The Analysis On The Change Characteristic And Driving Forces Of River Runoff In Shaanxi-Gansu-Ningxia Region

Under the background of global climatic change, the responses in different areas have been recognized as a global issue. At present domestic and international research work of river hydrology system responses to global climatic change focus on the change character of river runoff, and the study scope is mostly macroscopic of nation or large district, and few study involve in the reason of local river runoff change. Although there are several studies on influence degree of human factors on river runoff, generally acknowledged model to appraisal the weight of human activities has not show yet at present because the regional natural conditions differ widely. So further study on model of influence of human activities on river runoff change and simulation in different regions is necessary.Global climatic change would cause the response of ecosystem. In arid and semi-arid regions such as Shaanxi-Gansu-Ningxia region, what is the response of regional river runoff? Would it cause river runoff to increase or reduce? How are the trends of these changes? This paper tried to discuss the reason.In this paper, the characteristics and tendency of annual runoff changes of Wudinghe River, Malianhe River and Qingshuihe River are analyzed. Moreover,the aid of gray interrelation analysis and the plural regression model are applied to discuss the reason of runoff decrease and abrupt changes.For over 40 years, under the background of climatic warming, river runoff of Shaanxi-Gansu-Ningxia region has showed a generally reduction trend. Observation on the spot has verified this conclusion, too. There is also a difference in all rivers in this region. Annual runoff of Wudinghe river reduced notably in both general tendency and periodic change. Annual runoff of Malianhe river show a decline tendency in the period both between 1955-1986 and 1987-2000. Annual runoff of Qingshuihe river showed a similar tendency to Malianhe river in the period between 1956-1987 and the period between 1988-2000.Firstly established plural linear regression model to estimate the river runoff uninfluenced by human. Compare with the record of hydrology examinition stations,then analyze the influence degree of human factors, namely the diference of the two river runoff account.Human factor have made the river runoff reduce more and more and they are becaming the driving force. The account of human influence weights less than 20% in the end 1980's, 30% in 1990's. Human influence's degree reached the maximum in 1997. The influence of human activities on river runoff rises notably.Analysis proved that impact of human activities on Malianhe river runoff is still uncertain from the end of 1980's to 1990's. Since middle period of 1990's, river runoff has been reduced by human activities constantly, and maximum in 2000. The degree of human activities' influence in Qingshuihe river runoff aggravate by time.Therefore, this paper, taking the Shaanxi-Gansu-Ningxia region as a case area, preliminary discussed the ecosystem's responses under the background of climatic change. The decline of river runoff indicates the obvious trend of environmental aridity in the region. The impact of human activity on the runoff decline is obviously strengthening, and has already occupied a leading position in recent years.