Change of land use regime and water conservation function in the Qiantang River Basin during 2000-2020.

内容摘要

Land use change is a key factor regulating water conservation function of river basins. Qiantang River Basin is a crucial ecological barrier and water supply source for the Yangtze River Delta region. Understanding the long-term changes in land use and water conservation function has significant importance for regional sustainable development and water security. We used the InVEST model to analyze the changes in land use patterns and water conservation functions in the Qiantang River Basin in 2000, 2010, and 2020, and used random forest model to analyze the driving factors of water conservation function. The results showed that land use conversion in the Qiantang River Basin during 2000-2020 mainly occurred in the transfer among cropland, forest and construction land. A total area of 1317.26 km2 of cropland and 158.67 km2 of forest had been converted into construction land, while 1301.15 km2 of forest had been transformed into cropland. The total water conservation volume of the Qiantang River Basin in 2000, 2010, and 2020 was 1053090.56×104, 1431102.37×104, and 1204484.25×104 m3 respectively, showing a trend of increasing first and then decreasing. There were significant differences in water conservation capacity among land use types. The total water conservation amount during the study period ranked as forest>cropland>construction land>water area>grassland>shrubland>unused land. Precipitation exerted the greatest impact on water conservation capacity, followed by forest area, cropland area and slope. During the study period, the dominant role of precipitation was gradually weakening, while the regulatory effects of underlying surface factors such as forest area and water area had increased. The results would provide a basis for land use pattern optimization and water resources allocation in the Qiantang River Basin, and offer a reference for restoring water conservation functions in other river basins. 土地利用格局变化是调控流域水源涵养功能的关键因子。钱塘江流域作为长三角地区重要生态屏障和水源供给地,分析其长时间序列土地利用及水源涵养功能的变化特征及其对区域可持续发展和水安全保障具有重要意义。本研究利用InVEST模型分析了钱塘江流域2000、2010和2020年的土地利用格局和水源涵养功能变化情况,并利用随机森林模型分析水源涵养功能的驱动因素。结果表明:2000—2020年,钱塘江流域土地利用类型转化主要集中在耕地、林地与建设用地之间,有1317.26 km2耕地和158.67 km2林地被分别改造成建设用地,同时有1301.15 km2林地转为耕地。钱塘江流域2000、2010和2020年的水源涵养总量分别为1053090.56×104、1431102.37×104和1204484.25×104 m3,呈现先增加后减少的趋势。不同地类的水源涵养量有明显差异,研究期间水源涵养总量依次为林地＞耕地＞建设用地＞水域＞草地＞灌木＞未利用地。降水量对水源涵养能力的影响最大,其次是林地面积、耕地面积和坡度。研究期间,降水量的主导作用在逐渐减弱,而林地面积、水域面积等地表下垫面的调控作用在明显增强。研究结果能为钱塘江流域土地利用格局和水资源配置提供依据,也可为其他流域的水源涵养功能恢复提供借鉴。.