京津冀山区水平衡演变及其影响因素识别

定量识别水平衡演变影响因素及其贡献是开展生态环境保护和水资源科学管理的前提。以往成果对人类活动中不同影响因子的归因识别与定量研究较少。在识别京津冀山区水平衡演变的基础上，采用双累计曲线法、径流变化定量分离法分析了降水变化和人类活动对水平衡演变的影响；分别选择涞源盆地、清水河小流域，分析了用水增加以及林业耗水增加对水平衡演变的影响。结果显示：（1）近65 a来，京津冀山区年降水量总体呈缓慢减少趋势，速率为0.97 mm/a，21世纪以来，年降水量有小幅增加趋势；（2）相比于1956—1979年基准期，1980—2000年降水变化和人类活动对天然径流衰减的影响程度分别为49.25%、50.75%，水土保持和植树造林是影响水平衡变化的主要人类活动因素，2001—2020年天然径流衰减的主要原因为人类活动，影响程度达到68.2%，其中地下水开采增加是主要人类活动因素，林业耗水量增加是重要人类活动因素；（3）山区水库蓄水及用水增加直接造成实际径流衰减，是造成平原区水平衡加剧的主要原因；（4）清水河小流域研究结果表明，在一定规模下，林地耗水增加与山区径流衰减呈正相关关系。林地面积增加对径流衰减的影响存在15～20 a的滞后性。林地面积达到23.48%后，林地耗水增加对天然径流产生了明显负作用，平均每增加1 km2林地，耗水量增加37.25×104 m3/a，天然径流量衰减59×104 m3/a，林地年均耗水增加量占流域天然径流衰减量的63.22%，表明林地面积增加起到水源涵养的作用，同时也造成了有效径流的减少。研究成果对开展京津冀山区生态环境保护、水资源科学管理以及水平衡调控具有重要意义。

Identifying the evolution of water balance and influencing factors in the mountainous area of Beijing-Tianjin-Hebei

Quantitatively identifying the effects and contributions on the water balance evolution is the premise of ecological environmental protection and scientific management of water resources. However, most of the previous studies focused on the effects of climate change and human activities on runoff attenuation; few studies paid attention to the attribution and quantitative identification of different factors in human activities. On the basis of identifying the evolution process of water balance in the study area, the effects of precipitation change and human activities on the evolution of water balance at different time periods were analyzed by using the double cumulative curve method and the quantitative separation method of runoff change. The effects of the increase of water resource exploitation and forestry water consumption on water balance evolution were analyzed in the Laiyuan Basin and Qingshuihe Basin, respectively. The results show that: (1) The annual precipitation presented a slightly decreasing trend with a decreasing rate of 0.97 mm/a in the past 65 years; since the 21st century, precipitation has increased slightly. (2) Compared with the period of 1956−1979, the natural runoff attenuation during 1980−2000 was affected by precipitation change and human activities, with corresponding contributions of 49.25% and 50.75%, respectively. Soil and water conservation and afforestation are the main factors of human activity affecting the change of water balance. the decrease in natural runoff was mainly caused by human activities, with the influence contribution of 68.2%. The increase of groundwater exploitation was the main factor of human activity, and the increase of water consumption was the second factor of human activity. (3) The increase in reservoir storage and water consumption in mountainous areas led to the actual runoff attenuation directly, which was the main reason for the intensification of water balance in the plain areas. (4) In the Qingshuihe River Basin, there was a positive correlation between the increase of forest water consumption and the decline of mountain runoff at a certain scale. The effect of runoff attenuation on the increase of forest area was not immediate, with a lag of 15−20 a. As the forest area reached 23.48%, the increase in forest water consumption had a significant negative effect on the natural runoff. An average increase of 1 km2 of forest land led to water consumption being increased by 37.25×104 m3/a, and the natural runoff being decreased by 59×104 m3/a. The increase in annual water consumption of forest land accounted for 63.22% of the natural runoff attenuation. It indicated that the increase in forest area played an important role in water conservation, resulting in a decrease in effective runoff. The results of the study are of great significance for the ecological and environmental protection, scientific management of water resources and regulation of water balance in the Beijing-Tianjin-Hebei mountain area.