三峡库区端坊溪小流域的森林水文效益

Forest Hydrology Benefit of Duanfangxi Small Watershed in Three Gorges Reservoir Area

三峡库区的森林水文作用 ,对于长江三峡水利枢纽工程的安全运行和效益发挥具有重要意义 ,对于改善和维持三峡库区的生态环境具有重要作用。根据 1992— 2 0 0 0年实测降雨、径流等观测资料 ,分析了三峡库区端坊溪小流域森林的林冠截留作用、林地枯落物的水文作用及森林覆盖率与土壤容重、土壤孔隙和小流域径流的关系。结果表明 :三峡库区端坊溪小流域不同树种枝条基部直径与枝叶质量呈线性正相关 ,不同树种枝叶容水量与枝叶质量呈线性正相关 ,不同森林类型在场降雨中 ,林冠截留量为 0 38～ 8 78mm ,截留率为 10 2 7%～ 4 9 4 8% ,林冠截留量与降雨量呈幂函数关系 ;随着森林覆盖率的增加 ,林地的土壤容重减少 ,总孔隙度增加 ;主要森林类型中 ,针阔混交林林地枯落物的饱和持水量最大 ,端坊溪小流域枯落物层截留量可达到降水量的 2 8%～ 6 3% ;小流域径流量与同期降水量呈线性正相关。端坊溪小流域森林覆盖率每增加 1% ,小流域汛期径流深减少 6 95mm。

It is significant that the forestry hydrology function of reservoir area of Three Gorges gives play to the safe operation and benefit of the water control project in Three Gorges of Yangtze River. It all can play active roles in development and improvement on ecological environment in Three Gorges Reservoir Area. Based on the observation of the natural rainfall, runoff, etc. in 19922000, the roles of crown canopy, the roles of forest litter in Duanfangxi small watershed, the correlation between the forest coverage rates and the soil unit weight, total hole degree and the runoff have been analyzed. The result shows that, the weight of branches and leaves has linear positively correlated to the diameter of its stem, the water capacity of branches and leaves has linear positively correlated with its weight, the crown canopy cuts the allowance and rainfall and presents exponential functional relation. The interception amount of crown canopy of different forest type is 0.38mms～8.78mms, the interception rate of crown canopy is 10.27%～49.48%, and the crown canopy interception is exponential functional relation to its rainfall in Duanfangxi small watershed. With the increase of the coverage rate of forest, the soil unit weight of the forest land reduces, total hole degree increases; In the main forest type, the water capacity of litter in the conifer-broadleaf mixed forest is the largest, and the water capacity of litter can reach 2.8%～6.3% of rainfall, the runoff and precipitation is linear positively correlation in the same period in Duanfangxi small watershed, following the forest coverage rates increased by 1%, the depth of runoff reduces 6.95mm in flood season in Duanfangxi small watershed.