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。     

A dynamic corridor‐searching algorithm to seek time‐varying instream flow releases for optimal weir operation: comparing three indices of overall hydrologic alteration

A full range of natural flow regime has been widely recognized as a primary driving force for sustaining the integrity of a riverine ecosystem. Existing instream flow methods strive to assure a constant minimum flow but not the natural flow variability. We present in this paper a dynamic corridor‐searching algorithm to seek the optimal time‐varying scheme for instream flow releases. A compromise programming (CP) is employed to search the optimal solution of an objective function aggregating the ecosystem and human needs objectives. The ecosystem need objective is represented by an overall index of hydrologic alteration, which integrates 32 indicators of hydrologic alteration (IHA) derived from the range of variability approach (RVA). The human need objectives are expressed by shortage ratios for the agricultural and municipal water supplies. The proposed method is applied to a weir operation in Taiwan. Three approaches to evaluating the overall degree of hydrologic alteration (i.e., the three‐class, fuzzy‐based, and overall‐mean approaches) are compared here. The results show that the time‐varying schemes improve the human need objective, but only slightly deteriorate the ecosystem need objective. Such advantages increase with the time‐varying frequency. For the wet periods, smaller flow releases may be prescribed; for the dry periods, however, greater releases must be specified to secure a lower degree of overall hydrologic alteration. It is also revealed that use of the three‐class approach to evaluate the overall hydrologic alteration facilitates to eliminate highly altered IHA and maintain those low‐flow characteristics subtle to flow diversions. However, such outcomes are achieved at the cost of greater deficits for human water demands. Copyright © 2007 John Wiley & Sons, Ltd.     

Determining the Ecological Flow Regime for Existing Reservoir Operation

Maintaining the natural variability of a river’s flow regime is one of the most critical strategies sustaining the ecological integrity of aquatic ecosystems. This research seeks to determine the ecological flow regime for management of streamflow existing reservoirs. The ecological flow regime is a human-modified flow regime that captures the natural flow variability for maintaining the structure and the functional integrity of the aquatic ecosystems. The design procedure uses regionalization analysis, the ratio method, and linear regression analysis techniques with hydrologic indicators to simulate the altered flow variability caused by human-based annual streamflow reduction. Because it is difficult for reservoir operators to achieve the strict standard of natural flow regime, a discontinuity ratio method is used to express the reservoir’s expected effect on the change in hydrologic indicator values. The final product of the ecological flow regime analysis produces a target reservoir operation and management that will provide a flow regime necessary to sustain the integrity of aquatic ecosystems.     

考虑水文改变生态指标的丹江口水库多目标优化调度

对水文改变指标进行分类、筛选并赋权,构建流量等级和流量波动 2 个生态指标;使用高斯径向基函数拟合 水库调度规则,以供水量、发电量和水文改变生态指标为目标函数,在丹江口水库开展多目标优化调度研究;分析 供水、发电与生态效益各指标间的竞争关系,寻求社会经济和生态效益均较佳的调度方案,论证生态流量的合理 性。结果表明：丹江口水库调度的供水、发电和生态效益之间存在目标冲突;同时考虑供水、发电、流量等级、流 量波动 4 个目标的推荐方案,可在确保防洪安全并维持供水和发电量不变的前提下,保证流量等级和流量波动水 文改变生态指标与天然状态相近;推荐方案尽可能达到适宜生态流量,满足了汉江中下游水生物自然繁衍需求。 研究成果可为丹江口水库优化调度以及汉江中下游水生态环境保护提供参考。     

丹江口水库入出库径流多时间尺度变化特征分析

为了认识丹江口水库运行对河道径流改变的影响,更好地指导汉江流域水资源利用,采用Morlet小波分析方法,对丹江口水库1956~2012年入库及出库径流序列进行研究,探讨了该水库入出库径流的丰枯变化情况及其准周期特征。研究结果表明,20世纪90年代以前,丹江口水库来水量经历了多次丰枯交替变化过程,其中,60年代中后期、70年代中期和80年代前期为丰水期,其余为枯水期;20世纪90年代以后,丹江口水库来水呈现出整体偏枯的趋势;水库运行对径流的影响主要体现在对年内分配过程的改变上,通过拦蓄汛期洪水,加大了枯期的下泄水量;水库的调蓄并未改变径流的主要周期,入库和出库径流均保持10个月尺度的主周期,其他时间尺度上的周期变化不太明显。     

三峡水库运行对长江中下游水文情势的影响

为了定量评价人类活动对河道径流的影响,应用变化范围法（RVA法）评估了三峡水库运行后对长江中下游水文情势的影响。利用三峡水库以下6个水文站1961~1985年和2003~2008年的日均流量作为建库前后的资料进行IHA指标计算,分析了32个水文改变指标的中值及离差系数。结果表明,三峡水库运行后,在不同的丰枯水期,对长江中下游的影响程度是不同的,且影响分布沿河流流向逐渐减弱。总体来说,三峡水库运行对长江中下游的径流影响属于中度改变。     

RELATIONS BETWEEN ALTERED STREAMFLOW VARIABILITY AND FISH ASSEMBLAGES IN EASTERN USA STREAMS

Although altered streamflow has been implicated as a major factor affecting fish assemblages, understanding the extent of streamflow alteration has required quantifying attributes of the natural flow regime. We used predictive models to quantify deviation from expected natural streamflow variability for streams in the eastern USA. Sites with >25% change in mean daily streamflow variability compared with what would be expected in a minimally disturbed environment were defined as having altered streamflow variability, based on the 10th and 90th percentiles of the distribution of streamflow variability at 1279 hydrological reference sites. We also used predictive models to assess fish assemblage condition and native species loss based on the proportion of expected native fish species that were observed. Of the 97 sites, 49 (50.5%) were classified as altered with reduced streamflow variability, whereas no sites had increased streamflow variability. Reduced streamflow variability was related to a 35% loss in native fish species, on average, and a >50% loss of species with a preference for riffle habitats. Conditional probability analysis indicated that the probability of fish assemblage impairment increased as the severity of altered streamflow variability increased. Reservoir storage capacity and wastewater discharges were important predictors of reduced streamflow variability as revealed by random forest analysis. Management and conservation of streams will require careful consideration of natural streamflow variation and potential factors contributing to altered streamflow within the entire watershed to limit the loss of critical stream habitats and fish species uniquely adapted to live in those habitats. Published in 2011 by John Wiley & Sons, Ltd.     

三门峡水库进出库水沙过程变化趋势及变异点分析

采用时间序列分析方法对三门峡水库天然情况下及建库后进出库水沙过程进行了变化趋势以及变异点分析,结果表明天然情况下水沙序列基本处于无趋势状态;而三门峡水库运行后进出库水沙序列大多出现了较明显的下降趋势,并且趋势在未来仍将延续;三门峡水库的运行对流量序列的影响相对较小,对年内径流调节有一定影响,对入库含沙量的调整较大。     

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。     

水文改变指标体系在生态水文研究中的应用综述

回顾了水文改变指标体系的发展历程,详细介绍了水文改变指标体系所包含的水文改变指标、变化范围法和环境流量成分3部分内容,总结了水文改变指标体系在水文情势改变评估、生态环境影响评估、生态环境流量估算等方面的应用;指出水文改变指标体系是一种简便有效的评估工具,在水文情势变化及其生态效应评估和水资源管理实践上具有广泛的应用前景,但水文改变指标体系也存在参数冗余问题,未来发展可以耦合生态水文模型。     

二滩水库水温结构及其影响因素研究

采用三维水温模型，对二滩水库水温结构进行数值模拟，模拟了二滩水库水温结构特征，发现二滩水库水温垂向分布呈现单温跃层和双温跃层两种型式。研究了水库水温结构变化的影响因素，表明影响二滩水库水温结构的因素主要有气象要素、库区来水流量和水体温度、水库出流位置及流量大小等。夏季二滩水库随着上游来水水温的增大，水库水温相应增加，但在温度异重流和紊流扩散的双重作用下，仅是水库中层均温层水体温度同步增加。随着二滩水库大坝出水位置的改变，库区流态发生变化，随着出水口位置的下移，水库来水和出流形成的纵向水流随之向库底下潜，水库中层均温层垂向厚度增加，对库底水温的干扰增强。     

Uniform discrete wavelet spectrum for detection of hydrologic variability at multiple timescales

Detecting the signals of hydrologic variability, including both periodicities and trends, at multi-timescales with evaluation of their statistical significance is one of the primary goals in hydrology studies, but it is also a challenging task. While the discrete wavelet spectrum (DWS) has been widely used to meet this purpose, it has limitations in practical applications, especially with the difficulty in detecting the spatial heterogeneity in hydrologic variability. In this study, a uniform DWS method is developed by determining the spectral values of the reference DWS, which are used as a uniform criterion for significance evaluation to identify hydrologic signals and compare their spatial heterogeneity. Application of the uniform DWS method to three annual runoff (and the corresponding precipitation) time series in the Yarlung Tsangpo River basin indicates that the significance of the runoff variability increases from down- to up-streams. It is shown that the uncertainty becomes large when the variability at small timescales is considered in short hydrologic time series. It is also demonstrated that hydrologic variability at long timescales usually tends to have a non-monotonic trend and that a monotonic trend would misrepresent the true underlying behavior. The uniform DWS method proposed here, by identifying the periodicities, non-monotonic and monotonic trend with significance evaluation, has the potential for a much wider use in hydrologic and climate sciences.     

Monthly Hydrological Indicators to Assess Possible Alterations on Rivers’ Flow Regime

Assessing potential deviations of the fundamental river basins’ hydrological processes and streamflow characteristics from the “natural trajectory” represents a high-priority objective to understand the biological impact of altered flow regime on river ecosystems. Existing approaches are mainly based on the analysis of daily-based indicators of hydrologic alteration, which requires wide database, including “pre-impact” and “post-impact” daily flow data frequently unavailable. The hydrological modeling is commonly used to face data missing problems or reconstruct natural conditions, even if models, especially at the daily scales, are often complex and computationally intensive. The use of simpler and more parsimonious models results, sometimes, essential for practical applications, also in consideration of the typical scarce availability of some data. This paper proposes an alternative approach for the evaluation of rivers flow regime alterations, based on different monthly hydrological indicators that are first computed and then combined to provide a global index of alteration. The procedure, conceptually derived from the Range of Variability Approach (RVA), is applied and tested on two Sicilian river basins (Italy) subject to anthropogenic influence. Streamflow regime for both the basins results differently disturbed by upstream human pressures. An alteration index is computed using available observations as “post-impact” monthly flow time-series, while time-series relative to “pre-impact” conditions have been reconstructed by the Tri.Mo.Ti.S. model, an innovative monthly and high-performing regional regressive hydrological model. The methodology, easily transferable to other regions, has revealed particularly efficacious in identifying and quantifying the existing human pressures and can be considered as a suitable tool for water resource management and policy planning activities.     

刘家峡水库对水沙变异影响分析

利用刘家峡水库运行前后进出库控制站的水文资料,对水库运行以来的径流泥沙特征进行了分析。研究表明:(1)水库运行对进出库年径流量影响很小,对年内分配影响大;(2)单库运行期水库蓄水拦沙,出库洪峰流量削减,年内径流量分配发生变化,泥沙量大幅度减少;(3)龙羊峡水库运行后的联合运行期,洪峰流量略有削减,年内蓄水过程改变后仍有一定的拦沙作用,出库含沙量较单库运行期增加;(4)水库运行减小了出库含沙量,并没有改变出库含沙量与入库含沙量的线性关系。     

鄱阳湖水文情势演变原因及对策

由于气候变化以及人类活动的影响,鄱阳湖水文情势发生了一定程度的变化,需定量评估不同驱动因子对鄱阳湖水情演变的影响。采用一系列水文指标表征鄱阳湖水文情势,构建BP神经网络模型模拟鄱阳湖水位,通过情境对比分析长江干流流量、鄱阳湖子流域入湖流量以及地形变化对各水文指标变化的贡献率。结果表明:长江干流流量是鄱阳湖7—10月份月平均水位降低的主要驱动因子,贡献率为52%～67%,对年最高极值水位的拉低效应明显,对年最低极值水位起到一定的抬高作用;地形是鄱阳湖12月—翌年3月月平均水位下降的主要驱动因子,贡献率为92%～185%,对年最低极值水位的拉低效应明显。最后对鄱阳湖水资源管理和调控提出一些建议:优化三峡水库运行调度,根据实际情况将三峡水库汛末蓄水时间适当提前;加强鄱阳湖子流域水利工程建设,在三峡蓄水期间增加五河泄流;规范采砂。     

Historical patterns of river stage and fish communities as criteria for operations of dams on the Illinois river

The hydrologic regime of the Illinois River has been altered over the past 100 years. Locks and dams regulate water surface elevations and flow, enabling commercial navigation to continue year round. This study relates changes in water surface elevation to fish abundance in the river, and establishes target criteria for operating locks and dams. Using long‐term records of daily river stage, we identified ecologically meaningful hydrological parameters for eight gage locations along the Illinois River. Inter‐annual variability of a long‐term fisheries dataset beginning in 1957 was related to variability in stage, flood and recession duration, frequency, timing, and rate of change of water levels. Reversals in water surface elevation, maximum stage levels, and length of the spring flood were the most important parameters influencing abundance of age‐zero fishes in annual collections. Smallmouth buffalo (Ictiobus bubalus), black crappie (Pomoxis nigromaculatus), freshwater drum (Aplodinotus grunneins), and white bass (Morone chrysops) were most abundant in samples during years that approximated the natural water level regime. Of the 33 hydrologic parameters evaluated for the entire water year from an Illinois River gage site on La Grange Reach, all except average stage in January and Julian date (JD) of maximum stage had moderate or high hydrologic alteration based on the historical range of variation (RVA). The highest degree of hydrologic alteration was for minimum stage levels (1‐day, 3‐day, and 7‐day), rate‐of‐rise, and rate‐of‐fall. Other parameters that have been severely altered were 30‐day minimum stage, 90‐day maximum stage, and the annual number of water level reversals. Operations of the La Grange and Peoria locks and dams could be modified so water level variability would approximate that of the late 1800s, when fish and wildlife resources were abundant. The water regime could be regulated to maintain navigation and improve conditions for native plants and animals without increasing flood damages. Copyright © 2002 John Wiley & Sons, Ltd.     

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.     

Predicting the natural flow regime: models for assessing hydrological alteration in streams

Understanding the extent to which natural streamflow characteristics have been altered is an important consideration for ecological assessments of streams. Assessing hydrologic condition requires that we quantify the attributes of the flow regime that would be expected in the absence of anthropogenic modifications. The objective of this study was to evaluate whether selected streamflow characteristics could be predicted at regional and national scales using geospatial data. Long‐term, gaged river basins distributed throughout the contiguous US that had streamflow characteristics representing least disturbed or near pristine conditions were identified. Thirteen metrics of the magnitude, frequency, duration, timing and rate of change of streamflow were calculated using a 20–50 year period of record for each site. We used random forests (RF), a robust statistical modelling approach, to develop models that predicted the value for each streamflow metric using natural watershed characteristics. We compared the performance (i.e. bias and precision) of national‐ and regional‐scale predictive models to that of models based on landscape classifications, including major river basins, ecoregions and hydrologic landscape regions (HLR). For all hydrologic metrics, landscape stratification models produced estimates that were less biased and more precise than a null model that accounted for no natural variability. Predictive models at the national and regional scale performed equally well, and substantially improved predictions of all hydrologic metrics relative to landscape stratification models. Prediction error rates ranged from 15 to 40%, but were ≤25% for most metrics. We selected three gaged, non‐reference sites to illustrate how predictive models could be used to assess hydrologic condition. These examples show how the models accurately estimate pre‐disturbance conditions and are sensitive to changes in streamflow variability associated with long‐term land‐use change. We also demonstrate how the models can be applied to predict expected natural flow characteristics at ungaged sites. Copyright © 2009 John Wiley & Sons, Ltd.     

A Histogram Comparison Approach for Assessing Hydrologic Regime Alteration

The histogram comparison approach (HCA) is proposed to assess the alteration of hydrologic regimes, which are characterized by the hydrologic metrics, for example, the indicators of hydrologic alteration. The HCA method considers alterations within the whole range of the hydrologic regime and estimates the alteration degree by comparing the pre‐impact and post‐impact histograms. A key parameter of the HCA method is the similarity degree, which considers both the class‐by‐class and cross‐class information of histograms and reflects how many features of the pre‐impact histogram remain in the post‐impact histogram. The alteration degree is defined as the mathematical maximum similarity degree, that is, 100%, subtracted by the actual similarity degree in the HCA method. Comparing the HCA method to the existing range of variability approach and histogram matching approach through theoretical analysis and case studies, the HCA method can eliminate some limitations of the range of variability approach and histogram matching approach methods and can more accurately and effectively assess the hydrologic regime alteration. The Ob and Yangtze Rivers, which are located in different climatic zones, are used as case studies. Hydrologic regime alterations impacted by reservoirs with different regulation abilities (daily, seasonally and yearly) were assessed using the HCA method, the results of which verified its rationality and practicability. More sites with a wider range of flow variations will be examined in the future to assess the applicability of the HCA method. Copyright © 2017 John Wiley & Sons, Ltd.