中文摘要：

用归一化植被指数（NDVI）数据提取的农业绿洲NDVI累积作为人类活动因素综合，结合石羊河流域主要河流出山口水文站和下游控制站蔡旗水文站1981年10月至2003年9月平均径流资料，分析近20a来人类活动，主要是中下游人工绿洲农业活动对石羊河流域地表径流的影响．结果表明：近20a来在出山口径流变化不大的情况下，下游蔡旗水文站的来水量明显减少；中游人工绿洲NDVI累积与蔡旗水文站径流量呈明显负相关，而与上下游径流差呈正相关，这表明可用NDVI累积数据代表人类活动因素分析其对径流变化影响的研究．1992年以后中游人工绿洲NDVI累积与上下游径流差相关关系明显好于1992年以前的关系，由此可见1992年以后人类活动对径流的影响要强于1992年以前．中游人工绿洲NDVI累积与上下游径流差呈正相关表明，中游人类活动直接导致下游径流量的减少，而下游绿洲NDVI累积的变化与下游河流来水量没有直接的关系，这可能与下游绿洲的发展依靠地下水的过渡开采实现，这种方式的绿洲发展可能难以长期维持．农业绿洲NDVI累积趋势分析表明，中游农业绿洲有向外扩张趋势，而下游民勤农业绿洲有东退西进之势．

英文摘要：

The human activities, especially the agricultural activities in the middle and lower reaches of Shiyang River, have great impact on the runoff of the Shiyang River in the recent 20 years. The impact was analyzed by using the NDVI data, the cumulative values of agriculture oasis based-on ERDAS, combined with the discharge data of Shiyang River from 1982 to 2003. It is revealed that the discharge in Caiqi Station sharply decreased while the discharge of the outlets of Qilian Mountain varied weakly. The cumulative NDVI in the middle reaches showed a significant negative correlation with the discharge of Caiqi Station, but a positive correlation with the discharge difference between the upper reaches and lower reaches. Furthermore, bordered in 1992, the correlation between the cumulative NDVI and the discharge difference in 1993-2003 was better than that in 1982-1992. It implies that human activities lead to a decrease of runoff in the lower reaches and a greater effect after 1992. However, there was no positive relationship between discharge in Caiqi Station and the cumulative NDVI in the lower reaches. This may attribute to the overexploitation of groundwater in the downstream oasis. In addition, the spatialtemporal analyses of the cumulative NDVI show that there is an extending tendency of agriculture oasis in the middle reaches towards the lower reaches, while the Minqin Oasis in the lower reaches seems advance westwards and retreat from east.