Cumulative Effects of Cascade Reservoirs on Water Temperature from Longyang Gorge to Liujia Gorge in the Yellow River Upstream

This paper is to study the cumulative effect of water temperature via building cascade hydropower stations,thus,providing the scientific basis for working out the water temperature regulation scheme of reservoir united operation.With the cascade reservoirs on Longyangxia—Liujiaxia river section of the Yellow River Upstream as an example,and based on the data of water temperature observation and measurement in reservoirs and river courses,the typical reservoirs are selected to carry out the comparative analysis of the influence feature of water temperature;In different periods of reservoir united operation and in combination of reservoir operation conditions with the quantitative analysis of river course water temperature feature values,the contribution differences of cumulative effects by each reservoir are distinguished and the cumulative effects of cascade reservoir water temperature are discussed.The research results indicated that Longyangxia reservoir plays a dominant role in the cumulative effect of water temperature and appears to have a big fluctuation;Lijiaxia reservoir plays a synergistic role;and Gongboxia reservoir and other small reservoirs appear to have the weakened roles.When multi-reservoirs are in united operations,the construction of reservoirs between reservoirs can not cause the apparent effects,but compared with Lijiaxia reservoir in single operation,the water temperature synergistic effect at the end of cascade is still obvious.