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1.
The Bet She’an and Harod Valleys are regional recipients and mixing zones for groundwater draining to these valleys from a multiple aquifer system. This aquifer system includes two different carbonate aquifers, several groundwater-bearing basalt flows and deep-seated pressurized brine, the upflow of which causes salinization of fresh groundwater bodies. These aquifers drain through two groups of springs. Due to lack of information on the subsurface structure of the valley the flow-paths of groundwater feeding the springs, the initial distribution of salinities along the valley and particularly, the inflow-paths of the brines, have never been understood but were assumed to be fault-controlled. The interpretation of seismic profiles and analysis of gravity anomalies revealed the subsurface structure of the valley and namely the occurrence of a dense network of faults which branch out from those delineating the Jordan-Dead Sea Rift. The faults formed a series of uplifted and down-warped horst-and-graben structures. By joint analysis of structural, hydrological and geochemical evidence, it occurs that groundwater flow-paths leading to the springs emerging in the middle of the Bet She’an Valley are determined by structural elements such as major faults and fault-controlled structures. The penetration of the pressurized Ca-chloride Rift brines and their inflow into fresh groundwater bodies occurs prevalently along the faults outlining the western margins of the Dead Sea Rift Valley and at their intersection with outbranching NW–SE-striking faults.  相似文献   

2.
The effect of separation by aquitard layers on the distribution of saline groundwater in coastal aquifers has been demonstrated in two Israeli coastal aquifers: the Mediterranean and the Dead Sea aquifers. There is vertical separation in the Dead Sea area, even where the clayey aquitard layers are <1?m thick, exhibited by large differences in hydraulic head (2?C5?m), salinity (TDS of 50?C340?g/L) and chemical composition (e.g. Na/Cl range 0.28?C0.55). Similar features are found in the Mediterranean coastal aquifer, where the separating aquitard layers are thicker (??5?C10?m). Here, the different subaquifers host fresh and saline groundwater of different ages (tritium and 14C ages range from tens to thousands of years), as well as different chemical compositions. This high resolution of results can be obtained only by drilling without fluids; otherwise, the spatial information may lead to incorrect representation of the studied aquifer. This is especially important in saline systems where only partial flushing occurs and, thus, large variations in salinity and chemical composition are expected. The main factors controlling the salinity of groundwater in subaquifers in coastal aquifers are their connection to the sea or saline lakes, existence of brines, salinization and flushing rates, and separation by aquitard layers.  相似文献   

3.
Coastal aquifers are considered as major sources for freshwater supply worldwide, especially in arid zones. The weak rainfall as well as the intensive extraction of groundwater from coastal aquifers reduce freshwater budget and create local water aquifer depression, causing both seawater intrusion and a threat to groundwater. This phenomenon was observed in the Jerba Island which is located in southeast Tunisia. Jerba??s unconfined aquifer shows high values of groundwater salinity reaching, locally, 17?g/l and a strong contrast between some zones of the aquifer. High pumping rates and weak recharge disturb the natural equilibrium between fresh and saline water causing water salinization in most areas of the island. This study aims at establishing the salinity map of the aquifer and identifying the origin of groundwater salinization. The salinity map shows that zones characterized by low groundwater salinity are located in the center of the study area. High groundwater salinities are observed near the coast and in some parts having low topographic and piezometric levels. Groundwater geochemical characterization, and Br/Cl and Na/Cl ratios suggest that the origin of abnormal salinity is seawater intrusion. Considering groundwater salinity values and Br concentrations, a seawater intrusion map is established. It shows that many areas of the unconfined aquifer are contaminated by mixed groundwater and seawater. The statistical analysis demonstrates that high mineralization of the groundwater is due to gypsum and carbonate dissolution coupled with the mixed groundwater and seawater in many areas.  相似文献   

4.
云应盆地东北部属鄂北贫水地区,赋存于古近系—第四系含水层中的地下水是当地生产、生活用水的主要来源,亟需查明含水层的结构、含水层间地下水的转化关系等基本条件,为研究区内合理开发利用地下水提供依据。本研究通过野外水文地质调查、水文地质钻探工作,将研究区划分为单层含水层与双层含水层结构两个亚区（6个小区）。并通过地下水水位动态长期监测,获取了区内不同含水层的水位动态变化特征,分析各含水层之间的水力联系,建立了区域地下水转化的概念模式,即:研究区地下水以接受山前降雨入渗及风化裂隙水侧向径流补给为主,主要以水平径流的形式经古近系孔隙-裂隙含水层及第四系孔隙承压含水层往澴水方向运移,而后进入第四系孔隙潜水含水层。地下水和地表水在不同季节补排模式不同,雨季地表水（澴水）补给地下水,旱季地下水向地表水（澴水）排泄。古近系孔隙-裂隙水与上覆第四系孔隙水联系密切互为补给,共同构成具有统一水力联系的垂向多层结构的含水系统。独特的含水层结构决定了区内地下水接受降水补给的条件较差,地下水可开采资源量总体较贫乏,建议重点利用区域地表水资源,适度开发地下水资源,推进农业节水灌溉工程,实现水资源可持续利用。  相似文献   

5.
The Middle East and North Africa (MENA) region suffers from low precipitation and high evaporation. Coastal areas of the MENA region are usually densely populated; hence, the coastal aquifers are easily over-exploited beyond their safe yield, and seawater intrusion and aquifer salinization have been caused by the groundwater-level declines. Four studies in MENA coastal aquifers, on seawater intrusion modeling and aquifer recharge and salinization using isotopes, have been brought together in a topical collection and are discussed in this essay. A brief overview is given of managed aquifer recharge as an effective method to combat groundwater-level decline, seawater intrusion and aquifer salinization in MENA counties.  相似文献   

6.
The deterioration of groundwater quality, particularly due to salinization, because of the overexploitation of groundwater in the Lower Central Plain of Thailand remains a major concern. With increasing demand for water there is a growing need for sustainable management of the resource, which would benefit from an improved understanding of the sources of chloride contamination. Thus, a hydrochemical and isotopic study was carried out to chemically characterize groundwater and to investigate possible sources of salinization, and in particular of chloride contamination, in the multi-layered Bangkok aquifer system. Groundwater samples were taken from four topmost aquifers (Bangkok, Phra Pradaeng, Nakhon Luang, and Nonthaburi). Additionally, short-term rainwater sampling, as well as river and seawater sampling was performed and later analyzed for ionic composition and stable water isotopes. Ionic and isotopic data indicate at least three different recharge sources for groundwater. The major recharge source is rainwater. The influence of seawater is limited to the coastal region and tidally influenced areas of the two main rivers (Chao Phraya and Tha Chin). Bromide data also suggest the influence of saline water in deeper aquifers due to trapped water. Most importantly, although the influence of seawater on groundwater is recognizable, the surrounding geology contributes a significant number of dissolved ions detected in the groundwater.  相似文献   

7.
Wadi Zerka Ma’in catchment area is located to the north east of the Dead Sea. It has two types of aquifers: (a) an upper unconfined aquifer and (b) a lower confined aquifer. The two aquifers are separated by a marl aquiclude. A major strike slip fault passes perpendicularly through the two aquifers and the aquiclude layer with embedded normal faults. The aim of the study was to specify the effect of the major strike slip fault on the groundwater chemistry. The spatial variability of the hydrochemical compositions and physiochemical parameters of the groundwater were investigated. It was found that the embedded normal faults, of the strike slip fault, form conduits that allow groundwater to flow from the lower aquifer to the upper aquifer, resulting in mixed groundwater. The ratio of mixing was estimated to be 94 % groundwater from the upper aquifer and 6 % from the lower aquifer. Since groundwater in the lower aquifer is around three times more saline than the upper aquifer, water mixing into the upper water aquifer generates a salinity hazard.  相似文献   

8.
The spatial and temporal changes of the composition of the groundwater from the springs along the Wadi Qilt stream running from the Jerusalem–Ramallah Mountains towards the Jericho Plain is studied during the hydrological year 2006/2007. The residence time and the intensity of recharge play an important role in controlling the chemical composition of spring water which mainly depends on distance from the main recharge area. A very important factor is the oxidation of organics derived from sewage and garbage resulting in variable dissolved CO2 and associated HCO3 − concentration. High CO2 yields lower pH values and thus under-saturation with respect to calcite and dolomite. Low CO2 concentrations result in over-saturation. Only at the beginning and at the end of the rainy season calcite saturation is achieved. The degradation of dissolved organic matter is a major source for increasing water hardness. Besides dissolution of carbonates dissolved species such as nitrate, chloride, and sulfate are leached from soil and aquifer rocks together with only small amounts of Mg. Mg not only originates from carbonates but also from Mg–Cl waters are leached from aquifer rocks. Leaching of Mg–Cl brines is particularly high at the beginning of the winter season and lowest at its end. Two zones of recharge are distinguishable. Zone 1 represented by Ein Fara and Ein Qilt is fed directly through the infiltration of meteoric water and surface runoff from the mountains along the eastern mountain slopes with little groundwater residence time and high flow rate. The second zone is near the western border of Jericho at the foothills, which is mainly fed by the under-groundwater flow from the eastern slopes with low surface infiltration rate. This zone shows higher groundwater residence time and slower flow rate than zone 1. Groundwater residence time and the flow rate within the aquifer systems are controlled by the geological structure of the aquifer, the amount of active recharge to the aquifer, and the recharge mechanism. The results of this study may be useful in increasing the efficiency of freshwater exploitation in the region. Some precautions, however, should be taken in future plans of artificial recharge of the aquifers or surface-water harvesting in the Wadi. Because of evaporation and associated groundwater deterioration, the runoff water should be artificially infiltrated in zones of Wadis with high storage capacity of aquifers. Natural infiltration along the Wadis lead to evaporation losses and less quality of groundwater.  相似文献   

9.
Recharge to an aquifer can be estimated by first calculating the effective rainfall using a soil moisture budgeting technique, and then by applying a recharge coefficient to indicate the proportion of this effective rainfall that contributes to groundwater recharge. In the Republic of Ireland, the recharge coefficient is determined mainly by the permeability and thickness of the superficial deposits (subsoils) that overlie the country’s aquifers. The properties of these subsoils also influence groundwater vulnerability, and a methodology has been developed for determining the recharge coefficient using the groundwater vulnerability classification. The results of four case studies have been used to develop a quantified link between subsoil permeability, aquifer vulnerability, recharge and runoff. Recharge and runoff coefficients are each classed into three groupings: high, intermediate and low. A high recharge coefficient equates to a low runoff coefficient, and vice versa. A GIS-based tool enables preliminary estimates of recharge to be made using these recharge coefficient groupings. Potential recharge is calculated as the product of effective rainfall and recharge coefficient. The actual recharge is then calculated taking account of the ability of the aquifer to accept the available recharge. The methodology could be applied to other temperate climate zones where the main aquifers have a substantial covering of superficial deposits.  相似文献   

10.
In recent years, voices in Jordan became lauder to exploit the fresh to brackish deep groundwater overlain by fresh groundwater bodies. In this article the implications of such a policy on the existing fresh water bodies are worked out through studying the sources of salinity in the different aquifer systems and the potentials of salinity mobilization by artificial changes in the hydrodynamic regimes. It is concluded that extracting the groundwater of deep aquifers overlain by fresh water bodies, whether the deep groundwater is fresh to brackish, brackish or salty, is equivalent to extracting groundwater from the overlying fresh groundwater bodies because of the hydraulic connections of the deep and the shallow aquifers’ groundwaters. The consequences are even more complicated and severe because exploiting the deep groundwater containing brackish or salty water will lead to refilling by fresh groundwater leaking from the overlying aquifers. The leaking water becomes salinized as soon as it enters the pore spaces of the emptied deep aquifer matrix and by mixing with the deep aquifer brackish or saline groundwater. Therefore, the move to exploit the deep groundwater is misleading and damaging the aquifers and is unjust to future generation's rights in the natural wealth of Jordan or any other country with similar aquifers’ set-up. In addition, desalination produces brines with high salinity which cannot easily be discharged in the highlands of Jordan (with only very limited access to the open sea) because they will on the long term percolate down into fresh water aquifers.  相似文献   

11.
通过对朝阳勘查区露天采区的三个含水层和三个隔水层特征、地下水的补给、径流和排泄条件及含水层之间的水力联系等因素分析，认为三个含水层对矿坑均有充水影响，并预计了各含水层对矿坑的充水水量，为今后矿坑疏干排水提供了依据。  相似文献   

12.
The time domain electromagnetic (TDEM) geophysical method was employed to detect saline groundwater bodies within and in the close margins of the Arava Rift Valley. The Arava Valley aquifers are known to occupy fresh to saline groundwater. The lateral subsurface inflow to the Arava from west and east is characterized by fresh to brackish waters. The results of the present study indicate that salination of groundwater is controlled by both present day and ancient base levels, namely by the Dead Sea in the north and by the Gulf of Elat in the south. The configuration obtained by the TDEM survey exhibits interfaces and palaeo-interfaces between fresh to brackish waters and underlying seawater or diluted seawater intruded inland from both base levels as well as brines intruded from the northern base level. The central Arava structural and hydrological divide seems to escape seawater or brine encroachment at least to the considerable depth of the TDEM measurements.  相似文献   

13.
The Ca–Mg relationship in groundwaters strongly points to the overall dolomitization and local albitization. The Mg/Ca ratios reveal two trends by which saline waters develop: increase of Mg/Ca ratio by evaporation and decreasing Mg/Ca ratios due to dolomitization and albitization. Br/Cl vs. Na/Cl ratios demonstrate that albitization does not play a major role which leaves dolomitization to be the main source for decreasing Mg/Ca ratios in saline waters. In the eastern and southern Region of Lake Kinneret, salinization occurs by mixing with a Ca/Mg molar ratio <1 brine (Ha’On type). Along the western shoreline of the Lake, a Ca/Mg > 1 dominates, which developed by the albitization of plagioclase in abundant mafic volcanics and the dolomitization of limestones. The most saline groundwater of the Tabgha-, Fuliya-, and Tiberias clusters could be regional derivatives of at least two mother brines: in diluted form one is represented by Ha’On water, the other is a Na-rich brine of the Zemah type. Additionally, a deep-seated Ca-dominant brine may ascend along the fractures on the western side of Lake Kinneret, which is absent on the eastern side. Groundwaters of the Lower Jordan Valley are chemically different on both sides of the Jordan River, indicating that the exchange of water is insignificant. All saline waters from the Dead Sea and its surroundings represent a complex mixture of brines, and precipitation and local dissolution of halite and gypsum. Many wells of the Arava/Araba Valley pump groundwater from the Upper Cretaceous limestone aquifer, the origin of the water is actually from the Lower Cretaceous Kurnub Group sandstones. Groundwater drawn from the Quaternary alluvial fill either originates from Kurnub Group sandstones (Eilat 108, Yaalon 117) or from altered limestones of the Judea Group. The origin of these waters is from floods flowing through wadis incised into calcareous formations of the Judea Group. On the other hand, as a result of step-faulting, hydraulic contact is locally established between the Kurnub- and the Judea Groups aquifers facilitating the inter-aquifer flow of the confined Kurnub paleowater into the karstic formations of the Judea Group. Two periods of Neogene brine formation are considered: the post-Messinan inland lagoon resulting in drying up of the Sdom Sea and the evaporation of the Pleistocene Samra Lake, which went further through the stage of Lake Lisan to the present Dead Sea. For the first period, major element hydrochemistry suggests that the saline waters and brines in the Jordan-Dead Sea–Arava Valley transform evolved from the gradual evaporation of an accumulating mixture of sea-, ground-, and surface water. Due to the precipitation of carbonates, gypsum, and halite, such an evaporating primary water body was strongly enriched in Mg, Br, and B and shows high molar ratios of Br/Cl, B/Cl, and Mg/Ca but low Na/Cl ratios. The development of the Br/Cl ratio is chemically modelled, showing that indeed brine development is explicable that way. Along with the evaporation brine, evaporites formed which are leached by infiltrating fresh water yielding secondary brines with Na/Cl ratios of 1. When primary brines infiltrated the sub-surface, they were subjected to Mg–Ca exchange in limestones (dolomitization) and to chloritization and albitization in basic igneous rocks turning them into Ca-Cl brines. These tertiary brines are omnipresent in the Rift. The brines of the late Lisan and Dead Sea were generated by evaporating drainage waters, which leached halite, gypsum, and carbonates from the soil and from the sub-surface. All these brines are still being flushed out by meteoric water, resulting in saline groundwaters. This flushing is regionally enhanced by intensive groundwater exploitation. In variable proportions, the Neogene and late Lisan Lake and Recent Dead Sea brines have to be considered as the most serious sources of salinization of groundwaters in the Rift. Deep-seated pre-Sdom brines cannot strictly be excluded, but if active they play a negligible role only. An erratum to this article can be found at  相似文献   

14.
Control of sea-water intrusion by salt-water pumping: Coast of Oman   总被引：2，自引：1，他引：1  
A shallow alluvial coastal aquifer in the Batinah area of Oman, with sea-water intrusion that extends several kilometres inland, has been studied experimentally, analytically and numerically. The water table is proved to have a trough caused by intensive pumping from a fresh groundwater zone and evaporation from the saline phreatic surface. Resistivity traverses perpendicular to the shoreline indicated no fresh groundwater recharge into the sea. Using an analytical Dupuit-Forchheimer model, developed for the plain part of the catchment, explicit expressions for the water table, sharp interface location and stored volume of fresh water are obtained. It is shown that by the pumping of salt water from the intruded part of the aquifer, this intrusion can be mitigated. Different catchment sizes, intensities of fresh groundwater pumping, evaporation rates, water densities, sea level, incident fresh water level in the mountains and hydraulic conductivity are considered. SUTRA code is applied to a hypothetical case of a leaky aquifer with line sinks modeling fresh water withdrawal and evaporation. The numerical code also shows that pumping of saline water can pull the dispersion zone back to the shoreline.  相似文献   

15.
The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, δ2H and δ18O variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region.  相似文献   

16.
 The coastal aquifer of Oropesa is affected by salinization processes undoubtedly associated with intense groundwater exploitation for agriculture supply. The aquifer corresponds geologically to a tectonic depression with Plioquaternary fill. Hydrogeologically, this aquifer is detrital, with intergranular porosity, which receives substantial recharge from adjacent Mesozoic aquifers. Contact with the sea, in addition to the presence of cultivated soil requiring extreme exploitation of groundwater, frequently give rise to processes of seawater intrusion. The present research is an attempt to understand the saltwater intrusion in this aquifer, using hydrochemical analyses of the behavior of certain minor ions that could help in the characterization process. In the case of the Oropesa sector, groundwater salinization does not appear to be attributable solely to the intrusion of seawater, but there are also anomalies related largely to the geology of the sector and its surroundings, the type of recharge, the hydrodynamic conditions in the specific area, etc. Received: 23 January 1995 · Accepted: 12 September 1995  相似文献   

17.
In the Djerid-Nefzaoua region, southern Tunisia, about 80% of agricultural and domestic water supply is provided by the complex terminal (CT) aquifer. However, 20% of this demand is provided by other hydraulically connected aquifers, namely the continental intercalaire (CI) and the Plio-Quaternary (PQ). Overexploitation of the CT aquifer for agricultural practices has contributed to the loss of the artesian condition and the decline of groundwater level which largely increased the downward leakage from the shallow PQ aquifer. Excess irrigation water concentrates at different rates in the irrigation channels and in the PQ aquifer itself. Then, it returns to the CT aquifer and mixes with water from the regional flow system, which contributes to the salinization of the CT groundwater. A geochemical and isotopic study had been undertaken over a 2-years period in order to investigate the origin of waters pumped from the CT aquifer with an emphasis on its hydraulic relationships with the underlying and the overlying CI and PQ aquifers. Geochemistry indicates that groundwater samples collected from different wells show an evolution of the water types from Na-Cl to Ca-SO4-Cl. Dissolution of halite, gypsum and anhydrite-bearing rocks is the main mechanism that leads to the salinization of the groundwater. Isotopic data indicate the old origin of all groundwater in the aquifer system. Mixing and evaporation effects characterizing the CT and the PQ aquifers were identified using δ2H and δ18O relationship and confirmed by the conjunction of δ2H with chloride concentration.  相似文献   

18.
同位素技术是研究区域地下水循环规律的主要手段之一。本文对平原区地下水进行了取样分析,运用同位素技术并结合水文地质条件,研究了北京市平原区地下水循环演化规律。运用^3H和^14C的测年技术确定了地下水年龄;利用D和18^O关系曲线探讨了地下水的起源;按照是否积极参加了现代水循环的原则将第四系地下水划分为浅层水和深层水;对浅层水和深层水的更新状况进行了研究。研究表明,浅层水广泛分布于北京平原区,径流条件好,更新快;深层水主要分布于永定河、潮白河冲洪积扇下部及冲洪积平原的深部地区,补给条件相对差,与现代大气降水联系弱,径流条件差,更新慢。  相似文献   

19.
南皮县淡水资源严重短缺,制约工农业与经济社会的发展.春季开采浅层地下水包括微咸水和半咸水抗旱灌溉,腾出地下含水层空间;汛期增加降雨入渗,减少径流流失,防渍防涝,把时空分布不均的天然降雨转化为地下水资源;秋冬利用河道沟渠引蓄河水补源,淡化地下水质,增加地下水可采量.地上水地下水联合运用,保持水资源采补平衡.实现旱涝碱咸综合治理、水资源可持续利用与经济社会可持续发展.  相似文献   

20.
The Bet She’an and Harod Valleys in Israel are regional recipients and mixing zones for groundwater draining from a multiple aquifer system, which includes carbonate and basalt aquifers and deep-seated pressurized brines. The aquifers drain through two types of outlets, distinct and mixed. The latter type is mainly conditioned by the occurrence of fault-blocks related to the Jordan Rift system, which act as connecting media between the aquifers and facilitate interaquifer flow. Conjoint application of rare earth element distribution and water isotopes enables detection of the local areas replenishment by rainfall infiltration and, in connection with the position of wells or springs, the identification of groundwater flow paths. Once stationary equilibria are established changes of REY composition between REY in groundwater and their surface adsorption, are negligible. In areas with little soil coverage and vegetation even recharge over young Tertiary and diagenetic Cretaceous limestones is distinguishable by their REY distribution patterns. Groundwater recharged over Tertiary limestones show higher REY abundance and more significant Ce anomalies than those derived from the Cretaceous limestones. Weathering of alkali olivine basalts leads to REY patterns in groundwater depleted in the middle REE. The improved knowledge of the hydrological systems is thought to be useful for regional hydrogeological modeling and for designing rational water management schemes.  相似文献   

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