论水库工程之管运洪水

鉴于水库工程管理运用的重要性,提出管运洪水的新概念,并和设计洪水做了全面对比,指出二者异同。在此基础上提出了评判管运洪水是否合理的两个通用准则:条件合乎要求和防洪安全达标。将推求管运洪水的方法分为两大类:一类以分期内洪水最大值为依据,另一类以年最大值为依据。这两类方法本质不同,使用时各有优缺点。第一类方法的结果不完全符合现行标准的要求,而第二类方法的结果符合要求,但对资料条件要求较高。     

A GIS enabled nested simulation-optimization model for routing groundwater to overcome spatio-temporal water supply and demand disconnects in South Texas

Groundwater, under sustainable management policies, can be an invaluable source of water to municipal, agricultural, and industrial sectors. Management, however, can be challenging given that historically, these resources have been privately owned and minimally regulated. This research details the development of a decision support system (DSS) which couples a GIS-based multi-criteria decision-making (MCDM) scheme with simulation-optimization routines to identify suitable regions for groundwater development and optimal preferences for apportioning those supplies to areas of demand in South Texas. The developed DSS consisted of three modules: (1) a GIS-based MCDM for identifying suitable locations for groundwater production; (2) a simulation-optimization model for estimating available groundwater; and (3) a transportation optimization model for redistributing the groundwater. Applying a comprehensive suite of nine exclusionary criteria in GIS resulted in only 15,304 km² (5,909 mi²) suitable for groundwater production out of the original ~50,500 km² (19,500 mi²). Two ideal sites were selected in the suitable region based on proposed major water supply projects in the study area. The projected groundwater extraction rates per month varied considerably over a year emphasizing a need for storage technologies. Furthermore, a transportation optimization model, which considered cost of storage and movement, was developed and applied to obtain the most optimal scheme to transport groundwater from potential supply centers located in Bee and Kennedy counties to projected water deficit areas of San Antonio, Laredo, and McAllen, TX, USA. Lastly, a full-factorial sensitivity analysis was carried out to check the impacts of the supply and demand factors on groundwater production and transport. Policies at the supply centers had a larger impact on the total availability of water, and policies at the demand centers had a larger impact on the total cost of the management scheme. Furthermore, an analysis of total volume stored in a storage and recovery system exhibited an inverse relationship with the groundwater development (supply side) policies and a direct relationship with the demand requirements. The developed DSS proved useful for determining the most optimal siting and distribution network for groundwater sources in South Texas.     

控制海水入侵的地下水多目标模拟优化管理模型

为实现滨海含水层地下水开采-回灌方案优化、控制海水入侵面积和降低海水入侵损失等多重管理目标,建立了海水入侵条件下地下水多目标模拟优化管理模型SWT-NPTSGA。模拟模型采用基于变密度流的数值模拟程序SEAWAT来模拟海水入侵过程。优化模型采用小生境Pareto禁忌遗传混合算法NPTSGA来求解,该算法在保证多目标权衡解的收敛性和计算效率的前提下,能维护整个进化群体的全局多样性。将SWT-NPTSGA程序应用于一个理想滨海含水层地下水开采方案和人工回灌控制海水入侵的优化设计中,结果表明该管理模型能够同时处理最大化总抽水流量、最小化人工回灌总量和最小化海水入侵范围等3个目标函数之间的权衡关系。通过采用人工回灌海水入侵区的减灾策略,既能增加滨海地区的供水量,又可减少海水入侵的范围,由此进一步验证了模型的有效性和可靠性。     

基于栖息地突变分析的春汛期生态需水阈值模型

根据春汛期水生态系统的特点,应用河道内流量增量法,选用二维河流模型River2D,建立栖息地与流量变化的动态关系,进而应用Mann-Kendall方法,开发基于栖息地突变分析的生态需水阈值模型。以第二松花江支流辉发河五道沟断面附近河段为例,选择松花江流域分布较为广泛的鲤鱼作为对象物种,以流速和水深两个因素表征鱼类栖息地,利用1956～2000年45年的春汛期月径流资料,判定鱼类栖息地在1970年开始发生了突变。在突变前加权可用面积95%的置信区间范围为275.5～915.7m2/km,对应的流量范围为58.8～121.1m3/s,并将其作为研究区春汛期间的生态需水阈值。春汛发生在冰封期刚刚结束的时段,适宜的春汛期生态需水能够提高生态系统多样性,对于鱼类等水生生物乃至于整个生态系统都有重要的生态意义。     

梯级水库设计洪水最可能地区组成法计算通式

利用Copula函数建立各分区洪水的联合分布,基于联合概率密度最大原则,推导得到最可能地区组成法的计算通式,并用来推求梯级水库下游断面的设计洪水。选择清江流域水布垭-隔河岩-高坝洲梯级水库为例,开展了验证和方法比较研究。结果表明:最可能地区组成法计算得到的设计洪水值位于同频率地区组成法多方案计算结果的区间之内;受清江梯级水库调洪的影响,宜都断面设计洪水的削峰率十分显著,最可能地区组成法推求100年一遇设计洪水的削峰率达到30.2%。该法具有较强的统计基础,组成方案唯一,结果合理可行,为复杂梯级水库设计洪水的计算提供了一种新途径。     

Assessment of ecological flow rate by flow duration and environmental management class in the Geum River, Korea

This study attempted to analyze flow duration in a basin using a method to estimate environmental flow developed by the International Water Management Institute, and simulate the effects of runoff characteristics unique to a river and flow variability due to basin developments on aquatic ecosystems. To do so, KModSim, a simulation model for basin-wide water distribution, was used to assess flow duration in the Geum River basin, one of the four major river basins in Korea, by environmental management class (EMC). Flow duration curves by EMC at Sutong and Gongju sites were derived on the basis of natural flow in the Geum River basin. As a result, they were found to be consistent with the results of previous studies. Time series of mean monthly flow data by EMC were plotted together with those of simulated flow data by reservoir operation scenario; Sutong and Gongju points both showed flow behaviors corresponding almost to “A” in EMC. In addition, the characteristics of habitats by species of fish were identified through monitoring fish habitat at the Sutong site, so that optimal ecological flow rate was estimated. For this purpose, relations between flow discharge and weighted usable area for Coreoleuciscus splendidus and Pseudopungtungia nigra were projected using physical habitat simulation system, and EMCs consistent with flow duration curves (estimated taking in-stream flow) were assessed. The results or findings reported in this study are expected to serve as basic data for making a plan to efficiently monitor and manage aquatic ecosystems in the Geum River basin.     

Groundwater flow system in Bengal Delta,Bangladesh revealed by environmental isotopes

A total number of 328 groundwater samples are analysed to evaluate the groundwater flow systems in Bengal Delta aquifers, Bangladesh using environmental isotope (²H, ¹⁸O, ¹³C, ³H, and ¹⁴C) techniques. A well-defined Local Meteoric Water Line (LMWL) δ²H = 7.7 δ¹⁸O + 10.7 ‰ is constructed applying linear correlation analyses to the monthly weighted rainfall isotopic compositions (δ¹⁸O and δ²H). The δ¹⁸O and δ²H concentrations of all groundwater samples in the study area are plotted more or less over the LMWL, which provides compelling evidence that all groundwaters are derived from rainfall and floodwater with a minor localized evaporation effects for the shallow groundwaters. Tritium concentration is observed in 40 samples out of 41 with values varying between 0.3 and 5.0 TU, which represents an evidence of young water recharge to the shallow and intermediate aquifers. A decreasing trend of ¹⁴C activity is associated with the heavier δ¹³C values, which indicates the presence of geochemical reactions affecting the ¹⁴C concentration along the groundwater flow system. Both vertical and lateral decrease of ¹⁴C activity toward down gradient show the presence of regional groundwater flow commencing from the unconfined aquifers, which discharges along the coastal regions. Finally, shallow, intermediate, and deep groundwater flow dynamics has revealed in the Bengal Delta aquifers, Bangladesh.     

Integrated application of the analytic hierarchy process and the geographic information system for flood risk assessment and flood plain management in Taiwan

Flooding is one of the major natural hazards in Taiwan, and most of the low-lying areas in Taiwan are flood-prone areas. In order to minimize loss of life and economic losses, a detailed and comprehensive decision-making tool is necessary for both flood control planning and emergency service operations. The objectives of this research were (i) to develop a hierarchical structure through the analytic hierarchy process (AHP) to provide preferred options for flood risk analysis, (ii) to map the relative flood risk using the geographic information system (GIS), and (iii) to integrate these two methodologies and apply them to one urban and one semi-rural area in central Taiwan. Fushin Township and the floodplain of Fazih River (1 km on either side of the channel) in Taichung City were selected for this study. In this paper, the flood risk is defined as the relative flood risk due to broken dikes or the failure of stormwater drainage systems. Seven factors were considered in relation to the failure of stormwater drainage, and five to that of broken dikes. Following well-defined procedures, flood maps were drawn based on the data collected from expert responses to a questionnaire, the field survey, satellite images, and documents from flood management agencies. The relative values of flood risk are presented using a 200-m grid for the two study areas. It is concluded that integration of AHP and GIS in flood risk assessment can provide useful detailed information for flood risk management, and the method can be easily applied to most areas in Taiwan where required data sets are readily available.     

防汛会商系统集成化管理研究及应用

分析总结了目前防汛会商系统在集成管理及其应用方面存在的主要问题,提出了防汛会商系统集成化管理的设计思想,研究了其体系结构,指出了采用的新技术,从而形成了防汛会商系统集成化管理的总体设计方案.通过理论研究,设计和开发了防汛会商系统集成化管理的模板.基于该设计方案而建立的防汛会商系统,在会商模板对防洪信息的有效管理下,高度集成了各种雨情、水情、工情、灾情、险情等防洪信息和知识,对当前防汛形势和决策问题进行分析和总结;通过会商平台将面向防汛决策热点的主题信息,形象、直观、全面、实时地呈现到会商现场,辅助决策者进行防洪调度决策.该研究成果已应用到黑龙江省防汛会商系统中,并取得了良好的应用效果.     

A new model for flow in shale-gas reservoirs including natural and hydraulic fractures

In this work, we construct a new coupled Multiscale/Discrete Fracture Model for compressible flow in a multiporosity shale gas reservoir containing networks of natural and hydraulic fractures. The geological formation is characterized by four distinct length scales and levels of porosity. The window of observation of the finest (nanoscale) portraits the nanopores within organic matter containing adsorbed gas. At the microscale, the medium is formed by two solid phases: organic, composed by kerogen aggregates, and inorganic (clay, quartz, calcite). Such phases are separated by the network of partially-saturated interparticle pores where microscopic free gas flow influenced by Knudsen effects along with gas diffusion in the immobile water phase occur simultaneously. The upscaling of the local flow to the mesoscale gives rise to a nonlinear homogenized pressure equation in the shale matrix which lies adjacent to the system of natural fractures. Homogenization of the coupled matrix/preexisting fractures to the macroscale leads to a microstructural model of dual porosity type. Such homogenized model is subsequently coupled with the hydrodynamics in the network of induced fractures which, in the context of the discrete fracture modeling, are treated as (n ? 1), (n = 2, 3) lower dimensional objects. In order to handle numerically the nonlinear interaction between the different flow equations, we adopt a superposition argument, firstly proposed by Arbogast (1996), in each iteration of a fixed-point algorithm. The resultant governing equations are discretized by the finite element method and numerical simulations of gas production in stratified arrangements of the fracture networks are presented to illustrate the potential of the multiscale approach.     

A real-time operation optimization model for flood management in river-reservoir systems

In this paper, a new methodology has been developed for real-time flood management in river-reservoir systems. This methodology is based upon combining a Genetic Algorithm (GA) reservoir operation optimization model for a cascade of two reservoirs, a hydraulic-based flood routing simulation model in downstream river system, a Geographical Information System (GIS) based database, and application of K-Nearest Neighbor (K-NN) algorithm for development of optimal operating rules. The GA optimization model estimates the optimal hourly reservoirs’ releases to minimize the flood damages in the downstream river. GIS tools have also been used for specifying different land-uses and damage functions in the downstream floodplain and it has been linked to the unsteady module of HEC-RAS flood routing model using Hec-GeoRAS module. An innovative approach has also been developed using K-NN algorithm to formulate the optimal operating rules for a system of two cascade reservoirs based on optimal releases obtained from the optimization model. During a flood event, the K-NN algorithm searches through the historical flood hydrographs and optimal reservoir storages determined by the optimization model to find similar situations. The similarity between the hydrographs is quantified based on the slopes of rising and falling limbs of inflow hydrographs and reservoir storages at the beginning of each hourly time step during the flood events for two cascade reservoirs. The developed methodology have been applied to the Bakhtiari and Dez River-Reservoir systems in southwest of Iran. The results show that the proposed models can be effectively used for flood management and real-time operation of cascade river-reservoir systems.     

Inactive supply wells as conduits for flow and contaminant migration: conditions of occurrence and suggestions for management

Water supply wells can act as conduits for vertical flow and contaminant migration between water-bearing strata under common hydrogeologic and well construction conditions. While recognized by some for decades, there is little published data on the magnitude of flows and extent of resulting water quality impacts. Consequently, the issue may not be acknowledged widely enough and the need for better management persists. This is especially true for unconsolidated alluvial groundwater basins that are hydrologically stressed by agricultural activities. Theoretical and practical considerations indicate that significant water volumes can migrate vertically through wells. The flow is often downward, with shallow groundwater, usually poorer in quality, migrating through conduit wells to degrade deeper water quality. Field data from locations in California, USA, are presented in combination with modeling results to illustrate both the prevalence of conditions conducive to intraborehole flow and the resulting impacts to water quality. Suggestions for management of planned wells include better enforcement of current regulations and more detailed consideration of hydrogeologic conditions during design and installation. A potentially greater management challenge is presented by the large number of existing wells. Monitoring for evidence of conduit flow and solute transport in areas of high well density is recommended to identify wells that pose greater risks to water quality. Conduit wells that are discovered may be addressed through approaches that include structural modification and changes in operations.     

Monitoring system for environmental risk management of a landfill disposal site

A landfill disposal site can be described as “an artificial vessel” and must satisfy the following three demands (1) storage and disposal of waste; (2) protection of the environment; and (3) benefit for nearby residents by taking advantage of consequential effects. The concept of risk was effectively considered to emphasize the importance of monitoring systems in landfill disposal sites, especially to protect the environment. Because a part of the R&D was involved in creating a monitoring system for a landfill disposal site, the present development and future potential of a system which can detect the leakage of watershield sheets, was discussed.     

Use of documentary sources on past flood events for flood risk management and land planning

The knowledge of past catastrophic events can improve flood risk mitigation policy, with a better awareness against risk. As such historical information is usually available in Europe for the past five centuries, historians are able to understand how past society dealt with flood risk, and hydrologists can include information on past floods into an adapted probabilistic framework. In France, Flood Risk Mitigation Maps are based either on the largest historical known flood event or on the 100-year flood event if it is greater. Two actions can be suggested in terms of promoting the use of historical information for flood risk management: (1) the development of a regional flood data base, with both historical and current data, in order to get a good feedback on recent events and to improve the flood risk education and awareness; (2) the commitment to keep a persistent/perennial management of a reference network of hydrometeorological observations for climate change studies.     

The ebb and flow of power: British flood risk management and the politics of scale

This paper examines the rescaling of flood risk management (FRM) in Britain over the past 70+ years. Drawing on recent research in geography and elsewhere – which has engaged the politics of scale literature with the rescaling of water and environmental governance – we seek to illustrate the mis-match between the rescaling of the geographical unit of management and the nexus of power and control of those engaged in FRM. For those seeking positive examples of multi-level decentralised governance in water resource management, where power is shared across the spatial scales, our historical analysis struggles to find evidence. Rather, despite attempts to ‘hollow-out’ the state through the scaling ‘out’ and ‘down’ of FRM responsibilities, our evidence suggests that the control over key decision-making tools, resources and other modalities of power remains in the hands of a few key national-level decision-makers; it is the responsibility that has been decentralised, not least to those at risk of flooding. The application of the politics of scale theorising in a FRM context is innovative and, importantly, our case study demonstrates that such politics does not have to involve open conflict but is much more subtle in its deployment of power.