Development and Implementation of a Bayesian-based Aquifer Vulnerability Assessment in Florida

The Florida Aquifer Vulnerability Assessment (FAVA) was designed to provide a tool for environmental, regulatory, resource management, and planning professionals to facilitate protection of groundwater resources from surface sources of contamination. The FAVA project implements weights-of-evidence (WofE), a data-driven, Bayesian-probabilistic model to generate a series of maps reflecting relative aquifer vulnerability of Florida’s principal aquifer systems. The vulnerability assessment process, from project design to map implementation is described herein in reference to the Floridan aquifer system (FAS). The WofE model calculates weighted relationships between hydrogeologic data layers that influence aquifer vulnerability and ambient groundwater parameters in wells that reflect relative degrees of vulnerability. Statewide model input data layers (evidential themes) include soil hydraulic conductivity, density of karst features, thickness of aquifer confinement, and hydraulic head difference between the FAS and the watertable. Wells with median dissolved nitrogen concentrations exceeding statistically established thresholds serve as training points in the WofE model. The resulting vulnerability map (response theme) reflects classified posterior probabilities based on spatial relationships between the evidential themes and training points. The response theme is subjected to extensive sensitivity and validation testing. Among the model validation techniques is calculation of a response theme based on a different water-quality indicator of relative recharge or vulnerability: dissolved oxygen. Successful implementation of the FAVA maps was facilitated by the overall project design, which included a needs assessment and iterative technical advisory committee input and review. Ongoing programs to protect Florida’s springsheds have led to development of larger-scale WofE-based vulnerability assessments. Additional applications of the maps include land-use planning amendments and prioritization of land purchases to protect groundwater resources.     

Groundwater vulnerability and risk mapping for the Basaltic aquifer of the Azraq basin of Jordan using GIS, Remote sensing and DRASTIC

Water consumption in Jordan already exceeds renewable freshwater resources by more than 20% and, after the year 2005, freshwater resources are likely to be fully utilised. Over 50% of supply derives from groundwater and this paper focuses on a small part of the northern Badia region of Jordan that is underlain by the Azraq groundwater basin where it has been estimated that annual abstraction stands at over 100% of the projected safe yield. While water supply is a crucial issue, there is also evidence to suggest that the quality of groundwater supplies is also under threat as a result of salinisation and an increase in the use of agrochemicals. Focusing on this area, this paper attempts to produce groundwater vulnerability and risk maps. These maps are designed to show areas of greatest potential for groundwater contamination on the basis of hydro-geological conditions and human impacts. All of the major geological and hydro-geological factors that affect and control groundwater movement into, through, and out of the study area were incorporated into the DRASTIC model. Parameters included; depth to groundwater, recharge, aquifer media, soil media, topography, and impact of the vadose zone. The hydraulic conductivity of the aquifer was not included in calculating the final DRASTIC index for potential contamination due to a lack of sufficient quantitative data. A Geographical Information System (GIS) was used to create a groundwater vulnerability map by overlaying the available hydro-geological data. The resulting vulnerability map was then integrated with a land use map as an additional parameter in the DRASTIC model to assess the potential risk of groundwater to pollution in the study area. The final DRASTIC model was tested using hydrochemical data from the aquifer. Around 84% of the study area was classified as being at moderate risk while the re mainder was classified as low risk. While the analysis of groundwater chemistry was not conclusive, it was encouraging to find that no well with high nitrate levels was found in the areas classified as being of low risk suggesting that the DRASTIC model for this area provided a conservative estimate of low risk areas. It is recognised that the approach adopted to produce the DRASTIC index was limited by the availability of data. However, in areas with limited secondary data, this index provides important objective information that could be used to inform local decision making.     

地下水环境风险的模糊多指标分析方法

从影响地下水脆弱性的地质与水文地质条件、地貌特征、污染物性质、土地利用状况以及地下水社会价值功能等因素出发,筛选出22项评价指标,初步构建具有多层次结构特点的地下水环境风险评价指标体系。在将地下水环境风险定义为风险等级与风险重要性乘积的基础上,对风险等级与风险重要性等级的分级标准进行探讨,建立风险评价的模糊多属性决策分析模型。作为案例,将上述指标体系和评价模型应用于皖北3个城市浅层地下水环境风险的分析,取得较好效果,为地下水环境风险评价研究提供了新思路、新方法。     

塔里木盆地南缘地下水脆弱性评价

干旱区地下水脆弱性是地下水系统本身固有的不稳定属性,是系统结构、功能状态在人类活动干扰及气候变化等自然因素作用下具有的敏感性、易变性和弹性的综合反映。可以以河川径流中冰雪融水比重、地表径流入渗占地下水补给比例、地下水补给强度、地表水的引用率等十项指标(IRRUDQELTS)进行定量评价。通过对塔里木盆地南缘地下水脆弱性评价,表明该区属地下水严重脆弱区,其脆弱程度远大于地下水开发利用程度较高的河西走廊,其中又以民丰县、皮山县为极端脆弱。     

人类活动胁迫下岩溶含水层脆弱性分析

从水文地质本身的内部要素分析岩溶含水层高度脆弱的原因,详细论述了农业活动、工业和城市化以及矿山开采等对岩溶含水层脆弱性的影响,认为人类活动的叠加无疑加剧了岩溶含水层的脆弱性,并在很大程度上影响着地下水的水质、水量.因此,合理规范人类活动,减少人类活动对环境的污染,是岩溶地下水资源可持续利用的保证.     

Prediction of Aquifer Vulnerability to Pesticides Using Fuzzy Rule-Based Models at the Regional Scale

Contamination of ground water has been a major environmental concern in recent years. The potential for ground-water contamination by pesticides depends on porous media, solute, and hydrologic parameters. Although sophisticated deterministic computer models are available for assessing aquifer-contamination potential on a site-by-site basis, most deterministic models are too complex for vulnerability assessment on a regional scale because they require input data that are spatially and temporally variable, and which may not be available at this scale. Therefore, development of an affordable model that is robust under conditions of uncertainty at the watershed scale with minimum input of field data becomes a useful ground-water management tool. The purpose of this study was to examine the usefulness of fuzzy rule-based techniques in predicting aquifer vulnerability to pesticides at the regional scale. The objectives were to (1) develop fuzzy rule-based models using the same input parameters contained in an index-based model (i.e., the modified DRASTIC model), (2) determine the sensitivity of fuzzy rule model predictions, (3) compare the outputs of the fuzzy rule-based models with those of the modified DRASTIC model and with the results of aquifer water-quality analyses, and (4) examine the spatial variability of field parameters around contaminated wells of the Alluvial aquifer in Woodruff County Arkansas. The fuzzy rule-based model for objective (1) was developed using similar parameter weights and ratings as the modified DRASTIC model. For objective (2), fuzzy rule-based models were created using fewer parameters than the modified DRASTIC model. Sensitivity of the fuzzy rule-based models was determined using different combinations of weights of the four input parameters in DRASTIC. It was found that variations in the weights of the input parameters and number of fuzzy sets influenced the location of the aquifer-vulnerability categories as well as the area within each fuzzy category. The fuzzy rule models tended to predict somewhat higher vulnerabilities of the Alluvial aquifer than the modified DRASTIC model. The fuzzy rule base that had the soil-leaching index (S) as the highest weight was chosen as the best fuzzy rule model in predicting potential contamination by pesticides of the aquifer. In general, the fuzzy rule models tended to overestimate the vulnerability of the aquifer in the study area.     

Assessing the abilities of intrinsic and specific vulnerability models to indicate groundwater vulnerability to groups of similar pesticides: a comparative study

With continued population growth and increasing use of fresh groundwater resources, protection of this valuable resource is critical. A cost effective means to assess risk of groundwater contamination potential will provide a useful tool to protect these resources. Integrating geospatial methods offers a means to quantify the risk of contaminant potential in cost effective and spatially explicit ways. This research was designed to compare the ability of intrinsic (DRASTIC) and specific (Attenuation Factor; AF) vulnerability models to indicate groundwater vulnerability areas by comparing model results to the presence of pesticides from groundwater sample datasets. A logistic regression was used to assess the relationship between the environmental variables and the presence or absence of pesticides within regions of varying vulnerability. According to the DRASTIC model, more than 20% of the study area is very highly vulnerable. Approximately 30% is very highly vulnerable according to the AF model. When groundwater concentrations of individual pesticides were compared to model predictions, the results were mixed. Model predictability improved when concentrations of the group of similar pesticides were compared to model results. Compared to the DRASTIC model, the AF model more accurately predicts the distribution of the number of contaminated wells within each vulnerability class.     

毛乌素沙地海流兔河流域水文地质特征

海流兔河流域是毛乌素沙地的代表性流域,开展以流域为单元的研究,将为毛乌素沙地的流域水资源配置提供科学依据.通过系统分析海流兔河流域的含水层展布和地下水分布特征,创新性地将含水层厚度和地下水埋深的分区进行小波图像融合后,得到了新的水文地质参数分区.结果 表明:海流兔河流域的第四系及白垩系为该区域的巨厚含水层系统,其中白垩...     

Evaluation and Hotspots Identification of Shallow Groundwater Contamination Risk in the Lower Reaches of the Liaohe River Plain

As a prerequisite for groundwater protection and contamination control, evaluation of groundwater contamination risk was the extension of groundwater vulnerability assessment. Based on disaster theory and using shallow groundwater of the lower reaches of Liaohe River Plain as the study area, we built an evaluation index system and a contamination index model for groundwater contamination risks from the perspectives of intrinsic vulnerability, external stresses, and functional value. We used data acquisition technology (remote sensing) and spatial analysis technology (GIS) to calculate the value of groundwater contamination risks. The spatial distribution of hotspots was obtained by calculating G index. Results show that groundwater contamination is above a mid-level risk in most of the study area. Areas with extreme high risk account for 37.86%, areas with high risk 32.47%, areas with moderate risk 12.07%, areas with light risk 3.17%, and areas with slight risk 14.43%. Hotspots areas are mainly located in central Shenyang City, northwest of Xinmin City, Beizhen City and Liaozhong County. Coldspots are mainly in Panjin City, Yingkou City, Dashiqiao City, Dawa County and Panshan County. The results reflect the spatial distribution and mechanism of groundwater contamination risk in the study area and provide relative references for land use planning and groundwater resource protection in the lower reaches of the Liaohe River Plain.     

Data model for system conceptualization in groundwater studies

Development of a conceptualization of a hydrogeologic system serves as the basis of groundwater modeling. While existing groundwater data models are designed to store groundwater system information, none is designed to capture its conceptual view. This study addresses this need by presenting a new object-oriented Conceptualization Groundwater Data Model that represents a groundwater system as a series of aquifer layers with defined aquifer properties and water boundary conditions. A case study is presented that develops the conceptual view of the groundwater system beneath Konza Prairie. This single conceptualization is used to support groundwater models across existing technologies of finite difference, finite element, and analytical element methods. While the models each employ different mathematics, data input files, and formats, all models are founded on the same conceptualization process that is represented using this new data model. The case study illustrates the data model's promise as an effective mechanism for groundwater system conceptualization and data storage, and utility for various groundwater computational models. This conceptualization of a groundwater data model suggests a new focus on incorporating system conceptualization into data model design.     

半干旱区流域水文的景观生态研究与设计:地理信息系统辅助的过程模拟

人类正在面临严重的社会危机和环境危机,而这些危机均与人口的无节制增长及人类过分消耗能量有关。为了缓解或扭转这种危机,除了减缓人口的增长外,必须提高能量使用和土地空间使用的有效性。实现这个目标的根本在于掌握好经济的可计量价值与生态的不可计量价值的平衡。掌握这个平衡的有效手段便是景观生态规划。景观生态规划的关键在于:各类相互冲突的土地利用要在空间上做合理的安排,以致于各利用单元之间的负作用得以避免,生态系统的基本功能得以保存。景观生态规划的目的是寻求最佳土地管理措施。流域土地管理的核心是:保护生态景观,保护生物食物链的健康有序,增加土壤的储水和渗水能力,增加地表水的分散性分布和地下水的有效补给。为了达到这些目标,流域土地的管理和生态价值的恢复必须对人文与自然因子进行细致的调查和统筹地考虑。为了具体地实现这些目标,我们计划对兰州市及其潜在的生态依赖——马衔山/兴隆山进行整体的景观生态调查。建立一个适合于半干旱区的景观生态模式。     

结构—功能—生境框架下的西南喀斯特生态系统脆弱性研究进展

特殊的地质背景与生态环境叠加强烈的人类活动,导致中国西南喀斯特地区生态系统呈现显著的脆弱性特征。从生态系统敏感性和适应性角度出发,喀斯特生态系统结构、功能和生境对外界扰动响应的脆弱性特征研究已取得一定进展,尤其是借助物种多样性、生态系统生产力、土壤水分/养分等指标揭示了喀斯特生态系统对土地利用/覆被变化、石漠化等过程的敏感性等方面,但综合野外试验、数值模拟、数理统计等手段的生态系统敏感性定量化研究仍较薄弱。在生态系统适应性方面,虽然具有喜钙、耐旱以及石生等特性的植物种群通过形态结构和生理功能的自我调节能够呈现出对岩溶环境的适应性,但喀斯特生态系统对人类干扰和气候变化等环境胁迫响应的适应机制仍缺乏长期的生物及理化过程研究。今后,应针对生态系统结构、功能、生境间的正反馈机制,增强系统组分的耦合分析,加强喀斯特生态系统脆弱性驱动机制研究与定量评估,突出系统脆弱性在石漠化遏制和生态恢复重建中的关键地位。     

非均质条件下珠江口潮汐湿地地下水流动特征

开展非均质条件下潮汐湿地中地下水流动特征研究,成为深入揭示潮汐湿地水循环及物质循环过程的重要前提。以广州南沙区的河畔潮汐湿地为对象,基于放射性氡同位素示踪技术考察含水层非均质情况下地下水的流动特征。结果表明：1）研究区介质干容重、介质孔隙度和介质氡释放（E_{rn}）呈现空间异质性,介质氡释放是导致介质氡平衡能力（[R_n{]}_{gw}）呈现显著空间异质性（2 210.15~7 700.33 Bq/m³）的主要因素。2）非均质条件下地下水流动呈现显著的分区特征,根据氡的比活度可以划分为快速流动区和滞留区。其中,快速流动区地下水氡比活度较小,观测期内平均值为1 522.39 Bq/m³,地下水呈现由陆向海近似“U”型的流动模式。滞留区地下水氡比活度显著增大,观测期内平均值为3 858.40 Bq/m³,地下水受潮汐作用而滞留更久。滞留区地下水流动状态受潮高差影响,潮高差越大,潮汐对湿地地下水的整体驱动力越大,滞留区地下水渗出相对容易,反之滞留区地下水渗出较难。由此可见,潮汐湿地含水层介质的空间异质性是影响地下水流动特征的关键因素。     

Future Scenarios of Environmental Vulnerability Mapping Using Grey Analytic Hierarchy Process

Any sustainable resource utilization plan requires evaluation of the present and future environmental impact. The present research focuses on future scenario generation of environmental vulnerability zones based on grey analytic hierarchy process (grey-AHP). Grey-AHP combines the advantages of grey clustering method and the classical analytic hierarchy process (AHP). Environmental vulnerability index (EVI) considers twenty-five natural, environmental and anthropogenic parameters, e.g. soil, geology, aspect, elevation, slope, rainfall, maximum and minimum temperature, normalized difference vegetation index, drainage density, groundwater recharge, groundwater level, groundwater potential, water yield, evapotranspiration, land use/land cover, soil moisture, sediment yield, water stress, water quality, storage capacity, land suitability, population density, road density and normalized difference built-up index. Nine futuristic parameters were used for EVI calculation from the Dynamic Conversion of Land-Use and its Effects, Model for Interdisciplinary Research on Climate 5 and Soil and Water Assessment Tool. The resulting maps were classified into three classes: “high”, “moderate” and “low”. The result shows that the upstream portion of the river basin comes under the high vulnerability zone for the years 2010 and 2030, 2050. The effectiveness of zonation approach was between “better” and “common” classes. Sensitivity analysis was performed for EVI. Field-based soil moisture point data were utilized for validation purpose. The resulting maps provide a guideline for planning of detailed hydrogeological studies.

     

喀斯特地貌演化与喀斯特含水层特性

本文根据喀斯特含水层的结构、喀斯特地貌发育的动力过程,探讨不同的喀斯特地貌演化阶段及其相应的喀斯特含水层特征。     

基于GIS/RS的南方丘陵区农村水资源系统脆弱性评价——以衡阳盆地为例

采用GIS/RS的方法,以衡阳盆地为研究对象,构建由年降水量,少雨期干旱指数,坡度指数,土壤蓄水能力指数,植被覆盖指数,土地利用指数,水源可获得性指数和人类活动指数8个具体指标组成的基于GIS/RS方法的水资源脆弱性评价指标体系,对衡阳盆地农村水资源脆弱性进行定量评价。结果表明,衡阳盆地农村水资源系统脆弱度的空间分布总体表现为“南北低、中间高”的分布态势,北部的衡阳县、西部的祁东县和中部的衡南县是全区水资源脆弱性最高区域,而南部的常宁、耒阳和东北的衡东县是全区水资源脆弱性低值区。基于GIS/RS的水资源脆弱性评价方法与传统研究方法所得结果具有较好的相似性,但是,相对于传统的评价方法,GIS方法的评价结果更为细致和精确。     

Drought, groundwater management and land use planning: the case of central Oahu, Hawaii

A recent decision to allow higher levels of urban development in central Oahu, Hawaii, has heightened the concern about possible loss of agricultural land and further drops in aquifer levels. This paper examines such potential impacts and offers a procedure for incorporating them into land use planning. First, a water-balance simulation model computes the change in groundwater recharge under changes in land use and irrigation technology. The resulting changes, together with estimated water demands for the agricultural, commercial and residential sectors, are then included in a multiobjective programming model that identifies optimal patterns of land use conversion under different objective trade-offs. Objectives treated are the minimization of agricultural land loss and of water demand, and the maximumization of recharge over withdrawal. The second objective pertains to water management during drought, while the third refers to sustainable groundwater management. Results show that, depending on the relative importance given each of these two objectives, land moving out of sugar cane will differ significantly in amount and by type of irrigation presently used. The relative importance of these objectives thus needs to be determined if water is to play a coherent and guiding role in land use planning.     

社会-生态系统框架（SES）下区域生态系统适应能力建模研究

基于社会-生态系统框架下适应能力的概念,通过不良影响、抵御能力、恢复能力3个指标构建了生态系统适应能力指数模型ACI=CC·RC/EI,定量衡量区域生态系统对特定胁迫的适应能力并获得其空间分布情况。基于该模型,以兰州市为研究区,以水土流失为外界胁迫因素,评价了兰州市生态系统对水土流失的适应能力。结果表明,兰州市74%以上面积的区域水土流失适应能力指数为0.06~0.61,适应能力表现为中或低,生态系统总体具有高水土流失不良影响、低水土流失抵御能力及低水土流失恢复能力,在过耕、过牧等与水土流失恢复能力不一致的人类活动的胁迫下,易发生生态环境退化。     

区域土地利用变化对生态系统脆弱性影响评估——以广州市花都区为例

本文在分析生态系统脆弱性概念与评价方法基础上,以土地利用变化引起的生态系统服务价值改变为影响力指标,以社会经济发展程度表征社会经济适应能力指标,构建区域土地利用变化对生态系统脆弱性影响评价和和空间表达方法,将生态系统脆弱性研究拓展到人类(社会)—自然(生态、环境)耦合系统的综合分析与评价,以广州市花都区为例,从花都区、乡镇两个空间尺度上进行了评价。结果表明:(1)在1980～1990年、1990～2000年和2000～2005年三个时间段,耕地面积的变化对该区生态系统服务功能影响最为显著;(2)1990～2000年和2000～2005年间,研究区社会经济适应性指数保持为正,两期平均值分别为0.391和0.374;(3)从研究区1990～2000年和2000～2005年两期脆弱性空间分布来看,虽然适应能力的提高在一定程度上缓解了土地利用变化对生态系统的负向影响,但总体呈现脆弱趋势,且脆弱性严重的乡镇数在时间尺度上呈现增加趋势。     

土地利用对地下水系统的影响

土地利用对地下水系统的影响是近年来国内外水文地质领域研究的热点之一。该文阐述城镇化、工业和农业等土地利用方式对地下水资源及其环境的影响;分析土地利用对地下水系统的影响机制;提出保证地下水可持续利用的途径与措施。应注重地球物理技术和环境同位素在污染土壤和地下水调查中的应用,注重治理污染土壤和地下水新技术的开发,开展地下水环境脆弱性调查评价。