Fuzzy vulnerability mapping of urban groundwater systems to nitrate contamination

The aim of this study is to develop a new fuzzy optimization model to find the optimal factor weights of modified DRASTIC index for groundwater vulnerability mapping an urban aquifer to nitrate contamination. Eight factors including water table depth, recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity, and land use are considered and rated. A fuzzy linear regression is formulated between the values of eight factors and corresponding nitrate concentration in groundwater. An optimization model based on real code genetic algorithm with objective of minimizing the sum of the fuzzy spread of the regression coefficients is implemented. Aquifer of Mashhad metropolis (northeast of Iran) is chosen to evaluate the proposed model. The results show the proposed model is a promising tool for weighting the factors with avoiding the subjectivity and also ambiguities accompanied by parameters to produce an accurate specific vulnerability mapping of an urban aquifer.     

DRASTIC模型在贵州省毕节地段浅层地下水脆弱性评价中的应用

为了实现贵州省毕节地段地下水系统脆弱性评价的直观展示,选取含水层埋深、含水层补给、含水层介质类型、土壤介质类型、坡度、包气带厚度和渗透系数七项评价因子,采用DRASTIC模型建立了地下水系统脆弱性评价模型,通过模糊层次分析法(FAHP)确定了评价因子的权重,并基于ArcGIS软件对毕节地段地下水资源的各项数据指标进行了矢量化,实现了毕节地段地下水脆弱性等级划分的直观性分布图。评价结果表明,该区域地下水脆弱性较高且分布不均。     

江汉平原浅层地下水污染脆弱性评价

根据江汉平原实际的地质、水文地质条件,采用DRASTIC模型对研究区浅层地下水进行了污染脆弱性评价,分析了区内浅层地下水的防污性能,在此基础上,提出了江汉平原地下水污染防治的对策建议。     

基于熵权的DRASTIC模型在地下水脆弱性评价中的应用

对目前广泛应用于地下水脆弱性评价中的DRASTIC模型进行了评述,在指出该模型存在的问题基础上提出了基于熵权的DRASTIC评价模型。在新的耦合模型中,各项指标的权重由客观数据计算得到,消除了人为确定权重的主观误差。将该模型应用于实例研究,评价结果表明所建立的新模型是科学合理的,其结果更加客观,它为该地区地下水资源的开发利用和保护提供决策依据。     

云南省玉溪盆地地下水防污性评价

随着地表水资源开发利用潜力降低和污染加剧,人类对地下水的开发利用程度不断增加,不同程度改变了地下水环境,尤其是城市地区的地下水环境有恶化趋势。采用DRASTIC指标体系和MAPG IS的空间叠加功能,对玉溪盆地地下水防污性进行评价,评价结果表明,该区地下水防污性总体在差—中等范围,可分为三种等级区。其中,盆地区地下水防污性基本在较差—差的范围,盆地周边山地防污性中等。反映人类工程和经济活动易对盆地地下水造成污染。     

云南曲靖盆地地下水脆弱性模糊评价

在DRASTIC指标的基础上,运用层次分析法构建了云南省曲靖盆地地下水脆弱性指标体系,并采用多级二层模糊评价方法进行脆弱性评价。结果表明:曲靖盆地地下水脆弱性分区为四级,西部基岩地下水和孔隙水脆弱性高,东部的孔隙水及少量岩溶水处于脆弱性中等。评价结果有利于地下水环境的保护。     

邢台山前倾斜平原区孔隙水脆弱性评价

利用DRASTIC模型和MAPGIS叠加技术,并采用层次分析法,构建地下水脆弱性评价系统,将该评价系统应用于邢台市山前倾斜平原区孔隙水脆弱性评价。结果表明,评价结果与实际情况比较吻合。     

页岩气开采区地下水脆弱性评价模型

为了更准确评价页岩气开采过程中水力压裂和废水回注对地下水的影响,需要采用不同指标体系的模型对地下水脆弱性进行评价。通过分析页岩气开采过程中污染物的潜在运移途径,在DRASTIC模型的基础上分别建立了开采井区地下水脆弱性评价模型DIRTEV和回注井区地下水脆弱性评价模型DIRWOCT。根据相关资料对模型中各评价因子进行了分级及评分,运用模糊综合矩阵法确定了各因子权重,并利用单参数法对评价结果进行了敏感性分析。对四川某页岩气采区的评价结果表明,所建模型能较好地应用于页岩气开采区地下水脆弱性评价。     

Geostatistical Assessment of Groundwater Nitrate Contamination with Reflection on DRASTIC Vulnerability Assessment: The Case of the Upper Litani Basin, Lebanon

Groundwater constitutes the largest single source of fresh water in many parts of the world and provides a risk buffer to sustain critical water demands during cyclic and prolonged dry periods, especially in semi-arid and arid regions. However, unprecedented socio-economical growths are threatening the viability of these precious resources through fast depletion of already critically low stocks accompanied by persistent degradation of water quality due to salinization, and contamination by pesticides and fertilizers, urban sewage and industrial waste. These circumstances are particularly true of the Upper Litani Basin (ULB), which houses over 500,000 of Lebanon’s 4 million population and provides the bulk of the country’s agricultural output. Uncontrolled urban, agricultural and industrial growths following a prolonged civil strife and foreign occupation have resulted in the deterioration of the quality of the basin’s surface water and potentially its groundwater resources. An assessment study of groundwater quality conditions in the ULB was conducted in support of efforts to manage water quality in the basin. Geostatistical analysis of groundwater nitrate levels was conducted using data collected through an extensive basin-wide water quality survey sponsored by the USAID and covered two periods representing the summer and winter periods. The results of analysis include maps of nitrate contamination and probability of exceedance of drinking-water nitrate regulatory limit. The results indicate a significant, widespread and persistent nitrates contamination of groundwater in the ULB. Nitrate levels in groundwater exceed standard limits for drinking water in many parts of the basin. These findings were examined with respect to those of a DRASTIC groundwater vulnerability assessment conducted by the USAID BAMAS project. Comparative analysis of the two assessments shed the light on several issues related to the application and interpretation of DRASTIC scores and the groundwater nitrate contamination process.