岷江流域径流变化趋势及水文情势变异研究

为探究水文变异法(RVA)评估流域下游河流水文情势变异情况的准确性,选取岷江流域为研究区域,首先还原高场站天然径流过程,采用Mann-Kendall非参数检验、Kendall秩次相关检验等方法分析得出岷江流域径流有显著下降趋势;然后采用RVA法分析现有梯级水库运行对岷江河流水文情势的影响程度,得出高场站整体水文指标改变度为高度;最后模拟双江口水库投运情景,预测高场站水文情势变异情况。结果表明,高场站汛期来水相比现状将减少、枯期来水相比现状将有所增加。     

基于IHA/RVA法的修水流域上游大型水库影响下的枯水变异研究

根据水文变异指标法及变化范围法(IHA/RVA),对江西修水流域上游两个大型水库启用日期差异进行组合,定量计算、分析了水利工程影响下的修水流域上游枯水流量的时序变异特征,探讨了水利工程建设前后导致的水文变异程度,揭示了对河流生态系统至关重要的低流量范围内多个枯水情势高改变度的存在,为水库生态调度与河流生态保护提供了有益的参考。     

变化范围法评估北江流域水文情势变化

通过分析北江石角站实测径流资料,应用变化范围法(RVA)评估北江流域水文情势变化.认为总体上属低改变度到中改变度阶段,个别指标达到高改变度;干支流径流式水库,其枯水期运行调度对北江流域水文情势影响较大,而汛期运行调度对水文情势影响较小;飞来峡水库运行对北江中下游水文情势的改变幅度不大,但个别水文改变指标(IHA)改变度较高,有必要进一步优化飞来峡水库调度方案,减轻对北江河流自然生态的破坏,把IHA改变度降至最低,实现人水和谐.     

三峡水库对长江中下游河流水文情势影响评估

运用Mann-Kendall法分析长江中下游河流水文变化特征,并应用生态水文指标变动范围法(RVA)综合分析了三峡水库蓄水对长江中下游河流生态水文指标改变程度及其生态效应。研究结果表明,1952年～2014年长江中下游年均流量呈现减少趋势,其中宜昌水文站减少趋势显著;长江中下游宜昌、汉口和大通水文站整体水文改变度属于中度改变,其中宜昌站和汉口站的整体水文改变度分别为61%和63%,接近于高度改变;三峡水库蓄水引起长江中下游河流水文情势发生了较大改变。     

基于RVA法的尼尔基水库下游水文变异分析

采用Mann-Kendall检验法对嫩江流域同盟(二)站年均流量进行突变性检验,采用RVA方法从河流水文情势指标和生态多样性指标两方面分析尼尔基水利枢纽运行对下游河流水文情势的影响。研究表明:尼尔基水库运行后,下游河流极值流量、低流量脉冲的频率及历时、径流涨、落水率次数和流量涨落逆转次数都发生了明显改变,尼尔基下游河流整体水文改变度为51%,为中度改变;受尼尔基水利工程建设的影响,下游河道内的生物多样性指数均值由水库运行前的24减小到水库运行后的18,生物多样性和生物量减少,生态系统呈现退化趋势。     

龙羊峡水库对坝下河段生态水文情势影响研究

选取1988—2016年黄河唐乃亥水文站逐日平均流量和龙羊峡水库逐日出库流量数据进行水文变化指标(IHA)计算,采用水文变化范围法(RVA)并结合水库运行特点及黄河上游生态特征,评估龙羊峡水库运行对其坝下河段水文情势的改变程度及生态影响。结果表明:龙羊峡水库的运行对其坝下河段水文情势的影响属于高度改变,河流整体水文情势改变度为68.31%;指标体系中1—3月、12月平均流量,年最大1、3、7 d平均流量,年最小7、30、90 d平均流量,最小流量发生时间,低流量发生次数及延时,流量改变率及频率等指标改变显著。     

基于IHA-RVA法金沙江下游生态水文情势评价

为了定量评价长江上游鱼类保护区河流生态水文情势的变化,选取金沙江下游屏山水文站(1956—2012年)逐日流量数据,采用Mann-Kendall法、累积距平法和滑动T检验法进行流量特征分析,并应用生态水文指标变化范围法(RVA)以及水文改变度法,综合评价了长江上游鱼类保护区河段生态水文情势变化及其对河流生物多样性的影响。结果表明:(1)屏山站年均流量总体呈现微弱增长趋势,突变年份出现在1997年,表明1997年以来气候变化和人类活动尤其是水电开发对长江上游水文影响加剧;(2)金沙江下游屏山站的整体水文改变度为51%左右,属于中度改变,其中流量下降率和逆转次数受影响最为明显;(3)水电工程建设一定程度上改变了长江上游河流生态水文情势,导致了长江上游鱼类数量减少。研究成果能够为长江上游河流生态保护以及开展水库生态调度提供参考。     

RVA/IHA法在万安水库下游水文情势变化的应用研究

水电工程的建设运行会对周边生态环境造成不同程度的影响.以江西省最大的赣江流域为例,根据栋背水文站实测径流资料计算各类别的水文改变指标（IHA）,结合变异范围法（RVA）,分析并评估万安水库建设运行对流域水文情势的影响.结果表明,万安水库施工运行后综合改变度为49.24%,属于中度改变.     

基于RVA法的沙颍河周口段水文情势评价

沙颍河周口闸的建成运行,使得下游河流水文情势发生较大改变,对其水生态系统结构功能产生了显著影响。为定量评价周口段的水文情势变化,选取周口水文站1951-2016年的日径流资料,采用RVA法评估水闸建成前后33个水文指标的改变度及其生态影响。结果表明:(1)1975年后,人类活动尤其是周口闸的运行对沙颍河干流水文情势影响加剧,月均流量均呈明显下降趋势,河道内多次出现断流情况;(2)周口站的整体水文改变度为42.23%,属于中度改变,其中11月月均流量、最小1d流量出现时间和流量下降率受到的影响最为强烈,为高度改变;(3)沙颍河流域水资源供需矛盾突出,水闸的运行调度对水生态系统的稳定性产生不利影响,迫切需要对沙颍河进行生态修复,对河流流量适时调整,实现区域经济和水生态系统协调发展。     

黑水河流域生态系统完整性评价

为评估黑水河流域受人为干扰的实际情况,依托流域范围内的基础地理、生物多样性、环境数据、其他威胁等调查资料,构建包含水文情势、水质、连通性、栖息地、生物群落5项关键属性的淡水生态系统完整性评价指标体系。通过变化范围法RVA、综合连通系数、栖息地比例相似PSI指数、入侵指标和捕捞指标等对黑水河流域生态系统完整性进行评价,黑水河流域水文情况属性现状为差、连通性属性现状为差、栖息地属性现状为差、生物群落属性现状为一般;河流水质现状较优,但黑水河支流存在一定富营养化风险,评估为一般。结果表明：流域生态系统完整性评价指标体系,应围绕淡水生态系统五大关键生态属性,并结合流域生态特征及生态现状来确定;RVA、综合连通系数、PSI 指数等的综合运用能够科学地确定指标阈值,进而正确进行流域生态完整性评价;受不同流域鱼类生态学习性差异等因素影响,还需通过长期监测不断完善评价理论和方法。     

Impact of Human Intervention and Climate Change on Natural Flow Regime

According to the ‘natural flow paradigm’, any departure from the natural flow condition will alter the river ecosystem. River flow regimes have been modified by anthropogenic interventions and climate change is further expected to affect the biotic interactions and the distribution of stream biota by altering streamflow. This study aims to evaluate the hydrologic alteration caused by dam construction and climatic changes in a mesoscale river basin, which is prone to both droughts and monsoonal floods. To analyse the natural flow regime, 15 years of observed streamflow (1950–1965) prior to dam construction is used. Future flow regime is simulated by a calibrated hydrological model Soil and Water Assessment Tool (SWAT), using ensemble of four high resolution (~25 km) Regional Climate Model (RCM) simulations for the near future (2021–2050) based on the SRES A1B scenario. Finally, to quantify the hydrological alterations of different flow characteristics, the Indicators of Hydrological Alteration (IHA) program based on the Range of Variability Approach (RVA) is used. This approach enables the assessment of ecologically sensitive streamflow parameters for the pre- and post-impact periods in the regions where availability of long-term ecological data is a limiting factor. Results indicate that flow variability has been significantly reduced due to dam construction with high flows being absorbed and pre-monsoon low flows being enhanced by the reservoir. Climate change alone may reduce high peak flows while a combination of dam and climate change may significantly reduce variability by affecting both high and low flows, thereby further disrupting the functioning of riverine ecosystems. We find that, in the Kangsabati River basin, influence of dam is greater than that of the climate change, thereby emphasizing the significance of direct human intervention.     

一种新的水文情势改变度综合估算法

基于 33 个水文改变指标,分别采用变化范围法、直方图匹配法、直方图比较法和修正变化范围法 4 种方法, 计算汉江中下游黄家港水文站的水文变异性,并对比分析各方法的优缺点。变化范围法忽略了水文指标在极值 和目标范围的具体变化;直方图匹配法和比较法考虑了水文指标在各范围的分布;修正变化范围法涵盖了形态变 化的概念。通过主客观组合赋权,融合直方图比较法和修正变化范围法的结果,提出一种新的综合估算法,既保 留水文情势的分布、频率和时空变化信息,又避免数据冗余。综合估算法结果表明：各月月均流量和极端流量大 小的改变度均为中度改变,分别为 41.28% 和 64.83%;流量增减变化率的改变度为高度改变（80.53%）;汉江中下游 水文情势的整体改变度为中度改变（55.70%）。该法可降低计算结果的不确定性,避免水文变异性结果出现异常, 从而更加合理可靠。     

基于RVA法的河流生态基流过程研究

针对我国目前生态需水量研究难以反映河流水文情势自然涨落变化的问题,从河流水文情势的整体角度出发,采用IHA法分析了金沙江上游岗托至巴塘河段的天然水文情势特征,得到了该河段各指标的RVA阈值范围。在总结前人研究的基础上,对计算河流生态基流量的RVA法进行了改进,提出非汛期、汛前期和汛后期采用RVA目标差值的75%推荐河流生态基流量,主汛期采用RVA目标差值的50%推荐河流生态基流量。采用改进的RVA法计算了金沙江上游巴塘断面的生态基流过程,得到巴塘断面各月的生态基流量分别为39.5 m~3/s、42.5 m~3/s、33.0 m~3/s、74.2 m~3/s、124.4m~3/s、259.3 m~3/s、394.0 m~3/s、581.0 m~3/s、493.5 m~3/s、259.7 m~3/s、131.1 m~3/s、71.0 m~3/s,占相应多年月均流量的比例范围为14.0%~32.9%,并与Tennant法的结果进行了对比分析。结果表明,该方法能够更好地反映金沙江上游天然河流水文情势的动态变化特征,可为金沙江上游水电开发生态保护提供技术参考。     

HYDROLOGIC MODIFICATION FROM HYDROELECTRIC POWER OPERATIONS IN A MOUNTAIN BASIN

The natural flow paradigm suggests that components of the natural streamflow regime and variability should be managed to maintain important ecosystem functions and services. Mountain rivers can exhibit extreme flow variability and provide critical aquatic habitat and ecosystem services but can be severely impacted by hydroelectric power (HEP) development and operations that will likely increase in the future. The hydrologic modification from HEP operations in the Upper San Joaquin River Basin, California, was evaluated across 15 river and stream locations throughout the basin. Flow modifications in Bear Creek, an otherwise unimpacted high‐elevation subbasin, were evaluated in detail using a number of hydrologic metrics, including Indicators of Hydrologic Alteration (IHA), environmental flow components of IHA, flow duration curves, ecodeficit and comparisons using equivalence testing. The uncertainty of the metrics based on confidence intervals was also evaluated for unimpaired (upstream) and existing (impaired or downstream) conditions. Results showed that metrics for median values changed considerably for most locations under impaired conditions, but the direction and extent of change varied depending on the location and flow metric. Metrics for variability (coefficients of dispersion) changed even more. Most metrics showed that flow modifications in Bear Creek were substantial, including decreases in high flows and increases in most low‐flow metrics. However, some flow variability metrics increased because of large flood flows during several years overwhelming and bypassing the dam/diversion structure. Uncertainty in metrics varied considerably throughout the basin but generally increased for impaired conditions. Uncertainty should be explicitly considered when evaluating hydrologic modification from HEP in mountain watersheds. A number of metrics should be used depending on objectives and spatial scale, including a subset of key IHA metrics across multiple sites and other methods to provide detailed information on flow modification in conjunction with other environmental flow assessment techniques at key locations. Copyright © 2011 John Wiley & Sons, Ltd.     

CLASSIFICATION OF FLOW REGIMES FOR ENVIRONMENTAL FLOW ASSESSMENT IN REGULATED RIVERS: THE HUAI RIVER BASIN,CHINA

Flow regime characteristics (magnitude, frequency, duration, seasonal timing and rates of change) play a primary role in regulating the biodiversity and ecological processes in rivers. River classification provides the foundation for comparing the hydrologic regimes of rivers and development of hydro‐ecological relationships to inform environmental flow management and river restoration. This paper presents a classification of natural flow regimes and hydrologic changes due to dams and floodgates in the Huai River Basin, China, in preparation for an environmental flow assessment. The monthly natural flow regime of 45 stations in the upper and middle Huai River Basin were simulated for the period 1963–2000, based on the hydrological model SWAT (Soil and Water Assessment Tool). Six classes of flow patterns (low or high discharge, stable or variable, perennial or intermittent, predictable or unpredictable) were identified based on 80 hydrologic metrics, analysed by hierarchical clustering algorithms. The ecologically relevant climatic and geographic characteristics of these flow classes were tested for concordance with, and to strengthen, the hydro‐ecological classification. The regulation of natural flow patterns by dams and floodgates changed flows at some locations within each flow class and caused some gauges to shift into another class. The research reported here is expected to provide a foundation for development of hydro‐ecological relationships and environmental flow methods for wider use in China, as well as setting a new scientific direction for integrated river basin management in the Huai River Basin. Copyright © 2011 John Wiley & Sons, Ltd.     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

长江中游水文情势变化及对鱼类的影响分析

为分析三峡水库蓄水后长江中游河道水文情势变化情况及其对鱼类产卵繁殖的影响,采用水文变化指标体系和变动范围法,对宜昌站水文情势变化进行了定量分析,得出了变化程度较为剧烈的水文参数。通过对照典型鱼类的历史产卵量与历史流量过程,归纳了典型鱼类四大家鱼的生态水文需求,得出了影响鱼类产卵繁殖的主要水文参数。提出了水文情势变化影响鱼类产卵繁殖过程的概念性模型。在分析的基础上,揭示了长江中游水文情势变化对鱼类产卵繁殖的影响。     

An Optimal Reservoir Operation Model Based on Ecological Requirement and Its Effect on Electricity Generation

Rather than optimizing water regimes for one or a few species, a better approach is to approximate the natural flow regime that maintains the entire panoply of species. RVA method generally describes flow regimes through 32 hydrologic indicators, quantifies the changes of the indicators post-dam, and distinguishes the highly changed indicators. Based on this function, an ecological objective which takes natural flow regimes into consideration is established. The objective synthesize highly changed indicators selected from the 32 hydrologic indicators and minimize their degree of change to approximate the natural status. The function of the hydrologic indicators are quantified through fuzziology according to their effect on river environment when changed. The model is applied to Xiangyang section of the Han River downstream the Danjiangkou reservoir, which maximizes the ecological objective to close to a natural flow regime. By optimization, model results indicate that the maximum synthetical membership of the selected indicators is 0.5, which means that the post-regulation optimum release is 50?% closer to the natural flow regime. It is much better than the traditional power generation regulation model, the membership of which is only 0.2. The result indicates that the ecological model is better in improving the river ecosystem, but with reduced power generation because of excessive abandon water. However, when deeply evaluate the effect of the new model, it shows the possibility of a win-win scenario between maintaining ecosystem health and power generation.     

Determining the effects of dams on subdaily variation in river flows at a whole‐basin scale

River regulation can alter the frequency and magnitude of subdaily flow variations causing major impacts on ecological structure and function. We developed an approach to quantify subdaily flow variation for multiple sites across a large watershed to assess the potential impacts of different dam operations (flood control, run‐of‐river hydropower and peaking hydropower) on natural communities. We used hourly flow data over a 9‐year period from 30 stream gages throughout the Connecticut River basin to calculate four metrics of subdaily flow variation and to compare sites downstream of dams with unregulated sites. Our objectives were to (1) determine the temporal scale of data needed to characterize subdaily variability; (2) compare the frequency of days with high subdaily flow variation downstream of dams and unregulated sites; (3) analyse the magnitude of subdaily variation at all sites and (4) identify individual sites that had subdaily variation significantly higher than unregulated locations. We found that estimates of flow variability based on daily mean flow data were not sufficient to characterize subdaily flow patterns. Alteration of subdaily flows was evident in the number of days natural ranges of variability were exceeded, rather than in the magnitude of subdaily variation, suggesting that all rivers may exhibit highly variable subdaily flows, but altered rivers exhibit this variability more frequently. Peaking hydropower facilities had the most highly altered subdaily flows; however, we observed significantly altered ranges of subdaily variability downstream of some flood‐control and run‐of‐river hydropower dams. Our analysis can be used to identify situations where dam operating procedures could be modified to reduce the level of hydrologic alteration. Copyright © 2009 John Wiley & Sons, Ltd.