Optimal Allocation of Flood Control Capacity for Multi-Reservoir Systems Using Multi-Objective Optimization Approach

Operation of multi-reservoir systems during flood periods is of great importance in the field of water resources management. This paper proposes a multi-objective optimization model with new formulation for optimal operation of multi-reservoir systems. In this model, the release rate and the flood control capacity of each reservoir is considered as decision variable and the resulting nonlinear non-convex multi-objective optimization problem is solved with ε-constraint method through the mixed integer linear programming (MILP). Objective functions of the model are minimizing the flood damage at downstream sites and the loss of hydropower generation. The developed model is used to determine optimal operating strategies for Karkheh multi-reservoir system in southwestern Iran. For this purpose, the model is executed in two scenarios based on “two-reservoir” and “six-reservoir” systems and for floods with return periods of 25 and 50 years. The results show that in two-reservoir system, flood damage is at least about 114 million dollars and cannot be mitigated any further no matter how hydropower generation is managed. But, in the case of developing all six reservoirs, optimal strategies of coordinated operation can mitigate and even fully prevent flood damage.     

Designing a Policy Mix and Sequence for Mitigating Agricultural Non-Point Source Pollution in a Water Supply Catchment

Agricultural non-point source pollution, common in water supply catchments worldwide, can have significant environmental and human health impacts, and its mitigation poses a challenge for policymakers. We used deliberative multi-criteria evaluation (DMCE) to identify a mix and sequence of policy instruments (or policy design) to address agricultural non-point source pollution using a case study of Cryptosporidium contamination in the Myponga River water supply catchment, South Australia. The major impediments to adoption of on-farm water quality management and benefits for ecosystem services were identified using a landholder survey for use as decision criteria in DMCE. The DMCE approach involved stakeholders in policy design during two community fora held in the catchment. We developed six policy scenarios and quantified their impact on decision criteria. The relative importance of decision criteria was quantified using swing weights and consensus was reached on the preferred policy scenario. The mix, sequence, and targeting of instruments in the preferred policy scenario were refined based on information obtained through the deliberative process. Impediments to adoption included a lack of both information/knowledge and financial resources. The recommended policy scenario involved targeted information, followed by an incentive program, and finally the regulation of a mandatory code of practice for water quality management. Detailed, catchment-specific context obtained through DMCE was critical for refining an effective mix and sequence of policy instruments. The techniques may be readily used to select and schedule policy instruments for effective mitigation of agricultural non-point source pollution in other drinking water supply catchments elsewhere.     

小流域设计洪水误差分析及改进措施

推理公式法是小流域设计洪水常用的一种简单易行的方法.推理公式计算中涉及较多参数,参数的准确与否,直接影响计算精度.在推理公式计算的各种参数中,暴雨衰减指数n不确定性较大,而且n值变化对设计结果影响也较大.暴雨过程是一个复杂的多维随机过程,年最大时段暴雨xt,p与暴雨历时t的暴雨公式属于经验相关关系,忽略了不少影响因素,因此,公式中参数n值不会是稳定不变的.20世纪80年代以后,随着自记雨量观测应用,到目前已经有20多年的资料系列,小流域暴雨设计的计算就可以直接利用时段实测降水资料系列进行计算,设计洪水时,可根据实测雨量时段资料,计算该设计流域的n值,可提高计算精度.因此,在当地自记降水资料系列允许的情况下,尽量采用实测降水资料直接计算参数,可避免设计暴雨的误差.     

河流控制断面非点源和点源污染输送量分割方法初探

根据非点源和点源污染的产生机理,提出了一套计算河流控制断面非点源和点源污染输送量的分割方法。这套方法将全年分成无雨期和雨洪期两种时段,并根据引起非点源污染的大小程度将降雨分成三类,在控制断面开展典型监测,根据监测数据来计算场次洪水的总产污量．再从中分割出非点源产污量。此套方法简便实用,已在广东省鉴江流域进行了试验。     

Estimation of Design Flood Hydrograph for an Ungauged Watershed

Based on the physiographical features of the studied watershed of 102.5 km² in northern Ontario and the meteorological data of one nearby climatic station, through the combination of the regionalization of flood and the HEC-1 modeling, this article presents an approach that may be used to determine the desired peak flows for the ungauged watershed. The empirical equations used to determine the desired peak flows were developed by the Cumming Cockburn Ltd. (CCL) who has carried out the studies on flood regionalization by using flow data at 380 gauging stations in Ontario. CCL has proposed four methods to estimate peak flows, namely 1) regression method describing multiple linear relationships between flood flow and related parameters; 2) index flood frequency curve; 3) regional flood frequency curve and 4) isoline map for unit peak flow. The desired peak flows for studied watershed determined by CCL methods were used to calibrate the HEC-1 model for the rainfall-runoff simulation for this watershed which consists of 15 subwatersheds. Through slight adjustment in the CN number used in the HEC-1 model, the calibrated HEC-1 model could be used for rainfall-runoff simulation for this ungauged watershed. This approach could be recommended for hydrological design and watershed management for ungauged watersheds provided the analyses of flood regionalization could be conducted. In addition, comparing to the Bavaria forest region, Germany, some questions have been discussed in this article.     

An Integrated Approach for Targeting Critical Source Areas to Control Nonpoint Source Pollution in Watersheds

This study presents an integrated approach for targeting critical source areas (CSAs) to control nonpoint source pollution in watersheds. CSAs are the intersections between hydrologically sensitive areas (HSAs) and high pollution producing areas of watersheds. HSAs are the areas with high hydrological sensitivity and potential for generating runoff. They were based on a soil topographic index in consistence of a saturation excess runoff process. High pollution producing areas are the areas that have a high potential for generating pollutants. Such areas were based on simulated pollution loads to streams by the Soil and Water Assessment Tool. The integrated approach is applied to the Neshanic River watershed, a suburban watershed with mixed land uses in New Jersey in the U.S. Results show that several land uses result in water pollution: agricultural land causes sediment, nitrogen and phosphorus pollution; wetlands cause sediment and phosphorus pollution; and urban lands cause nitrogen and phosphorus pollution. The primary CSAs are agricultural lands for all three pollutants, urban lands for nitrogen and phosphorus, and wetlands for sediment and phosphorus. Some pollution producing areas were not classified into CSAs because they are not located in HSAs and the pollutants generated in those areas are less likely to be transported by runoff into streams. The integrated approach identifies CSAs at a very fine scale, which is useful for targeting the implementation of best management practices for water quality improvement, and can be applied broadly in different watersheds to improve the economic efficiency of controlling nonpoint source pollution.     

Multi-Criteria Decision Making Approach for Watershed Prioritization Using Analytic Hierarchy Process Technique and GIS

Watershed prioritization based on the natural resources and physical processes involves locating critical areas of erosion, which produce maximum sediment yield to take up conservation activities on priority basis. The present study was taken up with a specific objective of prioritization of micro-watersheds using Multi-Criteria Decision Approach – Analytic Hierarchy Process (AHP) based SYI model (AHPSYI) under GIS environment for a case study area of Mayurakshi watershed in India. This method basically uses information of Potential Erosion Index (PEI) and Sediment Delivery Ratio (SDR), indicative of transport capacity. In the present study, sediment delivery factors viz., topography, vegetation cover, proximity to water courses and soil were translated into GIS layers and integrated using Boolean conditions to create a data layer of spatially distributed SDIs’ across the watershed. For assessment of PEI, important watershed parameters viz., land use/land cover, soil, slope, and drainage density maps were integrated in the GIS environment using Weighted Linear Combination method (WLC) by assigning weights to themes and ranks to features of individual theme using AHP technique. A comparison between AHPSYI based sub watershed prioritization map with that of prioritization map based on the observed sediment yield data revealed that about 78 % of the area showed concurrence. Thus, it can be inferred that the watershed prioritization based on only thematic layers can be dependable to maximum extent. Subsequently, proposed approach was adopted for prioritization of the study area at micro watershed scale, where area under high and very high categories together constitutes around 33 % of the study area. Around 100 micro-watersheds out of 276 watersheds are under moderate to very high category respectively, signifying the need for watershed management.     

Simulation of Agricultural Management Alternatives for Watershed Protection

The Bosque River Watershed in Texas is facing a suite of water quality issues including excess sediment, nutrient, and bacteria. The sources of the pollutants are improperly managed cropland and grazing land, dairy manure application, and effluent discharge from wastewater treatment facilities. Several best management practices (BMPs) have been proposed for pollution reduction and watershed protection. The overall objectives of this study were to demonstrate a modeling approach using Soil and Water Assessment Tool (SWAT) model to simulate various BMPs and assess their long-term impacts on sediment and nutrient loads at different spatial levels. The SWAT model was calibrated and validated for long-term annual and monthly flows at Valley Mills and for monthly sediment, total nitrogen (TN) and total phosphorus (TP) at Hico and Valley Mills monitoring locations. The BMPs including streambank stabilization, gully plugs, recharge structures, conservation tillage, terraces, contour farming, manure incorporation, filter strips, and PL-566 reservoirs were simulated in the watershed areas that met the respective practice’s specific criteria for implementation. These BMPs were represented in the pre- and post-conditions by modifying one or more channel parameters (channel cover, erodibility, Manning’s n), curve number (CN), support practice factor (P-factor), filter strip width, and tillage parameters (mixing efficiency, mixing depth). The BMPs were simulated individually and the resulting Hydrologic Response Units (HRUs), subwatershed, and watershed level impacts were quantified for each BMP. Sensitivity of model output values to input parameters used to represent the BMPs was also evaluated. Implementing individual BMPs reduced sediment loads from 3% to 37% and TN loads from 1% to 24% at the watershed outlet; however, the changes in TP loads ranged from 3% increase to 30% decrease. Higher reductions were simulated at the subwatershed and HRU levels. Among the parameters analyzed for sensitivity, P-factor and CN were most sensitive followed by Manning’s n. The TN and TP outputs were not sensitive to channel cover. This study showed that the SWAT modeling approach could be used to simulate and assess the effectiveness of agricultural best management practices.     

Rainfall-runoff Modeling in a Watershed Scale Using an Object Oriented Approach Based on the Concepts of System Dynamics

Relying on a linear causal thinking, most of the hydrological models fail to incorporate socio-economic characteristics of a watershed with hydrological and environmental attributes. Based on a systems thinking philosophy, the paper aims to adopt an Object-Oriented (OO) approach based on the concepts of System Dynamics (SD) such as stocks and flows to analyze the dynamics in a hydrological system in a watershed scale. Object-Oriented modeling is a way to organize data into discrete, recognizable entities called objects. These objects could be concrete (such as a river reach) or conceptual (such as a policy decision). In the present paper, VENSIM PLE has been used for the modeling purpose. The application was illustrated in an Iranian watershed. The model was examined using validity and verifying tests. The results showed that the model is capable of generating the monthly runoff quite well. The values of R² are 0.69 and 0.61 for generated discharge values at Polchehr and Doab stations respectively. Also the values of NSE are 0.66 and 0.64 for estimated discharge values at the same stations. The capability of model was more clarified comparing R² and NSE coefficients obtained by a SWAT model with those obtained by Watershed Hydrological Model developed in this study.     

Comparison of Computer Models for Estimating Hydrology and Water Quality in an Agricultural Watershed

Various computer models, ranging from simple to complex, have been developed to simulate hydrology and water quality from field to watershed scales. However, many users are uncertain about which model to choose when estimating water quantity and quality conditions in a watershed. This study compared hydrologic/water quality models including Spreadsheet Tool for the Estimation of Pollutant Load (STEPL)-Purdue, Soil and Water Assessment Tool (SWAT), High Impact Targeting (HIT), Long-Term Hydrologic Impact Assessment (L-THIA), Pollutant Load (PLOAD), Spatially and Temporally Distributed Model for Phosphorus Management (STEM-P), Region 5, and ensemble modeling (using STEPL-Purdue, SWAT, L-THIA, PLOAD, and STEM-P). Model capabilities, inputs, and underlying methods to estimate streamflow, surface runoff, baseflow, nutrients, and sediment were examined. Uncalibrated, calibrated, and validated outputs of these models and uncalibrated ensemble modeling in estimating water quantity and quality for a 41.5 km² agricultural watershed in Northeastern Indiana were explored, and suggestions were provided on the selection and use of models. Models need to be selected carefully based on the simulation objectives, data availability, model characteristics, time constraints, and project budgets.

     

Linked Simulation-Optimization based Dedicated Monitoring Network Design for Unknown Pollutant Source Identification using Dynamic Time Warping Distance

Implementation of monitoring strategy for increasing the efficiency of groundwater pollutant source characterization is often necessary, especially when only inadequate and arbitrary concentration measurement data are initially available. Two main parameters that need to be estimated for efficient and accurate characterization of groundwater pollution sources are: location of the source and the time when the source became active. Complexities involved with the explicit estimation of the time of start and source activity have not been addressed so far in previous studies. The main complexity arises due to the fact that the spatial location and time of activity are inter-related. Therefore, specifying one and solving for the other simplifies the source characterization problem. Hence, in this study, both the source location and time of initiation are treated as unknowns. The developed methodology uses dynamic time warping distance in the linked simulation-optimization model to address some complex issues in designing a monitoring network to efficiently estimate source characteristics including the time of first activity of unknown groundwater source. Performance of the developed methodology is evaluated on illustrative contaminated aquifer. These evaluation results demonstrate the potential use of the developed methodology.     

南水北调中线水源区农业面源污染防治对策研究

南水北调工程的成败在水质,农业面源污染是南水北调中线水源的主要污染源之一。近年来为了保护水源水质安全,水源区开工建设了一大批点源污染治理项目,但是对农业面源污染的重视和投入还很不够。北京市水源地延庆县在生态县的建设过程中,始终重视经济和生态协调发展,大力发展循环经济,在面源污染防治方面取得了巨大成就,为南水北调中线水源区生态环境保护树立了学习的榜样。建议国家和地方在南水北调水源区面源污染防治方面加大投入力度,加强基础设施和能力建设,确保南水北调中线水源水质长期稳定达标。     

永州市城市饮用水源区主要污染物总量控制研究

应用水质数学模型定量分析了永州市城市饮用水源区水污染物现状量，允许排污量及现状削减量。对该水域水质目标的实现和水资源保护管理提出相应的工程和非工程措施。     

Pareto Optimization of Water Resources Using the Nexus Approach

The continuously growing population in combination with the escalating urbanization and economic growth increase the pressure on water, energy and food resources of our planet. This entails an urgent need for proper water resources management within the water-energy-food (WEF) nexus concept. The WEF nexus considers water, energy and food as three continuously interconnected sectors, whose complex interactions lead to an increased number of trade-offs and potential conflicts. Computational modeling can be used to quantify these interactions, reduce trade-offs and promote synergies. We investigate the water resources in the Upper Blue Nile River (UBNR) basin, one of the two main sources of the Nile, using the Hydronomeas tool. Hydronomeas is based on the parameterization-simulation-optimization method; optimization is implemented in two levels, using a holistic approach and multiple criteria. We assign various targets, constraints and priorities to the UBNR system of reservoirs, hydropower plants and irrigation projects and derive a Pareto front that contains alternative, optimal solutions, for which improvement of one objective can be achieved only at the expense of another. By visualizing the trade-offs between the conflicting objectives of hydropower and irrigation, we aim to help decision makers understand changes due to different management policies and thus, achieve greater efficiency in water resources management in the Nile region.     

农村非点源污染特征及控制对策研究

为了解农村非点源污染的特征,以南京市远郊的汤山街道上峰社区李岗头村为典型村,采用污染排放系数法估算典型村的非点源排放负荷,并采用等标污染负荷法对典型村非点源污染源进行了评价。结果表明:李岗头村非点源污染源共向水体排放污染物36 263.58 kg/a,其中COD为29 110.04 kg/a、NH3-N为1 612.97 kg/a、TN为4 489.71 kg/a、TP为1 050.86 kg/a;生活污水、畜禽养殖、农田地表径流、水稻田排水、村镇地表径流、渔业养殖的等标污染负荷率分别为59.12%、13.68%、12.14%、7.10%、7.52%、0.44%;COD、NH3-N、TN、TP的等标污染负荷率分别为11.36%、12.59%、35.04%、41.01%。根据非点源污染的特征,提出了南京市农村非点源污染的控制对策。     

A Stochastic Optimization Approach in the Design of an Aquifer Remediation under Hydrogeologic Uncertainty

A stochastic optimization approach is presented for the remediation design of a contaminated aquifer with limited hydrogeologic information. Stochastic simulation using the Monte Carlo technique, produces a series of equally probable realisations of the spatially varying random hydraulic conductivity field. The stochastic flow and transport simulation model is coupled, using the response matrix approach, with a nonlinear optimization algorithm. The whole process is integrated into an algorithm which is effectively applied in the case study of the Kalamaria aquifer, Chalkidiki, Greece. The stochastic optimization procedure is followed by a reliability analysis, giving useful information to the decision makers concerning the effectiveness of the optimal results.     

Development of Design Hyetographs for Ungauged Sites Using an Approach Combining PCA,SOM and Kriging Methods

A design hyetograph represents the temporal distribution of rainfall intensity associated with a return period. The choice of the design hyetograph will have a significant influence on the shape and peak value of the hydrograph. Hence, the determination of design hyetographs is an important task in the hydrologic designs. In this paper, an approach is proposed to develop design hyetographs for ungauged sites. The proposed approach is composed of four steps: principal component analysis (PCA), self-organizing map (SOM)-based clustering, region delineation, and kriging-based construction. Firstly, PCA is applied to obtain the principal components of the design hyetographs. Then the transformed data resulting from PCA and the three geographic characters of the gauges are used as input data to the SOM, which is applied to group the rain gauges into specific clusters. Thirdly, the regions for these clusters are delineated and then the regions map is made. Finally, the design hyetographs for ungauged sites is constructed by using the kriging method. The proposed approach is applied to estimate the design hyetographs of ungauged sites in Taiwan. For comparison with the proposed approach, three other approaches are executed. Four gauges are treated as ungauged and the three approaches are used to construct the design hyetographs. The results show that accurate estimated design hyetographs can be obtained by the proposed approach. Cross-validation tests further have been performed to examine the stability and the accuracy of these approaches. Again, the results indicate that the proposed approach is more accurate and stable than the other approaches. Overall, the results demonstrate that the proposed approach is useful to develop design hyetographs for ungauged sites.     

嫩江齐齐哈尔江段污染物总量控制

以系统工程的理论和方法为指导，在分析嫩江齐齐哈尔江段水环境问题的基础上，对该江段水污染控制技术路线进行了全面研究，提出了水污染的总量控制方案及水污染综合整治实施目标。     

低水头船闸自动控制程序的优化设计

针对船闸输水孔一次开启出现的闸室浪涌现象，按照水位差把闸室状态分为五级，采用分级阀门控制方法对输水孔进行分级控制．从而大大减少了闸室浪涌的波动，保障闸室船只和人身的安全；在实际运行的过程中，取得了很好的效果。     

Optimal Management of Coastal Aquifers Using Linked Simulation Optimization Approach

Saltwater intrusion management models can be used to derive optimal and efficient management strategies for controlling saltwater intrusion in coastal aquifers. To obtain physically meaningful optimal management strategies, the physical processes involved need to be simulated while deriving the management strategies. The flow and transport processes involved in coastal aquifers are difficult to simulate especially when the density-dependent flow and transport processes need to be modeled. Incorporation of this simulation model within an optimization-based management model is very complex and difficult. However, as an alternative, it is possible to link a simulation model externally with an optimization-based management model. The GA-based optimization approach is especially suitable for externally linking the numerical simulation model within the optimization model. Further efficiency in computational procedure can be achieved for such a linked model, if the simulation process can be simplified by approximation, as very large number of iterations between the optimization and simulation model is generally necessary to evolve an optimal management strategy. A possible approach for approximating the simulation model is to use a trained Artificial Neural Network (ANN) as the approximate simulator. Therefore, an ANN model is trained as an approximator of the three dimensional density-dependent flow and transport processes in a coastal aquifer. A linked simulation – optimization model is then developed to link the trained ANN with the GA-based optimization model for solving saltwater management problems. The performance of the developed optimization model is evaluated using an illustrative study area. The evaluation results show the potential applicability of the developed methodology using a GA- and ANN-based linked optimization – simulation model for optimal management of coastal aquifer.