Impacts of Climate Change on Runoff in Qujiang River Basin Based on SWAT Model

The climate change caused by global warming has resulted in a great impact on the global water circulation system. Therefore, the hydrological process under the conditions of climate change has become one of the research hotspots in international water sciences. The Qujiang River is the largest tributary of the Jialing River on the left bank of the Yangtze River, and its drainage area is about 39,000 km2. According to the measured data from the meteorological stations within the basin, the annual average temperature of the basin has increased by 0.53 C from 2009 to 2015 compared with 1970 to 1985, and the annual total precipitation increased by 85.55mm Exploring the regularity of runoff changes in the Qujiang River basin under the conditions of climate change is of great significance in supporting the construction of the Yangtze River Economic Belt. The distributed hydrological model SWAT (Soil and Water Assessment Tool) is one of the rapidly developing and widely used hydrological models in recent years. In this paper, the Qujiang River basin is selected as the research area, and the observed meteorological data from 1970 to 2015 in the three meteorological stations and the measured runoff data from the Luoduxi Hydrometric Station from 1970 to 1985 and other hydrologic data are used as support for SWAT setup. The model simulates monthly and daily runoff to analyze the runoff variations in the basin. The monthly runoff simulation results show that the Nash-Sutcliffe efficiency coefficient (NS) and coefficient of determination (R-2) of the calibration period are 0.93 and 0.91 respectively, and the NS and R-2 are both 0.94 during the verification period. It indicated that the SWAT model has good applicability in the Qujiang River basin. Furthermore, 25 scenarios of climate change have been set up according to the climate change of Qujiang River basin in the past 50 years. The results show that for every 5% increase in precipitation, the average increase in runoff is 66.91 m(3)/s, for every 0.5 C increase in temperature, the average runoff decreases by 3.01 m(3)/s, runoff is positively correlated with precipitation and negatively correlated with temperature. This study will provide reference for runoff simulation in similar areas and provide data and technical support for water resources management and drought prevention and flood control in the basin.