基于DEM的黄河中游植被恢复对年均径流量影响的估计

 植被恢复及其对年均径流量影响的空间格局对黄土高原生态环境建设及水资源管理具有重要指导作用。在分析植被适宜性分布规律的基础上, 基于黄河中游河口-龙门区间100 m 地形高程模型(DEM)和专家经验进行了区域植被适宜性制图, 并基于参数率定后的多年平均蒸散量计算公式和水平衡模型, 估算了不同植树造林情景下年均径流量的变化。结果表明, 河龙区间符合植被带分布规律的适宜区植树面积为6.6×10³ km², 次适宜区植树面积为4.8×10³ km², 分别占研究区总面积的5.8%和4.3%。土地覆被现状条件下区域产水约为33.8 mm (38.07×10⁸ m³)。适宜区植树后, 区域产水减少量约为1.9 mm (2.12×10⁸ m³), 减少5.6%。适宜区和次适宜区均植树后, 区域产水减少量约为3.1 mm (3.49×10⁸ m³), 减少9.2%。空间分布格局表明, 区域局部减水最大达到48 mm。受气候条件影响, 东南部高降雨量地区的流域适宜植树面积达45.1%, 相应减水比例达36.0%。西北部低降雨量地区的流域植树面积约为0.7%, 相应的减水比例为0.4%。

DEM-BASED MODELING OF THE IMPACT OF VEGETATION RESTORATION ON ANNUAL STREAMFLOW IN THE LOESS PLATEAU OF CHINA

Aims Vegetation is the fundamental measure to control erosion in the Loess Plateau. It is believed that forests use more water than grasslands and hence reduce average annual streamflow; however, the spatial distribution of vegetation restoration and its impacts on annual streamflow, especially on the regional scale, are poorly known. Our objectives were to map the vegetation suitability in the Hekou-Longmen (Short with He-Long) region of the middle reaches of Yellow River and assess the impact of afforestation on streamflow based on two plantation scenarios.Methods We assumed 1) the combined effects of bio-climatic zones on regional scale and local land-form determined vegetation suitability, 2) higher precipitation is more suitable for plantations and 3) the extent of soil moisture availability defmed by three local factors (slope, aspect and slope profile) depends on precipitation. We defined high, moderate and low vegetation suitability classes and developed a vegetation suitability map for the region using 100 m Digital Elevation Model (DEM) and the above assumptions. Plantation scenario 1 was developed using only the highly suitable area, and scenario 2 comprised both the highly and moderately suitable areas. The locally calibrated average annual water balance model of Zhang et al. (2001) was used to assess the impacts of afforestation on annual stream-flow in the study area.Important findings The highly suitable area for plantation covers 6.6×10~3 km~2, and the moderately suitable area covers 4.9×10~3 km~2, representing 5.8% and 4.3% of the total area, respectively. The plantation area made up 0-45% of individual catchments. The area suitable for plantation became increasingly patchy and sparse from south to north. Under current land cover status, average annual streamflow in the region was estimated to be 3.81×10~9 m~3 or 33.8 mm. Under scenario 1, average annual streamflow would be reduced by 2.12 ×10~9 m~3 or 1.9 mm (5.5%). Under scenario 2, the modeled streamflow reduction is 3.49×10~9 m~3 or 3.1 mm (9.2%). Corresponding to the spatial distribution of plantation, the reduction in streamflow is spatially variable. The rate of streamflow reduction varies from 0 to 36%. Minimum reduction occurred in the northwestern part of the region, where there is little area suitable for plantation development. Maximum reduction of 36% occurred in the southeastern part of the region where precipitation is highest.