北部湾防城河流域水源涵养格局及其对降雨的响应特征

Water conservation pattern of Fangcheng River Basin in Beibu Gulf and its response to precipitation

评估南亚热带季风气候影响下流域水源涵养量的时空格局及其对降雨的响应特征,可为揭示不同时间尺度流域降水变化下水源涵养演变规律提供科学依据。本研究以北部湾防城河流域为研究对象,基于水量平衡原理,应用SWAT模型探究水源涵养量的时空格局及其对降水的响应特征。结果表明:防城河流域水源涵养量为1637.4 mm·a^(-1),占年均降水量的50.7%。不同子流域的水源涵养变化量的差异明显,其中,森林植被覆盖度高、坡度较陡的子流域水源涵养量大,而其他土地利用类型(如田地、草地)、坡度较缓、人类活动强度大的子流域水源涵养量较低。在月尺度上,水源涵养量和水源涵养变化量均与流域降水呈现相似的变化特征。水源涵养变化量对次降水量的响应呈现两种类型:短期降雨(降雨持续时长≤2 d)与水源涵养变化量呈线性变化,中长期降雨(2 d<降雨持续时长≤10 d)与水源涵养变化量呈非线性曲线变化,且主要受到蒸散发等过程的影响。高频次短持续时间的降水事件相对于长持续时间的降水事件更有利于增加生态系统水源涵养。

Assessing the spatiotemporal patterns of watershed water conservation under the influence of the South Asian monsoon climate and its response to precipitation is essential for revealing the evolving patterns of water con⁃servation under different temporal scales.Following the principles of water balance and using the Soil and Water Assessment Tool(SWAT)model,we investigated the spatiotemporal patterns of water conservation and its response to precipitation in the Fangcheng River Basin of Beibu Gulf.The results showed that water conservation in Fangcheng River Basin calculated by SWAT model were 1637.4 mm·a^(-1),accounting for 50.7%of the mean annual precipitation.The variation of water conservation in different sub⁃basins was obviously different.Sub⁃basins with high forest coverage and steep slopes exhibited higher water conservation,while sub⁃basins with other land use types(such as cropland and grassland),gentle slopes,and intense human activities showed lower water conserva⁃tion.At the monthly scale,both water conservation and its variation showed similar response characteristics to pre⁃cipitation in the basin.The response of water conservation variation to sub⁃precipitation events could be classified into two types.For the short⁃term rainfall events(duration≤2 days),water conservation variation showed a linear relationship.For the medium to long⁃term rainfall events(2 days<duration≤10 days),water conservation variation showed a nonlinear curve,being influenced mainly by processes such as evapotranspiration.High⁃frequency short⁃duration precipitation events were more conducive to increasing ecosystem water conservation compared to the long⁃duration precipitation events.