土地利用对流域水源涵养及水质净化的影响——以乌江流域为例

Impact of land use change on watershed water conservation and water quality purification service:a case study of Wujiang River Basin

乌江流域是长江上游重要的水源涵养区和生态屏障,基于InVEST模型中水源涵养和水质净化模块,利用2000-2020年3期土地利用为数据源,对乌江流域水源涵养、水质净化服务时空变化及其土地利用变化响应进行了分析。结果表明:(1)乌江流域平均水源涵养总量达到449.13×10^(9)m^(3),在时间上呈现先减少后增加的趋势,空间上呈现由西到东逐渐递增特征。不同土地利用类型中水源涵养能力大小依次为草地>林地>耕地;(2)水质净化方面,2000-2020年总氮(TN)年均输出总量均在3.2×10^(4)t以上;总磷(TP)年均输出总量均在3.0×10^(2)t以上,高强度输出区域主要分布在耕地覆盖区域,低强度输出区域主要分布在林地、草地覆盖区域;(3)流域土地利用变化对水源涵养、水质净化的响应主要体现在作用强度、面积变化、转化类型等方面,草地、林地与水源涵养和水质净化呈明显的正相关关系,耕地与水质净化呈负相关关系。研究有助于山区生态服务研究的发展,结果可为乌江流域土地利用格局优化调整和水质保护、水污染控制、水资源配置提供科学依据。

The Wujiang River Basin is an important water conservation area and ecological barrier in the upper reaches of the Yangtze River.Based on the water source conservation and water quality purification modules of the InVEST model and using three periods(2000—2020)of land use data as the data source,this study analyzed the spatiotemporal changes of water source conservation and water quality purification services in the Wujiang River Basin and the land use changes that influenced them.The results showed that:(1)the average amount of water source conservation in the Wujiang River Basin was 449.13×109 m3,showing a decreasing trend followed by an increasing trend over time and an increasing trend from west to east spatially.The order of water conservation capacity in different land use types is grassland>forest land>cultivated land.(2)In terms of water quality purification,the average annual output of TN and TP was above 3.2×104 t and 3.0×102 t,respectively,from 2000—2020,with high⁃intensity output areas mainly distributed in arable land cover areas and low⁃intensity output areas mainly distributed in forest and grassland cover areas.Cultivated land was the main contribution source of TN and TP output in the basin.N and P nutrients produced during fertilization were the main factors causing the deterioration of water purification in the basin,and also were important sources of non⁃point source pollution in the basin.(3)The land use changes in the basin primarily affected water source conservation and water quality purification in terms of intensity,area,and transformation type.Grassland and forest land were significantly positively related to water source conservation and water quality purification,while the arable land was negatively related to water quality purification.This study is helpful for the development of ecological service research in mountainous areas and the results can provide scientific basis for optimizing and adjusting land use patterns,water quality protection,water pollution control,and water resource allocation in the Wujiang River Basin.