基于水文水力学水生态结合法的大渡河生态流量研究

Study on Ecological flow of Dadu River Based on combined hydrology-hydraulics-water ecology method

大渡河是长江上游重要支流,水电资源丰富,流域内现存大量特有物种和珍惜物种,具有较高的生态及经济价值。生态流量是保障河道生态环境不退化、维持河道健康的重要指标,开展对大渡河生态流量的计算,对大渡河水生态环境保护和水资源合理利用具有重要意义。当前对生态流量的研究众多,本文基于大渡河中下游2008—2017年天然来水情况,分别选取水文学方法中的Tennant法、改进Tennant法,水力学法中的湿周法,以及鱼类生境适宜度法,提出了水文-水力学-水生态的结合法(下称结合法)。将结合法计算的生态流量与多年实测流量对比,确定需要进行生态补水的月份,并根据水利部印发的第四批重点河湖生态流量保障目标对大渡河生态流量进行满足程度分析。研究结果表明:结合法考虑了水文学、水力学以及不同月份鱼类繁殖的需求,满足年内不同时段河道生态需求。大渡河中下游泸定站2—4月、沙湾站2月的来流量无法满足生态需水,应进行生态补水,使河道流量满足鱼类繁殖要求。与水利部制定的大渡河生态流量保障目标相比,本文计算的生态流量在鱼类繁殖期高于保障目标,在非鱼类繁殖期低于保障目标。本文提出的结合法考虑了河道生态需水的年内差异,且计算方法简便,实用性较强,大渡河生态流量的计算能够为年内生态补水提供科学依据。

The Dadu River is an important tributary of the upper reaches of the Yangtze River,rich in hydropower resources,with a large number of endemic and rare species in the basin,and has high ecological and economic values.Ecological flow is an important indicator to ensure the ecological environment of river and maintain the health of river,and it is of great significance to study the calculation method of the ecological flow for the ecological environmental protection and rational utilization of water resources in the Dadu River Basin.Currently,there are many studies on ecological flow.Based on the natural flow discharge in the middle and lower reaches of the Dadu River from 2008 to 2017,this paper selected the Tennant method and the improved Tennant method in the hydrological method,the wet cycle method in the hydraulics method,and habitat suitability method,and proposed a combination method of hydrology,hydraulics,and aquatic ecology(hereinafter referred to as the combined method).The ecological flow calculated by the combined method was compared with the multi-year measured flow.Then the months that needed to be replenished were determined.The ecological flow of the Dadu River was compared with the fourth batch of ecological flow guarantee targets of key rivers and lakes issued by the Ministry of Water Resources.The results showed that the combined method took into account the needs of hydrological,hydraulic and fish breeding in different months to meet the ecological needs of the rivers.The flow discharge of Luding Station in the middle and lower reaches of the Dadu River in February—April and Shawan Station in February could not meet the ecological water demand,so ecological water replenishment should be carried out to make the river flow meet the requirements of fish reproduction.Compared with the ecological flow target of the Dadu River set by the Ministry of Water Resources,the ecological flow calculated in this article is higher than the target during the fish breeding period and lower than the guarantee target during the non-fish breeding season.The combined method proposed in this paper considers the annual difference of river ecological water demand,and the calculation method is simple and practical,and the calculation of the ecological flow of the Dadu River can provide a scientific basis for ecological water replenishment within the year.