Effects Of Climate Change And Human Activities On The Hydrological Processes Of Xilinhe River

The grassland animal husbandry is one of the economic development indispensable pillar industries in China.In recent years,on the background of climate changes.the drought disasters occur frequently in the Inner Mongolia grassland regions.Water is the limiting factor of biological production in arid regions, Water become the decisive link between the human and the nature harmonious coexistence in arid regions.To solve the core issue of sustainable development in arid regions,we should study the drive mechanism of water resources system in watershed scale and explore orderly human adaptation model in the process of climate change.Based on the main weather station and hydrological station observed data of Xilinhe river in 1960-2010, to analyse the trend,mutation and cycle changes of Climate and runoff,to discuss the meteorological hydrological characteristic of basin changing environment.trough the partial correlation and path analysis to identify the main factors that affecting the runoff change.Quantitative analysis of the influence of the distribution of climate change and human activities on runoff.In combination with the distributed hydrological model SWAT and digital filtering technology simulated hydrological runoff and base flow.Applicating 10 kinds of the latest climate patterns of CMIP5.Based on the integration scenarios predicted results and has build distributed hydrological model SWAT model coupling to complete the basin runoff simulation prediction in the future.The major research result as follows:(1)The average temperature change of Xilinhe river in 1960-2010 is on the rise, the increase rate is 0.426 C/10a, The the largest contribution to the basin temperatures is warming temperatures in winter. The average temperature changed in 1987,after that,average temperature increase 1.36℃ before mutation. The temperature appeared two cold-warm quasi shocks alternately on the time scale of 20 to 32a.Evaporation increased 39.524 mm/10a and changed in 1989. Evaporation increased by 133.32 mm after the mutation. It appeared one quasi shocks on the time scale of 20 to 32 a for the local cycle oscillation. The decrease rate of precipitation of Xilinhe river is 2.5mm/10a. the trend were not significant. The decrease of the summer precipitation is the main reason for the overall decline. Precipitation in a period of 20 to 32 a timescale changes are very stable,appeared a wet-dry alternate two shocks.The decrease rate of Runoff of Xilinhe river is 13.902mm/10a.The first main cycle is 28a, the second main cycle occurs is 10a.(2) The Size analysis show that precipitation, evaporation, and the effective accumulated temperatures are the main factors effecting on the runoff in scale in the fact of air temperature, sunshine time, precipitation, evaporation, low temperature, high temperature, active accumulated temperature.Different weather factors have different contribution to the runoff of Xilinhe river in different seasons,in spring, the main control factors is effective accumulated temperature, in summer and autumn, it is precipitation.(3) Anti easy-restoration degree of runoff years in international distribution is obvious "twin peaks".The index of non-uniform coefficient,concentration in 2000s significantly higher than 60s to 90s. Distribution non-uniform coefficient and anti easy-restoration degree of runoff years completely adjustment coefficient in 1998 mutations. Human activity T1 (1980-1989), T2 (1990-1997), T3 (1998-2010) on the influence degree of the runoff value were 57.1%,57.1% and 67.8% respectively. The contribution of Climate change and human activitiesont to the index distribution non-uniform coefficient of runoff during the year was 11.48%,88.52% and 9.35%,90.65% respectively.Human activity is the main driving factors of runoff distribution changes of Xilinhe River during the year.(4)Lyne-Hollick,Chapman,Chapman-Maxwell,Boughton-Chapman four filter-ing methods of baseflow are increased with the number of filter decrease, Compared to the filter frequency,the influence of filter parameters on the baseflow is smaller.We should adjust the filter when separated baseflow, then adjusting the parameters of the filter. The result of Chapman and Chapman-Maxwell is low, while the result of Lyne-Hollick is good. The optimal segmentation parameter of Lyne-Hollick is n=3,f=0.8,Nash-Sutcliffe efficiency coefficient is 0.974, the average relative error is 3.95%.The optimal segmentation parameter of Boughton-Chapman is n=4,f=0.95, Nash-Sutcliffe efficiency coefficient is 0.975, the average relative error was 0.3%.(5) Base flow and precipitation on the scales of year time has more 45,135,-45 phase, reflect that base flow were lagging of precipitation.In most cases, base flow were positivly influenced by precipitation, in few cases,they were negativly impacted by precipitation.Base flow lags 0-1.5 months of precipitation on years scale.In day time scales, the largest base flow relative maximum runoff lagging 1-16d in spring season, the maximum base flow relative maximum runoff lagging 1-11d in summer flood season, the time lagging difference between maximum base flow and maximum runoffr were existing.(6)Simulate the year time scale runoff and base flow based on the SWAT model.The results show that runoff evaluation index of Ens, R2, and Re were in 0.7-0.77,0.71-0.77 and 4.6%-5.9%. The effect of base flow evaluation index of Ens. R2, and Re were in 0.574-0.586,0.63-0.586 and 17.6%-18.9%.Base flow simulation results relatively lower than runoff simulation results.Due to the base flow is not sensitive to the precipitation and the watershed division comparing with runoff. In addition,it is difficult for flow observating. The evaluation value and the actual observation data has certain deviation.(7) Through 10 kinds of weather patterns to predict the future tempera-ture,precipitation, runoff in two kinds of RCP situation.The results show the highest temperature warming is significant in the middle of the 21st century. The highest temperature under RCP 8.5 scene mode is higher than RCP 4.5 scene mode.In both situations.the maximum and minimum temperature in the 2020s performance the warming slow phenomenon.Overall, the changes trend of the precipitation is consistent with runoff in the future, the trend were decreasing,and the decreasing trend were gradually become slower.