ABSTRACT
ABSTRACT: The nature flows are the suitable processes for the river form and ecosystem, whereas the big dam built on the river great changed the nature flows regimes. This paper analyzes the characteristics of daily runoff series from 1952 to 2010 of Dongjiang section on Leishui River in china. Based on the analyzing results of IHA (Indicators of Hydrologic Alteration), the paper researches the characters of the flows before the Dongjiang dam build, and outflows after the dam operation. The paper uses two main factors, basic monthly flow and special daily flow. Basic monthly flow adopts the median flow of each month; the special daily flow considers four benchmarks and five especially flows. There are extreme flood events, small floods, high flows, low flows and extreme low flows. For large flood and small flood events, peak flows, frequency, return periods and the shape of flood are concerned with. For high flows, the magnitude, timing and frequencies are obtained. The case study shows that the median flows are reversed after the dam operation, and the large flood and small flood are not occurred post-dam. The results of comparing pre-and post-dam shows that the Dongjiang dam building has greatly changed the rivers nature flow regimes, we must pay more attention to the dam’s reoperation in order to protect the river ecological system.
