基于生态安全的雅砻江减水河段最小下泄流量保障调度研究

Research on minimum discharge flow protection scheduling strategies in flow-reduced reaches of Yalong River based on ecological security

摘要

【目的】探索雅砻江大河湾减水河段最小下泄流量调度保障方式，维护减水河段水生态健康。【方法】采用M-K法开展径流序列变异诊断，利用Copula函数构建雅砻江泸宁断面以上干支流来水联合概率分布模型，分析干支流径流丰枯遭遇特性，提出径流非一致性条件下的泸宁断面最小下泄流量保障策略；构建梯级水库水量联合调度模型，分析干支流遭遇平水、特枯水情境下的泸宁断面最小下泄流量保障方案和梯级电站调度方式。【结果】结果显示：锦屏二级坝址径流在1989年前后发生突变，突变前后干支流来水丰-枯、枯-丰遭遇概率均较低；为保障泸宁断面最小下泄流量，锦屏梯级需进行补水调度，干支流来水正常、遭遇枯水情境下，锦屏二级闸址除下泄生态基流外，需分别额外补水0~18.2 m³/s、11~48 m³/s;日内锦屏梯级无负荷运行中，利用梯级上下游水位衔接特性，挖掘锦屏二级调节能力，开展干支流联合调度，保障泸宁断面最小下泄流量目标。【结论】M-K方法可有效识别锦屏二级坝址径流的突变点；基于Copula函数的联合概率分布模型能够精确描述干支流径流之间的相依关系；不同情境下的最小下泄流量保障方案和梯级电站调度方式可有效保障雅砻江大河湾减水河段的最小下泄流量，维护水生态健康。

Abstract

[Objective] To explore scheduling strategies for ensuring minimum discharge flow in flow-reduced reaches of the Great Bend of the Yalong River, thereby safeguarding aquatic ecosystem health. [Methods] The Mann-Kendall(M-K) test was used to detect non-stationarity in runoff series. A joint probability distribution model was established for mainstream and tributary inflows of the Luning cross-section of the Yalong River using the Copula function to analyze the wet-dry encounter characteristics of mainstream and tributary runoff. Subsequently, a strategy for ensuring minimum discharge flow at the Luning cross-section under inconsistent runoff conditions was proposed. A joint scheduling model for cascade reservoirs was established to analyze schemes for ensuring minimum discharge flow at the Luning cross-section and scheduling strategies for cascade hydropower stations under normal and extremely dry scenarios in the mainstream and tributaries. [Results] The result showed that an abrupt change in runoff occurred at the Jinping-II dam site around 1989. Both pre-and post-change periods exhibited low probabilities of wet-dry or dry-wet encounters in mainstream and tributary inflows. Compensation water releases from the Jinping cascade were necessary to maintain minimum discharge flow at the Luning cross-section. Under normal and dry scenarios of mainstream and tributary inflows, Jinping-II gate site required additional compensation water releases of 0 to 18.2 m³/s and 11 to 48 m³/s, respectively, beyond the ecological base flow. During intraday no-load operation of the Jinping cascade, the hydraulic connectivity between upstream and downstream reservoirs was leveraged to enhance the regulation capability of Jinping II. Joint scheduling of mainstream and tributaries was implemented to achieve the goal of minimum discharge flow at the Luning cross-section. [Conclusion] The M-K method effectively identifies abrupt change points in runoff at the Jinping-II dam site. The joint probability distribution model based on Copula function accurately describes the dependency between mainstream and tributary runoff. The proposed scheme for ensuring minimum discharge flow and scheduling schemes for cascade hydropower stations under different scenarios can effectively ensure the minimum discharge flow in flow-reduced reaches of the Great Bend of the Yalong River, thereby preserving aquatic ecosystem health.

关键词

丰枯遭遇 / Copula函数 / 梯级水库 / 最小下泄流量 / 调度策略 / 雅砻江 / 影响因素

Key words

wet-dry encounter / Copula function / cascade reservoir / minimum discharge flow / scheduling strategy / Yalong River / influencing factor

基金资助

国家重点研发计划课题(2021YFC3200303)

长江勘测规划设计研究有限责任公司自主创新项目(CX2023S034)

雅砻江流域水电开发有限公司科研试验项目(000645-22ZB0528/01)