一个强烈水土流失小流域(准格尔五分地沟),经过20多年水土保持植被建设,乔灌草人工植被镶嵌分布,覆盖率达80%,在有效遏制水土流失的同时,也消耗相当量的水资源———生态用水。2002年生长季节,采用实验研究方法,测定了该小流域各不同类型植被蒸散量、各不同类型土壤贮水量及降水量等,计算出该小流域四大类型植被生态用水(按大小顺序):①农田为5321.3m³/hm²;②乔木林为4654.8m³/hm²;③灌木林为4047.8m³/hm²;④草原为3244.3m³/hm²。估算出全小流域生态用水量:①各类植被生态用水量约150×10⁴m³;②水库湿地生态用水量约26×10⁴m³;③居民点生态用水量约4000m³。三项合计,即五分地沟小流域总生态用水量约176×10⁴m³。值得重视的问题是:该小流域植被生态用水量和总生态用水量均超出同期降水量(130×10⁴m³)达20×10⁴～40×10⁴m³。这意味着土壤贮水量耗减20～30mm。因此,在生态环境建设中,构建适宜的植被模式,调控生态用水量,将对维持生态系统稳定及其环境改善起重要作用。

Vegetation construction in a serious water loss and soil erosion area—— — Wufendigou small catchment has been performed for more than20years.The various plant communities of high-forest,shrub-forest and grassland are mosaically distributed over the small catchment.Its cover ratio of the vegetation to the area has come up to80%.Such vegetation construction has efficiently controlled water loss and soil erosion,but a quite amount of water resource has also been consumed,which is called ecological use of water(EUW).During the growing season of the year2002,evapotranspiration of the various vegetations,water storage capacity of the various soil types and precipitation etc.were measured in the small catchment.Then EUW of the four vegetation types was calculated as:①agricultural field,5321.3m³ /hm² ;②the high-forest,4654.8m³ /hm² ;③the shrub-forest,4047.8m³ /hm² ;and④the grass-land,3244.3m³ /hm² .While,EUW amount of different components in the catchment was esti-mated as follows:①EUW amount of all the vegetations,1500000m³ ;②the reservoir marsh,260000m³ ;and③the villages,4000m³ .Thus,the total EUW amount of the whole catchment was1700000m³ .It is noticeable that EUW amount of all the vegetations and the whole catchment exceeded precipitation about 200000and400000m³ in the same period respectively.This figure means that soil water storage capacity of the catchment would be consumed20～30mm.Therefore,con-struction of appropriate vegetation pattern and control of EUW amount would have very impor-tant role for maintaining stability of ecosystem and improving eco-environment.