水电站日内调峰对鱼类栖息地适宜性影响

Impact of intra-day peak regulation of hydropower stations on fish habitat suitability

摘要

【目的】控制性电站泄流深刻改变了河流的水文过程与水动力特征,日调节水电站的日内调峰可对上游控制性电站泄流形成的流量过程进行再调节,但这种再调节作用对坝下鱼类栖息地的影响尚不明晰。【方法】以泸定南桥产卵场河段为研究对象,构建平面二维水动力模型,基于泸定水电站2018—2021年齐口裂腹鱼产卵期(3、4月)典型日的逐时入库、出库流量过程,模拟分析各典型流量工况下,以及典型日内逐时流量过程下产卵场河段的水动力特征,并采用栖息地模拟法,分析各典型流量下产卵适宜栖息地的空间分布规律和水电站日内调峰对栖息地加权可利用面积(Weighted Usable Area,WUA)日内变化的影响。【结果】流量变化显著影响泸定南桥产卵场河段的流速与水深分布,其WUA随流量增加而呈单峰变化,并在80 m³/s时达到峰值(3.38万m²)。从生境总体水平上看,相较于入库流量情景,出库流量情景下大部分典型日的WUA平均值小幅下降,下降率为1.96%~10.45%,日内WUA最低值显著提升,提升率为13.82%~40.89%。从生境稳定性上看,出库流量情景下多数典型日的生境变异系数、日内WUA平均变化量出现下降,仅2020年部分典型日内的生境变异系数、日内WUA平均变化量上升。从短时生境退化风险上看,大部分典型日内的WUA小时最大减量降低,下降量为903~11747 m²。但在2020年3、4月典型日,出库流量情景的WUA小时最大减量上升。【结论】泸定水电站日内调峰对产卵场栖息地的影响因调度过程而异,其日调度在大部分典型日内对泸定南桥产卵场河段的生境总体水平影响较小,但在一定程度上提高了产卵场栖息地的稳定性,降低了短时生境退化风险。而在个别调度工况下,其调度仍可能增加产卵场的生境波动和短时生境退化风险。

Abstract

[Objective] Regulating reservoir releases profoundly alters river hydrology and hydrodynamics. While intra-day peak regulation by daily-regulating hydropower stations can re-regulate the flow processes generated by upstream regulating reservoir releases, the impact of this re-regulation on fish habitats downstream of the dam remains unclear. [Methods]The Luding Nanqiao spawning reach was selected as the research object, and a two-dimensional planar hydrodynamic model was constructed. Based on the hourly inflow and outflow hydrographs on typical days during the spawning season(March and April) of Schizothorax prenanti from 2018 to 2021, the hydrodynamic characteristics of the reach under various typical flow conditions and intra-day hourly flow variations were simulated. Furthermore, the physical habitat simulation method was used to analyze the spatial distribution patterns of suitable spawning habitats and assess the impact of intra-day peak regulation on the intra-day variations of the weighted usable area(WUA). [Results] Flow variations significantly altered the distribution of flow velocity and water depth in Luding Nanqiao spawning ground reach. The WUA exhibited a unimodal response to increasing discharge, peaking at 33 800 m² at 80 m³/ s. Regarding overall habitat suitability, compared to inflow scenarios, the average values of WUA on most typical days under outflow scenarios showed a slight decrease, with a reduction rate of 1. 96% ~ 10. 45%, while the intra-day minimum WUA increased significantly, with an increase rate of 13. 82% ~ 40. 89%. In terms of habitat stability, both the coefficient of variation for the habitat and the average intra-day WUA variation decreased on most typical days under outflow scenarios, with increases observed only on certain days in 2020. Concerning the risk of short-term habitat degradation, the maximum hourly WUA reduction effectively decreased by 903 ~ 11 747 m² on most days. However, the maximum hourly WUA reduction increased during the typical days of March and April 2020 under outflow scenarios. [Conclusion] The impact of intraday peak regulation at Luding hydropower station on spawning habitat suitability varies with the operational regime. For most typical days, daily regulation has a limited influence on the overall habitat suitability of the Nanqiao spawning reach. However, it improves habitat stability to some extent and reduces the risk of short-term habitat degradation. Nevertheless, under certain operating scenarios, hydropower regulation may increase habitat fluctuations and exacerbate the risk of short-term habitat degradation within the spawning reach.

关键词

鱼类栖息地 / 日内调峰 / 生态调度 / 水动力模拟 / 齐口裂腹鱼 / 鱼类产卵期 / 泸定水电站 / 大渡河中游

Key words

fish habitat / intra-day peak regulation / ecological operation / hydrodynamic simulation / Schizothorax prenanti / fish spawning season / Luding hydropower station / middle reaches of Dadu River

基金资助

国家自然科学基金长江水科学研究联合基金项目(U2240212)

科技基础资源调查专项(2022FY100203)