水库运行对漫湾库区洲滩水热交换影响

Influence of reservoir operation on water and heat exchange in the Manwan's island

以澜沧江漫湾水库库区洲滩为研究对象,依据水库运行导致的水位波动特征,同步监测洲滩内部水位、水温变化过程,核算洲滩侧向潜流交换量,建立水温与水位之间的响应关系,分析潜流交换水流路径上溶解氧、溶解性碳素变化。结果表明:水库运行引起洲滩水位周期性波动,侧向潜流交换加强,洲滩水位最大变幅达2.2 m,水库一次蓄泄过程进出洲滩的水量达3 956 m^3,洲滩边缘区潜流交换量为中心区的4~5倍;在涨水过程中,洲滩水温下降,中底层温度梯度较大,而在落水过程中,洲滩水温上升,中表层温度梯度较大;溶解氧、溶解性有机碳和无机碳在河流至洲滩潜流交换路径上同步递减,分别从3.27 mg/L、7.3 mg/L和66.0 mg/L下降至0.17 mg/L、2.4mg/L和40.6 mg/L。水库运行导致的水位波动加强了库区洲滩潜流交换,对河流物质循环产生潜在影响。

This study investigated the effects of water fluctuations induced by reservoir operations on hyporheic exchanges in an island in Manwan Reservoir of Langcan River. In-situ measurements of water level and temperature were conducted synchronously in the study area. The lateral hyporheic exchange flux was calculated,and the relationship between water temperature and water level was established. The dissolved oxygen and soluble carbon were also analysed along the hyporheic flow path. Results showed that periodic fluctuations of water level due to reservoir operations enhanced lateral hyporheic exchange in the island. The maximum variation of water level was 2. 2 m,and the amount of water flowing in and out of the island reached 3 956 m3 during one filling-releasing cycle. The water exchange at the edge of the island was 4 to 5 times higher than that at the island centre. During water level rising,water temperature in island decreased and the temperature gradient was larger at the middle-bottom layer; while during water level falling,water temperature in island increased and the temperature gradient was larger in the upper-middle layer. The contents of dissolved oxygen, dissolved organic carbon and inorganic carbon decreased from 3. 27 mg/L, 7. 3 mg/L,66. 0 mg/L to 0. 17 mg/L,2. 4 mg/L and 40. 6 mg/L along the hyporheic flow path from reservoir to island,respectively. These results indicated that reservoir operations could enhance hyporheic exchange between reservoir and island,which imposed potential influences on the biogeochemical cycle of elements in the river.