Influence of hydroelectric development on water temperature downstream the Pubugou hydropower station of the Dadu River

To research the influence of hydroelectric development on water temperature of the Dadu River, a comparative analysis was done to describe the characteristics of temporal and spatial water temperature changes downstream river reach after and before completion of the Pubugou hydropower station by means of prototype observation and numerical simulation. The study showed that compared with natural condition, the current water temperature downstream the Pubugou reach had clear features of both averaging and delayed effects, as well as the phenomena of low temperature water in spring and summer and high temperature water in autumn and winter with the biggest drop of 2.4 ℃ at Gongzui tailrace in April and the biggest rise of 3.3 ℃ at Pubugou tailrace in December. The temperature stratification didn't occur in small lower reservoirs downstream the Pubugou reach, but the reservoir water weakened the water temperature rising along the reach. The water temperature process downstream the Pubugou reach was simulated well by the model that took the mechanical energy conversion into consideration, and the conversion rate of "mechanical energy and internal energy" came to 55% after calibration.