Climate Change Impact On Hydrological Cycle And Water Resources

Climate change is a global issue that is greatly concerned by the international community. As one of the important components of the climatic system, hydrological cycle has to bear the brunt of climate change. Therefore, the study of climate change impacts on hydrological cycle and water resources can play an important role in maintaining river health, protecting water resources sustainable utilization and ensuring sustainable socio-economic development of the watershed. The present situation and advancement of related research were concisely reviewed. Supported by the National Natural Science Foundation of China, this thesis was mainly focused on coupling the general circulation model (GCM) and hydrological model by statistical downscaling to investigate climate change impact on spatial-temporal distribution of water resources, discuss and analyze the vulnerability of hydrological cycle and the extreme hydrological evens to climate change. The main works and innovations were summarized as follows:(1) The simulated results of precipitation and temperature by five statistical downscaling methods, including Artificial Neural Network (ANN), Smooth Support Vector Machine (SSVM), Statistical Downscaling Model (SDSM), Automated Statistical Downscaling model (ASD) and Long Ashton Research Station Weather Generator (LARS-WG), were compared with the output of CGCM2. The results show that statistical downscaling can significantly improve the precipitation and temperature output of general circulation model. It is found that SSVM is the best at simulating amount of precipitation in the five methods, while SDSM and ASD are better at simulating variability of precipitation and temperature. Furthermore, the comparison results also show that the simulation of temperature by the five downscaling methods are basically the same, and better than the simulation of precipitation.(2) Under A2 climatic scenario, the change of precipitation and temperature in the Hangjiang Basin during 2020s (2011～2040),2050s (2041～2070) and 2080s (2071～2100) were predicted by SSVM, SDSM and ASD, respectively. In spite of the predicted trends of precipitation corresponding to CGCM2 and HadCM3 by the three downscaling methods are rather different, it is shown that the precipitation will increase during these three periods compared with baseline value. For predicting the trend of temperature, the results are more consistent than precipitation, and it is shown that the temperature will decrease during 2020s, no significantly change during 2050s, and, increase during 2080s. Throughout these three periods, there is increase temperature trend in the Hanjiang Basin.(3) The future runoffs of the Danjiangkou Reservoir and whole Hanjiang Basin were predicted by Bay-LSSVM to downscale the output of GCM, and then coupled with two parameter monthly water balance model and the distributed VIC model, respectively. The results show that the runoff will increase in these three periods in future.(4) The socio-economic development, population growth and water demand in the Hanjiang Basin were predicted. By taking account of the prediction runoff under A2 climatic scenario downscaled by SSVM, the vulnerability response of water resource system in the basin to the climate change was analyzed. The results indicate that the regulation ability of water resources system in the Hanjiang Basin is strong, and it is not found the threshold of deteriorating the system.(5) Under A2 and B2 climatic scenarios, the runoff of the upstream Hanjiang Basin were predicted by coupling CGCM2 with HBV hydrologic model by means of ASD downscaling method. The study results show that the intensity and frequency of flood and drought events, measured by peak discharge and low flow duration, respectively, will increase significantly in the period of 2011 to 2100 compared to the period of 1961 to 2000 under A2 climatic scenarios, which give the adverse effects to flood control in the Danjiangkou Reservoir, implement of the middle route of South-to-North Water Diversion Project and utilization of water resources in the whole basin. However, under B2 climatic scenarios, both flood and drought events will moderate, which is beneficial to comprehensive utilization of water resources in the basin.(6) An automated statistical downscaling method (ASD) was first presented to downscale the output of HadCM3 and predict the precipitation of the Yangtze Basin under A2 and B2 climatic scenarios. The Mann-Kendall test was applied to investigate spatial and temporal changes of precipitation extremes over the Yangtze Basin at 95% confidence level under the climate change conditions. It was revealed that the annual precipitation has an increasing tendency during in the period of 2010 to 2099, and the significant increasing trend would mostly dominate in the eastern part of the upper region and the southern and central parts of the middle region. The results also show that the significant increasing trend of precipitation maxima are mainly occurred in the northwest upper part and the middle part of the Yangtze Basin for the whole year and summer under the both climate change scenarios, and the starting point for pattern change of precipitation maxima will appear about 2050. Therefore, it can be concluded that the northwest upper and middle Yangtze Basin might encounter higher risk of flood hazards after about 2050.