陕北植被变化遥感监测及对径流的影响

Remote Sensing of Vegetation Cover Variation over Northern Shaanxi Province

陕北北部是我国水土流失最为严重的地区,年输入黄河的泥沙量占全河的38%。1999年实施退耕还林草工程后,退耕还林草面积达9617.2 km2。利用1998-2004年NOAA卫星遥感资料,计算陕北北部地区归一化植被指数,发现陕北植被指数增幅在50%-200%之间,其中吴旗县增幅最大。对延安北部及榆林市1998-2004年降水量资料分析,得出植被指数增加是退耕还林草工程初见成效,不是由于降水变化引起的。利用1980-2004年吴旗县气象站观测的降水量和水文站所测径流量进行时间序列相关分析、典型年对比分析,得出该县植被变化对年径流量产生了影响,年径流量和泥沙量减少近一半,对保持水土有积极意义。

By means of NOAA satellite data from 1998 to 2004, NDVI （Normalized Difference Vegetation Index） over the northern Shaanxi Province is calculated. The results indicate that the increase of NDVI is between 50 % to 200 % with the maximum at Wuqi County. The analysis of rainfall data of the northern Yanan and Yulin from 1998 to 2004 indicates that the NDVI increase mainly attributes to the countermeasure of ＂converting farmland to forest＂ , but not to precipitation change. The correlative analysis of time series and the comparative analysis of typical years are made of the precipitation measurements at the Wuqi meteorological station and the runoff data from the Wiqi hydrological station from 1980 to 2004. The results indicate that the vegetation cover variation had impact on the annual runoff, which decreased by half, being of positive significance to water and soil conservation.