Runoff Simulation Based On GIS And SWAT Model In The Jialingjiang Watershed

Rainfall is one of important parts of the water cycle, and also is the foundation of the formation of surface runoff, scientific master of hydrological processes provide scale effect of hydrological process is the hotspot and focus of research in watershed hydrology. In this thesis, the the lower reaches of the Jialing River is chosen as the research object, which as a water supplies and important resources of the Yangtze River Basin. Which plays a decisive role position in the support of economic development in this region.Furthermore, how to establish a suitable watershed hydrological model is particularly important in the hydrological process. Recently, the distributed hydrological model SWAT and GIS technologies have been widely used to simulate the hydrological process of Watershed, monthly runoff. The SWAT model developed rapidly in recent years due to consideration of various factors of distribution of soil of the study area, land use, climate, topography and other space, through the terrain data DEM catchment a certain threshold based on water division and combination of automatic is hydrological process, soil data, land use data,meteorological data simulation, and has been one of the larger impact of distributed hydrological model. In this study, the meteorological data of Jialingjiang River and hydrological data from Beibei station during 2003-2011 have been utilized to analysis of temporal and spatial changes of rainfall- runoff, the main conclusions are as follows:(1)Of 30 m resolution digital elevation of DEM data, analyzing the relationship between drainage density and area threshold, when the area threshold is 4000 grid number, change between the extracted river network density and area threshold tends to be stable, this proves that this threshold is optimal threshold to simulate the catchment in the lower reaches of the Jialing River Basin. Ultimately, the catchments number of 4000 has been used to of extract the drainage network, and grid, and this catchment is divided into 25 sub basins.(2)The hydrologic unit can be categories into 162 using landuse map, soil type map of the study area, soil attribute data, meteorological data during 2000-2010, the establishment of SWAT model in soil database, the landuse database and meteorological attribute database.(3)Established the SWAT model in the lower reaches of the Jialing River Basin, month runoff as the time step was used to simulate the mouth runoff in the basin. On the support of annual runoff data from Beibei hydrological control station during 2003-2006 to analysis the sensitivity, and then selected eight parameters from parameters calibration of runoff effects; verification of simulated accuracy was used annual runoff data during 2007-2011 of the jialing River, the resluts showed that, the results of the relative error of model simulation approximately in the range of 15% except for 24.3% in 2006, the deterministic coefficients in the regular and verification periods w-ere 0.83 and 0.81, respectively, this indicated that the SWAT model is suitable for using to simulate the mouth runoff in the lower reaches of the Jialing River basin.(4)The five scenarios of land use and coverage have been established using 2000, 2005, 2010 three periods of landuse data, such as forest coverage and Cultivated land cover, and then study the changes of runoff in these conditions, the simulation results showed that, the land cover change will cause changes in runoff corresponding, but the variation is not large, runoff reduce by 5.85% during in 2000-2010, increase of woodland and arable landuse will reduce the catchment runoff in some extent, the spatial difference of precipitation is the the main factor influences the watershed runoff.