首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 140 毫秒
1.
A numerical assessment of seawater intrusion in Gaza, Palestine, has been achieved applying a 3-D variable density groundwater flow model. A two-stage finite difference simulation algorithm was used in steady state and transient models. SEAWAT computer code was used for simulating the spatial and temporal evolution of hydraulic heads and solute concentrations of groundwater. A regular finite difference grid with a 400 m2 cell in the horizontal plane, in addition to a 12-layer model were chosen. The model has been calibrated under steady state and transient conditions. Simulation results indicate that the proposed schemes successfully simulate the intrusion mechanism. Two pumpage schemes were designed to use the calibrated model for prediction of future changes in water levels and solute concentrations in the groundwater for a planning period of 17 years. The results show that seawater intrusion would worsen in the aquifer if the current rates of groundwater pumpage continue. The alternative, to eliminate pumpage in the intruded area, to moderate pumpage rates from water supply wells far from the seashore and to increase the aquifer replenishment by encouraging the implementation of suitable solutions like artificial recharge, may limit significantly seawater intrusion and reduce the current rate of decline of the water levels.  相似文献   

2.
Optimal Groundwater Development in Coastal Aquifers Near Beihai, China   总被引：1，自引：0，他引：1  
INTRODUCTIONThe city of Beihai,located on the south coast ofGuangxi,China,relies heavily on groundwater for its potablewater supply and agricultural irrigation.With rapid increasein population (for instance,from 134 0 0 0 in 1987to 47930 0in1995 ) and in developm ent program s,the demand for freshwater has been growing. Approxim ately 170 0 0 0 m3/ d ofgroundwater has been pumped from the productive coastalaquifers in recent years.Contamination of the fresh water inthe coastal aquifers b…  相似文献   

3.
Data for the Waimea Plains, New Zealand indicate that the lower confined groundwater aquifer is hydraulically homogeneous and that shallow groundwater levels inland are affected mostly by anthropogenic processes, while those near the coast are affected more by sea level variation. Analysis of long-term data for New Zealand indicates that sea level has increased continuously, but trends are not spatially uniform. Results from non-parametric trend analysis show that rising trends for groundwater levels are predominant in the shallow aquifer both inland on the Waimea Plains and, for recent years, near the coast, while decreasing trends are evident in the underlying confined aquifer near the coast. Groundwater level change in the shallow aquifer appears to be more affected by climate change than the lower confined aquifer. Correlation analysis indicated that groundwater levels are more affected by rainfall during the rainy season than the dry season and more influenced by rainfall inland than near the coast. Groundwater level declines in the lower confined aquifer near the coast, which has its major recharge area inland in the catchment, may be substantially affected by groundwater abstraction in inland areas as well as sea level variation, but there are little evidences of seawater intrusion. Meanwhile, groundwater recharge over the catchment area has great influence on rising groundwater levels in the shallow aquifer and its recharge is estimated to be 417.8 mm/year using chloride concentrations of precipitation and groundwater.  相似文献   

4.
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   

5.
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   

6.
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   

7.
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   

8.
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   

9.
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   

10.
Integrated hydrogeochemical and geophysical methods were used to study the salinity of groundwater aquifers along the coastal area of north Kelantan. For the hydrogeochemical investigation, analysis of major ion contents of the groundwater was conducted, and other chemical parameters such as pH and total dissolved solids were also determined. For the geophysical study, both geoelectrical resistivity soundings and reflection seismic surveys were conducted to determine the characteristics of the subsurface and groundwater contained within the aquifers. The pH values range from 6.2 to 6.8, indicating that the groundwater in the study area is slightly acidic. Low content of chloride suggests that the groundwater in the first aquifer is fresh, with an average concentration of about 15.8 mg/l and high geoelectrical resistivity (>45 ohm m). On the other hand, the groundwater in the second aquifer is brackish, with chloride concentration ranging from 500 mg/l to 3,600 mg/l and very low geoelectrical resistivity (<45 ohm m) as well as high concentration of total dissolved solids (>1,000 mg/l). The groundwater in the third aquifer is fresh, with chloride concentrations generally ranging from 2 mg/l to 210 mg/l and geoelectrical resistivity of greater than 45 ohm m. Fresh and saltwater interface in the first aquifer is generally located directly in the area of the coast, but, for the second aquifer, both hydrogeochemical and geoelectrical resistivity results indicate that the fresh water and saltwater interface is located as far as 6 km from the beach. The considerable chloride ion content initially suggests that the salinity of the groundwater in the second aquifer is probably caused by the intrusion of seawater. However, continuous monitoring of the chloride content of the second aquifer indicated no significant changes with time, from which it can be inferred that the salinity of the groundwater is not affected by seasonal seawater intrusion. Schoeller diagrams illustrate that sulphate concentrations of the groundwater of the second aquifer are relatively low compared to those of the recent seawater. Therefore, this result suggests that the brackish water in the second aquifer is probably from ancient seawater that was trapped within the sediments for a long period of time, rather than due to direct seawater intrusion.  相似文献   

11.
山东烟台夹河中、下游地区海水入侵三维水质数值模拟研究   总被引：17，自引：0，他引：17  
建立了三维变密度对流弥散水质数学模型来研究山东省烟台夹河中、下游地区咸淡水界面的运移规律。以四面体为基本离散单元 ,推导出三维海水入侵变密度水质模型求解的数值方法 ,其中水流方程求解时运用了迦辽金有限单元法。溶质运移方程求解时运用了欧拉拉格朗日混合方法 ,将对流项与弥散项分离 ,用传统迦辽金有限元方法求解弥散项 ;采用自适应MOC MMOC法求解对流项 ,以消除人工过量和数值弥散。根据地下水的潮汐效应观测信息 ,确定了含水系统的海底延伸边界 ;利用该地区地下水水头及水质长观资料识别了模型的水文地质参数 ,探讨了夹河地区海水入侵的原因 :认为夹河下游地区滨海地带地下水过量开采是造成烟台地区海水入侵的主要原因。此外 ,海水随潮定期地倒灌进入夹河 ,通过局部岩性天窗侵入淡水含水层加剧了沿夹河河床两侧地下水的咸化。同时还预测了几种情况下地下水的水质演化趋势 ,为防止和减轻夹河地区海水入侵提供合理、科学的依据。  相似文献   

12.
Ongoing hydrogeological research aims to develop a correct management model for the Plio-Pleistocene multi-aquifer system of the Albegna River coastal plain (southern Tuscany, Italy); overexploitation of this aquifer for irrigation and tourism has caused seawater intrusion. The conceptual model is based on field and laboratory data collected during the 1995–2003 period. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer. Natural outflow occurs through a diffuse flow into the sea and river; artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage, closing of aquitard) and artificially (multiscreened wells). The aquifer was represented by a three-dimensional finite element model using the FEFLOW numerical code. The model was calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (February 1995–February 1996). The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it occurs above all in the Osa-Albegna sector, as well as along the river that at times feeds the aquifer. The effects of hypothetical aquifer exploitation were assessed in terms of water budget and hydraulic head evolution.  相似文献   

13.
Seawater intrusion is a major problem to freshwater resources especially in coastal areas where fresh groundwater is surrounded and could be easily influenced by seawater. This study presents the development of a conceptual and numerical model for the coastal aquifer of Karareis region (Karaburun Peninsula) in the western part of Turkey. The study also presents the interpretation and the analysis of the time series data of groundwater levels recorded by data loggers. The SEAWAT model is used in this study to solve the density-dependent flow field and seawater intrusion in the coastal aquifer that is under excessive pumping particularly during summer months. The model was calibrated using the average values of a 1-year dataset and further verified by the average values of another year. Five potential scenarios were analyzed to understand the effects of pumping and climate change on groundwater levels and the extent of seawater intrusion in the next 10 years. The result of the analysis demonstrated high levels of electrical conductivity and chloride along the coastal part of the study area. As a result of the numerical model, seawater intrusion is simulated to move about 420 m toward the land in the next 10 years under “increased pumping” scenario, while a slight change in water level and TDS concentrations was observed in “climate change” scenario. Results also revealed that a reduction in the pumping rate from Karareis wells will be necessary to protect fresh groundwater from contamination by seawater.  相似文献   

14.
The Kingston Basin in Jamaica is an important hydrologic basin in terms of both domestic and industrial sector. The Kingston hydrologic basin covers an area of approximately 258 km2 of which 111 km2 underlain by an alluvium aquifer, 34 km2 by a limestone aquifer and the remainder underlain by low permeability rocks with insignificant groundwater resources. Rapid development in recent years has led to an increased demand for water, which is increasingly being fulfilled by groundwater abstraction. A detailed knowledge of the water quality can enhance understanding of the hydrochemical system, promoting sustainable development and effective management of groundwater resources. To achieve this, a hydrochemical investigation was carried out in the Kingston Basin. Results showed that the water is Na–Ca–Cl–HCO3 and Na–Ca–HCO3 type with higher concentrations of nitrate, sodium and chloride as the leading causes of contamination in most of the wells. High concentrations of nitrate correlate with wells from areas of high population density and could be attributed to anthropogenic causes, mainly involving improper sewage treatment methodologies or leaking sewer lines. Jamaica, owing to its island nature, has the continuous problem of saline water intrusion, and this is reflected in the higher levels of chloride, sodium and conductivity in the water samples collected from the wells. The wells studied show higher concentrations of chloride ranging from around 10.2 mg/l in wells located approximately (4931.45 m) from the coast to around 234 mg/l in the well located near to the coast. The conductivity values also closely correlate with the chloride levels found in the wells.  相似文献   

15.
A seawater-intrusion study was conducted at an oil-refinery site located on the coast in the lower Esino Valley, Italy. A steady-state density-dependent flow model was used in order to understand the position of the freshwater/salt-water interface, as influenced by the hydrogeologic structure and the presence of industrial activities and a river. Collected data and model results showed that in a large part of the area, the salt-water interface is steep and can penetrate only a few meters inland. On the other hand, close to the river mouth, seawater represents the main saline source for the aquifer. The river, in connection with the sea, can enhance seawater encroachment into the coastal aquifer; a long-term survey of river level and chloride concentrations in groundwater is recommended to further improve the physical model and to obtain a better calibration. At the refinery site, two “secondary” sources of saline water were identified and were demonstrated to have had a great influence on the presence of brackish waters in the unconfined aquifer: leakage from the fire-extinguishing system (network of pipes containing seawater) and rough sea events. This confirmed that groundwater contamination by chloride can result from means other than seawater intrusion.  相似文献   

16.
Salinization in coastal aquifers is usually related to both seawater intrusion and water–rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl?, Na+, Ca2+, Mg2+ and SO 4 2– ), as well as the isotopic content and ratios (2H, 18O, 87Sr/86Sr and 13C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region.  相似文献   

17.
Elevated salinity in groundwater (over 250?mg/l chloride) in a fractured chalk aquifer in the municipality of Greve, Denmark, has been attributed to seawater intrusion from the Baltic Sea, resulting in the closure of a number of wells nearest to the coastline. However, a recent study in eastern Denmark shows that the salinity could also be from ancient connate pore waters. Historical chemistry data from bulk-water samples collected from wells have been used to determine the source. The sample data were studied with respect to their historical changes and temporal trends in chloride, carbonate, sulfate, sodium, potassium, magnesium, and calcium. Wells in the southern third of the municipality are relatively low in sodium and carbonate and high in chloride and calcium/magnesium, indicating waters undergoing saline intrusion. Wells in the northern two-thirds of the municipality are high in carbonate and sodium, but low in chloride and calcium/magnesium, indicating a freshening of the aquifer. This is confirmed by the temporal trends in chloride, where chloride levels in the northern wells remain constant, whereas in the south, chloride increases as abstraction continues. Therefore close monitoring for seawater intrusion should be conducted in the southern third of the municipality.  相似文献   

18.
The overexploitation of groundwater in coastal aquifers is often accompanied by seawater intrusion, intensified by climate change and sea level rise. Heading long-term water quality safety and thus the determination of vulnerable zones to seawater intrusion becomes a significant hydrogeological task for many coastal areas. Due to this background, the present study focussed the established methodology of the GIS-based GALDIT model to assess the aquifer vulnerability to seawater intrusion for the Algerian example of the Quaternary coastal Collo aquifer. According to the result analysis overall, more than half of the total surface of the northern study area can be classified as highly vulnerable. Besides the coastline, the areas nearby the local wadis of Guebli and Cherka occur to be the most vulnerable in the region. In view of further map removal performance as well as single-parameter sensitivity analyses from a coupled perspective respectively the GALDIT parameters, distance from the shore (D) and aquifer hydraulic conductivity (A) have been found to be of key significance regarding the model results (mean effective weightings ~?18–19%). Overall, the study results provide a good approximation basis for future management decisions of the Collo aquifer region, including various perspectives such as identification of suitable settings for prospective groundwater pumping wells.  相似文献   

19.
 The Gaza Strip coastal aquifer is under severe hydrological stress due to over-exploitation. Excessive pumping during the past decades in the Gaza region has caused a significant lowering of groundwater levels, altering in some regions the normal transport of salts into the sea and reversing the gradient of groundwater flow. The sharp increase in chloride concentrations in groundwater indicates intrusion of seawater and/or brines from the western part of the aquifer near the sea. Simulations of salt-water intrusion were carried out using a two-dimensional density-dependent flow and transport model SUTRA (Voss 1984). This model was applied to the Khan Yunis section of the Gaza Strip aquifer. Simulations were done under an assumption that pumping rates increase according to the rate of population growth, or about 3.8% a year. Model parameters were estimated using available field observations. Numerical simulations show that the rate of seawater intrusion during 1997–2006 is expected to be 20–45 m/yr. The results lead to a better understanding of aquifer salinization due to seawater intrusion and give some estimate of the rate of deterioration of groundwater. Received, September 1997 Revised, January 1998, July 1998 Accepted, August 1998  相似文献   

20.
Seawater intrusion in the Salalah plain aquifer,Oman   总被引：2，自引：0，他引：2  
Salalah is situated on a fresh water aquifer that is replenished during the annual monsoon season. The aquifer is the only source of water in Salalah city. The rainfall and mist precipitation in the Jabal AlQara recharges the plain with significant renewable fresh groundwater that has allowed agricultural and industrial development to occur. In Salalah city where groundwater has been used extensively since the early 1980s for agricultural, industrial and municipal purposes, the groundwater has been withdrawn from the aquifer more rapidly than it can be replenished by natural recharge. The heavy withdrawal of large quantities of the groundwater from the aquifer has led to the intrusion of seawater. Agricultural activities utilize over 70% of the groundwater. For the study of the saltwater intrusion, the area has been divided into four strips, A, B, C and D, on the basis of land-use in the area. Water samples were collected from 18 water wells. Chemical analysis of major ions and pollution parameters in the groundwater was carried out and compared to the previous observed values. The electrical conductivity and chloride concentrations were highest in the agricultural and residential strips and Garziz grass farm. Before 1992 the aquifer was in a steady state, but presently (2005) the groundwater quality in most of the agricultural and residential strips does not meet drinking water standards. In addition, model simulations were developed with the computer code MODFLOW and MT3DMS for solute transport to determine the movement of the freshwater/saltwater interface. The study proposes the protection of the groundwater in Salalah plain aquifer from further encroachment by artificial recharge with reclaimed water, preferably along the Salalah coastal agricultural strip. This scheme can also be applied to other regions with similar conditions.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号