大渡河干流已建梯级水电站生态基流目标回顾性评价研究

生态流量是维持河湖等水生态系统良好状态所必需的流量（包括水量、水位或水深），而生态基流是确保其水生态系统功能不丧失的最低要求。作为我国重要的水电开发基地和生物多样性保护中心，大渡河流域极有必要定期开展生态基流目标回顾性评价。本研究使用了多种水文学方法，包括Tennant 法、Texas法、Q90法、多年最小月平均流量法和Northern Great Plains Resource Program （NGPRP）法，计算了大渡河干流已建梯级水电站的生态基流目标值。根据计算结果中各控制断面的最小值、最大值和平均值，建立了生态基流目标值的参考区间，分别对应底线、优和良好的标准线，并对大渡河干流已建梯级水电站生态基流目标进行了回顾性评价。针对不同历史条件下或不同行业领域中存在的生态基流相关概念内涵和适用边界条件的不一致问题，以及拦河工程生态基流调度的实际问题，研究提出生态基流目标体系的双指标控制法，并提出了大渡河干流已建梯级水电站生态基流目标建议值。研究结果为开展流域尺度生态基流目标回顾性评价提供了新的方法，并为推动后续生态基流研究和管理中类似问题的解决提供了有益线索。

Retrospective assessment of ecological base flow targets of existing cascade hydropower plants on the Dadu River mainstream

Ecological flow is the flow (or water quantity, level or depth) that must be retained in rivers or lakes in order to maintain the essential structure and function of aquatic ecosystems, while ecological base flow has been recognized as the minimun requirement for the aquatic ecosystems not to suffer from the loss of the ecological function. The Dadu River Basin, as an important hydropower development base and also an important biodiversity conservation center of China, has a great need to conduct regular retrospective assessments for the ecological base flow targets. In this study, the Tennant method, the Texas method, the Q90 method, the multi-year average monthly minimum flow method and the Northern Great Plains Resource Program (NGPRP) method are used to calculate the target values of ecological base flow for the cascade hydropower plants on the mainstream of the Dadu River. A reference range of ecological base flow targets is established based on the minimum, maximum and average values of each control reach. The ecological base flow targets of the cascade hydropower plants on the mainstream of Dadu River were retrospectively evaluated by the three-line range system, which consists of the bottom line, good status line and moderate status line, respectively. In view of the controversies on the connotation and applicable boundary conditions of the ecological base flow resulting from different historical conditions or different industries, as well as the actual problems and difficulties of ecological base flow dispatching for the hydrological regime-alterating projects, the study provides a double-indexed control method for ecological base flow target system and proposes target values of ecological base flow of cascade hydropower plants in the mainstream of the Dadu River. The results of the study provide good methods for retrospective evaluation of ecological base flow targets at the watershed scale, and reveal useful clues for solving similar problems in subsequent ecological base flow research and management.