Hydrological Periods And Its Responses To Climate Change In The Source Region Of Yangtze River, China

The source region of Yangtze River is located in the middle of Qinghai-TibetPlateau described as high-cold-arid area, which eco-environment is fragile. In recentyears, with global climate change, there exist eco-environmental problems as riverdry-up, permafrost degradation and vegetation deterioration, which has caught worldattention. These problems are related closely with climatic and hydrological change,and the regional hydrological cycle is sensitive to climate change. Thus, it isimportant to study hydrological response with climatic variation, which is helpful toexplain processing of runoff and baseflow in similar regions or with extreme climaticconditions.Based on many methods applied in dissertation, the baseflow is calculated byadvanced Kalinin Baseflow Separation and yearly spatial variation of climatic factors(precipitation, temperature and evaporation) is shown by SLOPE. The periods ofclimatic and hydrological factors (runoff and baseflow) are decomposed by wavelettransformation, which their correlations are exposed and climatic contributions arefigured out by its further research. To built climate-hydrology TANK model in wholeregion, the sensitivity to climate change is analyzed and hydrological responses toeach extreme climatic scene is simulated.According to advanced Kalinin Baseflow Separation, relation order betweenparameters and baseflow is runoff, B, Q0and a. The value of B can reflecttransforming features of runoff and baseflow, which changed as trend of precipitationand temperature yearly. According to SLOPE, the warm-wet trend existed in largepart of region, but warm-arid trend only existed in south-east part.Through wavelet method, each meteorological station has its own periodicalfeature in Tuotuohe, Wudaoliang, Qumalai and Yushu. By considered whole region,its climatic factors have common periods of4,8,29-30and43year, which it havesingle periods of14-15year (only in temperature) and18year(only in evaporation).The runoff and baseflow have common periods of7-8,20-21and43year, which trend of hydrologic factors is almost controlled by the medium period.By correlative analysis of wavelet coefficients in whole periodical scale, thecorrelation between hydrological factors of precipitation is positive. The correlationbetween hydrological factors of temperature is negative in partial temporal scale, andthe correlation between hydrological factors of evaporation is located between twoformal relations. Based on climatic influence analysis, the impact order to runoff isprecipitation, temperature and evaporation. However, the impact order to baseflow isevaporation, precipitation and temperature. Comparing with non-normalized andnormalized wavelet transformation, the later one is more reasonable.With considerations of snow and permafrost in source region, by indentifiedsolid/liquid precipitation, the established TANK model simulates runoff pattern well.According to climatic sensitive analysis, precipitation can only influence value ofrunoff, but temperature can change its processing shape easily. Based on climaticscene analysis, it deduces that precipitation has positive impact on value of runoff.However, temperature has negative impact on monthly runoff processing by its effecton water freezing.