长江流域典型区河-库水文网络连通综合评估

Comprehensive Evaluation of the Hydrologic Connectivity of River-Reservoir Systems in the Yangtze River Basin

为合理评估水电建设背景下的河流连通性,选择长江流域高坝大库(金沙江下游)、低坝枢纽(汉江中下游)和山区小水电(景谷)3种典型的河-库系统为研究区。概化典型研究区河-库连通的水文网络模型,将水电站、过渡区、河流汇聚点、闸坝作为重要的网络节点。然后基于网络的水文连通功能、生态环境功能和社会贡献功能构建水文网络连通评估指标体系,利用熵权模糊综合评估方法对典型河-库进行分析。结果表明,高坝大库和低坝枢纽连通性为四级(差),山区小水电连通性为五级(极差)。基于评估结果,针对不同类型的河-库系统给出改善连通性的建议。金沙江下游高坝大库可通过电站的联合调度,对下泄流量进行调控;汉江中下游低坝枢纽应当进一步对流量和水华的相关关系进行研究,确定最佳生态流量,通过对上游水电站进行联合调度,得到抑制水华的下泄流量;景谷河山区小水电需要对网络连通影响较大的小水电实施生态调度,并拆除、改建水库调节能力较差、水力发电效率较低的小水电,改善河网连通状态。

The Yangtze River is rich in water and hydropower resources. In recent years, a large number of river network sluice dams, hydropower stations and other water conservancy facilities have been built on the river, leading to a decline in hydrologic connectivity that has resulted in a series of ecological and environmental problems. Thus, it is important to evaluate river-reservoir connectivity in the Yangtze River basin. In this investigation, the connectivity of three types of river-reservoir systems in the Yangtze River basin were studied: high dam reservoirs in the lower Jinsha River, low dam reservoirs in the middle and lower Hanjiang River, and small hydropower stations in the mountainous terrain of Jinggu River. Firstly, the hydrologic network of river-reservoir connection in a typical study area was modeled, with hydropower stations, transition areas, river convergence points, gates and dams taken as network nodes. Then, an indexed evaluation system of hydrologic network connectivity was constructed using a hydrological connectivity function, an ecological environment function, a social contribution function. Finally, the entropy weighted fuzzy comprehensive method was used to evaluate typical river-reservoir systems on a scale of 1 to 5. Results show that the connectivity of high dams and low dams was bad(Level 4), while the connectivity of the small hydropower station in a mountainous area was extremely bad(Level 5). Based on the results, recommendations for improving the connectivity of different river-reservoir systems were made. For high dam reservoirs in the lower Jinsha River, we recommend that regulation of discharge from the hydropower stations should be jointly developed by stakeholders. For the low dam reservoirs in the middle and lower Hanjiang River, we recommend determining the optimal ecological flow by exploring the relationship between water flow and algae blooms, and then regulating the discharge volume to control algae blooms. For small hydropower stations in mountainous areas, we recommend ecologic regulation of hydropower stations and demolishing or rebuilding hydropower stations that dramatically affect connectivity in order to improve river network connectivity.