Runoff evolution and wetland ecological response in Lake Baiyangdian Basin in recent 60 years

Abstract

白洋淀是雄安新区的核心生态功能区，近几十年来面临水源不足、湿地萎缩等生态环境问题.选取白洋淀流域上游王快、西大洋及拒马河3个子流域开展河川径流演变研究，结合1969年以来18期白洋淀湿地遥感影像，揭示白洋淀流域河川径流驱动湿地演变的过程机制.结果表明：近60年来白洋淀流域山区径流量呈持续衰减趋势，从P1阶段（1961—1979年）至P3阶段（1997—2019年），典型子流域年径流系数均值由0.29降至0.12，山区年径流总量由30.84×10⁸ m³/a降至11.37×10⁸ m³/a，降幅达63.1%，梯田修建、地下水开采等人类活动是导致径流衰减的主要原因；不同子流域产流和基流减少对径流衰减的贡献率存在差异，以变质岩为主的王快子流域径流衰减的主要原因是地表产流减少，碳酸盐岩分布较广的拒马河子流域径流衰减的主要原因是基流减少；白洋淀湿地面积变化受控于地表水位波动，近60年来白洋淀湿地退化的直接原因是入淀流量减少，根本原因是人类活动影响导致的山区径流衰减.;Baiyangdian Wetland is the main ecological functional area of Xiong'an New Area. In recent decades, Baiyangdian Wetland has been faced with ecological and environmental problems, such as water shortage and wetland degradation. Three typical sub-basins (Wangkuai, Xidayang and Juma River) in the upper reaches of Lake Baiyangdian Basin were selected to study the runoff evolution in the past 60 years. Based on 18 remote sensing images of Lake Baiyangdian Wetland since 1969, the evolution process of Lake Baiyangdian Wetland was analyzed. The results showed that the mountain runoff in Lake Baiyangdian Basin decreased continuously in the past 60 years. From P1 (1961-1979) to P3(1997-2019), the average annual runoff coefficient in typical basins decreased from 0.29 to 0.12, and the total annual runoff in mountainous areas decreased from 30.84×10⁸ m³/a to 11.37×10⁸ m³/a, decreasing by 63.1%. Human activities such as terrace construction and groundwater exploitation are the main causes of runoff attenuation. There are differences in runoff and baseflow reduction in different sub-basins. The lithology of Wangkuai sub-basins is mainly metamorphic rock. The main reason for runoff attenuation is the decrease in surface runoff. The karst strata in the Juma River basin are widely distributed, and the main reason for runoff attenuation is the decrease in base flow. The direct factor affecting the area of Lake Baiyangdian Wetland is the fluctuation of surface water level. The decrease of water inflow is the direct cause of the degradation of Lake Baiyangdian Wetland in recent 60 years, and the fundamental reason is the attenuation of mountain runoff caused by human activities.