以潮河密云水库上游流域为研究对象, 利用双累积曲线将1961~2005 年期间年降水- 径 流关系演变划分为三个阶段: 1961~1978, 1979~1993, 1994~2005。第二和第三阶段相对第一阶段 而言, 平均年径流有较大幅度的减少, 年径流对降水的响应程度在减弱。与此相对应, 进入1980 年代后, 流域内的人类活动强度在增加, 主要表现为小水库、塘坝等水利设施的大规模建成并投 入使用, 以及农垦和造林等土地利用活动导致耕地和林地面积的增加。人类活动使得流域总蒸发 和入渗增加, 从而改变水量平衡, 径流对降水的响应变得迟缓, 减少流域总径流; 不同降水年型降 水- 径流的关系表现出很大差异, 人类活动对枯水年份年径流的影响相对较大。

This paper focuses on the upper Chao Watershed, which is the important water source for Beijing and 40% of the upper Miyun Reservoir Catchment, aiming at the analysis of the changes of rainfall - runoff relationship from 1961 to 2005 and the impacts of human activities (especially ecological construction projects, e.g. planting trees) upon the rainfall- runoff relationship. By drawing a double mass curve of rainfall and stream flow data from 1961 - 2005, 3 periods could be divided: 1961 ~1978, 1979 ~1993 and 1994 ~2005. The correlation between rainfall and stream flow kept weaken, as well as average annual stream flow kept reducing from period I to period II and III. Corresponding with the changes of rainfall- runoff relationship, the human activities in this watershed became more and more intense. In period II, most of the irrigation works and water conservancy establishments were built and applied, at the same time, the areas of forest and cultivated land increased by 7.8% and 7.5% respectively under the impacts of land use activities. In period III, forest lands increased by 11.8% as the results of afforestation and reafforestation aiming at water and soil conservancy. All kinds of human activities results in the weakened response of stream flow to rainfall and the reduced water yield. In different rainfall type years, the rainfall - runoff relationships have shown much difference. Comparing to high - rainfall years, the human activities exerted more influence on rainfall- runoff relationship in low- rainfall years.