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1.
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   

2.
Integrated geoelectrical resistivity, hydrochemical and soil property analysis methods were used to study the groundwater characteristics of sandy soils within a shallow aquifer in the agriculture area, Machang. A pilot test investigation was done prior to the main investigation. The area was divided into two sites. Test-Site 1 is non-fertilized; Test-Site 2 is the former regularly fertilized site. From the surface to depths of 75 cm, a lower average resistivity was obtained in Test-Site 2 (around 0.37 less than in Test-Site 1). The presence of nitrate and chloride contents in pore water reduced the resistivity values despite the low moisture content. The pH values for the whole area range from 4.11 to 6.88, indicating that the groundwater is moderately to slightly acidic. In the southern region, concentration of nitrate is considered to be high (>20 mg/l), while it is nearly zero in the northern region. In the south, the soil properties are similar. However, the geoelectrical model shows lower resistivity values (around 18 Ω m) at the sites with relatively high nitrate concentration in the groundwater (>20 mg/l). Conversely, the sites with low nitrate concentration reveal the resistivity values to be higher (>35 Ω m). Basement and groundwater potential maps are generated from the interpolation of an interpreted resistivity model. The areas that possibly have nitrate-contaminated groundwater have been mapped along with groundwater flow patterns. The northern part of the area has an east to west groundwater flow pattern, making it impossible for contaminated water from the southern region to enter, despite the northern area having a lower elevation.  相似文献   

3.
Groundwater in Sfax City (Tunisia) has been known since the beginning of the century for its deterioration in quality, as a result of wastewater recharge into the aquifer. An average value of 12 × 106 m3 of untreated wastewater reaches the groundwater aquifer each year. This would result not only in a chemical and biological contamination of the groundwater, but also in an increase of the aquifer piezometric level. Quantitative impacts were evaluated by examining the groundwater piezometric level at 57 surface wells and piezometers. The survey showed that, during the last two decades, the groundwater level was ever increasing in the urban area with values reaching 7 m in part; and decreasing in Sidi Abid (agricultural area) with values exceeding −3 m. Groundwater samples for chemical and microbial analysis were collected from 41 wells spread throughout the study area. Results showed significantly elevated levels of sodium, chlorides, nitrates and coliform bacteria all over the urban area. High levels (NO3: 56–254 mg/l; Na >1,500 mg/l; Coliforms >30/100 ml) can be related to more densely populated areas with a higher density of pit latrine and recharge wells. Alternatively results showed a very variable chemical composition of groundwater, e.g. electrical conductivity ranges from 4,040 to19,620 μs/cm and the dry residual varies between 1.4 and 14 g/l with concentrations increasing downstream. Furthermore a softening of groundwater in Set Ezzit (highly populated sector) was observed.  相似文献   

4.
现有的井群疏干、地下巷道集中排水、地表地下联合疏干方法都已比较成熟有效,但当矿区的地下水系统由非均质各向异性、低渗透性含水介质组成时,井群疏干受到低渗透性含水层和高倾角裂隙的制约,无法达到良好的疏干效果。地下巷道集中排水方法一次性工程投入很大,含水层富水性极度不均时易造成许多不必要的浪费;地表地下联合疏干方法的地面部分对矿坑边坡安全和采场作业都会造成一定的影响。结合马钢集团南山矿业公司高村露天铁矿的地下水疏干技术研究专项,调查分析了矿区地质和水文地质条件,含水介质特点及含水层富水特征,借助GMS软件建立了高村矿区地下水水流模型,提出了辐射井疏干技术的设想,并依据前人提出的＂渗流-管流耦合模型＂模拟辐射井,完成了此类矿山的地下水辐射井疏干方法的初步研究。  相似文献   

5.
该文通过对会泽铅锌矿区水文地质条件的研究，采用等效裂隙介质模型概化矿床充水含水层，并利用矿坑涌水资料及矿区地下水水位观测资料，应用里兹有限元法计算和预测了麒麟厂矿坑深部1511、1451中段的涌水量。  相似文献   

6.
Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow (<25 m) and deep aquifer (>25 m) in the Varanasi area. Hydrochemical facies, Mg-HCO3 dominated in the largest part of shallow groundwater followed by Na-HCO3 and Ca-HCO3 whereas Ca-HCO3 is dominated in deep groundwater followed by Mg-HCO3 and Na-HCO3. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump) within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals.  相似文献   

7.
The hydrodynamic groundwater data and stable isotopes of water have been used jointly for better understanding of upward leakage and mixing processes in the Djerid aquifer system (southwestern Tunisia). The aquifer system is composed of the upper unconfined Plio-Quaternary (PQ) aquifer, the intermediate (semi-)confined Complex Terminal (CT) aquifer and the deeper confined Continental Intercalaire (CI) aquifer. A total of 41 groundwater samples from the CT and PQ aquifers were collected during June 2001. The stable isotope composition of waters establishes that the CT deep groundwater (depleted as compared to present Nefta local rainfall) is ancient water recharged during late Quaternary time. The relatively recent water in the shallow PQ aquifer is composed of mixed water resulting from upward leakage and sporadic meteoric recharge. In order to characterize the meteoric input signal for PQ in the study area, rainfall water samples were collected during 4 years (2000–2003) at the Nefta meteorological station. Weighted mean values of isotopic contents with respect to rainfall amounts have been computed. Despite the short collection period in the study area, results agree with those found in Beni Abbes (southwestern Algerian Sahara) by Fontes on 9 years of rainfall surveillance. Stable isotopic relationships provide clear evidence of shallow PQ aquifer replenishment by deep CT groundwater. The 18O/upward leakage rate allowed the identification of distinctive PQ waters related to CT aquifer configuration (confined in the western part of the study area, semi-permeable in the eastern part). These trends were confirmed by the relation 18O/TDS. The isotope balance model indicated a contribution of up to 75% of the deep CT groundwater to the upper PQ aquifer in the western study area, between Nefta and Hazoua.  相似文献   

8.
Recently, Ras Sudr (the delta of Wadi Sudr) area received a great amount of attention due to different development expansion activities directed towards this area. Although Quaternary aquifer is the most prospective aquifer in Ras Sudr area, it has not yet completely evaluated. The present work deals with the simulation of the Quaternary groundwater system using a three-dimensional groundwater flow model. MODFLOW code was applied for designing the model of the Ras Sudr area. This is to recognize the groundwater potential as well as exploitation plan of the most prospective aquifer in the area. The objectives were to determine the hydraulic parameters of the Quaternary aquifer, to estimate the recharge amount to the aquifer, and to determine the hydrochemistry of groundwater in the aquifer. During this work, available data has been collected and some field investigation has been carried out. Groundwater flow model has been simulated using pilot points’ method. SEAWAT has been also applied to simulate the variable-density flow and sea water intrusion from the west. It can be concluded that: (1) the direction of groundwater flow is from the east to the west, (2) the aquifer system attains a small range of log-transformed hydraulic conductivity. It ranges between 3.05 and 3.35 m/day, (3) groundwater would be exploited by about 6.4 × 106 m3/year, (4) the estimated recharge accounts for 3 × 106 m3/year, (5) an estimated subsurface flow from the east accounts for 2.7 × 106 m3/year, (6) the increase of total dissolved solids (TDS) most likely due to dilution of salts along the movement way of groundwater from recharge area to discharge area in addition to a contribution of sea water intrusion from the west. Moreover, it is worth to note that a part of TDS increase might be through up coning from underlying more saline Miocene sediments. It is recommended that: (1) any plan for increasing groundwater abstraction is unaffordable, (2) reliable estimates of groundwater abstraction should be done and (3) automatic well control system should be made.  相似文献   

9.
A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10?5 m/d to 7.14 × 10?4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast–southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization.  相似文献   

10.
鲁西南地区高氟水分布规律与成因分析   总被引：1，自引：0，他引：1  
地方性氟中毒是我国北方地区最为典型的地方病之一,查明高氟地下水的空间分布及其成因是除氟改水、防治氟害的前提。通过对鲁西南地区不同层位地下水水质分析结果及水文地质、地质条件等多个环境影响因素的综合分析,查明了鲁西南地区高氟水的空间分布规律,并分析了影响浅层和深层高氟水形成的环境因素。浅层高氟水呈片状分布于洼地、缓平坡地等地势较低的区域,占鲁西南地区总面积的47%,大部分地区高氟水氟离子含量为1.2～2.0 mg/L,局部大于4.0 mg/L,其形成受气候、地质环境、地形地貌特征及水化学环境等多个因素的影响,成因类型为溶滤-蒸发浓缩型。深层高氟水具有水平分带性,占鲁西南地区总面积的65%,大部分高氟水氟离子含量为2.0～4.0 mg/L,氟离子含量分布与晚更新世沉积相带呈现很好的相似性,推测其为地质历史时期形成的古地下水。  相似文献   

11.
矿井水深井回灌是矿井水“转移存储”处理的主要形式,根据鄂尔多斯盆地煤矿区地质和矿井水特征,从回灌目的层地下水与矿井水的匹配性、上下岩层的隔水性、回灌层的渗透性以及封闭性角度提出了矿井水回灌目的层选取依据。并以地下水达西定律和Dupuit理论为基础,建立极坐标系完整注水井稳定流数学模型,得出在稳定注水条件下,回灌量与注水层渗透系数、厚度、回灌压力、水位埋深以及回灌井直径正相关,与影响半径负相关,与回灌层埋深无关。提出了矿井水深层回灌水动力和溶质运移耦合仿真模型构建方法,并以矿井水回灌试验案例为分析对象,模拟得出矿井水回灌过程中含水层水压形成以注水井为中心的“高位水丘”,且注水压力越大,回灌量增加较为明显,模型分析结果与现场试验结果基本一致。溶质运移范围形成以注水井为中心的“圆柱状”弥散形态,特征离子浓度沿回灌井两侧变化剧烈,回灌层特征离子浓度被迅速稀释,随着时间的延伸,弥散稀释范围增加相对较小,说明矿井水回灌对深部高浓度含水层地下水水化学影响程度不大,研究成果可为西部煤矿区矿井水高效回灌处理提供科学依据。   相似文献   

12.
In this case study, silica concentration, oxygen and strontium isotopes of water samples were used to study surface water–groundwater interaction at the Xin’an karst water system. The silica concentration in rain water is commonly less than 1 mg/l. In the areas around the south tributary of the Zhuozhang River, silica concentrations in the groundwater in Quaternary aquifers range between 4.04 and 7.66 mg/l while that of the surface water varies from 1.49 to 6.9 mg/l. Silica concentrations of most surface water samples increase with TDS, indicating the effect of groundwater recharge on river water chemistry. On the contour map of silica concentration of groundwater in Quaternary aquifers, samples located close to surface water often have lower silica concentrations as a result of surface water recharge. Both overland flow and surface water have impact on karst water according to our hydrogeochemical study of stable oxygen isotope, Sr isotope and strontium contents. Calculation results of three end member mixing model show that the contribution of karst water, surface water and overland flow water is 45, 28 and 27%, respectively.  相似文献   

13.
Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr+6) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03–0.8 mg/l in shallow hand pumps and 0.05 and 1.22 mg/l in quarry seepage. The concentration of Cr+6 in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying in the vicinity of mine waste dump shows highest concentration of Cr+6. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden dump of chromite ore and will be helpful in making strategic planning for limiting the contaminant migration in the ground water regime in and around the mining areas.  相似文献   

14.
The oxidation of pyrite results in sulphate concentrations from 1,300 to 2,000 mg/l in the dump water of the open cast mine Inden, which is located in Germany. Under near-neutral pH and reduced redox conditions, precipitation of siderite (FeCO3) retains up to 85% of the pre-liberated ferrous iron, so that iron concentrations in the dump water are relatively low as compared to the concentrations of sulphate. The highly mineralised dump water will enter the aquifer system northwards of Inden during the next centuries. This area is used intensely for water extraction. Model calculations show that there will be no problem of acidification in the adjacent aquifer system and, therefore, no problem of high heavy metal concentrations during the next centuries. The most important problem will be high sulphate concentrations in the groundwater. Besides dispersion and diffusion, there are no chemical mechanisms that lower the sulphate concentrations downstream. On the basis of the simulations, sulphate plumes of about 1–2 km in width and up to 15 km in length are expected. Within the core of these plumes, sulphate concentrations will be above the drinking water limits.  相似文献   

15.
Groundwater plays an important role in the economic development and ecological balance of the arid area of northwest China. Unfortunately, human activity, for example groundwater extraction for irrigation, have resulted in excessive falls in groundwater level, and aquifer overdraft in the oasis, disrupting the natural equilibrium of these systems. A groundwater numerical model for Minqin oasis, an arid area of northwest China, was developed using FEFLOW software to simulate regional groundwater changes under transient conditions. The vertical recharge and discharge (source/sink terms) of the groundwater models were determined from land-use data and irrigation systems for the different crops in the different sub-areas. The calibrated model was used to predict the change for the period from 2000 to 2020 under various water resources management scenarios. Simulated results showed that under current water resources management conditions groundwater levels at Minqin oasis are in a continuous drawdown trend and groundwater depth will be more than 30 m by 2020. Reducing the irrigation area is more effective than water-saving irrigation to reduce groundwater decline at Minqin oasis and the annual groundwater budget would be −0.978 × 108 m3. In addition, water-diversion projects can also reduce the drawdown trend of groundwater at Minqin oasis, and the groundwater budget in the Huqu sub-area would be in zero equilibrium if the annual inflow into the oasis was enhanced to 2.51 × 108 m3. Furthermore, integrative water resources management including water-diversion projects, water-saving irrigation, and reducing the irrigation area are the most effective measures for solving groundwater problems at Minqin oasis.  相似文献   

16.
The study was carried out in order to investigate existing hydrogeochemical relationships between groundwater environment and geological units in the Kazan trona deposit area, Ankara, Turkey. Evaluations indicate that concentrations of alkalinity, boron, chloride and sodium in the upgradient groundwater of the Eocene sedimentary units gradually increase toward downgradient by the interactions of saline minerals (searlesite, shortite, northupite and pyrite) present in the secondary structures (microfractures and irregular voids) at various levels. Inverse modeling calculations suggest that the range of dissolved mass amounts in millimoles per kilogram of water for searlesite, shortite and northupite minerals are 0.05–28.67, 2.62–24.39 and 0.01–24.19, respectively, in the aquifer between the upgradient and downgradient locations. The ranges of accompanying calcite and dolomite precipitations are 4.54–48.71 and 2.16–24.08 mmol per kg of water, respectively. Chemical composition of the groundwater in the overlying Neogene sedimentary unit includes also higher concentrations of the major ions as measured in groundwater of the underlying units. However the lack of saline mineral zones in the Neogene unit indicates that upward groundwater mixing takes place from the underlying aquifer as also suggested by the measured upward gradient. The mixing percentage of the underlying groundwater as determined from the nested wells ranges from 2.7 to 48.3%, from upgradient to downgradient, respectively. The unconfined alluvium aquifer overlying the Neogene unit includes relatively dilute groundwater except in two locations, where high-ion concentrations detected in groundwater of the underlying units are also high in these locations, suggesting upward groundwater mixing from the underlying aquifer due to upward gradient. However, groundwater input investigations from the alluvium aquifer to the nearby Ova stream indicate that the detected high concentrations in these locations are diluted or sorbed by the aquifer material toward downgradient (Ova Stream).  相似文献   

17.
This paper reviews, compiles and comprehensively analyzes spatial variations in hydrogeologic characteristics of shallow and deep groundwater aquifers in Kathmandu Valley. To estimate transmissivity (T) (and then hydraulic conductivity) as a function of specific capacity (SC), an empirical relationship between T and SC is developed for shallow and deep aquifer. The results show that T and SC are log linearly related by an equation T = 0.8857(SC)1.1624 [R 2 = 0.79] in shallow and T = 1.1402(SC)1.0068 [R 2 = 0.85] in deep aquifer. The estimated T ranges from 163 to 1,056 m2/day in shallow aquifer and 22.5 to 737 m2/day in deep aquifer. Finally, mapping of spatial distribution in hydrogeologic characteristics (thickness, T, hydraulic conductivity and storage coefficient) in shallow and deep aquifers are accomplished using ArcGIS9.2 and such maps would be useful in delineating potential areas for groundwater development and simulating groundwater flow in the aquifer system.  相似文献   

18.
Since the 1980s, high-nitrate concentration in one of the groundwater sampling wells at the Nankou site, northwest of the Beijing Plain, has become a major concern for the local water authority. In a previous study (Sun et?al. in Environ Earth Sci 64(5):1323?C1333, 2011), a hydrogeological structural model was developed based on the borehole logs of this area and the steady, as well as transient groundwater-flow models, were calibrated using the measured hydraulic heads. In this paper, the potential pollution sources in this area are investigated. The chemical analysis of the groundwater is also presented. The results demonstrate that the most likely pollution source is the untreated wastewater discharge from a nearby fertilizer factory. Furthermore, a mass transport model is developed to reproduce the nitrate transport process in the aquifer at the Nankou site under different pollution sources, i.e., a fertilizer factory, river with wastewater and an agriculture field. The combined effects of the river and agriculture fields present a better understanding of the nitrate transport in the local aquifer. In addition, a pumping scenario is designed to clean up the current nitrate concentration. The pumping rate and the well location are first estimated with 2-D analytical solutions of the type curves method. Then a 3-D numerical model is used to calculate the nitrate-concentration changes after the pumping activities start. In the downstream direction of the regional groundwater flow, three pumping wells are set up for the clean-up strategy. The calculated pumping rate in each well is about 1,500 m3/day. After 1?year, the nitrate concentration in the observation well recedes to 68?mg/l from the initial value of 72.9?mg/l, and it will be lower than the limitation value (20?mg/l) after 5,400 days of groundwater extraction. The data assessment and clean-up scenarios reported in this paper are fundamental for the contaminated aquifer management in the future.  相似文献   

19.
Arsenic and fluoride in a loess aquifer in the central area of Argentina   总被引：3，自引：0，他引：3  
The objective of this study is to analyze the geochemical conditions associated with the presence of arsenic (As) and fluoride (F) in the phreatic aquifer of Coronel Moldes, in the central sector of the Argentine Chacopampean plain. The studied aquifer is composed of silty sand sediments of aeolian origin, typically loess-like sediments. The geochemical composition of water varies from sodium bicarbonate to sodium sulfate-chloride water. As contents range from low concentrations, below detection level, to 250 μg/l. High values of F (up to 12 mg/l) were recorded. A high As–F correlation was found (R 2 = 0.84). The pH varied from 7.31 to 8.85 and the nitrates reached concentrations up to 200 mg/l, indicating an oxidant environment. The highest values of As and F agreed with sodium bicarbonate waters as well as with the highest values of pH recorded. There was a high correlation between As and F− as well as between As and the Na/Ca ratio. The composition and texture of loess, low permeability and hydraulic gradients together with the geochemical features of sodium bicarbonate waters are proper conditions for the mobilization of As and F in groundwater in the central area of Argentina.  相似文献   

20.
This paper describes the implementation of process-based models reflecting relative groundwater nitrate vulnerability of the shallow alluvial Lower Savinja Valley (LSV) aquifer in Slovenia. A spatially explicit identification of the potentially vulnerable priority areas within groundwater bodies at risk from a chemical point of view is being required for cost-effective measures and monitoring planning. The shallow LSV unconfined aquifer system consists of high-permeable Holocene and middle- to low-permeable Pleistocene gravel and sand, with a maximum thickness of about 30 m, mainly covered by shallow eutric fluvisoils or variously deep eutric cambisoil. The hydrogeological parameters, e.g. the depth to the groundwater, hydrological role of the topographic slope, etc. usually used in different point count schemes are, in the case of the lowland aquifer and shallow groundwater, spatially very uniform with low variability. Furthermore, the parametric point count methods are generally not able to illustrate and analyze important physical processes, and validation of the results is difficult and expensive. Instead of a parametric point count scheme, we experimentally used the Arc-WofE extension for weights-of-evidence (WofE) modelling. All measurement locations with a concentration higher than the value of 20 mg NO3 − per litre of groundwater have been considered as training points (173), and the three process-based models generalized output layers of groundwater recharge (GROWA), nitrate leached from the soil profile (SWAT) and groundwater flow velocity (FEFLOW), served as evidential themes. The technique is based on the Bayesian idea of phenomena occurrences probability before (prior probability) and after consideration of any evidential themes (posterior probability), which were measured by positive and negative weights as an indication of the association between a phenomena and a prediction pattern. The response theme values describe the relative probability that a 100 × 100 m spatial unit will have a groundwater nitrate concentration higher than the training points’ limit values with regard to prior probability value. The lowest probability of groundwater nitrate occurrence is in the parts of the LSV aquifer, which are known as anoxic condition areas with very likely denitrification processes. The cross-validation of the dissolved oxygen and dissolved nitrate response theme confirmed the accuracy of the groundwater nitrate prediction. The WofE model results very clearly indicate regional groundwater nitrate distribution and enable spatial prediction of the probability for increased groundwater nitrate concentration in order to plan the groundwater nitrate reduction measures and optimize the programme for monitoring the effects of these measures.  相似文献   

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