基于校正和验证后的SWAT模型，分析了密云水库沿湖区7种不同施肥情景的氮磷流失状况，结果表明：研究区现有施肥方案下总氮的流失量达1 427 t，但在采用专家推荐施肥情况下均能较少30%左右；总磷流失问题不显著，现有施肥方案下每年流失量为0.7 t，在各改进施肥方案下流失量减少不显著.因此，氮素流失控制是密云水库水质保护首要需要解决的问题.氮素流失控制的关键区域主要为冯家峪东南部、太师屯中东西部、不老屯中东部、新城子中西部，白马关河中下游、清水河中上游、安达木河中下游这些具有较高的氮流失负荷且氮肥过量施用问题严重的区域.

The total nitrogen and total phosphorus loss were evaluated in the study by using a calibrated Soil and Water Assessment Tool (SWAT) model under seven nutrient application scenarios.The results showed that the total nitrogen losses reached about 1 427 t per year in the research region but can be decreased greatly by about thirty percent when the experts′ suggested nitrogen input scenarios applied. In contrast, the loss of total phosphorus was not so seriously in the region with about 0.7 t loss per year and little can be decreased under the six improved scenarios. It indicated controlling the nitrogen loss in the region was urgently needed in the lakeshore region of Miyun Reservoir. And the critical areas for nutrient control were located at southeast Fengjiayu town, central and eastern, western of Taishitun town, central and eastern of Bulaotun town, midwest of Xinchengzi town; middle and lower of Baimaguan reach, upstream of Qingshui reach, middle and lower of Andamu reach, which have high rate of nitrogen application and nitrogen loss.