Runoff Simulation And Responses To Climate Change In The Upper Reaches Of The Urumqi River Basin

As a vital carrier of lives, water resources seriously restrict the economic and social development in the arid and semi-arid area, and it is also an indispensable factor to maintain the ecological environment. Under the background of climate change, the temporal and spatial changes of temperature, precipitation and other factors must cause the change of hydrological cycle in mountainous area. So the research of exploring the impact of climate change in alpine mountain runoff has important guiding significance to water resources management and the protection of domestic water and ecological water in the lower reaches.This research selects the mountainous watershed of Urumqi River as a study area to simulate the hydrological processes of mountainous watershed in inland river basins by using soil and water assessment tool(SWAT) and takes full advantage of meteorological observation data, DEM data, land use data and soil data to establish SWAT model. The watershed is divided into 25 sub basins by SWAT model, and the research also evaluates the performance of SWAT simulation results in both calibration period(2002-2006) and validation period(2007-2011). At the same time, the NCEP reanalysis data and HadCM3 output are used to construct the SDSM model and the research focus on the performance evaluation of SDSM model and the prediction of future climate scenarios. Finally, through the coupling of these two models to forecast the runoff changes of the future scenarios. The main conclusions are as follows:(1) Considering the vertical change rate of meteorological elements and the snow melting process in the high mountains, the partition of elevation bands is a necessary process in the runoff modeling with SWAT. SWAT model parameter sensitivity analysis results show that ALPHA_BNK, SOL_K, GW_DELAY, TLAPS, SMFMX, SFTMP, CH_N2, PLAPS, CANMX, SMTMP have obvious effect to runoff simulation in the study areas.(2) The SWAT model shows good applicability in runoff modeling of Urumqi river basin. SWAT daily simulation results show that both the Nash-Sutcliffe efficiency and the determination coefficient values of the calibration period(2002-2006) and validation period(2007-2011) are higher than 0.75(monthly simulation results surpassed 0.85), and the percent bias is controlled within ±25%, which indicated that the simulation results are satisfactory. The uncertainty analysis results show that the model uncertainty is relatively small in both calibration and validation period.(3) This research establish SDSM model by using the meteorological data and GCMs predictor and evaluate the simulation performance in the baseline period. The results show that both the maximum temperature and the minimum temperature are highly fitted with the observation data respectively, the R2 is higher than 0.99 and the precipitation simulation is also satisfactory.(4) By using SDSM model, the future climate scenarios are generated. The prediction results show that: under the A2, B2 emission scenario, the climate demonstrates new features in the Urumqi river basin. The statistical analysis of prediction result indicates that in 2021-2050 s the maximum temperature under two scenarios is increased 0.51℃ and 0.59℃; the minimum temperature is increased 0.34℃ and 0.43℃; the precipitation is increased 51.22 mm and 30.56 mm.(5) Through coupling SDSM and SWAT, the future runoff in Urumqi river basin is predicted. Prediction results show that the future runoff will increased to a certain extent and this increase reached the maximum between 2041 and 2050. Under A2 scenario, the annual flow increase rate is 0.16×108/10a; under B2 scenario, the annual flow increase rate is 0.12×108/10 a.