基于临界雨强方法的孤山川水土保持效益评估

为了区分孤山川流域降雨变化和下垫面变化对产水、产沙的影响,经过统计分析,得到孤山川流域1970年前产水、产沙临界雨强均为12 mm/d,1970年后产流临界雨强增大到21 mm/d,产沙临界雨强增大到28 mm/d。通过建立孤山川流域有效降雨与产水、产沙的相关方程,评价了水土保持措施的减水减沙效果。结果表明:孤山川流域1970—2006年水土保持措施平均减水比例、减沙比例分别为45.4%、48.5%,水土保持措施的减水减沙效果略低于气候变化的效果,两者所起作用之比大致为4.7∶5.3;2000年以来水土保持措施减水减沙效果略高于气候变化效果,两者所起作用之比大致为6.2∶3.8。这说明2000年后黄土高原还林还草的生态建设使水土保持措施的减水减沙效果显著提高。

Soil and Water Conservation Effect Evaluation of Gushanchuan Watershed Based on “Critical Precipitation Intensity” Method

The flow and sediment had changed by the influence of precipitation and the underlying surface changing of the Gushanchuan Watershed.Its critical precipitation of the flow production had been changed from 12 mm/d before 1970 to 21 mm/d after 1970 and sediment production had been changed from 12 mm/d before 1970 to 28 mm/d after 1970.Build the statistical model to evaluate the water soil conservation effect of Gushanchuan Watershed,with the model parameter of effective precipitation flow and effective precipitation sediment.According to the model results,the soil and water conservation effect proportion of flow and sediment reduction is 45.4% and 48.5% respectively during 1970-2006,and the soil and water conservation effect is lower than the climate change effect,with the radio of 4.7∶5.3.After 2000,the soil and water conservation effect is higher than the climate change effect,with the radio of 6.2∶3.8,which shows that the ecological building is the most important factor.