Regulation of sediment regime of river ecosystems

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 23–28, August, 1991.     

Ecological connectivity in alluvial river ecosystems and its disruption by flow regulation

The dynamic nature of alluvial floodplain rivers is a function of flow and sediment regimes interacting with the physiographic features and vegetation cover of the landscape. During seasonal inundation, the flood pulse forms a ‘moving littoral’ that traverses the plain, increasing productivity and enhancing connectivity. The range of spatio-temporal connectivity between different biotopes, coupled with variable levels of natural disturbance, determine successional patterns and habitat heterogeneity that are responsible for maintaining the ecological integrity of floodplain river systems. Flow regulation by dams, often compounded by other modifications such as levee construction, normally results in reduced connectivity and altered successional trajectories in downstream reaches. Flood peaks are typically reduced by river regulation, which reduces the frequency and extent of floodplain inundation. A reduction in channel-forming flows reduces channel migration, an important phenomenon in maintaining high levels of habitat diversity across floodplains. The seasonal timing of floods may be shifted by flow regulation, with major ramifications for aquatic and terrestrial biota. Truncation of sediment transport may result in channel degradation for many kilometres downstream from a dam. Deepening of the channel lowers the water-table, which affects riparian vegetation dynamics and reduces the effective base level of tributaries, which results in rejuvenation and erosion. Ecological integrity in floodplain rivers is based in part on a diversity of water bodies with differing degrees of connectivity with the main river channel. Collectively, these water bodies occupy a wide range of successional stages, thereby forming a mosaic of habitat patches across the floodplain, This diversity is maintained by a balance between the trend toward terrestrialization and flow disturbances that renew connectivity and reset successional sequences. To counter the influence of river regulation, restoration efforts should focus on reestablishing dynamic connectivity between the channel and floodplain water bodies.     

京沪高速铁路南京越江大桥方案对河道水流的影响

本文通过实测资料，分析了工程河段河床演变特性。利用二维κ ε紊流数学模型，较好地模拟了天然水流运动，计算分析各桥式方案壅水和对下游八卦洲汊道分流比的影响，初步探讨了越江大桥对长江行洪、河势及航行条件的影响。     

Flow regime alterations under changing climate in two river basins: implications for freshwater ecosystems

We examined impacts of future climate scenarios on flow regimes and how predicted changes might affect river ecosystems. We examined two case studies: Cle Elum River, Washington, and Chattahoochee–Apalachicola River Basin, Georgia and Florida. These rivers had available downscaled global circulation model (GCM) data and allowed us to analyse the effects of future climate scenarios on rivers with (1) different hydrographs, (2) high future water demands, and (3) a river–floodplain system. We compared observed flow regimes to those predicted under future climate scenarios to describe the extent and type of changes predicted to occur. Daily stream flow under future climate scenarios was created by either statistically downscaling GCMs (Cle Elum) or creating a regression model between climatological parameters predicted from GCMs and stream flow (Chattahoochee–Apalachicola). Flow regimes were examined for changes from current conditions with respect to ecologically relevant features including the magnitude and timing of minimum and maximum flows. The Cle Elum's hydrograph under future climate scenarios showed a dramatic shift in the timing of peak flows and lower low flow of a longer duration. These changes could mean higher summer water temperatures, lower summer dissolved oxygen, and reduced survival of larval fishes. The Chattahoochee–Apalachicola basin is heavily impacted by dams and water withdrawals for human consumption; therefore, we made comparisons between pre‐large dam conditions, current conditions, current conditions with future demand, and future climate scenarios with future demand to separate climate change effects and other anthropogenic impacts. Dam construction, future climate, and future demand decreased the flow variability of the river. In addition, minimum flows were lower under future climate scenarios. These changes could decrease the connectivity of the channel and the floodplain, decrease habitat availability, and potentially lower the ability of the river to assimilate wastewater treatment plant effluent. Our study illustrates the types of changes that river ecosystems might experience under future climates. Copyright © 2005 John Wiley & Sons, Ltd.     

River-bed quarry excavations and their effect on the hydraulic regime of river flow

Conclusion The proposed hydraulic calculation is sufficiently universal. It makes it possible to take into account, under conditions of the two-dimensional problem, the effect of the length of a quarry, its depth, ratios of the upstream and downstream slopes of the quarry, and surface roughness within the quarry excavation on a drop of the water level. As a first approximation the proposed method can be applied also to the case of the three-dimensional problem.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 5, pp. 19–21, May, 1991.     

基于生态指标的水库影响下河流水文情势评价

本文通过基于FDC的生态指标综合评价了太子河流域上水库建设对水文情势的影响.结果表明:(1)水库建设后,秋季高流量组分与发生频率减小,春季和夏季低流量组分值显著增加;(2)年生态盈余受水库影响小,生态赤字受水库影响较大,季节生态指标受水库影响较大,尤其在春季和夏季.     

用变化范围法(RVA)确定河流环境流量

介绍了确定河流环境流量的一种新方法--变化范围法(RVA)的形成、研究现状及应用进展.在分析水文变化指标(IHA)的基础上,总结未受干扰的时间序列中的流量范围作为初始的环境流量范围,并通过监测生态影响来修正该流量范围,并论述了水文变化指标与变化范围法的关系.     

Regionalization of natural flow regime: application to environmental flow optimization at ungauged sites

In this work we use the regionalization approach (RA) to derive the natural flow regime at an ungauged site. The derived natural flow regime, expressed by the regional cdf models of 32 indicators of hydrologic alteration (IHA) is used in the histogram matching approach (HMA) to seek the optimal environmental flows for a proposed multiobjective diversion weir in Taiwan. The results reveal that the outcomes associated with the planning constant scheme are significantly improved by the optimal time‐varying scheme. The histogram dissimilarities of 32 IHA associated with the planning scheme are consistently greater than those associated with the optimal scheme, especially for low‐flow IHA. Despite the inherent discrepancy between different approaches to generating flow data at the ungauged site, the optimal outcomes resulting from the RA‐based natural flow regime appear to be plausible and consistent with those reported in the previous work, thus validating the RA used in this work. We also explore the effect of weighting factors on the optimal outcomes. The results reveal that the weighting factor of the ecosystem needs objective dominates all optimal outcomes, while those of the agricultural demands and interbasin transfers objectives have minor effects on the optimal outcomes. The global optimal solution is obtained with a full or null weighting assigned to the ecosystem needs objective, while the least optimal solution is obtained as the interbasin transfers objective is given a null weighting and the agricultural demands objective is weighted more than the ecosystem needs objective. River managers and decision makers may select more balanced weir operation strategies based on the results presented in this work. Copyright © 2008 John Wiley & Sons, Ltd.     

河道生态环境需水研究方法比较

对近年来的河道生态环境需水研究方法进行了回顾和分析，包括水文学法、水力学法、水文—生物分析法、生境模拟法、综合法以及作者参与研究的环境功能设定法等。文章对这些方法的理论基础、优缺点、适用范围进行了重点研究和评述，并结合我国情况分析了其在国内的应用前景。认为水文学法、生境模拟法、综合法和环境功能设定法相对来说都较适合于我国研究，其中生境模拟法由于实施比较复杂，应用性受到一定的限制。     

清潩河流域河流环境流量计算与应用

针对北方地区河流环境流量短缺和污染并存的现状,在综合考虑水质保护与水量维持的情况下界定了河流环境流量的概念和内涵,并探讨不同功能目标下河流环境流量的组成。通过分析河流水系特征及河段的空间结构特征,建立了改善河流水质所需环境流量计算模型,同时建立了Tennant和湿周模型计算河流生态系统所需环境流量。利用临颍高村桥的水文水质数据,对清潩河为改善河流水质和生态系统所需环境流量进行了初步评价,为河流应急补水提供了调控建议,并提出了河道应常年保持的流量水平。     

Macroinvertebrate community response to inter‐annual and regional river flow regime dynamics

Spatio‐temporal variability in river flow is a fundamental control on instream habitat structure and riverine ecosystem biodiversity and integrity. However, long‐term riverine ecological time‐series to test hypotheses about hydrology–ecology interactions in a broader temporal context are rare, and studies spanning multiple rivers are often limited in their temporal coverage to less than five years. To address this research gap, a unique spatio‐temporal hydroecological analysis was conducted of long‐term instream ecological responses (1990–2000) to river flow regime variability at 83 sites across England and Wales. The results demonstrate clear hydroecological associations at the national scale (all data). In addition, significant differences in ecological response are recorded between three ‘regions’ identified (RM1–3*) associated with characteristics of the flow regime. The effect of two major supra‐seasonal droughts (1990–1992 and 1996–1997) on inter‐annual (IA) variability of the LIFE scores is evident with both events showing a gradual decline before and recovery of LIFE scores after the low flow period. The instream community response to high magnitude flow regimes (1994 and 1995) is also apparent, although these associations are less striking. The results demonstrate classification of rivers into flow regime regions offers a way to help unravel complex hydroecological associations. The approach adopted herein could easily be adapted for other geographical locations, where datasets are available. Such work is imperative to understand flow regime–ecology interactions in a longer term, wider spatial context and so assess future hydroecological responses to climate change and anthropogenic modification of riverine ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.     

浅析黄河小浪底水库异重流演进规律

通过实测资料对小浪底水库异重流演进规律的初步分析,定性地提出了影响其运动的因素;同时,对某些影响因素进行了定量分析,得出了异重流到达小浪底大坝坝前的条件和时间的经验公式。验证了范家骅在水槽内异重流潜入条件试验的研究成果。     

Effects of regulation on the flow regime of the river Murray,Australia

The flow regime of the River Murray has changed markedly over the last century, and especially the last 50 years, through increased diversions, construction of dams, weirs and levees and changes in operational procedures. A model developed by the Murray–Darling Basin Commission is used to compare simulated natural (unregulated) flows at eight stations with those at seven consecutive stages in the development of regulation. Monthly and annual average flows and coefficients of variation and skewness were computed, and the flow-duration, peak-flow and low-flow characteristics curves plotted. The results confirm that average monthly and annual flows are now considerably lower than those which prevailed under natural conditions. The seasonal distribution of flows has changed in the upper Murray, owing to the influence of dams. Flow-duration characteristics now vary considerably along the river, whereas there was little change under natural conditions. The effect of regulation on flow-duration characteristics is minimal at Albury and becomes more pronounced downstream; it is most apparent in regard to flows exceeded 20–80% of the time. The magnitude of average annual floods (annual exceedance probability 50%) has been reduced by over 50% at all stations, but big floods (average recurrence interval 20 years or more) are little affected. Further, the low flows for a given annual non-exceedance probability are higher under regulated conditions than those under natural conditions. These changes have profound implications for communities of native plants and animals in both riverine and floodplain environments, and also for the long-term utility of the river as a resource.     

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.     

水库及河道整治对黄河下游游荡性河道河势演变的影响

研究了修建水库及河道整治对黄河下游白鹤镇至高村游荡性河道河势演变的影响，探讨了游荡性河道向弯曲性河道转化的可能性。认为经过水库调节后，进入下游的来沙量减少，洪峰削平及中水持续时间加长，有利于游荡性河道游荡程度的降低及向弯曲方向的发展；河道整治工程对于减小河道的摆动强度，稳定流路，促使河道由游荡向弯曲方向发展的作用是显著的。在小浪底水库下泄有利水沙条件下，若能利用现有的河道整治工程，并补充必要的河道整治措施，黄河下游游荡性河道有可能逐步转化为象高村至陶城铺河段那样的限制性弯曲河道。     

Bio-geomorphic alteration through shifting flow regime in a modified monsoonal river system in Korea

River processes and patterns are affected by changes in the watershed driven by natural and human-induced causes. A sudden pattern alteration from a “white river” (bare soils) to a “green river” (vegetated) influences riverine biodiversity and can increase flood risk. Despite these significant impacts, knowledge on the triggers that kickstart feedback exacerbating changes in bio-geomorphic patterns is insufficient. In this study, we collected and analyzed detailed monitoring data on a sandy, hydro-morphologically active, and monsoon-driven river in Korea. The surface area covered by vegetation has been increasing; this increase intensified after the 2014–2015 drought, which provided a window of opportunity for vegetation establishment. During the drought, pioneer vegetation densely colonized bare sandbars and temporarily exposed riverbed. Despite partial rejuvenation by several subsequent floods, succession to woody vegetation occurred, resulting in a stable vegetation cover. Narrowing and incision of a low-water channel occurred, and secondary channels formed inside the floodplain. The results of this study show a rapid bio-geomorphic alteration triggered by the shifts in flow regime in a river primed by human-induced changes. Furthermore, modified monsoon-driven rivers might be on the brink of similar bio-physical alterations triggered through shifting flow regime following climate change, leading to increased flood risk and impacts on endemic biodiversity.     

基于二元水循环的河流环境流量预警

根据河流的自然和社会功能将河流流量分为环境流量与水利流量,并探讨其确定方法及计算模型。以环境流量作为河流健康表征因子,通过建立二元水循环下河流环境流量最小阈值模型,探讨了河流环境流量的预警问题,并以颍河登封河段为案例进行分析。计算结果表明：二元水循环条件下,河流环境流量是决定河流健康的主要因子,它与开发利用率、回归率、消耗率、污径比等有直接的函数关系。应用河流环境流量最小阈值模型能预警河流健康,具有广泛应用前景。     

A Histogram Matching Approach for assessment of flow regime alteration: application to environmental flow optimization

In this paper we present a Histogram Matching Approach (HMA) for assessment of the flow regime alteration. The HMA uses the degree of histogram dissimilarity as a metric for impact assessment, which is based on the quadratic‐form distance between the frequency vectors of the pre‐ and post‐impact histograms weighted by a specified similarity matrix. The HMA is coupled with an aggregated multiobjective optimization genetic algorithm and applied to a case study on the Kaoping diversion weir (Taiwan) for determining the optimal environmental flow scheme that balances the ecosystem and human needs objectives. Two key issues are addressed in this study. First, we compare the performances of the HMA and existing Range of Variability Approach (RVA). Second, we employ three types of similarity function to investigate their effect on the outcomes of the HMA. The results reveal that the HMA consistently outperforms the RVA in preserving the natural flow variability regardless of what type of similarity function is used. No single type of similarity function can be found that would simultaneously best preserve the natural patterns of 32 Indicators of Hydrologic Alteration (IHA). For the situations where the water‐supply reliability is of critical concern, the pulse similarity is recommended because it would assure the smallest water‐supply deficit. If, however, minor degradation in the water‐supply reliability may be overlooked, the linear similarity is suggested because it would generally result in the post‐impact flows that most satisfactorily resemble to the natural flow regime. Copyright © 2008 John Wiley & Sons, Ltd.     

面向河流生态完整性的黄河下游生态需水过程研究

提供适宜的生态流量对维护河流健康和支撑人类社会发展具有重要意义。尽管栖息地模拟法物理机制清晰、应用广泛,但对生物群落考虑不足、生命节律信号缺失等问题长期存在。以维护河流土著生物群落完整性为目标,本文将天然水文情势作为参照系统,结合栖息地模拟与水文参照系统特征值,建立了一种面向河流生态完整性的生态需水过程评估方法,兼顾指示物种生存繁衍和土著生物群落基本生存。黄河下游利津断面评估结果显示:利津断面年最小生态需水量119亿m³,适宜生态需水量130～137亿m³,涨水期需提供1～2次持续时间不低于7 d、流量不低于1220 m³/s的高流量脉冲。对比历史实测流量过程与本文生态需水成果,发现利津断面水量充足,但流量过程不满足生态需求。黄河需加强水库群调度,协调径流年际和年内分布,塑造适宜的生态流量过程,并适时塑造高流量脉冲。     

三峡水库2003年蓄水对长江中下游水情影响分析

三峡工程经过近10 a的建设于2003年6月上旬蓄水至135 m,工程进入围堰发电运行期,10月由于航运等方面的需要,水库第2次蓄水至139 m.水库蓄水减少了上游来水,使中下游的水情发生了相应的变化,其变化也引起了社会各界的关心.根据三峡水库的蓄水情况,对2003年三峡水库蓄水期间长江中下游主要站螺山、汉口、大通站水位、流量进行研究,分析三峡水库蓄水对长江中下游水情的影响.