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1.
Significant upward movement of mineralized water takes place in the Puebla aquifer system. Preferential groundwater flow paths related to the geological structure and the lowering of the potentiometric surface are suspected to be the prime factors for this intrusion. A combined approach of geochemical and isotope analyses was used to assess the sources of salinity and processes that are controlling the changes in groundwater chemical composition in the Puebla aquifer. Geochemical and isotope data indicate that the likely source of increased solutes is mineralized water from the dissolution of evaporites of the Cretaceous age at the base of the Upper deep aquifer, which is deeper than the intakes of the shallow wells. Dedolomitization and cation exchange seems also to occur along flow paths where sulphate concentrations tend to increase. The deep regional flow paths controls the chemical stratification of groundwater in response to decreased heads through interconnecting vertical and horizontal pathways, such as in the Fosa Atlixco. The results also suggest that high sulphate concentrations originating in the Lower deep aquifer are currently affecting shallow production wells. It is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution in the stratified aquifer.  相似文献   

2.
The Central Godavari delta is located along the Bay of Bengal Coast, Andhra Pradesh, India, and is drained by Pikaleru, Kunavaram and Vasalatippa drains. There is no groundwater pumping for agriculture as wells as for domestic purpose due to the brackish nature of the groundwater at shallow depths. The groundwater table depths vary from 0.8 to 3.4 m and in the Ravva Onshore wells, 4.5 to 13.3 m. Electrical Resistivity Tomography (ERT) surveys were carried out at several locations in the delta to delineate the aquifer geometry and to identify saline water aquifer zones. Groundwater samples collected and analyzed for major ions for assessing the saline water intrusion and to identify the salinity origin in the delta region. The results derived from ERT indicated low resistivity values in the area, which can be attributed to the existence of thick marine clays from ground surface to 12–15 m below ground level near the coast and high resistivity values are due to the presence of coarse sand with freshwater away from the coast. The resistivity values similar to saline water <0.01 Ω m is attributed to the mixing of the saline water along surface water drains. In the Ravva Onshore Terminal low resistivity values indicated up coning of saline water and mixing of saline water from Pikaleru drain. The SO 4 ?2 /Cl?and Na+2/Cl?ratios did not indicate saline water intrusion and the salinity is due to marine palaeosalinity, dilution of marine clays and dissolution of evaporites.  相似文献   

3.
The city of Querétaro, located near the political boundary of the Mexican states of Querétaro and Guanajuato, relies on groundwater as it sole water supply. Groundwater extraction in the city increased from 21?×?106 m3/yr in 1970 to 104?×?106 m3/yr in 2010, with an associated drawdown of 100 m in some parts of the aquifer. A three-dimensional numerical groundwater-flow model has been developed that represents the historical evolution of the aquifer’s potentiometric levels and is used to simulate the effect of two scenarios: (1) a 40 % reduction in the extraction rate from public water supply wells in early 2011 (thus reducing the extraction to 62?×?106 m3/yr), and (2) a further reduction in 2021 to 1?×?106 m3/yr. The modeling results project a temporary recovery of the potentiometric levels after the 40 % reduction of early 2011, but a return to 2010 levels by 2020. If scenario 2 is implemented in 2021, the aquifer will take nearly 30 years to recover to the simulated levels of 1995. The model also shows that the wells located in the city of Querétaro started to extract water from part of the aquifer beneath the State of Guanajuato in the late 1970s, thus showing that the administrative boundaries used in Mexico to study and develop water resources are inappropriate, and consideration should be given to physical boundaries instead. A regional approach to studying aquifers is needed in order to adequately understand groundwater flow dynamics.  相似文献   

4.
福州温泉区地下热水开采与水位动态响应研究   总被引：2，自引：0，他引：2  
地下热水是一种极其宝贵的资源，然而长时间的过量开采，使资源濒临枯竭，同时还会产生一系列的环境负效应。福州温泉区蕴藏着丰富的地下热水，多年开采，水位不断下降，已使部分泉消失。针对这一状况，笔者对福州温泉区地下双层热储层——第四系孔隙热储层及下伏基岩裂隙热储层中热水的赋存条件，补给与排泄条件，开采的历史与现状，热储层历年地下水位动态变化特征及漏斗展布状况进行了详细的对比分析与研究。研究结果显示第四系孔隙热储层北部抽水漏斗较深，南部补给相对充分而漏斗不明显，经过10a的变化漏斗中心最大变化幅度为7．6m；基岩裂隙热储层出现南北2个漏斗，10a间漏斗中心水位最大变化幅度为12．61m。表明随着开采的进行，地下热水水位在持续性下降，热资源在逐渐流失。指出加强地热资源开采量监控及建立比较完善的地热资源管理系统的迫切性，以实现资源的合理利用和可持续发展。  相似文献   

5.
The aquifer system in the Thon Buri sedimentary basin below the deltaic flood plain of the Chao Phraya River, central Thailand, has been exploited for public water supply for the capital Bangkok since the early 1920s. Groundwater withdrawal, currently 1.4 million m3/d, has resulted in a maximum decline in hydraulic head of up to 40 m. This has induced land subsidence of as much as 1.7 m (1940–1992) in the eastern suburbs of the metropolis. Artificial injection of purified water within an area-wide network of recharge wells could constitute a remedy to slow the water level depression within the sedimentary basin, and thus the subsidence. This requires a prior shutdown of water withdrawal. The flow paths of the injected water can be traced by changes in the 87Sr/86Sr ratio of the groundwater and injected water mixture within the three main aquifers in the basin that are used for public supply. The ratios, monitored at five monitoring stations within the cone of depression, have been constant over 3 years. Injection of the calculated cone volume of 5.2?×?109 m3 would take at least 10 years, depending on the injection pressure and the number and position of wells.  相似文献   

6.
Increased groundwater withdrawals for the growing population in the Rio Grande Valley and likely alteration of recharge to local aquifers with climate change necessitates an understanding of the groundwater connection between the Jornada del Muerto Basin and the adjoining and more heavily used aquifer in the Mesilla Basin. Separating the Jornada and Mesilla aquifers is a buried bedrock high from Tertiary intrusions. This bedrock high or divide restricts and/or retards interbasin flow from the Jornada aquifer into the Mesilla aquifer. The potentiometric surface of the southern Jornada aquifer near part of the bedrock high indicates a flow direction away from the divide because of a previously identified damming effect, but a groundwater outlet from the southern Jornada aquifer is necessary to balance inputs from the overall Jornada aquifer. Differences in geochemical constituents (major ions, δD, δ18O, δ34S, and 87Sr/86Sr) indicate a deeper connection between the two aquifers through the Tertiary intrusions where Jornada water is geochemically altered because of a geothermal influence. Jornada groundwater likely is migrating through the bedrock high in deeper pathways formed by faults of the Jornada Fault Zone, in addition to Jornada water that overtops the bedrock high as previously identified as the only connection between the two aquifers. Increased groundwater withdrawals and lowering of the potentiometric surface of the Jornada aquifer may alter this contribution ratio with less overtopping of the bedrock high and a continued deeper flowpath contribution that could potentially increase salinity values in the Mesilla Basin near the divide.  相似文献   

7.
The present study indicates that the factors controlling the hydraulic relation between surface water and groundwater at the western lake shoreline change from one locality to another. This depends upon the lithological characteristics and the major structures. In the southern sectors, sedimentation at the bottom and sides of the lake prevents the water movement to the Nubian sandstone aquifer. The potentiometric map reveals that the water level altitudes range between 170 m in the vicinity of the lakeshore line and 110 m west of the lake. The groundwater flow lines show that the main recharge to the aquifer comes from the southwest direction, as well as from the lake inland to variable distances (about 30 Km). During the present study, Darcy’s law was applied to calculate the recharge from the western shoreline of Lake Nasser to the adjacent Nubian aquifer. The maximum value of seepage was at Garf Hussein (27.71?×?106 m³/year), which may be related to high permeability and hydraulic gradient. Also, it may be related to the N–S strike faults that cut the area on both sides of the Lake, and the groundwater is expected to have free circulation through the faults of this trend. The minimum value was recorded in Adindan section (0.61?×?106 m³/year). This may be related to the limited recharge from the lake to the aquifer, due to the sedimentation that dislocates this recharge.  相似文献   

8.
The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (18O/16O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl? > HCO 3 ?  > SO 4 2?  > N-NO3 ? while cations showed a decreasing order of abundance with Na+ > Ca2+ > Mg2+ > K+. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region.  相似文献   

9.
A significant component of domestic demand for water of urban areas located in the Gangetic plains is met by heavy pumping of groundwater. The present study is focused on the Patna municipal area, inhabited by 17 million people and spanning over 134 km2, where entire urban water demand is catered from pumping by wells of various capacities and designs. The present study examines the nature of the aquifer system within the urban area, the temporal changes in the water/piezometric level and the recharge mechanism of the deeper aquifers. The aquifer system is made up of medium-to-coarse unconsolidated sand, lying under a ~40-m-thick predominantly argillaceous unit holding 8- to 13-m-thick localised sand layers and continues up to 220 m below ground. Groundwater occurs under semi-confined condition, with transmissivity of aquifers in 5,500–9,200 m2 day?1 range. Hydraulic head of the deeper aquifer remains in 9–19 m range below ground, in contrast to 1–9 m range of that of the upper aquitard zone. The estimated annual groundwater extraction from the deeper aquifer is ~212.0 million m3, which has created a decline of 3.9 m in the piezometric level of the deeper aquifer during the past 30 years. Unregulated construction of deep tube wells with mushrooming of apartment culture may further exacerbate the problem. The sand layers within the aquitard zone are experiencing an annual extraction of 14.5 million m3 and have exhibited stable water level trend for past one and half decades. This unit is recharged from monsoon rainfall, besides contribution from water supply pipe line leakage and seepage from unlined storm water drains.  相似文献   

10.
The decline of the potentiometric surface of the Ozark aquifer underneath Springfield Missouri intensified during the 1980s and has been of concern since. From 1990 to the present, the shifting of population from urban to rural areas and water management changes to use more surface water created an opportunity for groundwater levels to recover. However, in 2002 private well owners reported low levels and water problems, which prompted mapping the new cone of depression. To this purpose, well data measured from private wells and data available elsewhere were mapped using GIS mapping tools. The results show a cone of depression extending towards the recently developed areas south of Springfield while the potentiometric levels of some areas within the city had recovered. The maps show that, compared to the 1987 conditions, the present cone of depression has changed significantly in extent and shape while its maximum depth has changed only slightly.  相似文献   

11.
It is assumed that the groundwater dam under consideration is located in the lower Oshipcheon River along Yeongdeok-gun County, Gyeongsangbuk-do Province, eastern Korea. In this study, changes in groundwater level and construction effects of the groundwater dam were analyzed using a SWAT–MODFLOW model designed for integration of surface water and groundwater, and validity analysis before and after construction of the groundwater dam was evaluated. There are an average increase of 0.46 m and a maximum increase of 1.16 m, respectively, at the upstream region due to the groundwater dam. Groundwater levels at the upstream region show an average increase of 0.42 m by the groundwater dam when the water quantity of demand (10,080 m3/day) is pumped. The groundwater dam has potential as an alternative for the surface water dam to secure water resources in the study area.  相似文献   

12.
Korba aquifer is one of the most typical examples of overexploited coastal aquifer in the Mediterranean countries. In fact, from 1985, a considerable piezometric level drop, water salinization, and seawater intrusion were registered in the aquifer. In December 2008, Tunisian authorities initiated a general plan to groundwater management in order to augment groundwater resources, restore the piezometric levels, and improve water quality. The plan consists of artificial recharge of groundwater used treated wastewater through three infiltration basins. During the first 4 years (from December 2008 to December 2012), 1.41 Mm3 of treated wastewater was injected to the Korba aquifer. This study presents a hydrogeological assessment of groundwater evolution during the recharge processes. In this study, 32 piezometric and chemical surveys of 70 piezometers and observed wells are used to present hydrogeological investigation and water quality evolution of wastewater reuse through artificial recharge in Korba coastal aquifer. The piezometric evolution maps are used to specify the positive effect in groundwater level that exceeding 1.5 m in some regions. The interpretation of salinity evolution maps are used to indicate the improving of groundwater quality.  相似文献   

13.
This paper focuses on a small back-barrier sand-island on the southeast coast of Queensland. The freshwater lens in the study area exhibits anomalously high short-range salinity gradients at shallow depths, which cannot be explained using a standard seawater intrusion model. The island groundwater system consists of two aquifers: a semiconfined aquifer hosting saline to hypersaline groundwater and an overlying unconfined freshwater aquifer. The deeper aquifer is semiconfined within an incised paleovalley, and groundwater flow is restricted to an east – west direction. Tidal response observations show that the tidal signal propagates far more rapidly and is of much higher magnitude in the semiconfined aquifer than the unconfined aquifer. The tidal wave-pulse amplitude is also subject to greater attenuation in the unconfined aquifer. A conceptual hydrogeological model illustrates how upwelling of hypersaline groundwater, induced by density-dependent flow and tidal pumping, has contaminated the shallow groundwater resource. Salinisation at shallow depths is restricted to an area proximal to the paleovalley aquifer. The spatial distribution of lithological heterogeneity is an initial limiting control on the movement of the upwelling saline plume. The extent of shallow groundwater contamination is also limited by the presence of a baroclinic field, resulting from lateral variations in fluid density. Hydrochemical signatures have been used to support the model hypothesis and link the salinisation of fresh groundwater with the semiconfined aquifer as opposed to the surrounding estuarine surface water. The geometry and thickness of the freshwater lens are further controlled by the presence of the largely impermeable bedrock paleosurface between 9 and 12 m depth. The combination of hypersaline groundwater and hydraulically restrictive lithology at shallow depths has produced excessive thinning of the freshwater lens, demonstrating that the application of a model such as the Dupuit – Ghyben – Herzberg relationship would grossly overestimate the available groundwater resource.  相似文献   

14.
The Paris–Abu Bayan area located along the Darb El Arbaein road is involved in the New Valley Project in the Egyptian Western Desert (EWD) as part of ongoing efforts since the 1960s. In this dryland area, groundwater stored in the Nubian Sandstone Aquifer System (NSAS) serves as the only water resource for a number of different uses. A major concern is the significant groundwater withdrawals from 74 pumped wells since the beginning of agricultural activities in 2000. The recent rapid expansion of agricultural activity and the lack of sufficient groundwater recharge as a result of unplanned groundwater development have led to severe stress on the aquifer. Field measurements have shown a rapid decline in groundwater levels, creating a crisis situation for this sole source of water in the area. In this study, mathematical modeling of the groundwater system (single aquifer layer) of the Paris–Abu Bayan reclaimed area was implemented using MODFLOW to devise a new strategy for the sustainable use of groundwater, by applying a number of scenarios in a finite-difference program. The conceptual model and calibration were developed by generating and studying the hydrogeological records, NSA parameters, production wells, and water level measurements for 2005 and 2012. Three management scenarios were applied on the calibrated model to display the present and future stresses on this aquifer over a 30-year period (2012–2042). The results clearly show a high decline in the heads of the NSA, by about 13.8 m, due to the continuous withdrawal of water (first scenario: present conditions, 102,473 m3/day). In the second scenario, the water level is expected to decrease significantly, by about 16 m, in most of the reclamation area by increasing the pumping rates by about 25% (over-pumping) to meet the continuous need for more cultivation land in the area. To reduce the large decline in water levels, the third plan tests the aquifer after reducing the water withdrawal by approximately 25%, applying modern irrigation systems, and suggesting two new reclaimed areas in the northeastern and northwestern parts (areas 1 and 2), with 20 new wells, at 500 m3/day/well. The results in this case show that groundwater levels are slightly decreased, by about 9.5 m, while many wells (especially the new wells in the northern part) show a slight decrease in groundwater levels (0.8 m). The results comparison shows that the groundwater level in the modeled area is lowered by 0.3 m/year with an increase in the number of wells to 94 and increased cultivation area by about 18% (third scenario), versus 0.45 m/year and 0.60 m/year recorded for the first and second scenarios, respectively. Therefore, based on the results, the third scenario is recommended as a new strategy for improving groundwater resource sustainability in the region.  相似文献   

15.
To identify impacts of air pollution, sewage drainage, agricultural production, over-pumping and reservoir storage on groundwater, a field survey was conducted in the Baiyangdian catchment of the North China Plain. Major ions and water isotopes were measured. Results show that hydrological processes and hydrogeochemical evolution of shallow groundwater were greatly disturbed by human activities. Excessive pumping resulted in significant declines of groundwater levels over the study area. This also induced infiltration of surface water into groundwater. A groundwater depression cone was the conflux center of groundwater surrounded by recharge zones including alluvial fans and surface water in alluvial plain. Pumping almost was the only way to discharge groundwater. Emission of SO x and NO x contributed at least 11% of rock weathering by dissolving into infiltrating precipitation. Surface waters containing sewage replenished ambient groundwater with an average mixing ratio of 74 ± 17% due to groundwater level drawdown. As a result, groundwater had elevated concentrations of Na+ and SO4 2? with Na+ exchanged into aquifer sediments. About 29 ± 16% of Na+ was exchanged from groundwater into soil matrix. Agriculture nitrate was high only in the recharge zones. The most important result is that the transformation of the study area from a place rich in water resource into an area lack of water just took several decades with the joint action of the heavily human activities. Our study also indicates that shallow groundwater could sensitively respond to and record environmental changes.  相似文献   

16.
Properties of geothermal resources in Kebilli region, Southwestern Tunisia   总被引：2，自引：2，他引：0  
The Kebilli region is located in the Southwestern part of Tunisia, and is characterized by the presence of deep and shallow geothermal systems (continental intercalary and complex terminal). Chemical and isotopic contents are used to classify the type and determine the origin of thermal water. An evaluation of reservoir temperature and a possible geothermal fluid mixing are also carried out. Both continental intercalary-deep aquifer and complex terminal-shallow aquifer are of Na–(Ca)–Cl–(SO4) mixed water type. The use of different geothermometers and the computation of saturation indexes for different solid phases suggests that the thermal reservoir temperature of the continental intercalary is between 92 and 105 °C, while the fluid temperature from the shallow complex terminal aquifer ranges from 50 to 75 °C. Also, the isotopic data indicates the old origin of all groundwater of Southwestern Tunisia. Mixing effects characterizing the continental intercalary and the complex terminal aquifers were identified using δ2H and δ18O relationship. It appears that the upward movement of thermal water from the deep aquifer to shallow ones is probably due to the abundant fractures in the research area.  相似文献   

17.
Water-table elevation measurements and aquifer parameter estimates are rare in alpine settings because few wells exist in these environments. Alpine groundwater systems may be a primary source of recharge to regional groundwater flow systems. Handcart Gulch is an alpine watershed in Colorado, USA comprised of highly fractured Proterozoic metamorphic and igneous rocks with wells completed to various depths. Primary study objectives include determining hydrologic properties of shallow bedrock and surficial materials, developing a watershed water budget, and testing the consistency of measured hydrologic properties and water budget by constructing a simple model incorporating groundwater and surface water for water year 2005. Water enters the study area as precipitation and exits as discharge in the trunk stream or potential recharge for the deeper aquifer. Surficial infiltration rates ranged from 0.1–6.2×10?5 m/s. Discharge was estimated at 1.28×10?3 km3. Numerical modeling analysis of single-well aquifer tests predicted lower specific storage in crystalline bedrock than in ferricrete and colluvial material (6.7×10?5–2.0×10?3 l/m). Hydraulic conductivity in crystalline bedrock was significantly lower than in colluvial and alluvial material (4.3×10?9–2.0×10?4 m/s). Water budget results suggest that during normal precipitation and temperatures water is available to recharge the deeper groundwater flow system.  相似文献   

18.
The paper aims at evaluating the interaction between ground and surface water along the Langat River in Malaysia through the development of a numerical simulation. Malaysia has been experiencing a rapid economic growth since the last few decades, driven by many factors such as agriculture, industry, and the like. The demand for water in these sectors has increased so tremendously that surface water has been utilized in conjunction to groundwater. Approximately 18,184 m3 of water per day is obtained from the aquifer to supply to the steel factory. There are also workshops, petroleum stations, and houses in the area thus causing the water quantity and quality to degrade. In terms of quantity, the pumping activity has altered the interaction between the groundwater and surface water. Therefore, a numerical model was proposed and two aquifer layers were simulated, with the first layer being approximately >20 m in depth and the second layer >100 m. The recharge estimated from the tank model was input into the groundwater modeling. The effects of the surface water to the aquifer were included in the simulation by defining the river conductance, river bed, and river level. The calibrated model (error about 0.9 m) was achieved and applied to predict the flow pattern in its natural state without the pumping and with the pumping states. As a result, in the first scenario, the stream was in an effluent condition influenced by the groundwater from the northeast to the west. A hyporheic flow occurred and was observed from the contour map. The flow system was changed in the second scenario when the pumping activity was included in the simulation. The groundwater lost its original function but received leakage from the stream near the pumping sites. The findings of this study will help the local authorities and other researchers to understand the aquifer system in the area and assist in the preparation of a sustainable groundwater management.  相似文献   

19.
A heterogeneous anisotropic steady-state groundwater flow model for the multi-aquifer system of a part of southern Bengal Basin shows that human intervention has changed the natural groundwater flow system. At present, the shallow groundwater flow is restricted within the aquifer, with very short travel time of tens of years and vertical path length. The deep aquifer is fed by surface water or rainwater from distant locations with travel time of thousands of years and has no hydraulic connection with the arsenic-rich shallow aquifer. Numerical simulations indicate that the future pumping of deep groundwater is not likely to drive in arsenic from the shallow aquifer. Therefore, new wells may be installed in the deep aquifer. High pumping of shallow unpolluted aquifer consisting of brown sand will drive in groundwater containing organic matter from the post-Last Glacial Maximum aquifer-aquitard system. The organic matter drives reduction of manganese oxides at strip interfaces between palaeo-channel and palaeo-interfluve. After the completion of manganese reduction, FeOOH reduction may take place in the marginal palaeo-interfluvial aquifer and release sorbed arsenic. Arsenic then moves into the interior of palaeo-interfluvial aquifer polluting its fresh groundwater. Arsenic migration rates ranges between 0.21 and 6.3 and 1.3 × 10?2 and 0.4 m/year in horizontal and vertical directions, respectively. Therefore, palaeo-interfluvial aquifer will remain arsenic-free for hundreds to thousands of years to supply safe drinking water.  相似文献   

20.
Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO4 2? concentrations in groundwater near the shoreline, where localized SO4 2? anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO4 2? concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.  相似文献   

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