| Over the past century, the impacts of climate change on the human society has been widespread concerned around the world because of the rise of the average global temperature caused by the significant increase of world’s population and greenhouse gas emissions. The hydrological cycle as an important part in the climate system, is also affected by climate change. Water resources in our country are faced with three big problems:floods, drought, and water environment deterioration. Global climate change will certainly cause the change of the global water cycle, and have direct impacts on the precipitation, evaporation, runoff, soil humidity etc. Finally, this will significantly alter the hydrological processes and the structure of the water resources system and increase the intensity and frequency of extreme disaster such as flood and drought which makes the regional water resources shortage problem become more prominent. The human society development and utilization of water resources and thereby a lot of link such as planning and management will be affected seriously. And it will further affect the sustainable development of ecological environment and social economy. Therefore, there is very important practical significance to put forward the adaptive management of water resources and plan to manage the water resources for researching the impact of climate change on hydrological cycle and assessment of water resources security. It is also the important research content of harmonious development in our country. Zhejiang province located in·China’s southeastern coast and the Yangtze River delta is a big economy province with very developed industry and agriculture. Rivers, lakes and wetlands located in Zhejiang province not only can regulate and unload runoff; also have the function of storing, purifying as well as conserving water at the same time. It not only can further perfect the evaluation system and methods of the effects of climate change in theory, also make the research results and conclusions more scientific and reliable to further study the influence of climate change on hydrology and water resources. Meanwhile it is of great significance to further study the rule of flood and drought to prevent the disaster and scientifically establish river basin water resources development and utilization plan. At the same time, there is very important reference value for the effective allocation of watershed water resources and protection of water environment. Finally, the sustainable development of social and economic in the basin and maintaining river health life were ensured to the greatest extent.Currently, the main tools to study the influence of climate change on hydrological processes are global climate model (GCM) or regional climate model (RCM) and hydrological models, etc. The general steps are firstly to obtain climate change by GCMs under the future scenarios. But usually the low accuracy of GCM output data cannot satisfy input requirements of high resolution in the hydrology study based on the basin scale. If used directly, it will produce big error. Therefore, more precise data on climate change was attained through the downscaling methods include statistical downscaling (SDSM) and dynamical downscaling (RCM). Then the downscaled data was input to the hydrological models, such as the wide application of SWAT model to make a forecasting evaluation of the water cycle and water quality for the study area in the future.The main purpose and meaning were as follows through studying on the effect of climate change on hydrology cycle and water resources in order to adapt to the countermeasure research in Zhejiang province:(1)First of all, in the past nearly 60 years, Zhejiang province’s meteorological hydrological characteristics were identified (including trends, mutation and cycle analysis) to understand the implications of climate change on hydrological processes and the cause of hydrology and water quality change. It was on the whole to grasp the trend on the regional meteorological hydrological elements, analyze the variation law for macro adjustment of water resources and examine the rationality of the identification at the same time.(2) The precipitation and temperature in Zhejiang province in the future period (2015-2099) was downscaled based on three global climate modes-GCMs (HadCM3. CSIRO-Mk2 and CGCM2) under A2 and B2 greenhouse gas emissions scenarios by the statistical downscaling model SDSM. Then analyze the space-time distribution of precipitation and temperature and consider the different patterns of forecasting uncertainty from the different GCMs at the same time. It was to provide reliable scientific fundamental data for watershed hydrological model to evaluate on the climate on the hydrological cycle and water resources.(3) The hydrological extremes cases (mainly droughts and floods) were analyzed during the historical period (1954～2013) and predicted the effects of drought and flood during the future period (2015～2099) based on the multiple time scales SPEI drought index in Zhejiang. Study the monthly, seasonal and annual trend and the space-time frequency change of drought and flood in Zhejiang to reveal the evolution trend. And this is to provide scientific reference for flood control and drought relief to establish the reasonable policy.(4) The database of SWAT model were established in a typical watershed from Zhejiang province-Changle River basin according to the basin information including watershed DEM, land use, soil, hydrology and meteorology data. Then annual and monthly hydrological cycle and water environment changes were simulated using the SWAT model. The results show that the runoff, sediment concentration, TN and TP simulation of Ens and R2 were greater than or equal to 0.5 and 0.6, respectively and the relative error was within 20%. The result is satisfactory since the model has good fitting precision. Therefore, SWAT model can be used to simulate the annual and monthly hydrological cycle and water quality changes of Changle River basin.(5) Finally, the future downscaled precipitation and temperature under different scenarios were input to the validated SWAT model to study the impacts of the different climate change scenarios on basin hydrological cycle (surface runoff, groundwater recharge, potential evaporation) and actual evaporation processes and water quality of water environment (TN and TP concentration, and the changes of loads) of Changle river. It was to develop adaptive mitigation policies to provide certain reference in order to reduce the future of the adverse impact of climate change on river hydrology and water environment. |
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