Study On Changes Of Runoff In Cuntan Catchment Of The Yangtze River

The Cuntan catchment of the Yangtze river, covering more than80%of the Upper Yangtze, has a complex terrain. And it is a sensitive area of climate change, because it is not only influenced by southeast monsoon and southwest monsoon, but also influenced by the Tibetan Plateau. So it has important theoretical and realistic significance on the characteristic research of fucture climate change and the variation of water resources under the background of climate change. Based on daily datasets of fifty weather stations(1961-2010) and Cuntan hydrological station(1893-2010) in the watershed, the dataset of regional climate model CCLM driven by MPI-ESM-LR model, and geography information in the watershed, the climate change and changes of water resources under the background of climate change are studied by combining the hydrological model(HBV or SWAT model) with the climate model(CCLM regional climate model). The main contents of the paper are:the study of climate change and runoff change characteristics during history period; the applicability of the HBV and SWAT hydrological models in the study area; the capability of CCLM climate model to reproduce the spatial and temporal variability of the observed data and the future climate change under RCP4.5scenario; the analysis of runoff change in the future.The results show that:(1) Significant changes can be seen in annual variation and interannual variation of precipitation and temperature during1961-2010. An abrupt warming occurred in about1997. While the annual precipiction has a down mutation in2005, and the main contribution comes from the reduction of the precipitation in summer and autumn. The standard variance of precipitation and temperature has a consistent decline significantly. Warm events have an increasing trend. And drought events may be more frequent in the future. All events tend to be "normalized". In spatial, the changes mainly manifested in the Yangtze river source region and the edge of the Sichuan Basin.(2)The standard variance of Cuntan runoff has an increasing trend during1961-2010. Despite the reduction in annual runoff, it has a large variability. At the same period, annual precipitation has a good correlationship with average annual runoff. And the significant related area is located in Jinsha River Basin and Jialing River Basin.(3)The runoff simulation ability of HBV and SWAT hydrological model is well in the study area. The Nash-Suttcliffe-Suttcliffe value was above0.77and variance was above0.79in daily runoff simulation. The Nash-Suttcliffe-Suttcliffe value was above0.91and variance was above0.93in monthly runoff simulation.(4)The regional climate model CCLM has a certain ability to simulate the climate change in the study area. But the simulation of temperature is better than precipitation, In spatial, better simulation is located in low-lying area, poor simulation is located in Jinsha River Basin and Mintuo River Basin where have a higher ground. The application of the bias correction has shown that it effectively improves the bias ub climate variables, it can be used to correct the future data for increasing the credibility of the projected data.(5)Compare with the baseline period(1986-2005), under RCP4.5scenario, the mean temperature, maximum, minimum temperature and precipitation will increase during2011-2040. The temperature shows a consistent rise in the whole region. But obvious differences of precipitation can be seen, the reduction of rainfall is mainly located in the downstream of Jinsha River Basin and the Jialing River Basin and most of the rest area has a increasing trend.(6) Compare with the baseline period(1986-2005), under RCP4.5scenario, mean annual runoff will be9553.8～17202.8cubic meters per second duing2011-2040. It has a decreasing trend, but peak flow may increase in the future. And the influence of temperature on the runoff become more and more obvious, especially in the upstream source area of the basin. With the increasing of the temperature in source area, the glacial melt water supply will increase.