Author(s): Tao Zhang; Xingnan Zhang; Dazhong Xia; Yuanhao Fang
Linked Author(s): Xingnan Zhang
Keywords: Land cover change; Hydrologic process; Macro-policy; VIC; CLUE-S
Abstract: Studies have shown that land-cover change has great effect on hydrologic process at watershed level. State's macro-policy is one of the most important reasons for land cover change besides natural factors. The Jialing River Basin, in upstream Yangtze River, has undergone dramatic land cover change in the past decades. And State's macro-policy will play a critical role in Jialing River Basin’s land cover change in the near future. Different State's land use macro-policy will lead to different behaviors in hydrologic process. Therefore the effect of land cover change under different macro-policy orientations on runoff (Rs and Base flow), evapotranspiration (ET), and soil moisture (SC) in watershed were assessed by using a large-scale Variable Infiltration Capacity (VIC) hydrologic model coupled with a land cover change model (CLUE-S). Three time periods land use data (1980s, 1995, and 2000) were used to construct and calibrate CLUE-S model. Based on the present land use pattern and the macroscopic factors influencing land cover change, two land cover change scenarios such as food security scenario and ecological security scenario were designed by means of CLUE-S model. The calibrated VIC model was finally applied in the two designed scenarios to assessing the effect of land-cover change. To eliminate the effect of climate change on simulation results, meteorological data was fixed on the period of 1980-1987. The simulation results show that: Compared with land cover scenario of 1985, wood, shrub and grass decreased by 1. 4% , 0. 6% and 7. 2% while crop increased by 9. 9% under food security scenario. For ecology security scenario, wood, shrub and grass increased by 8. 5% , 4. 0% and 16. 0% and crop decreased by 28. 6% . Land cover change in both scenarios mainly focused on middle and up of the catchment. It indicates that structure of vegetation in those areas is not stable. Results of hydrology simulation shows that ET increased and Rs, Base flow and soil water content decreased under food security scenario and opposite changes happened in ecology security scenario. Hydrology variables changes is a comprehensive response to land cover change on catchment scale. Magnitude of hydrology factors change in each subcatchement is affected by its land cover change.