黄河中游砒砂岩地区长川流域生态用水分析

Analysis on ecological use of water of Changchuan watershed in the Soft Rock Area of Middle Yellow River

在野外实地观测的基础上,利用GIS和情景分析方法,对地处典型黄河中游砒砂岩地区的内蒙古长川流域不同水土流失综合治理和退耕还林(草)情景下的生态用水特征进行分析。结果表明:长川流域平均蒸散量和平均生态用水量分别为274.3mm和370.7mm,植被蒸散的水分消耗较大,但流域降雨量基本能满足植被的蒸散耗水需求,流域的整体生态用水量处于较适宜水平。研究区水土保持生物措施情景(B2方案)的生态用水量小于适宜生态用水阈值(411.3mm),但其植被蒸散量大于有效降雨量(279.0mm),从长远角度看,B2方案还是受水分(降雨)条件的限制;而4种退耕还林(草)情景的生态用水量和植被蒸散量均小于适宜生态用水阈值和有效降雨量,不受降雨条件的限制。

The Changchuan watershed,Inner Mongolia,belongs to the typical region of the Soft Rock Area of Middle Yellow River.Based on experimental research data of the ecological use of water,this paper applies the GIS and scenarios analysis methods to analyse the ecological use of water of the Changchuan watershed and different scenarios of ecological construction in the water-shed.The vegetation evapotranspiration and ecological use of water at Changchuan watershed averaged 274.3mm and 370.7mm respectively.This indicates that though evapotranspiration of vegetation was quite high on the regional scale,yet the rainfall can still meet the requirement of evapotranspiration of vegetation. Generally speaking, the ecological use of water was moderate in this region.In terms of ecological use of water under different scenarios of ecological consreuction,4 land use patterns,B2RL1,namely restoring all bare land and sandy land at Changchuan watershed into woodland,brush-land or grassland,B2RL2,namely no bare land and turning cultivated land on above 5° slopes back into woodland or grassland at Changchuan watershed,B2RL3,namely no bare land and turning cultivated land on above 15° slopes back into woodland or grassland,and B2RL4,namely no bare land and turning cultivated land on above 25° slopes back into woodland or grassland can stand the water stress for a short term,but the vegetation can not grow and develop very well under the water regime of the watershed in the long run.