ZHANG Shi-jie 1, YAN Jun-ping 2, LI Guo-qiang 1

1. China Institute of Water and Hydropower Research, Beijing 100038, China;
2. the General Institute of Hydropower and Water Resource Planning and Design, Beijing 100120, China

Abstract: In order to mitigate the adverse impact of low-temperature discharge from reservoirs on aquatic ecosystems, it is necessary to consider the optimization and regulation of cascade hydropower development program in river basin planning. Taking the hydropower planning of the midstream of the Kaidu River in the Xinjiang Uygur Autonomous Region as an example, the thermal structure and outflow temperature is simulated by using reservoir water temperature model. The effects of adjustment of the reservoir scale and the layout and development timing of cascade power station are studied. The changes of the cumulative effects on water temperature between "one-reservoir with three-stage development project" and “one-reservoir with four-stage development project” for upside reach of the midstream in Kaidu River are discussed. The quantitative results show that: (1) Increased storage capacity or normal water level of a reservoir, the larger scale of reservoir is, the more effects on water temperature are caused. (2) The most decline of low-temperature caused by four-stage or three-stage development project is 4.8 ℃ and 4.6 ℃ respectively, the more hydropower stations in cascade development project the more effects on water temperature are accumulated. (3) Being the leading reservoir, Arensahentuohai Reservoir with big scale and high regulation plays an important role in controlling the cumulative effects on water temperature in Kaidu River. Without the leading reservoir, all levels of the reservoir has a positive effect on cumulative effects; while with the leading reservoir, the cumulative effect turn to the passive one, increasing the maximum temperature difference between the release temperature and the natural river water temperature from 2.3 ℃ to 4.5 ℃ at the most downstream Chahanwusu Reservoir. The research results indicate that hydropower cascade development in river basin has obvious cumulative effects on water temperature, and the number of cascade hydropower stations and the controlled reservoir play a decisive role for the cumulative effect on water temperature.

Key words: cascade hydropower; reservoir water temperature; cumulative effects; water temperature model

Published in: Journal of Hydraulic Engineering, Vol. 45, No. 10, 2014