Hydrological Response To Climate Change And LUCC Based On SWAT Model In Yanduhe Basin

Based on the available weather observational data and remote-sensing images, the basic characteristics and regular patterns of the LUCC (Land-Use and Land-Cover Change) and climate change in Three Gorges Reservoir Region were analyzed by RS (Remote Sensing) and GIS (Geographic Information System) in this study. According to the data requirements of model, the types of soil, land use and land cover in the study area were re-classified and encoded to make models. The Meteorological observation data of the study area in the last50years was used to figure out an applicable WGEN (weather generator). After sensitivity analysis, SWAT model for Yanduhe Basin was maintained. This model was calibrated by the measured runoff data from2001to2005, and verified by the measured runoff data from2007to2011. At last, we discussed the hydrological response to the change of climate and LUCC by scene assumptions for the better management and utilization of water resources. The main results were presented as follows:(1) The basic characteristics and regular patterns of the climate change and LUCC in Yanduhe Basin were found out. The temperature was rising in the last50years, with the annual average temperature change tendency rate at-0.003℃/10a. The seasonal distribution of precipitation was uneven and the annual average rainfall was reducing with its tendency rate at-5.216mm/10a. From1987to2010, forest, shrubland, grassland, farmland were the main land use types, and they occupied96%of the total area of the basin. The area of farmland, grassland, shrub land have been decreasing for nearly three decades. While the area of forest have increased since a large proportion of shrub land and grassland areas was converted into forest.(2) Using ArcGIS9.3software, SWAT model have established before all kinds of model database were built. The research area was divided into79sub-basins on the basis of hydrology information, and412HRUs (hydrologic response units) were created. The model sensitivity analysis results showed that CN2, SOL_AWC, SOL_K, ALPHA_BF were the most significant parameters with effect on the runoff. The Nash coefficient (Ens), the coefficient of determination (R2) and the relative error (Re) were applied as the standard of model evaluation. The calibration and verification results were0.71and0.62,0.76and0.68,9.1%and-14.1%, respectively. The simulation results meet the accuracy requirement of the model.(3) The analysis of extreme climate scene assumptions showed that the yearly average runoff was reduced with the rising of temperature at the rate of0.62%per1℃, increased with the growing of rainfall at the rate of10%per13.04%, and decreased with the reducing of rainfall at the rate of10%per11.28%. The coefficient of the annual runoff variation increased slightly with the increase of temperature, indicating that the annual runoff fluctuations was relatively small.(4) The analysis of extreme land use scene assumptions showed that the forests have the largest water conservation capability by saving rainfall in flood period, supplying runoff in dry season, and increasing the available water of the basin. Furthermore, the forests possesses a certain flood control effect by reducing the runoff volume of the flood crest in rainy season.