Study On The Characteristics And Driving Forces Of Annual Runoff Changes In Yulin City Based On GIS

Water resources are a basic natural resource of controlling eco-environmental and substance bases of all society development, and also a strategical economical resource of a national comprehensive power. All the human activity can't stand without water. With the development of society and more intensive human activities, especially after the large-scale economic construction in recent decades, the contradiction between supply and demand of water resources become more prominent, and some new characteristics appeared beyond the intrinsic laws in water resource, which has caused lots of problems such as water resource shortage, running out of rivers, water pollution, et al. That influenced the daily life of water consumpation, even handicaped the economic development.Research progress of water resources evolution, characteristics and driving forces of annual runoff changes are summarized, but the evolution law of water resources must be considered in both temporal and spatial. With the help of GIS spatial data management and the analysis function, the temporal and spatial evolution law of annual runoff changes can be analysised. The annual precipitation and runoff from 1956 to 2005 in the Yulin city were analyzed to obtain the temporal and spatial evolution law. And because of the small number of observatories and their asymmetric spatial distribution, the Kriging spatial interpolation and Supermap GIS are used to get the spatial evolution law. At the same time, datas of climate change and human activitiy were also getted to the driving forces for annual runoff changes.The main conclusions of this dissertation as follows:1. According to the various requirements and actual situation of Yulin, with the help of GIS software, we can get the topographic diagrams of Yulin, which including river system, hydrologic station, precipitation station, hydraulic engineering distribution and other layers. That not only facilitated the management of the water conservancy department, but also provided convenient to other sectors. Simultaneously, we established the database to save each kind of attribute data and the spatial data; this laid the foundation for digitization research work of Yulin.2. By the hydrological data of annual runoff from 1956 to 2005, with the unevenness, concentration and variation index, the moving average check and the Mann-Kendall non-parameter statistical method, the characteristics of runoff in the main river of Yulin city was analyzed. The results showed that the distribution of annual runoff was uneven; most have a small accumulation in July and August, especially in Kuye River. The changes seemed obvious dropping tendency between diffenert years, especially in Tuwei River.3. By the datas of land use, water conservancy and urbanization in recent years through the investigation, built the correlation between rainfall and runoff through multi-recursive analysis and accumulation curves, then the climate change and human activitiy for runoff change can be calculated. The results showed that human activities are the direct reason for the changes of river runoff, and by biggest is Wuding river, next is Kuye river, Jialu river is smallest.4. Using the function of data storage and the spatial analysis of GIS software, we have established a database, including precipitation, runoff. And through spatial analysis function, the isolines of annual runoff and precipitation and the thematic map of Mann-Kendall test U ( R ) are drawed. Then the spatial evolution law of annual runoff changes can be analysised.