Impact Of Climate Change On Hydrology And Water Resources In Yarlung Zangbo River Based On SWAT Model

Over the past century,with the rapid development of industrialization and economy,greenhouse gas emissions have increased significantly,leading to a general increase in global temperature.Climate change has become a challenge facing human society.Water cycle is an important part of the climate system;the global climate changes will inevitably lead to changes in water cycle.To be specific,climate change may cause the spatiotemporal redistribution in water resource,change the quantity of water resource,and affect the ecological environment and economic development of human society.Studying the impact of climate change on hydrology and water resources can be of utmost importance for rational utilization and planning of water resources.Based on the measured data of the Yarlung Zangbo River Basin,this thesis makes a comprehensive analysis of historical climate change and runoff change,and evaluates the applicability of the SWAT hydrological model and CMIP5 GCMs in the Yarlung Zangbo River Basin.Finally,the future runoff of the study area is projected based on the SWAT model and CMIP5 GCMs.The main conclusions are as follows:1)According to the historical data of the Yarlung Zangbo River Basin,the average annual temperature over the whole basin was found to significantly increase.The increasing rate of temperature in winter was the fastest,followed by spring,summer and autumn.The average annual temperature,highest temperature and lowest temperature in the middle and lower reaches of the basin showed a remarkable increase trend.The annual precipitation in the whole basin presented a slow increasing trend.Specifically,there was no noticeable increasing trend in spring and summer while there was no significant decreasing trend in autumn and winter.The potential evapotranspiration of the study area was relatively large in spring and summer.In the whole basin the potential evapotranspiration decreased significantly,with an obvious decrease in all seasons except winter.The decrease rate of potential evapotranspiration in the upper reach was the fastest,followed by the middle and lower reaches.2)The streamflow of three hydrological stations in the mainstream of Yarlung Zangbo River showed a decreasing trend,and the decrease was becoming less and less obvious from the upstream stations to the downstream stations.The streamflow at Nugesha station exhibits unapparent decrease in all four seasons,while the Yangcun station showed the similar trend only in summer,in the remaining seasons showing unnoteworthy increase trend.The changes of streamflow at Nuxia station showed no significant decrease in summer and autumn,but no significant increase in spring and winter.3)The SWAT model was calibrated and validated based on the measured hydrometeorology data.The results verified that the SWAT model was suitable in the Yarlung Zangbo River Basin.In the meantime,the GCMs data from 18 GCMs in CMIP5 were evaluated with the measured data.The results showed that the 18 GCMs can simulate the maximum and minimum temperatures accurately.The performance in relative humidity was also acceptable,while the rainfall,wind speed and solar radiation were poorly simulated.With the data extracted from the four selected desirable models from the 18 GCMs,future streamflow in the study area was simulated by SWAT model.The results indicated that areal precipitation in the future was highly likely to increase,while the future temperature is certain to increase with higher increase in spring and lower in autumn.Nuxia station probably encountered a decreased annual and seasonal streamflow in the future while the annual and seasonal streamflow at Yangcun station was predicted to decrease in most scenarios.