水库运行对下游河岸潜流带水位-温度影响研究

Impacts of reservoir operation on the water stage and temperature in the downstream riparian hyporheic zone

选取浙江省新安江大坝下游尾水至富春江水库某一河段作为试验场地,实时监测同一河流剖面的河道水位、温度以及河岸水位与温度分布。通过分析侧向潜流交换流量,定量描述侧向潜流交换的空间非均质性和动态特征,刻画河岸潜流带与河道水体水位、温度之间的响应关系。结果表明：本次试验剖面上的侧向潜流交换流量变化范围为-8.36～3.87 m2/s,监测时间段内单位长度上的潜流交换量可达2.49 m2;河岸带侧向潜流区同一剖面不同观测井处的潜流流量呈线性相关,且离河道越远,潜流区水位波动振幅消减越多,响应越滞后,潜流交换流量越小;受水库下泄水流影响,河道水温日波幅很小,河岸含水层具有显著的垂向温度分层。在垂直方向上,冬季浅层河岸温度较低,深层河岸温度较高,夏季则相反,同时浅层温度梯度较大,尤以地面以下0.8～1.7 m范围内温度梯度最大,深层温度梯度小;在水平方向上,离河道越远,受河道入渗水影响越小,温度越高。揭示了水库运行对下游河岸潜流带的影响规律,为河流潜流带生态影响评估提供参考。

A set of field experiments have been made between the downstream tail water of the Xin＇an Riv-er and Fuchun River Reservoir,in Zhejiang Province,for the real-time monitoring of the water stage andtemperature of the channel and the riparian hyporheic zone along a river transect. The riparian hyporheicvolumetric flow rate were analysed to quantitatively describe the spatial heterogeneity and dynamic character-istic of riparian hyporheic exchange and to explain the response relationship of the water stage and tempera-ture between the riparian hyporheic zone and the channel. The results show that the riparian hyporheic volu-metric flow rateis in the range of-8.36~3.87 m2/s,and the exchange volume per unit length across thebank in the monitoring period can be up to 2.49 m2. The water-table elevation in the riparian hyporheiczone is affected by the river stage. With the increase of distance from the shoreline,the amplitude of wa-ter-table fluctuations are attenuated and the phasesare lagged more obviously,and the hyporheic volumetricflow rate becomes smaller,which represents liner correlation between different wells. The daily temperaturefluctuations are little affected by the low temperature water discharged from reservoir with significant verti-cal temperature stratification. In vertical direction,the temperature in shallower bank is lower,and it isjust the opposite in winter. The temperature gradient in shallower bank is greater than deeper bank,andthe greatest gradientis in the range of 0.8~1.7 m underground. While in horizontal direction, the fartherfrom the channel,the smaller the effect under the low temperature water infiltration,and the higher thetemperature of the riparian aquifer would be. The impacts of reservoir operation on the downstream riparianhyporheic zone are revealed in the paper,which will provide the reference for the further ecological impactassessment of the hyporheic zone.