黄河下游典型悬河段地表水-地下水对湿地形成条件影响

The Influence of Surface Water and Groundater on Wetland Conditions in the Typical Suspended River Reach of the Lower Yellow River

对比分析黄河下游径流及河道变迁特征、不同时期地下水流场特征,结合遥感解译手段解析地下水和地表水对沿黄湿地条件的影响,为该区湿地生态修复提供理论依据。结果表明:(1)黄河下游典型悬河段人工湿地面积增幅较多,自然湿地仍呈萎缩趋势,滩涂湿地破碎度上升,生态环境稳定性较差。(2)地表水流量和水位整体呈现逐年降低的趋势,且河道的游荡摆动依然明显,直接影响了河流滩涂湿地面积及其稳定性。(3)研究区浅层地下水位十余年最大下降5 m、二十余年最大下降9 m。浅层地下水的持续下降导致北岸堤外湿地面积减少;南岸堤外因引黄水和退水侧渗形成新的背河洼地,湿地面积呈增长趋势,生态环境稳定性相对较好。地表水和地下水连通性较好,较低的地下水位将会削弱河道径流的作用,对沿黄湿地整体发展不利。(4)减少地下水的开采,确保引黄水量充足,对黄河大堤外背河洼地部位湿地的发展有利。

This study compared and analyzed the characteristics of the Yellow River runoff and channel changes,as well as the changes in groundwater flow field during different periods.The impact of groundwater and surface water on wetland changes along the Yellow River were analyzed,combined with remote sensing interpretation methods.The results show that:(1)the areas of artifi-cial wetlands increase significantly,while natural wetlands are still showing a shrinking trend.The fragmentation of mudflat wet-land is increasing,and the stability of ecological environment is poor.(2)The flow and water level of the surface water show a decreasing trend by year,and the wandering swing of the river is obvious,which directly affects the area and stability of the river mudflat wetland.(3)The shallow groundwater level in the research area has experienced a maximum decrease of 5 m in the past decade and a maximum decrease of 9 m in the past twenty years.Due to the continuous decline of groundwater level,the wetland area outside the north dike of the Yellow River decreased.Due to the diversion of Yellow River water and the lateral in-filtration of receding water,a new back river depression has been formed outside the south dike,with an increasing trend in wet-land area and relatively good ecological environment stability.The connectivity between surface water and groundwater is good,and a lower groundwater table will weaken the role of river runoff,which is unfavorable for the overall development of wetlands along the Yellow River.(4)Reducing the exploitation of groundwater and ensuring sufficient water diversion from the Yellow River is beneficial for the development of wetlands in the lower reaches outside the dike.