Monitoring and Predicting Saltwater Intrusion via Temporal Aquifer Vulnerability Maps and Surrogate Models

This article proposes a methodology to accurately monitor seawater intrusion (SWI) using time-varied GALDIT vulnerability maps. The properly produced samples are then used as input–output patterns for the approximate SWI simulation. As a novelty, the specific area of high susceptibility to SWI is proposed as the dynamic saltwater wedge position to suitably select the monitoring locations (MLs) from a narrowed area. It is observed that varied initial conditions over time periods have more influence than variable pumping rates on salinity at MLs far from the production wells. Support Vector Regression (SVR), Artificial Neural Network (ANN) and Gaussian Process Regression (GPR) models have been substituted for the numerical model of SWI. Input training patterns of the surrogate models are initial salinity concentrations at selected MLs plus transient pumping values via Latin hypercube sampling. The final salinity at MLs constitutes the output patterns. The paper applies this new methodology to a small study area subject to the SWI problem. The generalization ability of surrogate models for predicting new initial conditions-pumping datasets was evaluated using performance criteria considering the ML locations. All surrogates offered good results for predicting SWI at specified MLs. The SVR model had poor performance compared to ANN and GPR models in MLs near the pumping wells, due to their salinity fluctuations over time.

     

Correction to: Monitoring and Predicting Saltwater Intrusion via Temporal Aquifer Vulnerability Maps and Surrogate Models

Water Resources Management -     

Inclined Physical Subsurface Barriers for Saltwater Intrusion Management in Coastal Aquifers

Saltwater intrusion (SWI) has a negative environmental impact on groundwater quality in coastal areas. Therefore, effective management strategies are required to preserve fresh groundwater resources. Historically, vertical barriers have been exclusively considered in both numerical studies and practical applications. The novelty of this study consists in investigating the SWI mitigation effectiveness of inclined physical subsurface barriers (PSBs), and specifically cutoff walls (CWs) and subsurface dams (SDs). An initial benchmark analysis of the Henry problem was performed. Following verification, the proposed model was applied to a real case study - the Biscayne aquifer (Southeastern Florida, USA). The model simulations run for different scenarios considering the vertical placement of the PSB, an inclined placement of the PSB according to different slopes (1/4, 1/2 and 1/1, at sea- and landside) and the combination of the best scenario. The results showed that CWs are more effective in limiting SWI in comparison with SDs. The most positive impact in both cases was achieved for a slope of 1/4, indicating that a moderate vertical inclination of the PSB better preserve coastal groundwater resources. The model presented in this work can be a valuable tool for policy makers in predicting the coastal aquifer response. However, a comprehensive cost–benefit analysis is required to further account for the feasibility and the economic costs related to the construction of inclined PSBs.

     

Development and Implementation of Support Vector Machine Regression Surrogate Models for Predicting Groundwater Pumping-Induced Saltwater Intrusion into Coastal Aquifers

Predicting the extent of saltwater intrusion (SWI) into coastal aquifers in response to changing pumping patterns is a prerequisite of any groundwater management framework. This study investigates the feasibility of using support vector machine regression (SVMr), an innovative artificial intelligence-based machine learning algorithm for predicting salinity concentrations at selected monitoring wells in an illustrative aquifer under variable groundwater pumping conditions. For evaluation purpose, the prediction results of SVMr are compared with well-established genetic programming (GP) based surrogate models. SVMr and GP models are trained and validated using identical sets of input (pumping) and output (salinity concentration) datasets. The trained and validated models are then used to predict salinity concentrations at specified monitoring wells in response to new pumping datasets. Prediction capabilities of the two learning machines are evaluated using different proficiency measures to ensure their practicality and generalisation ability. The performance evaluation results suggest that the prediction capability of SVMr is superior to GP models. Also, a sensitivity analysis methodology is proposed for assessing the impact of pumping rates on salt concentrations at monitoring locations. This sensitivity analysis provides a subset of most influential pumping rates, which is used to construct new SVMr surrogate models with improved predictive capabilities. The improved prediction capability and the generalisation ability of the SVMr models together with the ability to improve the accuracy of prediction by refining the input set for training makes the use of proposed SVMr models more attractive. Prediction models with more accurate prediction capability makes it potentially very useful for designing large scale coastal aquifer management strategies.     

Groundwater Circulation Well for Controlling Saltwater Intrusion in Coastal aquifers: Numerical study with Experimental Validation

Saltwater intrusion into coastal aquifers has become a prominent environmental concern worldwide. As such, there is a need to prepare and implement proper remediation techniques with careful planning of freshwater withdrawal systems for controlling saltwater intrusion in coastal marine and estuarine environments. This paper investigates the performance of groundwater circulation well (GCW) in controlling saltwater intrusion problems in unconfined coastal aquifers. The GCWs have been established as a promising in-situ remedial technique of contaminated groundwater. The GCW system creates vertical circulation flow by extracting groundwater from an aquifer through a screen in a single well and injecting back into the aquifer through another screen. The circulation flow induced by GCW force water in a circular pattern between abstraction and recharge screens and can be as a hydraulic barrier for controlling saltwater intrusion problem in coastal aquifers. In this study, an effort has been made to investigate the behavior of saltwater intrusion dynamics under a GCW. An experiment has been conducted in a laboratory-scale flow tank model under constant water head boundary conditions, and the variable-density flow and transport model FEMWATER is used to simulate the flow and transport processes for the experimental setup. The evaluation of the results indicates that there is no further movement of saltwater intrusion wedge towards the inland side upon implementation of GCW, and the GCW acts as a hydraulic barrier in controlling saltwater intrusion in coastal aquifers. The present study reveals the GCWs system can effectively mitigate the saltwater intrusion problem in coastal regions and could be considered as one of the most efficient management strategies for controlling the problem.

     

Groundwater Vulnerability Modeling to Assess Seawater Intrusion: a Methodological Comparison with Geospatial Interpolation

Seawater intrusion has become a growing threat in coastal urban cities due to overexploitation of groundwater. This study examines the accuracy of the commonly used geospatial quality assessment models (GQA) and groundwater vulnerability assessment models (GVA) in determining the extent of seawater intrusion in urban coastal aquifers. For that purpose, interpolation methods (kriging, IDW and co-kriging) and vulnerability assessment models (DRASTIC, EPIK) were compared using groundwater salinity criteria (TDS, Cl^?) collected at three pilot areas along the eastern Mediterranean (Beirut, Tripoli, Jal el Dib). The results showed that while the GIS-based interpolation methods and the vulnerability assessment models captured elements of the groundwater quality deterioration, both had a limited ability to accurately delineate saltwater intrusion. This emphasizes that while interpolation methods and conventional vulnerability models may give general information about groundwater quality, they fail to capture the status of the aquifer at a finer spatial resolution.

     

A Model for the Optimal Allocation of Water Resources in a Saltwater Intrusion Area: A Case Study in Pearl River Delta in China

This paper presents a model for the optimal allocation of water resources in saltwater intrusion areas. The model is comprised of four modules: a joint operation of river and reservoirs module (JORRM), a saltwater intrusion analysis module (SIAM), an economic analysis and in-stream ecology demand module (EAIEDM) and a water allocation module (WAM). Considering the social, economic and environmental aspects, the model has three objectives: the maximization of economic interest (OF ₁), maximization of social satisfaction (OF ₂) and the minimization of the amounts of polluted water (OF ₃). A genetic algorithm is also employed to optimize the module. The model has then been applied to a case study of optimization of water resources for the Pearl River Delta in China. The results indicate that there is water shortage in Pearl River Delta and engineering projects are needed to satisfy water demand during the dry season when saltwater intrusion happens. The model provides a useful tool for the operation of reservoirs and freshwater allocation in saltwater intrusion area.     

Evaluation of a GIS-Based Integrated Vulnerability Risk Assessment for the Mancha Oriental System (SE Spain)

It is widely recognized that groundwater-vulnerability maps are a useful tool for making decisions on designating pollution-vulnerable areas, in addition to being a requirement of European Directive 91/676/EEC. This study addressed the vulnerability of the Mancha Oriental System (MOS) to groundwater contamination with an integrated Generic and Agricultural DRASTIC model approach. In the MOS, groundwater is the sole water resource for a total population of about 275,000 inhabitants and for 1,000 km² of irrigated crops. DRASTIC vulnerability maps have been drawn up for two different years (1975 and 2002) in which the potentiometric surface has dropped dramatically (80 m in some areas) due to the considerable expansion of irrigated croplands. The quality of available resources has also deteriorated due to the agricultural practices and the discharge of wastewater effluents. Vulnerability maps are used to test the data on nitrate, sulphate, and chloride contents in groundwater in the Central and El Salobral-Los Llanos hydrogeologic domains of the MOS for 2002. Regardless of the method applied, the dramatic alteration in land use leads to a change in the DRASTIC index and vulnerability to groundwater contamination decreases for the study period. Vulnerability in the MOS increases in areas where the irrigation return flow is notable. The lack of a statistical correspondence between the DRASTIC index and the spatial distribution of nitrate, chloride, and sulphate contents and the distribution of the pollution load suggest that this method does not accurately assess the risk of the MOS to groundwater pollution.     

土石坝坝坡失稳模糊风险分析

通过对土石坝坝坡失稳风险的不确定性进行分析,建立了考虑设计参数模糊性和失效准则模糊性的坝坡失稳模糊风险模型,并运用蒙特卡罗方法求解其风险概率,将模糊参数进行模糊化处理后,可直接采用现有传统风险计算方法计算失事概率。结果表明,坝坡失稳风险分析中考虑了风险的模糊性使计算结果更加合理,风险评价更加符合工程实际。     

索风营水电站水库调度方案探讨

索风营水电站是应用X形宽尾墩+台阶坝面+消力池联合泄洪消能方式(水力学研究模型试验研究发现的一种新型消能方式)的第1个工程,因此该电站的水库调度方案显得尤其重要。该水库于2007年7月30日首次开闸泄洪;2008年遭遇了凝冻灾害,为保证水库安全运行启动了水库紧急调度方案。本文根据2007年泄洪后的数据与试验资料以及紧急措施对索风营水电站水库调度方案进行探讨。     

Fuzzy Risk Assessment of Flash Floods Using a Cloud-Based Information Diffusion Approach

The assessment of flash flood risks is the basis on which flash flood prevention measures and early-warning systems can be proposed and reasonably implemented. However, inadequate monitoring of flash flood data which mainly occurs in remote areas restricts quantitative risk assessment. This study aimed to address the problems of limited data availability. A new model that integrating the Cloud-based Information Diffusion (CID) model and Analytic Hierarchy Process (AHP) approach is developed to assess flash flood risks. The proposed method improves the information diffusion function by introducing cloud model, while converting single-valued observations with incomplete information into fuzzy set-valued samples. The new approach can perform comprehensive risk assessment tasks with various indexes that are composed of incomplete information. Another advantage of this approach is that it can illustrate fuzzy uncertainty, fuzziness, and randomness of risk indexes by coupling with the cloud model, the risk magnitude is quantified with membership degree. A mountainous watershed in Southern China named Yangshan County was selected as the study area. Compared with information diffusion (ID) and entropy-based information diffusion (EID), the assessment results of the three models are, in general, consistent with one another, and agree with the reported values. According to the principle of maximum membership degree, Yangshan County is determined as a high-risk region when confronting with flash flood hazards. This model provides a feasible and effective method on fuzzy risk assessment of flash flooding, and is expected to be applied in other multi-criteria decision with limited available information or small sample problems.

     

绕阳河整治穿堤建筑物改建方案比较

绕阳河穿堤建设物在改建和续建过程中，发现有的涵洞出现裂缝，本文在分析其原因后，研究了三个处理方案，对其它涵洞的裂缝处理有一定指导意义。     

大坝安全风险评价的模糊层次综合模型

为了对大坝的安全进行有效的识别和评价,文中对大坝运行中的安全风险进行了分析和归纳,建立了模糊层次综合特性评价模型。运用层次分析法确立了各因素的权重,得到了评价矩阵并对其做了模糊化处理,通过运算得到综合评价结果,为大坝安全风险的控制以及评测提供了科学依据。     

基于AHP的老灌河流域环境风险评价

老灌河流域是南水北调中线工程上游重要水源涵养区,其水质状况的稳定对于调水安全极为重要。对流域进行风险评价可以为流域环境管理政策提供理论支持。以层次分析法和模糊逻辑法为基础,构建了老灌河流域环境风险评价指标体系,据此对老灌河流域环境风险状况进行评价。结果表明,老灌河流域综合风险等级处于中等水平,污染物排放压力值较大;上游栾川县和下游淅川县西峡县大部分处于中等、较高的风险等级。     

高等级公路水土保持方案编制探讨

在我国高等级公路建设发展的同时,也引发了一系列的水土流失问题。本文就公路水土保持方案编制的准备工作、编制过程中的技术要点分析和编制过程中存在的问题及建议等几个方面做一探讨,力求高等级公路水土保持方案的实施更具有可操作性。     

Updating of a DRASTIC-based Method for Specific Vulnerability Assessment in Carbonate Aquifers

Abstract

Some methodological modifications are suggested to improve a DRASTIC-based method as a reliable predictor of microbial contamination in extensively fractured and subordinately karstified carbonate aquifers. These modifications will allow a better assessment of vulnerability induced by the concentrated infiltration of surface runoff in two different scenarios: (a) when the karst system is entirely located within an unsaturated aquifer and (b) when the karst system is partially located within a saturated medium. The effectiveness of the updated method has been experimentally verified by comparing the vulnerability values with the results of a hydrogeological and microbiological study at a test site.     

基于模糊理论的土石坝风险综合评价方法研究

开展土石坝风险研究不仅能为大坝除险加固前期工作提供决策依据,而且可以通过比较加固前后大坝风险值,达到检验除险加固效果的目的.选取了与土石坝风险相关的八个指标:防洪能力、变形性状、渗流态势、生命损失、经济损失、社会环境影响、基础设施水平、管理水平,来构建土石坝风险综合评价指标体系;借鉴模糊数学的理论,建立了综合评价模型;...     

电排站水泵选型的Fuzzy排序与优选探讨

文章运用Fuzzy综合评价原理，对适合于电排站的几种水泵进行了排序和优选的探讨，为泵型选优提供了一种决策方法。     

搭接网络计划的多资源模糊优化及问题的探讨

针对工期固定情况下搭接网络中的多资源优化问题,运用模糊优选理论确定各种资源的重要性,进而对其进行同一化处理,最终解决搭接网络的多资源优化问题。同时,通过实例证明了该方法的实用性,并对存在的问题进行了研究和探讨,提出相应的解决方法。     

土石坝健康诊断重要性确定的模糊一致矩阵法

文章提出适用于土石坝健康诊断的多诊断项目重要性确定方法.重点探讨基于总体模糊一致矩阵的诊断重要性确定方法,给出模糊一致矩阵法的具体计算步骤,并结合计算实例予以验证.