Study On Runoff Change In The Representative Watersheds In The Dongjiang River Basin Based On GIS

With the growing population, accelerating economic development and urbanization, thus an increasing emission of the greenhouse gases, global climate is getting warm and warm. Studies on a series of hydrological effects due to LUCC have aroused great attention all over the world, and have been an important content of the International Geosphere-Biosphere Program (IGBP).As the complexity of its affecting mechanism of hydrological processes and the uncertainty of the hydrological effects caused by LUCC, it is very difficult to make a quantitative distinguish between the climate change and the impact of human activities on runoff,therefore the problem became a focus in the study field of geography and hydrology. Researchers have used stochastic hydrology in the past, as well as mathematical statistics to analyze the the spatial-temporal evolution of water balance elements; today distributed hydrological model is using more and more to evaluate the hydrological effects of climate and LUCC. But the hydrological model is uncertain itself, much more, according to the characteristics of the study area, a comprehensive method of multi-technology, multi-tools and multi-scale is chosen as the best way to accurately assess the hydrological effects caused by climate change and LUCC.Three representative watersheds respectively in the upper, middle and lower reaches of the Dongjiang River Basin have selected as the study area. Based on GIS combined with mathematical statistics, distributed hydrological model, watershed contrast and other means, search for a suitable method to evaluate quantitative the impact on runoff caused by climate change and LUCC.For a quantitative distinction of the impact on runoff between the climate change and LUCC in the representative watersheds, this paper includes four aspects of related researches: 1) Using GIS and mathematical statistics, study spatial-temporal distribution and trends of precipitation in the representative watersheds. Results show that from 1961 to 2000, precipitation trends of the study area have obvious spatial heterogeneity with time.2) Improved the actual evaporation model based on energy exchange and moisture condition, and estimate the actual evaporation in a typical watershed, and analysis its trends in actual evaporation, studies show that the actual evaporation is decreasing due to reduction in sunshine hours shortening and wind speed decreasing.3) Using GIS spatial and geo-statistical functions, overlay DEM and analysis land-use changes in spatial distribution and characteristics during 1973 to 2003, study showed the main features of land-use changes is that agricultural land shifted from high altitude to low altitude and steep slope areas to gentle slope area, and unused land decreased while forest land increased.4) Based on the above study, using a distributed hydrological model, quantitatively analyze on the impact of runoff caused by the climate change and LUCC in the different areas, studies show that climate change is the major factor, and land-use change on runoff is significant.In this study, GIS combined with the means of multi-scale and comprehensive research, study impact on runoff caused by climate change and LUCC in the representative watersheds, provide a scientific basis for rational utilization of water resources in the Dongjiang River Basin, and also provide a method for applied with in a similar background.The innovation in the paper:Explore a set of comprehensive and quantitative research methods using GIS combined with hydrological models, multi-research and multi-basin comparison, and successfully applied in the representative watersheds for case studies of hydrological effects due to climate change and LUCC.