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1.
The study presented in this paper constitutes an initial approach to the problematic task of evaluating the effects of possible climate change on natural water recharge to aquifers. To estimate such effects, a purpose-designed mathematical model termed Estimation of Recharge in Over-exploited Aquifers (ERAS) has been used. It enables to simulate the monthly water recharge to an aquifer, provided that prior knowledge of the exploitation to which it is subjected and the variation caused by these two actions on the piezometric level of the aquifer is available. The basic data required for its application are: precipitation, temperature, groundwater extraction, stored groundwater surface and storage coefficient. The main advantage presented by this model is its independence of the mechanism by which water is displaced through the ground and within the unsaturated zone. The ERAS code was applied to four over-exploited karstic aquifers in Alto Vinalopó (Alicante, Spain) with the goal of generating a synthesized series of values for natural groundwater recharge in each of the aquifers for the 100 years of the twentieth century. Each series thus obtained after being grouped into decades was subjected to statistical processing, which revealed that in every case a logarithmically decreasing trend was present.  相似文献   

2.
Aquifer recharge can be determined by conventional methods such as hydrodynamic or hydrologic balance calculations, or numerical, hydrochemical or isotopic models. Such methods are usually developed with respect to detrital aquifers and are then used on carbonate aquifers without taking into consideration their hydrogeological particularities. Moreover, such methods are not always easy to apply, sometimes requiring data that are not available. Neither do they enable determination of the spatial distribution of the recharge. For eight regions in southern Spain, the APLIS method has been used to estimate the mean annual recharge in carbonate aquifers, expressed as a percentage of precipitation, based on the variables altitude, slope, lithology, infiltration landform, and soil type. The aquifers are representative of a broad range of climatic and geologic conditions. Maps of the above variables have been drawn for each aquifer, using a geographic information system; thus they can be superimposed to obtain the mean value and spatial distribution of the recharge. The recharge values for the eight aquifers are similar to those previously calculated by conventional methods and confirmed by discharge values, which corroborates the validity of the method.  相似文献   

3.
Greece is dependent on groundwater resources for its water supply. The main aquifers are within carbonate rocks (karstic aquifers) and coarse grained Neogene and Quaternary deposits (porous aquifers). The use of groundwater resources has become particularly intensive in coastal areas during the last decades with the intense urbanization, tourist development and irrigated land expansion. Sources of groundwater pollution are the seawater intrusion due to over-exploitation of coastal aquifers, the fertilizers from agricultural activities and the disposal of untreated wastewater in torrents or in old pumping wells. In the last decades the total abstractions from coastal aquifers exceed the natural recharge; so the aquifer systems are not used safely. Over-exploitation causes a negative water balance, triggering seawater intrusion. Seawater intrusion phenomena are recorded in coastal aquifer systems. Nitrate pollution is the second major source of groundwater degradation in many areas in Greece. The high levels of nitrate are probably the result of over-fertilization and the lack of sewage systems in some urban areas.  相似文献   

4.
Understanding the transference of water resources within hydrogeological systems, particularly in coastal aquifers, in which groundwater discharge may occur through multiple pathways (through springs, into rivers and streams, towards the sea, etc.), is crucial for sustainable groundwater use. This research aims to demonstrate the usefulness of the application of conventional recharge assessment methods coupled to isotopic techniques for accurately quantifying the hydrogeological balance and submarine groundwater discharge (SGD) from coastal carbonate aquifers. Sierra Almijara (Southern Spain), a carbonate aquifer formed of Triassic marbles, is considered as representative of Mediterranean coastal karst formations. The use of a multi-method approach has permitted the computation of a wide range of groundwater infiltration rates (17–60%) by means of direct application of hydrometeorological methods (Thornthwaite and Kessler) and spatially distributed information (modified APLIS method). A spatially weighted recharge rate of 42% results from the most coherent information on physiographic and hydrogeological characteristics of the studied system. Natural aquifer discharge and groundwater abstraction have been volumetrically quantified, based on flow and water-level data, while the relevance of SGD was estimated from the spatial analysis of salinity, 222Rn and the short-lived radium isotope 224Ra in coastal seawater. The total mean aquifer discharge (44.9–45.9 hm3 year?1) is in agreement with the average recharged groundwater (44.7 hm3 year?1), given that the system is volumetrically equilibrated during the study period. Besides the groundwater resources assessment, the methodological aspects of this research may be interesting for groundwater management and protection strategies in coastal areas, particularly karst environments.  相似文献   

5.
Climatic instability during the late Pleistocene has been reflected in the pattern of groundwater recharge. This report summarizes palaeoclimate knowledge during the late Weichselian in Europe. During this period the majority of northern Europe was covered by thick ice sheets and permafrost, preventing aquifers from recharging. In contrast, southern Europe was generally free of these palaeoclimatic features. Palaeoclimatic information has been combined with isotope data to better understand the palaeorecharge conditions and recharge timing across the European continent. The 18O and 2H relationship shows latitudinal plus climatic influences. Radiocarbon data show that while southern European aquifers have generally been recharged continuously during the last 40,000 years, northern European aquifers typically show a recharge gap during the Last Glacial Maximum. Areas that underwent continuous recharge during the entire late Pleistocene period can also be distinguished from areas where recharge to aquifers was prevented during the Last Glacial Maximum. Finally, several examples are presented of melt-water recharge or subglacial recharge. The identification of such diversity in the groundwater palaeorecharge in Europe is of great importance for modellers developing management schemes for groundwater resources.  相似文献   

6.
The objective of this study was to test the applicability of groundwater sustainability indicators defined by UNESCO, together with the International Academy of Environmental Sciences (IAES), the International Association of Hydrogeology (IAH) Group on Groundwater Indicators and the Geological Survey of Spain (IGME), to the aquifer scale. We selected four main indicators based on their relevance in the field of groundwater sustainability and because they proved to be the most reliable, based on the data collection and methodology utilized. These indicators were applied to a small—26 km2 of permeable outcrops—carbonate aquifer situated in the province of Seville (southern Spain), which has semi-arid climate conditions (500 mm/year). The integral application of all these indicators in this particular groundwater body leads us to conclude that, at present, the aquifer is undergoing intensive use. Therefore, the exploitation of its water resources is surpassing the threshold of sustainability when both the quantity and the quality of the groundwater are taken into consideration. The continued increase in exploitation generates a descending trend in the evolution of the piezometric levels, a consequence of adaptation to the new hydrodynamic situation, and also results in exhaustion of the springs that drain the aquifer in undisturbed conditions. At the same time, there is a trend of increasing salinity in the groundwater and a risk of contamination by nitrate which, according to the EU Water Framework Directive and the Groundwater Daughter Directive (EU Official Journal of the European Communities L327, 2000; EU Official Journal of the European Communities L372/19, 2006), should be controlled and reduced. In the future, application of the methodology described here may prove useful for the evaluation of similar systems, either in southern Spain or in other countries with semi-arid climates.  相似文献   

7.
A methodological procedure is proposed for determining the renewal period (RP), which expresses the ratio of total storage to recharge of carbonate aquifers, and it was applied to the overexploited moderate-size Becerrero carbonate aquifer (southern Spain). To this end, geological and subsurface data—time domain electromagnetic (TEM) soundings and borehole logs—were integrated to construct a three-dimensional (3D) geological model of the aquifer. The interconnected porosity was estimated by analyzing 73 rock samples. The resulting 3D geometrical model makes it possible to quantify the fractions of the aquifer having a confined or unconfined behaviour. Based on the total storage capacity (179?·?106–514?·?106 m3) and available aquifer recharge estimation (4.8?·?106–6.4?·?106 m3/year), an RP between 37 and 106 years is obtained. In view of the RP, an exploitation rate slightly lower than the average recharge of the system is recommended, so that the piezometric level will be stable but below the discharge head that is produced through the springs in natural conditions. The proposed methodology to obtain an aquifer RP and the management strategies designed accordingly are of broad interest, especially for carbonate aquifers, which are abundant in arid and semiarid regions.  相似文献   

8.
This paper shows the results of a comparative study involving application of the vulnerability mapping methods known as AVI, GOD, DRASTIC and EPIK to a pilot carbonate massif in southern Spain, namely the Torremolinos aquifer. The main objectives of the study were to determine which methods are most suitable for diffuse flow carbonate aquifers such as in southern Spain, and to evaluate variations in the degree of vulnerability associated to the rainfall variations that normally occur in a Mediterranean climate. According to three of the above methods, the aquifer is moderately vulnerable, but the AVI method evaluated it as highly vulnerable—this, however, is improbable. The vulnerability maps reflect the great importance of geology-related parameters (mainly those concerned with lithology) and, to a lesser degree, that of the depth of the groundwater table which is related to the rainfall. After this latter parameter, it is possible to distinguish between humid and dry climatic situations; thus, vulnerability increases in a humid year, especially according to the GOD and AVI methods. In conclusion, the GOD method seems the most adequate of the methods applied in this work for vulnerability mapping of diffuse flow carbonate aquifers in the Mediterranean domains.  相似文献   

9.
The carbonate aquifers of Lora and Mingo form part of the hydrogeological unit of Sierra de Estepa (SE Spain). By means of time series analysis and a 1D numerical groundwater model, groundwater exploitation was quantified and the mean annual recharge in both systems was estimated (2001–2004). During this period, the Lora and Mingo aquifers received an average groundwater recharge of 0.29 × 106 m3/year and 0.14 × 106 m3/year, respectively, whereas an average of 0.34 × 106 m3/year and 0.21 × 106 m3/year, respectively, was extracted. These conditions led to a conspicuous lowering of the water table in both systems. In addition, the analysis of the evolution of the main hydrogeochemical parameters of the groundwater showed that the increased pumping rates produced an increase in total dissolved solids, and chloride and sodium ions in both aquifers. In the case of the Lora aquifer, the only ion that presented decreased levels was nitrate. The results show that groundwater pumping in both aquifers should not exceed the mean annual recharge of 0.29 × 106 m3/year and 0.14 × 106 m3/year in the Lora and Mingo aquifers, respectively. Nevertheless, it would be advisable to reduce pumping rates to below these values in order to restore piezometric levels and improve groundwater quality for different uses in the future.  相似文献   

10.
Groundwater is the major source of water and a critical resource for socioeconomic development in semi-arid environments like the Johannesburg area. Environmental isotopes are employed in this study to characterise groundwater recharge and flow mechanisms in the bedrock aquifers of Johannesburg, which is known for polluted surface water. With the exception of boreholes near the Hartbeespoort Dam, groundwater in the study area was derived from meteoric water that has undergone some degree of evaporation before recharge, possibly via diffuse mechanisms. Boreholes that tap groundwater from the Transvaal Supergroup Formation show depletion in δ18O and δ2H values. This is attributed to diffuse recharge through weathering fractures at high elevation that are undergoing deep circulation or recharge from depleted rainfall from the high-latitude moisture sources. The influence of focused recharge from the Hartbeespoort Dam was observed in the boreholes north of the dam, possibly as a result of the north–south trending fault lines and the north-dipping fractures in the bedding planes of quartzites. This is also supported by a reservoir water budget method which indicated a mean annual net flux of 2,084,131 m3 from Hartbeespoort Dam recharging groundwater per annum. Using tritium in the dam and boreholes located at 750 m and 5400 m downstream, average groundwater flow velocity was estimated as 202 m/year. An open system was observed in shale, andesite and granitic-gneiss aquifers indicating soil CO2 as a dominant source of carbon (δ13C) in groundwater. A closed system was also observed in dolomitic aquifers indicating carbonate dissolution as the predominant source of carbon.  相似文献   

11.
The intensive use of groundwater for irrigation in the area of Úbeda (‘Loma de Úbeda’, Jaén, southern Spain) has transformed an area of traditionally rain-fed dry farmland into fields with some of the highest olive oil productivity in the world. Early hydrogeological research studies, initiated just after the beginning of the groundwater exploitation, revealed that the water was collected from three different overlapping aquifers occupying an area of over 1,100 km2, with the lower aquifers located at depths from 300 to over 700 m in an area of 440 km2. Multidisciplinary research, based on geological characterization, and piezometric, hydrochemical and isotopic data, has led to a conceptual model of functioning in this complex hydrogeological system. The proposed model allows for the identification of the recharge areas, and the discharge, which is at present mainly associated with the groundwater pumping. Areas of mixing of waters from the different aquifers and the main hydrogeochemical processes affecting groundwater quality are described.  相似文献   

12.
岩溶区多重介质水流模型研究进展   总被引：9，自引：7，他引：2  
数值模拟技术广泛应用于地下水资源评价工作中,为水资源合理开发利用提供科学依据。本文针对岩溶区的数值模拟技术展开研究,综述了岩溶区地下水流建模技术的主要方法和研究进展,介绍了SWMM模型、UGRFLOW模型、CAVE模型、CFP模型等多重介质模型的建模方式和运行原理。岩溶区地下水赋存介质复杂,管道、裂隙和空隙多重介质并存,水流特征多样,等效连续介质模型不能很好地刻画岩溶区复杂的地下水流特征。随着对岩溶水流系统研究的深入,二重和三重介质模型逐渐应用于岩溶区地下水流模拟工作中,取得较好成果,但仍存在如忽略中宽裂隙的导水作用、岩溶管道设置单一、模型适用性不强等问题。今后应从解析岩溶含水介质的结构特征入手,关注中宽裂隙在地下水流系统中的导水作用和水流特征,改进管道流模块以更好地刻画复杂的地下河管道,改进不同介质间水流交换量算法,提高模型精确性和适用性。   相似文献   

13.
Overexploitation of shallow aquifers on the Syrian coast, north of Latakia (Damsarkho) for irrigation and tourism has caused an intrusion of seawater. The seawater intrusion into this aquifer has been presented by a three-dimensional finite element model using the FEFLOW numerical code. This conceptual model is based on field and laboratory data collected during the period 1966–2003. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer; natural outflow occurs through a diffuse flow into the sea; and artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage) and artificially (multi-screened wells). The model was calibrated for transient conditions. The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it mainly occurs in the Damsarkho plain. The effects of hypothetical aquifer exploitation were assessed in terms of salt budget.  相似文献   

14.
东刘家金矿矿区位于海阳市郭城镇,主要发育3组NE向断裂裂隙,含水岩组主要为第四系冲洪积、坡积孔隙含水岩组,碎屑岩类孔隙裂隙含水岩组,碳酸盐岩类岩溶裂隙含水岩组及基岩风化带裂隙含水岩组。文中在查清水文地质条件的情况下,详细分析了矿区含水层的富水性,地下水补给、径流、排泄及动态特征,矿区地下水开发利用现状。在此基础上,进行了地下水均衡计算,地下水补给来源主要为大气降水入渗和农灌入渗补给,补给方式为地表直接下渗补给、断裂带导水补给以及上覆松散层下渗补给,主要排泄方式为人工开采、矿坑涌水和蒸发,总体上矿区处于地下水均衡状态。研究成果为矿区在今后的开采过程中控制地下水,合理防治与排水,维持区域地下水自然动态等提供了科学的依据。。  相似文献   

15.
The systematic sampling of the chemical composition of the groundwater from five karst springs (including an overflow spring) and one outflowing borehole have permitted to determine distinctive chemical changes in the waters that reflect the geochemical processes occurring in a carbonate aquifer system from southern Spain. The analysis of the dissolution parameters revealed that geochemical evolution of the karst waters basically depends on the availability of the minerals forming aquifer rocks and the residence time within the aquifers. In the three proposed scenarios in the aquifers, which include the preferential flow routines, the more important geochemical processes taking place during the groundwater flow from the recharge to the discharge zones are: CO2 dissolution and exsolution (outgassing), calcite net dissolution, calcite and dolomite sequential dissolution, gypsum/anhydrite and halite dissolution, de-dolomitization and calcite precipitation. A detailed analysis of the hydrochemical data set, saturation indices of the minerals and partial pressure of CO2 in the waters joined to the application of geochemical modelling methods allowed the elaboration of a hydrogeochemical model of the studied aquifers. The developed approach contributes to a better understanding of the karstification processes and the hydrogeological functioning of carbonate aquifers, the latter being a crucial aspect for the suitable management of the water resources.  相似文献   

16.
With the increased demand for groundwater resulting from fast demographic growth, accelerated urbanization, economic and agricultural activity diversification, and the increase of per capita consumption, ground water resources, in particular in coastal regions, remain relatively low, compared to demand. The groundwater quality and piezometric variations result mainly from intensive exploitation, agricultural activities and the intrusion of seawater. This phenomenon is observed mostly in semi-arid areas, such as the oriental Sahel of Tunisia, where an apparent reduction in rainfall in recent years can be seen. Groundwater becomes overexploited especially as its natural recharge by rainwater does not succeed in maintaining the hydrologic balance. The imbalance between water demand and resources induces the degradation of the water quality. In such a case, the artificial recharge of water-table aquifers by water from dams is a credible alternative to improve the hydrodynamic and physicochemical conditions of the groundwater. Like most coastal aquifers, the Teboulba water-table aquifer is threatened by overexploitation for at least three decades. This threat appears by a considerable piezometric level drop and by water salinisation, due to seawater intrusion. Given this alarming situation, since 1971, artificial recharge through wells with surface water from a dam was tested in order to restore the water levels and to improve water quality. The piezometric and chemical surveys of the Teboulba aquifer permitted one to describe the temporal and spatial piezometric and geochemical conditions of the aquifer and to show the effect of the artificial recharge. Indeed, the artificial recharge undertaken since 1971 made the geochemical and piezometric conditions of the Teboulba aquifer improve. This example is a rare, well-documented case-study of the benefits of artificial recharge in a coastal aquifer, over the long term.  相似文献   

17.
KARSTIC: a sensitivity method for carbonate aquifers in karst terrain   总被引：5，自引：2，他引：5  
. Groundwater in karstic aquifers can be dangerously sensitive to contamination. Many cities in the western USA rely on karstic carbonate aquifers for municipal water supplies. For example, Rapid City, South Dakota, pumps more than half of its drinking water from wells in the Madison Limestone. This work examined the sensitivity of karstic aquifers to surface contamination in mountainous terrain. Where karstic carbonate aquifers are exposed at their outcrop areas, they are particularly susceptible to the introduction of contamination through diffuse recharge or through point recharge at swallow holes along streams. Residential developments in mountainous regions of the western USA are encroaching on the recharge areas of karstic aquifers. Many of these residential developments are served by onsite wastewater disposal systems such as septic tanks and drain fields, with the attendant danger of introduction of pathogens from malfunctioning treatment systems above fractured limestone which offers little filtering. Where streams disappear into karstic aquifers at swallow holes, microbial contaminants such as Giardia or Cryptosporidium are a concern, as well as potential spills, leaks, or accidents along roads near these streams. The KARSTIC method developed and modified in this work puts greater emphasis on karst features than previous sensitivity procedures such as the US Environmental Protection Agency's DRASTIC method. The modified method gives increased attention to highly sensitive areas of karstic carbonate aquifers by weighting the synergistic effects of fracturing, karst development, and swallow holes of recharging streams. In a field application, hydrogeologic maps of a watershed in the Black Hills, USA, were digitized into a geographic information system. The resulting sensitivity map and report can be used by planners, managers, and the public as a screening tool for assessing groundwater sensitivity in regions which include karstic aquifers.  相似文献   

18.
In this study, a hybrid multiple criteria decision-making (HMCDM) model was proposed for prioritizing scenarios for managing groundwater use from an aquifer. Three scenarios, including the construction of subsurface dams, the use of artificial recharge and reducing groundwater use by 5% and 10% were considered to assess the most sustainable development approach. The examined MCDM models were: simple additive weighting (SAW); and MTAHP which is a hybridization of the modified TOPSIS and the analytic hierarchy process models. The criteria proposed for determining the order preference of the scenarios included the sustainable development index (IU) and a modified water exploitation index as well as economic, social and environmental indices. To assess the technical and economic impacts of the management scenarios, modeling of the aquifer was simulated for a 3-year period using these scenarios. The results of the assessment indicated that the scenario of water withdrawal reduction by 10% was the best scenario determined in MTAHP followed by a reduction in groundwater withdrawal by 5%, the use of artificial recharge and the construction of a subsurface dam, respectively. The difference between the results of MTAHP and SAW models was in their first and third ranks, in such a way artificial recharge scored the first rank in SAW model and the third rank in MTAHP model, also withdrawal reduction by 10% scored third rank in SAW model and first rank in MTAHP model. The results of these two models have demonstrated that the construction of a subsurface dam in Shahrekord aquifer is not an appropriate management option. According to the results of this study, MTAHP models can be applied for ranking feasible management scenarios in aquifers using the redefined sustainable development and modified groundwater exploitation indices introduced in this study.  相似文献   

19.
天津平原地面沉降条件下的深层地下水资源组成   总被引：7，自引：4，他引：7  
根据天津平原地面沉降监测结果，采用水量均衡法，计算出深层地下水开采量中，浅层地下水越流补给量占38.2％，粘土性压密释水量占41．3％，弹性释水量占5．6％，侧向流入量占14．9％。在控制地面沉降的条件下，深层地下水持续利用的对策是调整开采三维布局，适度开发利用浅层地下水对深层地下水的越流补给。  相似文献   

20.
Seawater intrusion is one of the most serious environmental problems in many coastal regions all over the world. Mixing a small quantity of seawater with groundwater makes it unsuitable for use and can result in abandonment of aquifers. Therefore, seawater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents development and application of a simulation‐optimization model to control seawater intrusion in coastal aquifers using different management scenarios; abstraction of brackish water, recharge of freshwater, and combination of abstraction and recharge. The model is based on the integration of a genetic algorithm optimisation technique and a coupled transient density‐dependent finite element model. The objectives of the management scenarios include determination of the optimal depth, location and abstraction/recharge rates for the wells to minimize the total costs for construction and operation as well as salt concentrations in the aquifer. The developed model is applied to analyze the control of seawater intrusion in a hypothetical confined coastal aquifer. The efficiencies of the three management scenarios are examined and compared. The results show that combination of abstraction and recharge wells is significantly better than using abstraction wells or recharge wells alone as it gives the least cost and least salt concentration in the aquifer. The results from this study would be useful in designing the system of abstraction/recharge wells to control seawater intrusion in coastal aquifers and can be applied in areas where there is a risk of seawater intrusion. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

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