降水变化和人类活动对纸坊沟小流域年径流的影响

为在小流域尺度上深入认识并定量区分人类活动和降水变化对黄土高原年径流变化的影响,统计了甘肃省平凉市纸坊沟小流域49a间(1955—2003年)的年降水量和径流量实测数据。结果发现,年降水量虽无明显变化,但年径流深却呈显著减少趋势。从20世纪50年代的59.1 mm降到21世纪初的12.2mm,相对降幅高达72.4%。根据年降水量—年径流深双累积曲线,划分出了5个降水—径流关系变化时段(1955—1964,1965—1976,1977—1985,1986—1995,1996—2003年),然后以1955—1964时段为基准期,定量估算了各时段内人类活动和降水变化对年径流变化的贡献。结果表明,除在干旱时段内降水对年径流减少有明显贡献外,其他时段的径流变化主要是由人类活动引起的,并且其绝对贡献量呈逐渐增大趋势。合理规划人类活动是解决黄土高原水问题的重要途径。

Effects of Precipitation Change and Human Activities on Annual Runoff from Small Watershed of Zhifanggou Watershed

The measured data of annual precipitation and runoff during 49 years(1955—2003) for the small watershed of Zhifanggou located near Pingliang City,Gansu Province,were statistically analyzed in order to understand and quantify the contributions of human activities,and precipitation change to the variation of runoff on the Loess Plateau.It was found that although annual precipitation did not change significantly,annual runoff showed a tendency of significant reduction from 59.1 mm in the 1950′s to 12.2 mm in the early of the 21th century,a relative reduction of 72.4%.Based on the double-mass-curve of accumulated annual precipitation and annual runoff,the variation of precipitation—runoff was divided into five stages: 1955—1964,1965—1976,1977—1985,1986—1995 and 1996—2003.Then the stage of 1955—1964 was chosen as the base stage for comparisons,and the contributions of human activities and precipitation change to annual runoff variation were separated and quantified for each stage.Besides the obvious contribution of annual precipitation decrease to annual runoff reduction in dry stage,the variations of annual runoff in other stages were mainly caused by the human activities,and the absolute contribution of human activities showed an increasing tendency.All these indicate that a rational planning of human activities is an important approach to solve the water problems on the Loess Plateau.