长江流域土地利用/覆被变化的大尺度水文效应

土地利用/覆被变化(LUCC)对流域水文过程具有重要的长期影响作用。针对土地利用覆被变化对大型流域水文过程的影响程度,利用构建的长江流域分布式水文模型分析了土地利用变化情景下的水文效应特征。结果显示:分布式水文模型综合考虑了下垫面土壤、坡度、植被等特征,可以较好的反映降水发生后水分在不同土壤、植被和地形条组合件下,蒸散、地表和地下径流等组分的运移过程。根据不同土地覆被类型的径流成分差异,以及长江流域实际可供调节的土地利用方式,流域现有土地利用格局中农林地依然具有较大的转换空间。根据典型流域中预设的农林地转换情景下的径流效应看,各种情景虽然对流域径流总量变化影响较小,但对蒸散、地表径流和基流可以产生显著影响。其中,林地增加使基流最高提升超过15%,同时可使地表径流下降近5%,两者对蒸散的改变在1%左右,对径流总量变化幅度则只有0.7%左右。不同情景下的水文响应模式反映了未来土地利用调整的水文效应,因此可以基于不同的径流效应,开展有利于综合发挥流域持水能力的空间规划,提升林地所占比重。

Land Use-cover Change and Its Large Scale Hydrological Effects in Yangtze River Basin

Land use and land cover change(LUCC) is a major variable affecting the long-term hydrological processes. To quantify simulate the impact of land use cover change on hydrological processes in large basins, a large scale distributed hydrological model was developed. The hydrological effects of potential land use change scenarios are evaluated by using the distributed hydrological model based on theoretical scenarios. The results indicated that the output of the model successfully reveals the response character of ratios among ET, surface runoff, base flow under given precipitation at HRUs to basin scales. The evapotranspiration, surface runoff, groundwater flow and water yield were affected by the land use change scenarios in different magnitudes. Overall, changes of land use and land cover have significant impacts on runoff patterns at the watershed scale in terms of both the total water yield(i.e., sum of groundwater flow, surface runoff, and interflow) and the spatial distribution of runoff. The changes in runoff distribution were opposite within the two land use scenarios with the emphasis on forest or agriculture. The base flow was the most affected component in the hydrological cycle, which has a decrease of 15.3 percent in the forest-prone landscape scenario. Whereas, the surface runoff has a decrease of 5.2 percent. All scenarios show not significant impacts on the evapotranspiration and the general water yield, which were limited to the 1.2% and 0.7%. Thus, the different runoff patterns associated with each land use scenario imply the potential effect on flood or drought mitigation policy. The rational spatial planning can be conducted based on the hydrological impacts from HRUs to sub-basins.