永定河山峡段生态补水过程渗漏特征

Ecological water supplement leakage characteristics in the canyon section of Yongding River

以2019年和2020年春、秋两季共3次永定河生态补水的水文观测数据为基础,结合河道内砂石坑渗漏试验,并综合考虑补水时过流通道和水文地质条件等因素,分析永定河山峡段生态补水过程的渗漏特征。结果表明:3次生态补水期间,永定河山峡段渗漏损失率逐渐降低,渗漏损失率范围在20%~30%;落坡岭水库至下苇甸电站为现状永定河山峡段重点渗漏段,渗漏损失流量占山峡段渗漏损失流量的约60%;下苇甸电站至三家店拦河闸段由于河道减渗仅占山峡段的约10%;官厅水库至落坡岭水库段占山峡段的约30%。研究成果可为永定河山峡段生态治理与修复工程方案制定以及常态化生态补水的水资源配置提供依据。

Yongding River is one of the seven major water systems in the Haihe River basin.The canyon section refers to the section from the dam of Guanting reservoir to the Sanjiadian barrage.Affected by the reduction of rainfall and the impoundment of the upstream Guanting reservoir,the runoff of Yongding River is reduced and the flow below Sanjiadian is cut off.To restore the ecological environment of Yongding River basin,the state and local governments have taken a series of measures such as ecological water replenishment.The ecological water replenishment has been carried out three times in 2019 and 2020 in Yongding River.The leakage characteristics of the canyon section of Yongding River are analyzed and summarized under the specific mode of the three ecological water replenishment,to provide preliminary basic support for optimizing the allocation of water resources and formulating a scientific and reasonable water replenishment scheme.According to the different flow paths of ecological water replenishment and the discharge flow of the upstream section,the process of three ecological water replenishment is divided into different stages,and then the canyon section is further divided into three small sections based on collected flow of hydrological observation stations.Using the flow balance method,the leakage loss rate and leakage loss flow of each small section in each stage are calculated,and the proportion of leakage in each small section in the canyon section is obtained to analyze the causes of the leakage characteristics.Under the influence of different flow duration and discharge flow,the leakage loss flow and loss rate are different.The leakage loss rates of three water replenishments are 29.99%,24.67%and 20.62%respectively,showing a gradually decreasing trend.There is no obvious correlation between the leakage loss flow of the channel in the gorge section and the discharge flow of the Guanting reservoir.The length from Guanting reservoir(under the dam)to Luopoling reservoir is about 70%of the canyon section and the leakage loss flow accounts for about 30%.The length from the Loupoling reservoir to the Sanjiadian barrage is about 30%of the canyon section and the leakage accounts for about 70%.The length of the section from Loupoling reservoir to Xiaweidian hydropower station is about 14%of the canyon section and the leakage accounts for about 60%.The length from Xiaweidian hydropower station to the Sanjiadian barrage is about 16%of the canyon section and the leakage accounts for about 10%.The leakage loss rate of the three ecological recharges gradually decreases,ranging from 20%to 30%,i.e.the water recovery rate of the Sanjiadian barrage is 70%~80%.The section from Luopoling reservoir to Xiaweidian hydropower station is the main leakage section of the current canyon section of Yongding River,and its leakage loss flow accounts for about 60%of the canyon section.This section is located in the Cambrian Ordovician limestone stratum.Affected by the cutting of Jiulong Mountain-Xiangyu Daliang syncline and Yongding River fault,the karst caves and fissures in the bedrock are strongly developed,and there may be a"skylight"area in direct contact with the Quaternary groundwater,resulting in strong river permeability and large leakage loss flow,which constitute the internal cause of the hydrogeological conditions of the leakage characteristics.The external cause of the leakage characteristics is the river channel from Xiaweidian hydropower station to Sanjiadian barrage.