基于多水文改变指标评价东江流域河流流态变化及其对生物多样性的影响

新丰江、枫树坝和白盆珠3座大型水库的建立对东江流域河道流量和河流流态过程有了较大改变,威胁河道下游生态系统的健康。基于广义指标生态剩余和生态赤字评价了东江流域受水库影响后流域生态需水需求目标总的盈余和缺失变化过程,基于IHA32指标计算的Do和DHRAM评价了水库对下游河段河流水文过程总的改变程度以及威胁河道生态系统健康的风险性大小,并进一步分析了对河道生物多样性的影响。研究结果如下:(1)水库对流量历时曲线(FDC)有显著影响,曲线上部下降,尾部上升,尤其体现在秋季和冬季。降水对年与夏季生态剩余影响较大,水库对各季节生态剩余和生态赤字均有较大影响:秋季和冬季生态赤字几乎为0,生态剩余显著增加。生态剩余和生态赤字与大部分IHA中32个指标具有很强的相关性,可作为衡量东江流域年和季节径流变化的生态指标。(2)龙川、河源、岭下和博罗4站点总体改变程度分别为58.48%、54.04%、54.32%和52.47%。河流流态变化导致总季节生态剩余增加并维持在较高水平,进一步引起河流生物多样性下降,并维持在较低水平。龙川和河源两站河流流态的变化对河流生态系统造成了高风险性影响,岭下和博罗两站则为中等风险。

Based on multiple hydrological alteration indicators evaluating the characteristics of flow regime with the impact on the diversity of hydrophily biology

Dam-induced hydrological alterations and related ecological problems have created considerable concern for hydrologists, ecologists, and policy-makers. The East River basin in China is the primary provider of water resources for mega-cities within the Pearl River Delta and meets 80% of the annual water demand of Hong Kong. Daily streamflow data from 4 hydrological stations covering the period of 1954-2009 are analyzed with respect to eco-flow regimes of the East River basin using eco-flow metrics (ecosurplus and ecodeficit) and the Indicators of Hydrologic Alteration (IHA) technique. In this study, ecodeficit and ecosurplus were analyzed to determine the ecological impact of water impoundments. In addition, D_o and DHRAM (Dundee Hydrological Regime Assessment Method) were employed to evaluate the degree of alteration of hydrological regimes, and ERHIs (Ecologically Relevant Hydrologic Indicators) were used to analyze the influence of hydrological alterations on ecological diversity. Results indicate that the flow duration curve (FDC) is significantly affected by water reservoirs, which is largely mirrored by the running down of the upper curve tail and running up of the lower curve tail, especially in autumn and winter. In this way, the magnitude and frequency of high flows decrease and those of low flows increase because of reservoir regulation. Precipitation exerts greater influence on annual and summer ecosurplus, whereas seasonal ecosurplus and ecodeficit are more influenced by the hydrological regulations of the reservoirs. The ecodeficit in the autumn and winter is nearly zero, whereas the ecosurplus in these same seasons increases significantly. In addition, ecodeficit and ecosurplus in other seasons, particularly autumn and winter, are more influenced by reservoir regulation. Impacts of reservoirs on hydrological regimes and eco-flow regimes differ from one station to another owing to varying degrees of influence from the reservoirs on hydrological processes. The longer the distance between a reservoir and hydrological station, the weaker the influence the water reservoir has on hydrological processes. Because of changes in the streamflow mechanism, the fluvial ecosystems are under a high risk of degradation at the Longchuan and Heyuan stations and a moderate risk of degradation at the Lingxia and Boluo stations. The general alteration degrees of hydrology are 58.48%, 54.04%, 54.32%, and 52.47% at the Longchuan, Heyuan, Lingxia, and Boluo stations, respectively. The changes in the streamflow mechanism tend to increase seasonal ecosurplus and trigger risk of a high level of ecosurplus that causes a further decline in biodiversity. Comparing the eco-flow and IHA metrics demonstrated that combining these two groups has the potential to provide a sufficient measure of the change in the flow regime. Ecodeficit and ecosurplus can be accepted in the evaluation of alterations of hydrological processes at annual and seasonal time scales. This study provides a theoretical background for water resource management with consideration of eco-flow variations in response to reservoir regulation in other highly regulated river basins of the globe.