陆地水循环要素对黄河流域及周边退耕还林的响应

摘要

Reforestation has attracted worldwide attention because of its multiple environmental benefits,but its impact on water resources is complicated and still controversial.In this study,the authors conducted numerical experiments within and around the Yellow River basin under the Grain-forGreen project using the Weather Research and Forecasting model.The results showed that the terrestrial water cycle process was sensitive to land use/cover change in the study region.Under the increase of mixed forests within and below the basin,the basin-averaged precipitation and evaporation increased by 223.17 and 223.88 mm respectively,but the surface runoff decreased by 2.22 mm from 2006 to 2010.In other words,the forest-induced increase in evaporation exceeded that of precipitation along with decreased surface runoff.Importantly,the afforestation effects on water resources seemed to enhance with time,and the effects of the same vegetation change were different in dry and wet years with different precipitation amounts (i.e.different atmospheric circulation background).It should be noted that it is difficult to obtain one product that can explicitly reflect the spatial distribution of actual land cover change promoted by the Grain-for-Green project in the Yellow River basin,which is an important obstacle to clearly identify the reforestation impacts.A land cover dataset derived from advantages of multiple sets of data therefore needs to be proposed.%退耕还林对水资源的影响复杂且尚存在争议,鉴于此本文基于WRF模式对黄河流域及周边的退耕还林进行了模拟研究,结果表明研究区域的陆地水循环要素对土地利用/覆盖变化较为敏感.在耕地转变为混交林的情况下,黄河流域面平均降水量在2006-2010年间增多223.17 mm,蒸发增加223.88 mm,而产流减少2.22 mm.随着时间增长,植被变化对水资源的影响逐渐增强.对于降水明显偏多和偏少的年份,同一植被变化对水循环要素影响的空间分布不同.