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1.
A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea is vulnerable to changes in groundwater recharge, sea-level rise and human activities. Assessment of the intrinsic vulnerability of groundwater under climate scenarios was performed for the aquifer area by utilising the results of a published study on the impacts of climate change on groundwater recharge and sea-level rise on groundwater–seawater interaction. Three intrinsic vulnerability mapping methods, the aquifer vulnerability index (AVI), a modified SINTACS and GALDIT, were applied and compared. According to the results, the degree of groundwater vulnerability is greatly impacted by seasonal variations in groundwater recharge during the year, and also varies depending on the climate-change variability in the long term. The groundwater is potentially highly vulnerable to contamination from sources on the ground surface during high groundwater recharge rates after snowmelt, while a high vulnerability to seawater intrusion could exist when there is a low groundwater recharge rate in dry season. The AVI results suggest that a change in the sea level will have an insignificant impact on groundwater vulnerability compared with the results from the modified SINTACS and GALDIT. The modified SINTACS method could be used as a guideline for the groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow unconfined low-lying coastal aquifers under future climate-change conditions.  相似文献   

2.
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   

3.
Anthropogenic pressure influences the two-way interactions between shallow aquifers and coastal lagoons. Aquifer overexploitation may lead to seawater intrusion, and aquifer recharge from rainfall plus irrigation may, in turn, increase the groundwater discharge into the lagoon. We analyse the evolution, since the 1950s up to the present, of the interactions between the Campo de Cartagena Quaternary aquifer and the Mar Menor coastal lagoon (SE Spain). This is a very heterogeneous and anisotropic detrital aquifer, where aquifer–lagoon interface has a very irregular geometry. Using electrical resistivity tomography, we clearly identified the freshwater–saltwater transition zone and detected areas affected by seawater intrusion. Severity of the intrusion was spatially variable and significantly related to the density of irrigation wells in 1950s–1960s, suggesting the role of groundwater overexploitation. We distinguish two different mechanisms by which water from the sea invades the land: (a) horizontal advance of the interface due to a wide exploitation area and (b) vertical rise (upconing) caused by local intensive pumping. In general, shallow parts of the geophysical profiles show higher electrical resistivity associated with freshwater mainly coming from irrigation return flows, with water resources mostly from deep confined aquifers and imported from Tagus river, 400 km north. This indicates a likely reversal of the former seawater intrusion process.  相似文献   

4.
Water is a vital resource for the survival of not only human population, but also almost all ecosystems. Constituting 30 % of all freshwater, groundwater is the main source of available freshwater. Coastal aquifers, which serve as the major freshwater source for densely populated zones, are of vital importance and quite vulnerable to climate change. This paper examines the significant consequences of climate change, decreasing recharge rates, sea-level rise and increasing freshwater demand on the sustainable management of coastal aquifers, via a hypothetical case study. A 3-D numerical model is developed using SEAWAT, to simulate a circular island aquifer in the form of a freshwater lens surrounded by saltwater. Issues such as sloping land surface resulting in landward migration of the coastal boundary and transient response of the system due to pumping are considered through a set of predictive simulations. To assess the sensitivity of the model results to important parameters, a sensitivity analysis is performed. Results of this research, revealing the effects of mentioned pressures on the long-term sustainability of the freshwater resource, are evaluated on the basis of groundwater reserves and intrusion of the freshwater–saltwater interface in lateral and vertical directions. These outcomes are further used to determine the sustainable pumping rate of the system, considering both quantity and quality of the groundwater resources.  相似文献   

5.
Groundwater depletion and seawater intrusion constitute major challenges along coastal aquifers in arid areas. This paper assesses the role of groundwater recharge dams constructed to replenish aquifers and fight seawater intrusion with reference to AlKhod dam, Oman, sited 7 km from the coast on a gravely unconfined aquifer. Water table rise in piezometers located downstream from the dam shows regular patterns correlating with magnitude of wadi flow, whereas upstream piezometers show irregular patterns. Controlled release of water captured by the dam optimizes water percolation and enhances artificial recharge which was estimated in the wet years 1997, 2003 and 2005 as 15, 22 and 27 Mm3, respectively, using water table fluctuation method. Recharge contributed 40–60 % of the total annual abstraction. Groundwater salinity increased in the 1980s and 1990s and the saline/freshwater interface advanced inland, but has receded partially after 1997 (highest rainfall) and completely after 2005 indicated by reduction in electrical conductivity and thickening of freshwater lens. The recession is attributed to the dam’s induced recharge and reduction of pumping in 2004 following the commissioning of Barka desalination plant. Integrating artificial recharge with groundwater resources management is therefore an effective measure to replenish aquifers in arid areas and mitigate seawater intrusion along the coasts.  相似文献   

6.
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   

7.
A modeling study of seawater intrusion in Alabama Gulf Coast,USA   总被引：4，自引：0，他引：4  
A numerical model of variable-density groundwater flow and miscible salt transport is developed to investigate the extent of seawater intrusion in the Gulf coast aquifers of Alabama, USA. The SEAWAT code is used to solve the density-dependent groundwater flow and solute transport governing equations. The numerical model is calibrated against the observed hydraulic heads measured in 1996 by adjusting the zonation and values of hydraulic conductivity and recharge rate. Using the calibrated model and assuming all the hydrogeologic conditions remain the same as those in 1996, a predictive 40-year simulation run indicates that further seawater intrusion into the coastal aquifers can occur in the study area. Moreover, the predicted intrusion may be more significant in the deeper aquifer than the shallower ones. As the population continues to grow and the demand for groundwater pumping intensifies beyond the 1996 level, it can be expected that the actual extent of seawater intrusion in the future would be more severe than the model prediction. Better strategies for groundwater development and management will be necessary to protect the freshwater aquifers from contamination by seawater intrusion.
Jin LinEmail:
  相似文献   

8.
Shallow groundwater is one of the main water resources in the arid and semi-arid regions. However, it is threatened by not only the reduced rainfall and recharge capacity, but also the water table drawdown and seawater intrusion. Such factors could cause a deterioration of the water quality and consequently the loss of a valuable hydraulic resource. This study aimed to improve our knowledge on the groundwater chemical quality evolution of the Sfax shallow aquifer, one of the most vulnerable areas in Tunisia, by developing a geochemical study using statistical and numerical methods. Salinization was identified by factorial analysis, PCA, and hierarchical clustering analysis in addition to the numerical MODPATH model. These findings confirmed that the groundwater quality has deteriorated due to natural and anthropogenic processes with a different influence of mineralization factors. They also revealed the location of seawater intrusion by focusing on the most vulnerable areas which are Chaffar and Djbeniana. Methodologically, the use of MODPATH model for seawater intrusion determination might be considered as the backbone for future studies in Tunisian coastal aquifers. The numerical model supports the results obtained by the geochemical analysis. Both methods are valuable tools as they contribute to trend determinations, management, and recovery plans.  相似文献   

9.
控制海水入侵的地下水多目标模拟优化管理模型   总被引：3，自引：0，他引：3       下载免费PDF全文
为实现滨海含水层地下水开采-回灌方案优化、控制海水入侵面积和降低海水入侵损失等多重管理目标,建立了海水入侵条件下地下水多目标模拟优化管理模型SWT-NPTSGA。模拟模型采用基于变密度流的数值模拟程序SEAWAT来模拟海水入侵过程。优化模型采用小生境Pareto禁忌遗传混合算法NPTSGA来求解,该算法在保证多目标权衡解的收敛性和计算效率的前提下,能维护整个进化群体的全局多样性。将SWT-NPTSGA程序应用于一个理想滨海含水层地下水开采方案和人工回灌控制海水入侵的优化设计中,结果表明该管理模型能够同时处理最大化总抽水流量、最小化人工回灌总量和最小化海水入侵范围等3个目标函数之间的权衡关系。通过采用人工回灌海水入侵区的减灾策略,既能增加滨海地区的供水量,又可减少海水入侵的范围,由此进一步验证了模型的有效性和可靠性。  相似文献   

10.
The Wadi Watir delta, in the arid Sinai Peninsula, Egypt, contains an alluvial aquifer underlain by impermeable Precambrian basement rock. The scarcity of rainfall during the last decade, combined with high pumping rates, resulted in degradation of water quality in the main supply wells along the mountain front, which has resulted in reduced groundwater pumping. Additionally, seawater intrusion along the coast has increased salinity in some wells. A three-dimensional (3D) groundwater flow model (MODFLOW) was calibrated using groundwater-level changes and pumping rates from 1982 to 2009; the groundwater recharge rate was estimated to be 1.58?×?106 m3/year. A variable-density flow model (SEAWAT) was used to evaluate seawater intrusion for different pumping rates and well-field locations. Water chemistry and stable isotope data were used to calculate seawater mixing with groundwater along the coast. Geochemical modeling (NETPATH) determined the sources and mixing of different groundwaters from the mountainous recharge areas and within the delta aquifers; results showed that the groundwater salinity is controlled by dissolution of minerals and salts in the aquifers along flow paths and mixing of chemically different waters, including upwelling of saline groundwater and seawater intrusion. Future groundwater pumping must be closely monitored to limit these effects.  相似文献   

11.
 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   

12.
Groundwater sustainability assessment in coastal aquifers   总被引：1，自引：0，他引：1  
The present work investigates the response of shallow, coastal unconfined aquifers to anticipated overdraft conditions and climate change effect using numerical simulation. The groundwater flow model MODFLOW and variable density groundwater model SEAWAT are used for this investigation. The transmissivity and specific yield estimated from the existing database range from 10 to 810 m 2/day and 0.08% to 10.92% respectively. After successful calibration with Nash–Sutcliffe efficiency greater than 0.80, the values of horizontal hydraulic conductivity and specific yield of the unconfined aquifer were set in the range 1.85–61.90 m/day and 0.006–0.24 respectively. After validating the model, it is applied for forecasting the aquifer’s response to anticipated future scenarios of groundwater draft, recharge rate and sea level rise. The findings of the study illustrate that saltwater intrusion is intensified in the area adjoining the tidal rivers, rather than that due to the sea alone. Of all the scenarios simulated, the immense negative impact on groundwater quality emerges due to overdraft conditions and reduced recharge with the areal extent of seawater intrusion exceeding about 67% (TDS >1 kg/m 3). The study also arrives at the conclusion that, regional sea level rise of 1 mm/year has no impact on the groundwater dynamics of the aquifer.  相似文献   

13.
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   

14.
The Lei-Qiong Depression Zone, near the Leizhou Peninsula in southern China, consists of unconsolidated sediments of 500-3,000 m thickness. Groundwater occurs in a multi-aquifer system in the Leizhou Peninsula. The aquifers receive recharge from precipitation, canal and reservoir infiltration, and discharge mainly through subterranean drainage into the sea. Artificial pumping for drinking and agricultural purposes is another way of groundwater discharge. Groundwater development along the coast faces the threat of seawater intrusion. A quasi-three-dimensional finite element model, containing 457 nodes and 833 elements, has been used to simulate the spatial and temporal distribution of groundwater levels in the three-aquifer system. Verification of various aquifer parameters and boundary conditions was performed with the simulation model. Linear programming models have been developed for groundwater exploitation within the two confined aquifers. The objective function of the models is to maximize the total groundwater pumpage from the confined aquifers. Control of seawater intrusion is examined by restricting the water levels at points along the coast and the withdrawal rates in coastal management cells. A response matrix approach was used in the optimization models. The response matrix was obtained from the simulation model by forecasting drawdown produced by pumping at a unit impulse discharge. Groundwater development in the Leizhou Peninsula can be primarily optimized by allocating the pumping rates of the management cells.  相似文献   

15.
Management of freshwater lenses on small Pacific islands   总被引：3，自引：0，他引：3  
The nature of shallow aquifers and the impacts of seawater intrusion in small islands within the Pacific Ocean are reviewed. Many Pacific islands rely on shallow fresh groundwater lenses in highly permeable aquifers, underlain and surrounded by seawater, as their principal freshwater source. It is argued here that, in small islands, the nature of fresh groundwater lenses and their host aquifers coupled with frequent natural and ever-present anthropogenic threats make them some of the most vulnerable aquifer systems in the world. A simple steady-state approximation is used to provide insight into the key climatic, hydrogeological, physiographic, and management factors that influence the quantity of, and saline intrusion into freshwater lenses. Examples of the dynamic nature of freshwater lenses as they respond to these drivers are given. Natural and human-related threats to freshwater lenses are discussed. Long dry periods strongly coupled to sea surface temperatures impact on the quantity and salinity of fresh groundwater. The vulnerability of small island freshwater lenses dictates careful assessment, vigilant monitoring, appropriate development, and astute management. Strategies to aid future groundwater sustainability in small islands are presented and suggested improvements to donor and aid programs in water are also advanced.  相似文献   

16.
Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model. Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.  相似文献   

17.
Groundwater suitability for agriculture in an island with limited recharge area may easily be influenced by seawater intrusion. The aim of this study was to investigate seawater intrusion to the suitability of the groundwater for oil palm cultivation at the ex-promontory land of Carey Island in Malaysia. This is the first study that used the integrated method of geo-electrical resistivity and hydro-geochemical methods to investigate seawater intrusion to the suitability of groundwater for oil palm cultivation at two different land cover condition. The relationship between earth resistivity, total dissolved solids and earth conductivity was derived with crop suitability classification according to salinity, used to identify water types and also oil palm tolerance to salinity. Results from the contour conductivity maps show that area facing severe coastal erosion and area still intact with mangrove forest exhibits unsuitable groundwater condition for oil palm at the unconfined aquifer thickness of 15 and 31 m, respectively. Based on local sea-level rise prediction and Ghyben–Herzberg assumption (sharp interface), the condition in the study area, especially in severe erosion area, by the twenty-first century will no longer be suitable for oil palm plantation. The application of geo-electrical method combined with geochemical data, aided with the information on environmental history and oil palm physiography, has demonstrated that the integration of techniques is an effective tool in defining the status of agricultural suitability affected by salinity at the coastal aquifer area.  相似文献   

18.
The area of study lies at the northeastern part of Nile Delta. Global shoreline regression and sea-level rise have their own-bearing on the groundwater salinization due to seawater intrusion. A new adopted approach for vulnerability mapping using the hydrochemical investigations, geographic information system and a weighted multi-criteria decision support system (WMCDSS) was developed to determine the trend of groundwater contamination by seawater intrusion. Six thematic layers were digitally integrated and assigned different weights and rates. These have been created to comprise the most decisive criteria used for the delineation of groundwater degradation due to seawater intrusion. These criteria are represented by the total dissolved solids, well discharge, sodium adsorption ratio, hydrochemical parameter (Cl/HCO3), hydraulic conductivity and water types. The WMCDSS modeling was tried, where a groundwater vulnerability map with four classes ranging from very low to high vulnerability was gained. The map pinpointed the promising localities for groundwater protection, which are almost represented by the very low or low vulnerability areas (53.69 % of the total study area). The regions having high and moderate groundwater vulnerability occupy 46.31 % of total study area, which designate to a deteriorated territory of groundwater quality, and needs special treatment and cropping pattern before use. However, the moderate groundwater vulnerability class occupies an area of about 28.77 % of the total mapped area, which highlighted the need for certain management practices to prevent the saltwater intrusion from expanding further to the south. There was a good correlation of the constructed vulnerability map with the recently gathered water quality data and hydrochemical facies evolution. The plotting of water quality data on Piper trilinear diagram revealed the evolution of freshwater into the mixing and the saline zones as an impact of seawater intrusion, which validates the model results.  相似文献   

19.
Saltwater intrusion in coastal aquifers depends on the distribution of hydraulic properties, on the climate, and on human interference such as land reclamation. In order to analyze the key processes that control saltwater intrusion, a hypothetical steady-state salt distribution in a representative cross-section perpendicular to the coastline was calculated using a two-dimensional density-dependent solute transport model. The effects of changes in groundwater recharge, lowering of drainage levels, and a rising sea level on the shape and position of the freshwater/saltwater interface were modeled in separate simulations. The results show that the exchange of groundwater and surface water in the marsh areas is one of the key processes influencing saltwater intrusion. A rising sea level causes rapid progression of saltwater intrusion, whereas the drainage network compensates changes in groundwater recharge. The time scale of changes resulting from altered boundary conditions is on the order of decades and centuries, suggesting that the present-day salt distribution does not reflect a steady-state of equilibrium.  相似文献   

20.
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   

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