Analysis On Variation Characteristics Of The Flood Season’s Runoff Into Dongting Lake From The Four Rivers In Hunan Province And It’s Factors Of Driving Force Since 1990s

The river runoff had undergone significant change under the background of global warming and human activities enhanced, the shortage of water resources were exacerbated, and lead to the deterioration of the ecological environment. It is of great significance to cognitive variation laws of the flood season’s runoff and analyze the influence of climate change and human activities on runoff for river basin water resources development and management, promoting sustainable economic and social development and controlling of flood and drought disasters. Based on the monthly runoff data from 1990 to 2013 in the flood season of four representative stations and the economic and social data in Sishui River Basin, the inter-annual changes of runoff in the flood season was studied by moving average, wavelet analysis and Mann-Kendall mutation test; besides, the intra-annual changes of runoff in the flood season was analyzed by using nonuniformity coefficient and amplitude of variation; then application of these index values and flood and drought disasters in Hunan province had carried on grey correlation degree analysis. The factors of driving force which had led to changes in the total flood season’s runoff into the lake from the Four Rivers was analyzed by using double mass curve of annual runoff and precipitation, principal component analysis.In this paper the main research results were as follows:(1) The distribution of inter-annual flood season’s runoff into Dongting Lake from the Four Rivers was quite uneven. In general, the flood season’s runoff into Dongting Lake presented a trend of decreasing and a multi time scale features. For Xiangtan station, Taojiang station,Taoyuan station and Shimen station, the first main period was 6 years,6 years,4 years and 4 years. Taojiang station and Taoyuan station appeared mutational site in 2003 and 2004. For Xingtan station and Shimen station, there had been no mutational site. For the total flood season’s runoff into the lake from the Four Rivers, the first main period was 6 years, and mutational site was in 2003.(2) During the flood season, the distribution of runoff into Dongting Lake from the Four Rivers was quite uneven, however, the runoff distribution tended to be even with the lapse of time. The monthly runoff showed a decreasing trend with fluctuation. As a whole, the indicators from the four stations presented a decreasing trend. Runoff distribution characteristic index value of during the flood season and river basin’s flood and drought disasters of grey correlation degree was extremely high. And these indicators can reflect the situation of the basin’s flood and drought disasters.(3) The double mass curve of annual runoff and precipitation clearly displayed bottom-right deflexion, whose decay rate was 17.45%. Among the factors of driving force of the total flood season’s runoff into the lake from the Four Rivers in Hunan Province, the natural factors accounted for 26.82%, and the human activities’factors accounted for 73.18%. And at present, the human activities’factors was the dominant key to the runoff reduction of the total flood season’s runoff into the lake.