基于湿周法的河道最小生态需水量多目标评价模型

以湿周与流量关系为基础,建立了基于多目标评价方法的河道最小生态需水量估算模型,以湿周最大和河道流量最小作为栖息地保护和水资源开发利用的目标,采用理想点法求解,以增江下游麒麟咀站为例计算河道最小生态需水量,并将该模型的计算结果与斜率法和曲率法的计算结果进行了比较分析。结果表明:增江下游河道最小生态需水量阈值范围为20.8～26.3 m3/s,相应的平均流速范围为0.42～0.44 m/s;模型计算结果比传统的湿周法适用性更强,且能较好体现生态用水和经济用水的均衡发展。     

确定河流生态流量的几种湿周法比较

为比较不同湿周法在计算河流生态流量中的适用性,采用幂函数描述无量纲化的湿周～流量关系,利用曲率法、斜率法及多目标评价法中的线性加权和法、理想点法(尺度系数r分别取1,2,∞)、乘除法等7种方法计算河流生态流量。结果表明:曲率法的结果偏小;斜率法、理想点法(r=1)、线性加权和法的结果相同,且位于各方法的中间;另外3种多目标评价方法得到的河流生态流量大于斜率法等的结果,但湿周的增加比例明显小于流量增加比例。在湿周～流量关系符合幂函数关系时,利用斜率法或理想点法(r=1)、线性加权和法确定河流生态流量的方法是适宜的。     

Refinement of the wetted perimeter breakpoint method for setting cease‐to‐pump limits or minimum environmental flows

Analysis of inflections or breakpoints apparent in relationships between measures of wetted perimeter and discharge can be used to assist in the determination of minimum environmental flows for perennial rivers. This paper suggests refinements and provides an example application of the wetted perimeter method for the determination of cease‐to‐pump limits in a perennial, unregulated gravel‐bed river subject to increasing levels of surface water extraction. HEC‐GeoRAS modelling outputs of riffle wetted area are used to illustrate that the magnitude of the discharge selected to represent 100% habitat availability is of crucial importance to the breakpoint method. Because of the dependence of the technique on this assumption, we suggest that it is prudent to use an upper and lower limiting discharge based on an assessment of the degree of flow variability to develop a flow range around the zone of diminishing return in the wetted perimeter to discharge relationship. For rivers exhibiting a low degree of flow variability, the mean and median daily flows are likely to provide appropriate discharges for representation of 100% habitat availability. For perennial rivers with a higher degree of flow variability and considerable differences between the mean and median daily flows we suggest use of the 50th and 80th flow duration percentiles. Wetted perimeter breakpoint results are also influenced by the degree to which areas of non‐riffle habitat are included in the analysis. Inclusion of excessive pool areas can lead to significant reductions in resultant recommendations for cease‐to‐pump limits or minimum environmental flows. Integration of hydraulic model outputs with GIS for wetted perimeter analysis of riffles provides a useful, rapid, field‐based approach that can assist with determination of cease‐to‐pump limits or minimum environmental flows in gravel‐bed rivers. However, care is needed in its application and interpretation as the technique is prone to numerous subjective choices that have a substantial influence on results. Copyright © 2004 John Wiley & Sons, Ltd.     

基于改进湿周法的贾鲁河河道内生态需水量计算

针对贾鲁河实际情况,选取中牟和扶沟水文站作为控制断面,利用斜率法、曲率法和多目标评价法3种改进湿周法计算分析贾鲁河不同频率年河道内生态需水量。结果表明,采用多目标评价法(r=2)计算结果最大,曲率法最小,中牟断面用多目标评价法(r=2)计算生态需水量较为合理,扶沟断面用斜率法计算生态需水量较为合理。     

河流最小生态基础流量计算方法研究

为了能够计算几何断面复杂、泥沙淤积、河宽大、水深浅的河道生态基础流量,本文以渭河关中地区的生态基础流量计算为例,通过综合水力学中的湿周法和R2CROSS法建立了一套简单、适合管理的最小生态基础流量方法——综合法。该方法计算出的5个站的生态基础流量占多年平均流量的比值都在10.8%～14.9%之间,满足生态基流的合理要求。通过与Tennant方法比较,结果表明:综合法计算确定的生态基础流量更为合理、是一种在管理上更值得推广应用的方法。     

Use of multi‐criteria decision‐making for selecting spillway type and optimizing dimensions by applying the harmony search algorithm: Qeshlagh Dam Case Study

Economic considerations are significantly important in designing a dam and its related hydraulic structures. Considering the methods used for economic design of hydraulic structures such as a spillway, they are also dependent on the construction costs of the spillway. In addition to the spillway type and capacity being associated with the magnitude of floods. Selecting different options of a spillway, considering all their aspects, has always been one of the biggest issues in decision‐making. The present study determined the best spillway type (free‐flow, stepped, semicircular and cylindrical) for Qeshlagh Dam, Iran, by considering different aspects (costs, time and performance) and using the TOPSIS method. The obtained dimensions of the spillway from multi‐criteria decision‐making were then optimized using meta‐heuristic Harmony Search Algorithm (HSA). The results identified a free‐flow spillway was the best option in terms of cost and time, whereas a cylindrical spillway is the best choice in terms of performance. The optimal free‐flow spillway length is 31.8 m, and height is 3.45 m, being capable of passing a flood discharge of 452 m³/s. This discharge was calculated by a reservoir routing method. Moreover, the obtained solution led to reducing the spillway construction costs, one of the most important issues in civil engineering projects.     

Bayesian network models for environmental flow decision‐making: 1. Latrobe River Australia

Current methods underpinning environmental flow (eFlow) decisions often lack transparency, do not adequately consider uncertainties and rarely include adaptive management principles. We report the development and application of an eFlow Bayesian Network (BN) model that links four flow components with an ecological model to predict the spawning and recruitment of two important native fish species, the Australian Grayling and River Blackfish, in the highly regulated and flow‐stressed lower Latrobe River in Victoria, Australia. Autumn high flows, in conjunction with low stream temperature, are critical for Grayling spawning. The BN model was used to predict the probability of spawning and recruitment of these two native fish species for four flow scenarios. Quantitative data, flow simulation models and expert judgement were used to parameterize the BN model. The model results showed clearly that currently, and into the future, there is a very low likelihood of spawning and recruitment of Australian Grayling in the lower Latrobe. River Blackfish are minimally affected by the predicted reductions in flow and increased stream temperatures. Management scenarios aimed at modifying flows and stream temperatures to increase the likelihood of successful spawning and recruitment of Australian Grayling were assessed. Self‐sustaining populations of Australian Grayling could conceivably be achieved in the upper reaches of this river if fish passage was provided through an on‐stream reservoir. A major benefit in building and applying an eFlow BN model is that it can facilitate meaningful analysis and discussion of the ecological effects of particular eFlow regimes. Copyright © 2010 John Wiley & Sons, Ltd.     

引水式电站减水河段最小生态需水量模型研究

为了保护引水式水电站大坝与厂房之间减水河段的生态环境,需要确定河道最小生态需水量,以反映河道特征的差异.以湖南省一些典型引水式水电站下游减水河段为例,应用改进的湿周法计算了河道最小生态需水量,并通过单变量影响分析,研究河道最小生态需水量的影响因素;以幂函数对最小生态需水量与各单变量的关系进行了拟合分析,得到了合适的最小...     

An Objective Method to Prioritize Socio‐Environmental Water Management Tradeoffs Using Multi‐Criteria Decision Analysis

Rivers provide many social and environmental services that benefit humanity. A critical role of water mangers is to prioritize water allocation options that trade off socio‐economic and hydro‐ecological benefits in rivers. Methods for multi‐criteria decision analysis (MCDA) provide a structured and systematic manner for researchers to aid in this process. In this paper, we describe a new MCDA method that prioritizes large multi‐dimensional sets of tradeoffs to support well‐informed water management in rivers. The method was developed based on an environmental flows planning study in the Goulburn‐Broken River catchment, Victoria, Australia. A combined simulation and heuristic optimization procedure was previously integrated into a hydrological catchment network model. That process resulted in a large set of viable daily water allocation schedules that traded off long‐term irrigation and hydro‐ecological benefits at the catchment outlet. We provided new guidance procedures to identify priority tradeoffs that can be used in stakeholder deliberations and catchment decision‐making. Our MCDA method included combined multi‐dimensional ordination and cluster analysis to spread the water allocation alternatives onto a two‐dimensional plane to discover alternatives with similar criteria tradeoffs. A geometric distance‐based method was performed on the full set of alternatives and on the identified clusters to rank the alternatives in accordance with minimizing the distance of the alternatives to an ideal but non‐feasible reference point in multi‐dimensional space. This method complements the use of elicitation procedures when water manager or other stakeholder interaction is not an option or when objectivity is desired. Copyright © 2016 John Wiley & Sons, Ltd.     

A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications

The science and practice of environmental flows have advanced significantly over the last several decades. Most environmental flow approaches require quantifying the relationships between hydrologic change and biologic response, but this can be challenging to determine and implement due to high data requirements, limited transferability, and the abundance of hydrologic metrics available for evaluation. We suggest that a functional flows approach, focusing on elements of the natural flow regime known to sustain important ecosystem processes, offers a pathway for linking understanding of ecosystem processes with discrete, quantifiable measures of the flow regime for a broad range of native taxa and assemblages. Functional flow components can be identified as distinct aspects of the annual hydrograph that support key biophysical processes, such as wet season flood flows or spring recession flows, and then quantified by flow metrics, such as 5% exceedance flow or daily percent decrease in flow, respectively. By selecting a discrete set of flow metrics that measure key functional flow components, the spatial and temporal complexity of flow regimes can be managed in a holistic manner supportive of multiple ecological processes and native aquatic species requirements. We provide an overview of the functional flows approach to selecting a defined set of flow metrics and illustrate its application in two seasonally variable stream systems. We further discuss how a functional flows approach can be utilized as a conceptual model both within and outside of existing environmental flow frameworks to guide consideration of ecological processes when designing prescribed flow regimes.     

Contribution to decision‐making on establishing the maximum water level for Lake Vegoritida

The water level in Lake Vegoritida, Greece, has undergone great changes over the past decades attributable to severe water abstraction directly from the lake and its catchment, which affected not only the conditions of the natural environment, but also social and economic conditions. The water level of the lake is currently rising, with discussion of an agreeable decision about the desired maximum lake water level becoming a source of conflict among the lake stakeholders. The present study provides a framework for a participatory management plan, with the perspective of engaging all levels of lake stakeholders in the process of deciding and establishing the maximum lake water level. Kolb's learning cycle is used as a methodological vehicle in the proposed process of participatory decision‐making. Its contribution to decision‐making includes (a) identification of lake stakeholders and the issues arising from a potential establishment of a maximum lake water level; and (b) three suggested water level scenarios to facilitate a future constructive discussion directed to establishing a maximum water level in Lake Vegoritida.     

Tradeoffs associated with sediment‐maintenance flushing flows: a simulation approach to exploring non‐inferior options

Sediment‐maintenance flushing flows designed to mimic the action of natural floods in removing the accumulated fine sediments from the channel and loosening the gravel bed have been increasingly proposed as an effective alternative in dam management and a required component of riverine restoration programmes. However, reservoir releases are generally associated with financial and environmental costs, thus it is highly desirable to specify flushing flows as accurately as possible. In this paper we present a simulation approach to evaluating flushing flows and exploring the tradeoffs associated with non‐inferior flushing options. A two‐fraction sediment routing model is used to simulate the gravel‐sand bed response to flushing flows. The results reveal that the sand cleansing effect propagates from upstream to downstream and from surface to subsurface. Under a steady gravel supply from upstream, an equilibrium state of gravel transport and bed degradation is eventually reached in the simulation reach. The flushing flow and sediment transport system investigated in this study involves a transient state variable (bed sand content), a decision variable (flushing flow discharge), a flushing goal (ultimate bed sand content), and three outcomes to be minimized (flushing duration, released water volume, and total gravel loss). A series of numerical simulations are carried out with a range of flows and pre‐flushing bed sediment conditions. The results reveal that the flushing efficiency is higher for the larger flow. However, for flows greater than ～100 m³/s the flushing duration is less sensitive to the flow discharge, thus the system may be simplified as a bi‐objective one. The gravel loss and water volume are two conflicting outcomes within the non‐inferior flow region. Under a worse bed sediment condition, the feasible flushing options are constrained in a narrower range and also associated with higher costs. The tradeoffs between the conflicting outcomes are quantitatively displayed with the transformed feasible solutions in the objective space. We provide here a general and practical approach permitting a quantitative evaluation of the different flushing options that is appropriate to the level of data typically available. Copyright © 2004 John Wiley & Sons, Ltd.     

A hydrogeomorphic dynamics approach to assess in‐stream ecological functionality using the functional flows model,part 1—model characteristics

The functional flows model integrates hydrogeomorphic processes and ecological functions for stream physical habitat evaluations. Functional flows are discharge values that serve ecological uses. Assessments of functional flows are based on evaluation of shear stress dynamics. The analysis is based on the occurrence of sediment transport regimes defined by threshold values of Shields stress estimated from discharge (Q), a parameter (f) governing depth response to incremental discharge changes, water surface slope (S) and media grain size (D₅₀). As an example, the model was tuned for fall‐run Chinook salmon spawning. Ecological functions studied were bed occupation (spawning, incubation and emergence) and bed preparation (river bed reworking periods)—both reliant on shear stress dynamics. A numerical experiment and sensitivity analysis using a wide range of realistic values of input variables indicated the effect of each variable on flow functionality. Combinations of S = 0.001, 0.005 and 0.01, D₅₀ = 0.02, 0.05, 0.1 m, f = 0.2, 0.3, 0.4, 0.5 and four sediment transport stages produced 144 scenarios. Ranges of functional flows were greater for scenarios for low f (0.2) with low slope (0.001,0.05), for high f (0.5) with small grain size (0.02 m) and for intermediate low f (0.3) with coarse grain size (0.1 m). The functional flows model incorporates in‐stream habitat processes by including metrics of hydrologic, hydraulic, geomorphic and ecologic dynamics. Model uncertainties related to input data, calculation algorithms, and model structure are analysed. Functional flows analysis can be useful in studying water management alternatives to improve habitat conditions for target species and lifestages. Copyright © 2009 John Wiley & Sons, Ltd.