Simulation Based On Watershed Runoff Change HuangShui HIMS Model Scenarios

Hydrological response researches for watershed under climate change scenariosare an important part of hydrological process research. Hydrological model is a vitalfoundation for hydrological process simulating and recognizing hydrologicalregularity. Researches on hydrology and water resources under climate changegenerally follow scenarios design-hydrological model-impact assessment mode.Hydrological model can be often considered as an effective mean to explorewatershed runoff change under climate change.The Qinghai-Tibetan Plateau is one of the few areas which have relatively weakhuman impact, and it is the sensitive area of global climate. TheHuangshui riverbasin is located in the transition zone of the Qinghai-TibetanPlateau and the LoessPlateau, which has an altitude from1650m to4898m, cold climate, sensitive andfragile eco-environment with serious soil erosion. Corresponding, hydrologicalprocesses in response to climate change are also very sensitive. Therefore, it hasgreat significance to explorethe hydrological process response under climate changefor typical regions in Tibetan plateau.In this thesis, based on the HIMS (integrated water cycle simulation system),takingthe Huangshui river watershed ofQinghai, northwestern China, as case studyregion,distributed hydrological modelfor Huangshui river watershed was built andrunoff change was simulated. On this basis, by analyzing the change tendency ofaround50years’ temperature and precipitation in theHuangshui river basin, runoffchanges under climate change scenarios in the future was simulated and analyzed,therefore, providing a scientific basis for future water resource’ exploiting, planningand management for Huangshui river basin. The main researches conclusions are asfollows:1.Spatial database for HIMS model was built. Firstly, based on DEM, filling toDEM was finished using Hydrology function of ArcGIS,river network structurespatial distribution map were extracted and sub basins and HRU(hydrologicalResponses Units) were divided and generated; Secondly, attribute information such aslatitude and longitude, elevation and area for each sub basin were obtained from subbasin map. In the end,attribute data for HIMS modeling were analyzed andprocessed,which including temperature and precipitation data from meteorologicalstation and runoff from hydrological stations.2. The base flow separation results showed thatfrom1986to2000it has a highproportion in the total runoff of river basin, and average base flow accounted for about32%of total runoff, suggesting that it has great influence to total runoff. From1961to2010, because of climate change and human activities, base flow showed adecreasing tendency in recent15years. Reducing in base flow will inevitably affectthe water resources utilization of the entire basin. Therefore the research of base flowseparationcan help us to better buildHIMS model in the Huangshui River.3. The simulation results in the period of1986and2000showed that calibrationand validation simulation in daily, monthly and yearlyfor the HIMS modelhasrespectively good results in the Huangshui river basin; The efficiency coefficient andcorrelation coefficient of daily simulation results reached averagely0.5or more, andthe efficiency coefficient and correlation coefficient of monthly simulation resultsreached averagely0.9or more, the efficiency coefficient and correlation coefficient ofyearly simulation results reached averagely0.95or more. HIMS model in theHuangshui River has a good applicability.4. According to the change tendency of precipitation and temperature in the past50years of Huangshui river watershed, nine kinds of climate change scenarios wereconstructed. They are respectively temperature unchanged, rainfall increased by40%;temperature unchanged, rainfall decreased by30%; temperature unchanged, rainfallunchanged; rainfall unchanged, a rise of1.5℃in temperature; rainfall unchanged, adrop of1.5℃in temperature; rainfall increased by40%, a rise of1.5℃intemperature; rainfall increased by40%, a drop of1.5℃in temperature; rainfalldecreased by30%, a rise of1.5℃in temperature; rainfall decreased by30%, a dropof1.5℃in temperature. Simulation results showed that, when temperature was risingand precipitation reducing, runoff has a tendency to decrease; on the contrary, therunoff has a tendency to rise. It can be conclude from above that the temperature hasless impact on the runoff; however, the precipitation is the critical factor to affect therunoff in the future in the Huangshui river watershed.