水电工程干扰下澜沧江典型段的水温时空特征

以澜沧江流域漫湾库尾至大朝山坝下的水电工程干扰典型段为研究区域,利用1978～2005年建坝前后的水温实测资料,采用相关分析、线性回归的方法分析表层水温、下泄水温的时空分布特征.结果表明,水电工程建设后库区蓄水对表层水温有着明显的增温效应,坝前表层水温仅5～8月低于气温,其余所有月份坝前表层水温均高于建坝前的天然表层水温,时间分异性减弱.库区出水温度一般冬季(干季)高于气温和天然表层水温,而夏季(雨季)则相反,与天然水温和气温的变化趋势有2个月的滞后性.从库尾到坝前,表层水温与天然气温逐渐接近,水温/气温比与距离大坝距离之间存在正相关关系,漫湾库区下泄水对大朝山库区的水温具有一定的累积效应.本研究结果表明水电工程对澜沧江典型河段的水温时空分布存在显著效应.

Spatio-temporal characteristics of Lancangjiang River water temperatures along the representative reaches disturbed by hydroelectric power projects

This paper investigated spatio-temporal distribution characteristics of Laneangjiang River water temperatures along the reaches from Manwan Dam tail to downstream of Daehaoshan Dam by correlation analysis, and linear regression analysis. The data were derived from river section monitoring and sample analysis with several representative indices including surface water temperatures and water release temperatures from 1978 to 2005. Results showed that surface water average temperatures per month were lower than natural before dams construction, whose maximum amplitude was pronounced in May and the minimum was found in January. However, surface water temperatures after dams construction were higher than before and the temporal distribution became more homogeneous, and lower than air temperature only from May to August. Average temperatures of water released from dam were higher than natural air and surface water temperature during winter and lower than them during summer, whose tendency was postponed two months comparing that of natural air and surface water temperature averages. Reservoir filling has dominant thermal effects on water temperature. In reservoir area, daily surface water temperature averages were approaching natural air temperature from reservoir backwater station to dam gradually. There is positive correlation between the ratio of water temperature to air temperature and distance to dam. Therefore, water released from Manwan Dam results in accumulative thermal effects surface water temperatures on Daehaoshan Reservoir. It was concluded that hydroelectric power dominantly effeeted the spatio-temporal distributions of water temperature.