an effective aquifer thickness of 50–60 m in the west of the area, but less than 25 m where the Eocene London Clay boundary is met in the east of the area. Hydrochemical variations in the effective aquifer are related to different hydraulic conditions developed in the Chalk. Where the Chalk is confined by low-permeability Chalky Boulder Clay, isotopically depleted groundwater (δ18O less than −7.5‰) is present, in contrast to those areas of unconfined Chalk where glacial deposits are thin or absent (δ18O about −7.0‰). The isotopically depleted groundwater is evidence for groundwater recharge during the late Pleistocene under conditions when mean surface air temperatures are estimated to have been 4.5°C cooler than at the present day, and suggests long groundwater residence times in the confined aquifer. Elevated molar Mg:Ca ratios of more than 0.2 resulting from progressive rock-water interaction in the confined aquifer also indicate long residence times. A conceptual hydrochemical model for the present situation proposes that isotopically depleted groundwater, occupying areas where confined groundwater dates from the late Pleistocene, is being slowly modified by both diffusion and downward infiltration of modem meteoric water and diffusive mixing from below with an old saline water body.  相似文献   

10.
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11.
Evapotranspiration (ET) plays a crucial role in catchment water budgets, typically accounting for more than 50% of annual precipitation falling within temperate deciduous forests. Groundwater ET is a portion of total ET that occurs where plant roots extend to the capillary fringe above the phreatic surface or induce upward movement of water from the water table by hydraulic redistribution. Groundwater ET is spatially restricted to riparian zones or other areas where the groundwater is accessible to plants. Due to the difficulty in measuring groundwater ET, it is rarely incorporated explicitly into hydrological models. In this study, we calibrated Topographic Model (TOPMODEL) using a 14‐year hydrograph record and added a groundwater ET pathway to derive a new model, Groundwater Evapotranspiration TOPMODEL (GETTOP). We inspected groundwater elevations and stream flow hydrographs for evidence of groundwater ET, examined the relationship between groundwater ET and topography, and delineated the area where groundwater ET is likely to take place. The total groundwater ET flux was estimated using a hydrological model. Groundwater ET was larger where the topography was flat and the groundwater table was shallow, occurring within about 10% of the area in a headwater catchment and accounting for 6 to 18% of total annual ET. The addition of groundwater ET to GETTOP improved the simulation of stream discharge and more closely balanced the watershed water budget. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

12.
Surface water is a scarce resource in Namibia with about sixty percent of Namibia's population dependent on groundwater for drinking purposes. With increasing population, the country faces water challenges and thus groundwater resources need to be managed properly. One important aspect of Integrated Water Resources Management is the protection of water resources, including protection of groundwater from contamination and over-exploitation. This study explores vulnerability mapping as a basic tool for protecting groundwater resources from pollution. It estimates groundwater vulnerability to pollution in the upper Niipele sub-basin of the Cuvelai-Etosha in Northern Namibia using the DRASTIC index. The DRASTIC index uses GIS to estimate groundwater vulnerability by overlaying different spatially referenced hydrogeological parameters that affect groundwater contamination. The study assesses the discontinuous perched aquifer (KDP) and the Ohangwena multi-layered aquifer 1 (KOH-1). For perched aquifers, point data was regionalized by a hydrotope approach whereas for KOH-1 aquifer, inverse distance weighting was used. The hydrotope approach categorized different parts of the hydrogeological system with similar properties into five hydrotopes. The result suggests that the discontinuous perched aquifers are more vulnerable than Ohangwena multi-layered aquifer 1. This implies that vulnerability increases with decreasing depth to water table because contaminants have short travel time to reach the aquifer when they are introduced on land surface. The nitrate concentration ranges between 2 and 288 mg/l in perched aquifers while in Ohangwena multi-layered aquifer 1, it ranges between 1 and 133 mg/l. It was observed that perched aquifers have high nitrate concentrations than Ohangwena 1 aquifer, which correlates well with the vulnerability results.  相似文献   

13.
Xi Chen  Xunhong Chen   《Journal of Hydrology》2003,280(1-4):246-264
During a flood period, stream-stage increases induce infiltration of stream water into an aquifer; subsequent declines in stream stage cause a reverse motion of the infiltrated water. This paper presents the results of the water exchange rate between a stream and aquifer, the storage volume of the infiltrated stream water in the surrounding aquifer (bank storage), and the storage zone. The storage zone is the part of aquifer where groundwater is replaced by stream water during the flood. MODFLOW was used to simulate stream–aquifer interactions and to quantify rates of stream infiltration and return flow. MODPATH was used to trace the pathlines of the infiltrated stream water and to determine the size of the storage zone. Simulations were focused on the analyses of the effects of the stream-stage fluctuation, aquifer properties, the hydraulic conductivity of streambed sediments, regional hydraulic gradients, and recharge and evapotranspiration (ET) rates on stream–aquifer interactions. Generally, for a given stream–aquifer system, larger flow rates result from larger stream-stage fluctuations; larger storage volumes and storage zones are produced by larger and longer-lasting fluctuations. For a given stream-stage hydrograph, a lower-permeable streambed, an aquitard, or an anisotropic aquifer of low vertical hydraulic conductivity can significantly reduce the rate of infiltration and limit the size of the storage zone. The bank storage solely caused by the stage fluctuation differs slightly between gaining and losing streams. Short-term rainfall recharge and ET loss in the shallow groundwater slightly influence on the flow rate, but their effects on bank storage in a larger area for a longer period can be considerable.  相似文献   

14.
Stream–aquifer interaction plays a vital role in the water cycle, and a proper study of this interaction is needed for understanding groundwater recharge, contaminants migration, and for managing surface water and groundwater resources. A model‐based investigation of a field experiment in a riparian zone of the Schwarzbach river, a tributary of the Rhine River in Germany, was conducted to understand stream–aquifer interaction under alternative gaining and losing streamflow conditions. An equivalent streambed permeability, estimated by inverting aquifer responses to flood waves, shows that streambed permeability increased during infiltration of stream water to aquifer and decreased during exfiltration. Aquifer permeability realizations generated by multiple‐point geostatistics exhibit a high degree of heterogeneity and anisotropy. A coupled surface water groundwater flow model was developed incorporating the time‐varying streambed permeability and heterogeneous aquifer permeability realizations. The model was able to reproduce varying pressure heads at two observation wells near the stream over a period of 55 days. A Monte Carlo analysis was also carried out to simulate groundwater flow, its age distribution, and the release of a hypothetical wastewater plume into the aquifer from the stream. Results of this uncertainty analysis suggest (a) stream–aquifer exchange flux during the infiltration periods was constrained by aquifer permeability; (b) during exfiltration, this flux was constrained by the reduced streambed permeability; (c) the effect of temporally variable streambed permeability and aquifer heterogeneity were found important to improve the accurate capture of the uncertainty; and (d) probabilistic infiltration paths in the aquifer reveal that such pathways and the associated prediction of the extent of the contaminant plume are highly dependent on aquifer heterogeneity.  相似文献   

15.
ABSTRACT

Groundwater is used by 3?million inhabitants in the coastal urban city of Douala, Cameroon, but comprehensive data are too sparse for it to be managed in a sustainable manner. Hence this study aimed to (1) assess the potability of the groundwater; (2) evaluate the spatial variation of groundwater composition; and (3) assess the interaction and recharge mechanisms of different water bodies. Hydrogeochemical tools and methods revealed the following results in the Wouri and Nkappa formations of the Douala basin, which is beneath Douala city: 30% of water samples from hand-dug wells in the shallow Pleistocene alluvium aquifer were saline and highly mineralized. However, water from boreholes in the deeper (49–92 m depth) Palaeocene aquifer was saline-free, less mineralized and potable. Water in the shallow aquifer (0.5–22 m depth) was of Na+-K+-Cl?-NO3? type and not potable due to point source pollution, whereas Ca+-HCO3? unpolluted water dominates in the deeper aquifer. Water in the deep and shallow aquifers indicates the results of preferential flow pass and evaporative recharge, respectively. Possible hydrogeochemical processes include point source pollution, reverse ion exchange, remote recharge areas and mixing of waters with different chemical signatures.
EDITOR D. Koutsoyiannis ASSOCIATE EDITOR M.D. Fidelibus  相似文献   

16.
This study investigates spatial patterns and temporal dynamics of aquifer–river exchange flow at a reach of the River Leith, UK. Observations of sub‐channel vertical hydraulic gradients at the field site indicate the dominance of groundwater up‐welling into the river and the absence of groundwater recharge from surface water. However, observed hydraulic heads do not provide information on potential surface water infiltration into the top 0–15 cm of the streambed as these depths are not covered by the existing experimental infrastructure. In order to evaluate whether surface water infiltration is likely to occur outside the ‘window of detection’, i.e. the shallow streambed, a numerical groundwater model is used to simulate hydrological exchanges between the aquifer and the river. Transient simulations of the successfully validated model (Nash and Sutcliff efficiency of 0·91) suggest that surface water infiltration is marginal and that the possibility of significant volumes of surface water infiltrating into non‐monitored shallow streambed sediments can be excluded for the simulation period. Furthermore, the simulation results show that with increasing head differences between river and aquifer towards the end of the simulation period, the impact of streambed topography and hydraulic conductivity on spatial patterns of exchange flow rates decreases. A set of peak flow scenarios with altered groundwater‐surface water head gradients is simulated in order to quantify the potential for surface water infiltration during characteristic winter flow conditions following the observation period. The results indicate that, particularly at the beginning of peak flow conditions, head gradients are likely to cause substantial increase in surface water infiltration into the streambed. The study highlights the potential for the improvement of process understanding of hyporheic exchange flow patterns at the stream reach scale by simulating aquifer‐river exchange fluxes with a standard numerical groundwater model and a simple but robust model structure and parameterization. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

17.
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   

18.
The glacially formed northeastern German lowlands are characterized by extensive floodplains, often interrupted by relatively steep moraine hills. The hydrological cycle of this area is governed by the tight interaction of surface water dynamics and the corresponding directly connected shallow groundwater aquifer. Runoff generation processes, as well as the extent and spatial distribution of the interaction between surface water and groundwater, are controlled by floodplain topography and by surface water dynamics. A modelling approach based on extensive experimental analyses is presented that describes the specific water balance of lowland areas, including the interactions of groundwater and surface water, as well as reflecting the important role of time‐variable shallow groundwater stages for runoff generation in floodplains. In the first part, experimental investigations of floodplain hydrological characteristics lead to a qualitative understanding of the water balance processes and to the development of a conceptual model of the water balance and groundwater dynamics of the study area. Thereby model requirements which allow for an adequate simulation of the floodplain hydrology, considering also interactions between groundwater and surface water have been characterized. Based on these analyses, the Integrated Modelling of Water Balance and Nutrient Dynamics (IWAN) approach has been developed. This consists of coupling the surface runoff generation and soil water routines of the deterministic, spatially distributed hydrological model WASIM‐ETH‐I with the three‐dimensional finite‐difference‐based numerical groundwater model MODFLOW and Processing MODFLOW. The model was applied successfully to a mesoscale subcatchment of the Havel River in northeast Germany. It was calibrated for two small catchments (1·4 and 25 km2), where the importance of the interaction processes between groundwater and surface waters and the sensitivity of several controlling parameters could be quantified. Validation results are satisfying for different years for the entire 198 km2 catchment. The model approach was further successfully tested for specific events. The experimental area is a typical example of a floodplain‐dominated landscape. It was demonstrated that the lateral flow processes and the interactions between groundwater and surface water have a major importance for the water balance and periodically superimposed on the vertical runoff generation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

19.
Abstract

Groundwater, possibly of fossil origin, is used for water supply in some arid regions where the replenishment of groundwater by precipitation is low. Numerical modelling is a helpful tool in the assessment of groundwater resources and analysis of future exploitation scenarios. To quantify the groundwater resources of the East Owienat area in the southwest of the Western Desert, Egypt, the present study assesses the groundwater resources management of the Nubian aquifer. Groundwater withdrawals have increased in this area, resulting in a disturbance of the aquifer’s natural equilibrium, and the large-scale and ongoing depletion of this critical water reserve. Negative impacts, such as a decline in water levels and increase in salinity, have been experienced. The methodology includes application of numerical groundwater modelling in steady and transient states under different measured and abstraction scenarios. The numerical simulation model developed was applied to assess the responses of the Nubian aquifer water level under different pumping scenarios during the next 30 years. Groundwater management scenarios are evaluated to find an optimal management solution to satisfy future needs. Based on analysis of three different development schemes that were formulated to predict the future response of the aquifer under long-term water stress, a gradual increase in groundwater pumping to 150% of present levels should be adopted for protection and better management of the aquifer. Similar techniques could be used to improve groundwater management in other parts of the country, as well as other similar arid regions.
Editor D. Koutsoyiannis; Associate editor X. Chen  相似文献   

20.
Climate change and sea‐level rise will have severe impacts on coastal water resources around the world. However, whereas the influence of marine inundation is well documented in the literature, the impact of groundwater inundation on coastal communities is not well known. Here, core analysis, groundwater monitoring, and ground penetrating radar are utilized to assess the groundwater regime of the surficial aquifer on Bogue Banks Barrier Island (USA). Then, geospatial techniques are used to assess the relative roles and extents of groundwater and marine inundation on the dune‐dominated barrier island under sea‐level rise scenarios of 0.2, 0.5, and 1.0 m above current conditions by 2100. Additionally, the effects of rising water tables on onsite wastewater treatment systems (OWTS) are modelled using the projected sea‐level rise scenarios. The results indicate that the surficial aquifer comprising fine to medium sands responds quickly to precipitation. Water‐level measurements reveal varying thicknesses of the vadose zone (>3 to 0 m) and several groundwater mounds with radial flow patterns. Results from projected sea‐level rise scenarios suggest that owing to aquifer properties and morphology of the island, groundwater inundation may occur at the same rate as marine inundation. Furthermore, the area inundated by groundwater may be as significant as that affected by marine inundation. The results also show that the proportion of land in the study area where OWTS may be perpetually compromised by rising water tables under worst case scenarios may range from ~43 to ~54% over an 86‐year‐period. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

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