海河流域河道外生态需水研究

水土流失是海河流域较为突出的生态环境问题之一。经对比研究发现，植被覆盖度的变化会通过影响洪充量，土壤侵蚀量等因子，进而改变水土流失的状况。从提高植被覆盖度尤其是低覆盖度草地植被的角度出发，定量研究了为改善流域水土流失状况河道外生态需水的具体数额，得出海河流域现状年河道外生态耗水（降水）385亿m^3。另外，为改善河道外生态环境状况将低覆盖度草地提高地提高至中等覆盖度水平，则需要增加生态需水12．5亿m^3。

Study on ecological water requirements outside riverways in Haihe River Basin

Water and soil erosion is one of the prominent ecological environment problems of Haihe River Basin.Contrast researches found that the change of vegetation coverage can influence flood peek discharges,soil erosion and other factors,and further effect the level of water and soil erosion.From the view of improving vegetation coverage,especially the low coverage of grass vegetation,the quantitative analysis of ecological water requirements outside riverways has been calculated.The conclusion is that the annual precipitation of Haihe River basin is currently38.5billion m^3,an extra water of 1.25billion m^3is needed to improving ecological environment outside riverways,which can make vegetation from low coverage to middle coverage.