Hydrological Alteration Associated With Hydropower Development In The Jiuling River Watershed Under The Context Of Climate Change

It is essential to investigate hydrologic responses to dams operation under the context of climate change across different physiographic regions so as to formulate sound strategies for water resource management. Though most of studies suppoted that the sustainable water resource management requires dam operations that provide environmental flow to support the downstream riverine ecosystem, the studies of the effects of dams have emphasized large dams; less well understood are the impacts caused by smaller dams.This study highlights the effects of intensive small-and medium-sized dams on the whole watershed. Mann Kendall, wavelet, geospatial analyses. GCMs, indicators of hydrologic alteration and the range of variability approach were coupled in this study to evaluate the pre-and post-impact hydrologic regimes associated with dam construction under the context of climate change using44years of hydrologic data in the Jiulong River Basin (JRB), a medium-sized coastal watershed of Southeast China, which suffered from intensive damming, The major conclusion are as follows:In the last40years, the Jiulong River Basin suffered from intensitive human activities especially the effect from hydropower development. The Flashiness Index decreased significantly and the Baseflow Index increased significantly in the last40years. As the results of the dams construction the streamlfow regime change insignificant in the2000and1995in the North River and West River respectively. Though the source of water resource was increased by1.86%and3.06%respectively in the North River and West River for the climate variability and the water resource was decreased for decreasing available water resource as the water intake in the watershed.As result of climate change, the average annual precipitation presented an increasing trend and that this tendency has become weaker from estuary to inland in the JRB over the past fifty years. Annual fluctuations were the most representative signals in streamflow variability for the North River and West River over the period1967-2010though the ENSO index was related the streamflow variability in the4-5 year scale.The streamflow regime changed obviously especially the high and low flow. The mean daily streamflow increased during July to January while it decreased during February to May after dam construction in both reaches of the JRB. After dam construction, the monthly streamflow changed more significantly and a higher variability of monthly streamflow was exhibited in the West River than in the North River. The homogenized monthly streamflow was observed in both reaches of the JRB. The earlier occurrence time of an extreme low streamflow event and the later occurrence time of an extreme high streamflow event were noted after dam construction. All of the indicators especially for the low pulse count and the low pulse duration changed significantly in the North River. Suitable ranges of the streamflow regime in terms of magnitude, rate and frequency were further identified for environmental flow management in the North and West Rivers.