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 31 毫秒
1.
Groundwater aquifer vulnerability has been assessed by incorporating the major geological and hydrogeological factors that affect and control the groundwater contamination using GIS-based DRASTIC model along with solute transport modeling. This work demonstrates the potential of GIS to derive a vulnerability map by overlying various spatially referenced digital data layers (i.e., depth to water, net recharge, aquifer media, soil media, topography, the impact of vadose zone and hydraulic conductivity) that portrays cumulative aquifer sensitivity ratings in Kishangarh, Rajasthan. It provides a relative indication of groundwater aquifer vulnerability to contamination. The soil moisture flow and solute transport regimes of the vadose zone associated with specific hydrogeological conditions play a crucial role in pollution risk assessment of the underlying groundwater resources. An effort has been made to map the vulnerability of shallow groundwater to surface pollutants of thestudy area, using soil moisture flow and contaminant transport modeling. The classical advection-dispersion equation coupled with Richard’s equation is numerically simulated at different point locations for assessing the intrinsic vulnerability of the valley. The role of soil type, slope, and the land-use cover is considered for estimating the transient flux at the top boundary from daily precipitation and evapotranspiration data of the study area. The time required by the solute peak to travel from the surface to the groundwater table at the bottom of the soil profile is considered as an indicator of avulnerability index. Results show a high vulnerability in the southern region, whereas low vulnerability is observed in the northeast and northern parts. The results have recognized four aquifer vulnerability zones based on DRASTIC vulnerability index (DVI), which ranged from 45 to 178. It has been deduced that approximately 18, 25, 34, and 23% of the area lies in negligible, low, medium and high vulnerability zones, respectively. The study may assist in decision making related to theplanning of industrial locations and the sustainable water resources development of the selected semi-arid area.  相似文献   

2.
An aquifer vulnerability of the Benin Formation aquifer (Calabar, southern Nigeria) has been assessed using a combination of DRASTIC index and GIS technology. The assessment was necessitated by the fact that uncontrolled disposal of domestic, industrial and agricultural wastes have caused groundwater contamination. Therefore, prevention of contamination, monitoring and management of the aquifer was urgently required to increase the efficient use of the current water supplies. The DRASTIC method uses seven parameters (depth to groundwater table, net recharge, aquifer media, soil media, topography, influence of vadose zone and hydraulic conductivity), which were used to produce vulnerability maps. The drastic vulnerability index ranged between 124 and 170. The vulnerability map shows that the aquifer is highly vulnerable in southeastern parts of the area covering about 22 %. The medium vulnerability area covers about 56.8 % of Calabar extending from the southwest to northern parts. 21.2 % of the area covering the central and northern parts the area lies within the low vulnerability zone. The present industrial and activities are located in the eastern and western parts, which falls within the low-medium vulnerability areas. Documented nitrate concentration in hand-dug wells and boreholes are in agreement with vulnerability zones. Sensitivity analysis was performed to evaluate the sensitivity of each parameter between map layers such that subjectivity can be reduced to an extent and new weights computed for each DRASTIC parameter. As management options sensitive areas, especially in the southern parts of Calabar area, should be protected from future development.  相似文献   

3.
Groundwater vulnerability is a cornerstone in evaluating the risk of groundwater contamination and developing management options to preserve the quality of groundwater. Based on the professional model (DRASTIC model) and geographical information system (GIS) techniques, this paper carries out the shallow groundwater vulnerability assessment in the Zhangye Basin. The DRASTIC model uses seven environmental parameters (depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity) to characterize the hydrogeological setting and evaluate aquifer vulnerability. According to the results of the shallow groundwater vulnerability assessment, the Zhangye Basin can be divided into three zones: low groundwater vulnerability risk zone (risk index <120); middle groundwater vulnerability risk zone (risk indexes 120–140) and high risk zone (risk index >140). Under the natural conditions, the middle and high groundwater vulnerability risk zones of the Zhangye Basin are mainly located in the groundwater recharge zones and the important cities. The high, middle and low groundwater vulnerability risk zones of the Zhangye Basin cover around 17, 21 and 62% of study area, respectively.  相似文献   

4.
Wells along two regional flow paths were sampled to characterize changes in water quality and the vulnerability to contamination of the Memphis aquifer across a range of hydrologic and land-use conditions in the southeastern United States. The flow paths begin in the aquifer outcrop area and end at public supply wells in the confined parts of the aquifer at Memphis, Tennessee. Age-date tracer (e.g. SF6, 3H, 14C) data indicate that a component of young water is present in the aquifer at most locations along both flow paths, which is consistent with previous studies at Memphis that documented leakage of shallow water into the Memphis aquifer locally where the overlying confining unit is thin or absent. Mixtures of young and old water were most prevalent where long-term pumping for public supply has lowered groundwater levels and induced downward movement of young water. The occurrence of nitrate, chloride and synthetic organic compounds was correlated to the fraction of young water along the flow paths. Oxic conditions persisted for 10 km or more down dip of the confining unit, and the presence of young water in confined parts of the aquifer suggest that contaminants such as nitrate-N have the potential for transport. Long-term monitoring data for one of the flow-path wells screened in the confined part of the aquifer suggest that the vulnerability of the aquifer as indicated by the fraction of young water is increasing over time.  相似文献   

5.
Significant upward movement of mineralized water takes place in the Puebla aquifer system. Preferential groundwater flow paths related to the geological structure and the lowering of the potentiometric surface are suspected to be the prime factors for this intrusion. A combined approach of geochemical and isotope analyses was used to assess the sources of salinity and processes that are controlling the changes in groundwater chemical composition in the Puebla aquifer. Geochemical and isotope data indicate that the likely source of increased solutes is mineralized water from the dissolution of evaporites of the Cretaceous age at the base of the Upper deep aquifer, which is deeper than the intakes of the shallow wells. Dedolomitization and cation exchange seems also to occur along flow paths where sulphate concentrations tend to increase. The deep regional flow paths controls the chemical stratification of groundwater in response to decreased heads through interconnecting vertical and horizontal pathways, such as in the Fosa Atlixco. The results also suggest that high sulphate concentrations originating in the Lower deep aquifer are currently affecting shallow production wells. It is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution in the stratified aquifer.  相似文献   

6.
Jordan Valley is one of the important areas in Jordan that involves dense agricultural activities, which depend on groundwater resources. The groundwater is exploited from an unconfined shallow aquifer which is mainly composed of alluvial deposits. In the vicinity of the Kafrein and South Shunah, the shallow aquifer shows signs of contamination from a wide variety of non-point sources. In this study, a vulnerability map was created as a tool to determine areas where groundwater is most vulnerable to contamination. One of the most widely used groundwater vulnerability mapping methods is SINTACS, which is a point count system model for the assessment of groundwater pollution hazards. SINTACS model is an adaptation for Mediterranean conditions of the well-known DRASTIC model. The model takes into account several environmental factors: these include topography, hydrology, geology, hydrogeology, and pedology. Spatial knowledge of all these factors and their mutual relationships is needed in order to properly model aquifer vulnerability using this model. Geographic information system was used to express each of SINTACS parameters as a spatial thematic layer with a specific weight and score. The final SINTACS thematic layer (intrinsic vulnerability index) was produced by taking the summation of each score parameter multiplied by its specific weight. The resultant SINTACS vulnerability map of the study area indicates that the highest potential sites for contamination are along the area between Er Ramah and Kafrein area. To the north of the study area there is a small, circular area which shows fairly high potential. Elsewhere, very low to low SINTACS index values are observed, indicating areas of low vulnerability potential.  相似文献   

7.
The Paluxy aquifer in north-central Texas is composed primarily of Lower Cretaceous clastics. This aquifer provides water for both domestic and agricultural purposes in the region. The study area for this investigation incorporates the outcrop and recharge areas, as well as the confined and unconfined portions of the aquifer. The purpose of this investigation is to develop a predictive modeling approach for evaluating the susceptibility of groundwater in the Paluxy aquifer to contamination, and then compare this susceptibility evaluation to water-chemistry data collected from wells completed within the aquifer. Using such an approach allows one to investigate the potential for groundwater contamination on a regional, rather than site-specific scale. Based on data from variables such as land use/land cover, soil permeability, depth to water, aquifer hydraulic conductivity and topography, subjective numerical weightings have been assigned according to each variables' relative importance in groundwater pollution susceptibility. The weights for each variable comprise a Geographic Information System (GIS) map layer. These map layers are combined to formulate the final pollution susceptibility map. Using this method of investigation, the pollution susceptibility map classifies 32% of the study area as having low pollution susceptibility, 41% as having moderate pollution susceptibility, 25% as having high pollution susceptibility, and 2% as having very high pollution susceptibility. When comparing these modeling results with water-chemistry data from wells within the Paluxy aquifer, the four wells with the highest concentration of nitrate contamination are all found within regions of very high pollution potential. This confirms the accuracy and usefulness of the predictive modeling approach for assessing aquifer pollution susceptibility. Received: 1 June 1999 · Accepted: 30 August 1999  相似文献   

8.
The Quaternary deposits of the Ebro Basin in the surroundings of Zaragoza (Spain) form an unconfined alluvial aquifer with a high degree of permeability and low thickness of unsaturated materials. This fact causes a high degree of vulnerability to contamination, which implies consequences for land-use decisions and the risk management of existing industrial facilities. In addition, in the last decades the intense irrigation and the use of pesticides is threatening the quality of the groundwater and as a consequence the amount of usable groundwater at a low cost. Thus, the development of groundwater vulnerability maps has great importance in a regional planning process. Consequently, groundwater vulnerability maps have been developed following a method proposed by the German State Geological Surveys. In this paper the methodology developed within ArcGIS and Gocad, a two- and three-dimensional software, respectively, is presented. Although the results obtained within GIS (Geographical Information System) are acceptable it is to say that the 3D-model improves considerably the final product.  相似文献   

9.
The aquifer system in the Metropolitan Zone of the Mexican Basin is comprised by a higher, middle, and a lower aquifer, separated by less permeable elements. This study integrated a geographical database from which aquifer vulnerability values were obtained using the SINTACS method. The results show the lowest vulnerability values in the lacustrine zone of the basin, where most of the urban area is settled. The medium vulnerability indices are at the edges of the basin and are associated with tuffs, pyroclasts and alluvial deposits. The highest vulnerability values are in the ranges bordering the basin. High water quality values are toward the limits of the basin and in the recharge zones while lower quality water is in the Tlahuac and Iztapalapa zones. The results of this study enable a cause–effect relationship to be established between potential sources of contamination and groundwater quality indices only for Tlahuac and Iztapalapa, a notable finding since most of the urban area is settled over low and very low vulnerability zones.  相似文献   

10.
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   

11.
Groundwater plays a key role in arid regions as the majority of water is supplied by it. Groundwater pollution is a major issue, because it is susceptible to contamination from land use and other anthropogenic impacts. A study was carried out to build a vulnerability map for the Ordos Plateau using the DRASTIC model in a GIS environment. The map was designed to show the areas of the highest potential for groundwater pollution based on hydrogeological conditions. Seven environmental parameters, such as depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and hydraulic conductivity of the aquifer, were incorporated into the DRASTIC model and GIS was used to create a groundwater vulnerability map by overlaying the available data. The results of this study show that 24.8 % of the study area has high pollution potential, 24.2 % has moderate pollution potential, 19.7 % has low pollution potential, and the remaining 31.3 % of the area has no risk of groundwater pollution. The regional distribution of nitrate is well correlated with the DRASTIC vulnerability index. In contrast to this, although the DRASTIC model indicated that the western part had no risk, nitrate concentrations were higher in some of these areas. In particular, higher nitrate concentrations were recorded along river valleys and around lakes, such as the Mulin River valley. This is mainly caused by the intensive agricultural development and favorable conditions for recharge along river valleys.  相似文献   

12.
Three vulnerability index models were applied to assess the pollution potential of Nabeul-Hammamet shallow aquifer, Tunisia: DRASTIC, Pesticide DRASTIC and the Susceptibility Index (SI). An output map layer of each one was obtained using a geographic information system (GIS). The SI layer was overlain with DRASTIC and Pesticide DRASTIC and the percentage areas of agreement and divergence in vulnerability categories were extracted. DRASTIC results suggest the aquifer has mostly low vulnerability. Pesticide DRASTIC and SI identify three vulnerability categories (low, moderate, high) in the aquifer. Published data on current chemical groundwater composition indicate that parts of the aquifer are highly contaminated, revealing that DRASTIC underestimates the risk of pollution; Pesticide DRASTIC and SI reflect this risk better. Agreement in vulnerability categories between the two last models is found for 64 % of the aquifer area. To help manage land-use allocation and prevent Nabeul-Hammamet-aquifer contamination, DRASTIC is not recommended. Pesticide DRASTIC and SI are recommended but for slightly different applications. SI helps in the monitoring of current vulnerable areas and, thus, in contamination prevention. Pesticide DRASTIC could better intervene as a criterion in a multi-criteria analysis to select the best sites for specific on-the-ground practice or future land use.  相似文献   

13.
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   

14.
Aquifer vulnerability has been assessed in the Senirkent-Uluborlu Basin within the Egirdir Lake catchment (Turkey) using the DRASTIC method, based on a geographic information system (GIS). There is widespread agriculture in the basin, and fertilizer (nitrate) and pesticide applications have caused groundwater contamination as a result of leaching. According to hydrogeological data from the study area, surface water and groundwater flow are towards Egirdir Lake. Hence, aquifer vulnerability in the basin should be determined by water quality in Egirdir Lake. DRASTIC layers were prepared using data such as rainfall, groundwater level, aquifer type, and hydraulic conductivity. These data were obtained from hydrogeological investigations and literature. A regional-scale aquifer-vulnerability map of the basin was prepared using overlay analysis with the aid of GIS. A DRASTIC vulnerability map, verified by nitrate in groundwater data, shows that the defined areas are compatible with land-use data. It is concluded that 20.8% of the basin area is highly vulnerable and urgent pollution-preventions measures should be taken for every kind of relevant activity within the whole basin.  相似文献   

15.
Water quality data from 56 wells, aquifer characteristics, soil types and land use in the city suburb of Dakar were compared to assess the effects of land use on the Thiaroye groundwater quality. The study area encompassed an unsewered densely populated zone, agricultural land, low density villages, and undeveloped land located in the sand dunes. A method similar to GIS technologies was applied to evaluate the degree of vulnerability of the different parts of the aquifer in relation to urban development, land use and aquifer characteristics. The aquifer parameters (hydraulic conductivity, groundwater level depth, recharge, soil type) were re-evaluated qualitatively into three class rankings (high, moderate and low), depending on the likelihood for contaminants reaching the water table, then combined using the two matrix Boolean logic based approaches to identify the nine classes of vulnerability assessed in the aquifer domain. An attempt was made to explain the distribution of nitrate concentration with the assessed vulnerability. In the area assessed, in the densely populated zone running from Pikine, to Thiaroye and Yeumbeul, very high nitrate concentrations correspond with the highest vulnerability index (H1). Nitrate contamination in this area is a consequence of point-source seepage from individual septic systems improperly built in this area. In the eastern part of the aquifer, high nitrate concentrations at Deni B. Ndao, Mbawane and Golam localities coincide with a moderate vulnerability assessment. The major source of nitrate in these areas is induced by agricultural activities.  相似文献   

16.
Groundwater resources are vulnerable to contamination especially in shallow aquifers. The aquifer hydrogeological parameters and the Land Uses category combinations lead to subdivide areas according to their contamination likelihood. In arid and semi-arid regions, shallow aquifers are more exposed to groundwater contamination due to high population densities (extensive uses) and agricultural activities (nitrate contamination). Moreover, these regions are characterized by low rainfall and high evaporation. Furthermore, the spread of farmland, industrial and domestic sectors, is the principal contaminant producer which threats the groundwater quality. To protect these limited resources, the groundwater vulnerability assessment was developed in Maritime Djeffara shallow aquifer (Southeastern Tunisia). The study area is essentially occupied by agricultural areas (intensive use of chemical fertilizers) in addition to the discharge of industrial zones. The main objective of this study is to assess the aquifer vulnerability using the Susceptibility Index (SI) method as a specific vulnerability model. The results show that the study area is classified into five classes of vulnerability: very low, low, medium, high, and very high (1.54, 20, 41.54, 35.9, and 1.02%, respectively) with an uneven spatial distribution. The risk results exhibit three degrees: low, moderate, and high. The validation of the vulnerability model was performed by using salinity values and nitrate concentrations with a correlation coefficient of about 57 and 55%, respectively. This study could serve as a scientific basis for sustainable land use planning and groundwater management in the study area.  相似文献   

17.
Groundwater is inherently susceptible to contamination from anthropogenic activities and remediation is very difficult and expensive. Prevention of contamination is hence critical in effective groundwater management. In this paper an attempt has been made to assess aquifer vulnerability at the Russeifa solid waste landfill. This disposal site is placed at the most important aquifer in Jordan, which is known as Amman-Wadi Sir (B2/A7). The daily-generated leachate within the landfill is about 160 m3/day and there is no system for collecting and treating this leachate. Therefore, the leachate infiltrates to groundwater and degrades the quality of the groundwater. The area is strongly vulnerable to pollution due to the presence of intensive agricultural activity, the solid waste disposal site and industries. Increasing groundwater demand makes the protection of the aquifer from pollution crucial. Physical and hydrogeological characteristics make the aquifer susceptible to pollution. The vulnerability of groundwater to contamination in the study area was quantified using the DRASTIC model. The DRASTIC model uses the following seven parameters: depth to water, recharge, aquifer media, soil media, topography, impact on vadose zone and hydraulic conductivity. The water level data were measured in the observation wells within the disposal site. The recharge is derived based on precipitation, land use and soil characteristics. The aquifer media was obtained from a geological map of the area. The topography is obtained from the Natural Resources Authority of Jordan, 1:50,000 scale topographic map. The impact on the vadose zone is defined by the soil permeability and depth to water. The hydraulic conductivity was obtained from the field pumping tests. The calculated DRASTIC index number indicates a moderate pollution potential for the study area.  相似文献   

18.
A spatial relationship between high capacity municipal production wells (>5,000 m3/day), completed in a deep bedrock aquifer, and a buried bedrock valley was recognized in the city of Guelph, southwestern Ontario, Canada. Most production wells are completed in a discrete zone, ～60 m below ground surface, within flat-lying dolostones of the Silurian Amabel Formation. Thick overburden and limited subsurface data make characterization of the karstic aquifer difficult. This study integrates hydrogeologic data with models of karst formation, deriving a conceptual model of porosity development as it relates to valley incision. Bedrock valley incision likely occurred prior to the early Wisconsinan age (>60–75 ka). Incision created steep hydraulic gradients within the flat-lying bedrock, and provided the driving force required to integrate regional groundwater flow into karst conduits that drained at the base of the valley. Dissolution in production zone dolostones was favoured over dissolution in shallower bedrock due to abundant bedding plane partings and fossiliferous facies with high intercrystalline porosity. Burial of the valley during subsequent ice advances reduced the valley’s hydraulic influence and the efficacy of the flow system to cause dissolution. The high capacity municipal wells near the buried bedrock valley tap into the now dormant karst aquifer system.  相似文献   

19.
韩家哨村位于河北滦县李家屿灰场北部谷地,地势低于灰场,距离约800m。灰场运行期间,该区地下水出现水位升高及水质变差等问题。本文从水文地质条件角度,详细研究灰水的运移途径及其对该区地下水的影响。韩家哨村区域地下水系统分为上层滞水和孔隙一裂隙（溶隙）潜水含水层系统。潜水含水层系统水力传导系数为172．6～203．4m^2／d。地下水补给主要来源于韩家哨村以南坝后地形较高区域及灰水。灰水渗漏优势区韩家哨村南部宽约200m的带状区域。灰场堆灰形成新的地下水分水岭致使灰水在20副坝坝前垂直下渗进入风化带,沿白云岩裂隙（溶隙）补给潜水含水层,并向韩家哨村区域流动补给孔隙含水层,改变后的潜水部分通过民井向外排泄。  相似文献   

20.
Management of groundwater resources can be improved by using groundwater models to perform risk analyses and to improve development strategies, but a lack of extensive basic data often limits the implementation of sophisticated models. Dar es Salaam in Tanzania is an example of a city where increasing groundwater use in a Pleistocene aquifer is causing groundwater-related problems such as saline intrusion along the coastline, lowering of water-table levels, and contamination of pumping wells. The lack of a water-level monitoring network introduces a problem for basic data collection and model calibration and validation. As a replacement, local water-supply wells were used for measuring groundwater depth, and well-top heights were estimated from a regional digital elevation model to recalculate water depths to hydraulic heads. These were used to draw a regional piezometric map. Hydraulic parameters were estimated from short-time pumping tests in the local wells, but variation in hydraulic conductivity was attributed to uncertainty in well characteristics (information often unavailable) and not to aquifer heterogeneity. A MODFLOW model was calibrated with a homogeneous hydraulic conductivity field and a sensitivity analysis between the conductivity and aquifer recharge showed that average annual recharge will likely be in the range 80–100 mm/year.  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