Research On Water Resources Responses To Climate Changes In Lanhe Watershed Based On SWAT Model

For the past100years, there has been a high frequency of extreme weather events occurred due to global warming, which has a tremendous impact on the survival and development of human society. In the meantime, the processes of the hydrological cycle is continually changing caused by climate change, affecting the daily life of human society deeply. The shortage of water resources has already become one of the main factors that restrict the sustainable development of economic society, and hence studying on the effects of climate change on the processes of hydrological circle and water resources has turned out to be an important issue for now. Therefore, for the present study, Lanhe watershed, located in a typical semi-arid and arid region in Shanxi province, was taken as a case study. From the viewpoint of the effect of climate change on water resources, the variation of surface water, groundwater, and soil moisture in the Lanhe watershed under different climate conditions was investigated as to explore the response of water resources in small watershed to climate change, which could provide technical support for development and utilization of water resources as well as flood and drought disaster prevention in such areas.Research results are as follows:(1)Taking advantage of the observed data of temperature, precipitation, discharge and evaporation from the Lanhe watershed during the period of1967～2011, the annual and monthly variation trends of hydrometeor factors were analyzed by moving average and cumulative distance square methods, and the phasic and regular variation of hydrometeor factors were studied with the Mann-Kendall non-parameter method as well. (2)An applicable SWAT model for the Lanhe watershed was set up using the data of DEM, land use, soil and hydrometeorology, based on which the annual and monthly discharge process was simulated. The results show that the determination coefficient R2is0.78-0.95and the efficiency coefficient Ens is0.67-0.78. The accuracy of the simulated results is feasible and thus SWAT model can be used to simulate the annual and monthly discharge process in the Lanhe watershed.(3)Depending on the module of wave climate scenario settings in SWAT model, the annual and monthly variation of water resources under different climate conditions in the Lanhe watershed was investigated. The results show that when the precipitation is held constant, the effects on surface runoff are larger when the temperature decrease, compared to the increase in temperature, whereas the effects on underground runoff and soil water storage capacity are larger with the temperature increasing oppositely. When keeping the temperature constant, increasing precipitation has a larger influence on surface runoff than decreasing precipitation with the same amplitude. On the contrary, decreasing precipitation has a larger influence on underground runoff and soil water storage capacity instead.The monthly variation is expressed as follows:with the increase in temperature, the amount of surface and underground runoff appears trend of decrease. Changes in temperature and precipitation have a significant impact on surface runoff in flood season (Jun.～Sep.), underground runoff after flood season (Oct.～Nov.) and soil moisture storage capacity (Aug.～Oct.), while the effects are smaller on surface runoff in glacial period (Dec.～Feb.), underground runoff in spring period (Mar.～May) and soil moisture storage capacity (Mar.～Jun.).