Abstract:

Study on the changes of flow regime in the lower reach of dams provides a new way to research the river ecosystem stress coming from hydraulic engineering.Based on 32 hydrological parameters，RVA（Range of Variability Approach）quantified the changes of flow regime and gives the range of variability to control the flow，while the flow was characterized by five characters such as magnitude，frequency，duration，timing and rates of change.However，the estimation part of the RVA performed impropriate in some situation，for that reason，a new estimation way was proposed in the paper.The improved method was applied to Shanxi reservoir built on Feiyun River，and the daily flow data were obtained from the Xuekou hydrological station dated from 1956 to 2007.The flow variability range of the lower reach of Shanxi reservoir was calculated and the change degree was evaluated.By comparing the flow of predam to postdam，the 32 parameters of postdam all changed，among which the frequency and duration changed mostly.The improved estimation method performed better in determining the change range，and the estimation value showed that the river flow was moderate changed after the dam built.The change was mainly reflected on the shorter duration and more frequency of low flow event，which severely affected the river ecosystem.