以首都水源涵养功能区内的官厅水库和密云水库为研究对象，评估了两个水库1980年以来的水域面积变化，分析了降水量、植被覆盖度和人为用水量三项因素的影响。利用1980—2022年长时序遥感影像提取了水库水域面积，计算了植被覆盖度，使用Pearson相关分析探讨了影响因素相关关系。研究表明：（1） 自2013年以来，两个水库水域面积均持续增加至历史高位，表明水源涵养成效显著。（2） 近40 a来，两个水库的水域面积变化过程同步性明显，均表现为上升期-高位保持期-下降期-地物维持期-恢复期5个阶段。（3） 水库上游张家口段流域年降水量与水库面积之间没有表现出相关性；与解译影像同期的6—7月降水量与水库面积之间也没有表现出相关性。（4） 官厅水库上游张家口段的植被覆盖度整体呈现上升态势，2000年是一个变异点。密云水库上游张家口段的植被覆盖度持续稳定在0.7水平上。相关分析表明，植被覆盖度与水库水域面积之间没有相关性。（5） 永定河流域张家口段人为用水量从2000年来整体上逐年减少0.2×10⁸ m³，与官厅水库水域面积呈显著负相关，有效增加了水库入库水量。（6） 2019年以来流域水库集中输水和引黄补水，对官厅水库水域面积和沿河地区生态补水影响较大，建议对张家口水源涵养成效从地表径流入库量、地下水回升量、生态补水量等方面进行综合评估。

This study focuses on the Guanting and Miyun reservoirs in the capital water conservation functional area to evaluate water area changes and analyze the impact of precipitation, vegetation coverage, and human water consumption since 1980. The study used long-term remote sensing images from 1980 to 2022 to extract the water area of each reservoir and calculate vegetation coverage. Pearson correlation analysis was used to explore the correlation between the three impact factors. We found that the water area of both reservoirs continuously increased, with historical highs since 2013, indicating significant water conservation achievements since the 18th National Congress of the Communist Party of China. In the past 40 years, the water area change process of the two reservoirs has significantly synchronized, with five different periods, including rising, high level maintenance, falling, ground feature maintenance, and recovery periods. There was no correlation between annual precipitation and reservoir area in the Zhangjiakou section upstream of the reservoir and also no correlation between precipitation and reservoir area in June and July during the same period. The vegetation coverage in the Zhangjiakou section upstream of the Guanting reservoir had an overall upward trend, with 2000 being a variation point. The vegetation coverage of the Zhangjiakou section upstream of the Miyun reservoir continues to stabilize at a level of 0.7. Correlation analysis shows that there is no correlation between vegetation coverage and reservoir water area. The artificial water consumption in the Zhangjiakou section of the Yongding River Basin decreased by 20 million m³ per year since 2000, showing a significant negative correlation with the water area of the Guanting reservoir and effectively increasing the inflow volume of the reservoir since 2019. The centralized water conveyance and water diversion from the Yellow River have had a significant impact on the water area of the Guanting reservoir and on ecological water replenishment along the river. Future research is needed to comprehensively evaluate the water conservation effectiveness of Zhangjiakou in terms of surface runoff into the reservoir, groundwater recovery, and ecological water replenishment.