西北典型内陆流域地下水与湿地生态系统协同演化机制

以生态输水为代表的湿地修复工程在西北内陆流域得到了广泛应用,生态输水情形下地下水与湿地植被的交互作用决定着湿地生态系统的演化过程。以西北典型内陆流域—石羊河流域青土湖湿地为研究区,基于地下水-湿地生态系统多要素一体化动态监测网络,结合稳定同位素和卫星遥感技术手段,分析生态输水情形下的地下水动态变化与湿地植被恢复情况,从水文地质角度揭示地下水与湿地生态系统的协同演化机制。结果显示:夏季末和秋季生态输水时,湖水补给地下水且土壤含水率增大,最大土壤含水率可达0.45 m³/m³;冬季湿地湖面和表层土壤冻结,湖水对地下水补给量减少,春季冻土和湖面消融导致地下水略有回升,同时增大土壤含水率;夏季在下次生态输水前湖面面积最小(湖面面积最小约为1 km²,地下水水位最大埋深为3.6 m),部分区域地下水补给湖水,此时表层土壤含水率也最低(最小土壤含水率为0.01 m³/m³);夏季末和秋季生态输水通过将生态水储存在地下水和土壤中进而作用于次年的植被恢复与生长,增大生态输水所形成的湖面面积有助...

Co-evolution mechanism of groundwater and wetland ecosystem in a typical inland watershed in northwest China

Wetland restoration projects represented by ecological water conveyance have been widely used in the inland watersheds in northwest China. The interaction between groundwater and wetland vegetation under the ecological water conveyance determines the evolution of wetland ecosystems. In this study, the Qingtu Lake Wetland of the Shiyang River Basin in northwest China is taken as the research area, and the groundwater dynamic change and wetland vegetation restoration under the condition of the ecological water conveyance are analyzed based on a multi-element integrated monitoring network of groundwater-wetland ecosystem, combining with technologies of stable isotopes and satellite remote sensing. The purpose of this work is to reveal the co-evolution mechanism of groundwater and wetland ecosystems from the perspective of hydrogeology. The results show that the lake water recharges groundwater and the soil moisture increases during the ecological water delivery in late summer and autumn (the maximum soil moisture of observation sites is 0.45 m3/m3). In winter, this recharge decreases with the freezing of lake and surface soil. The thawing of frozen soil and lake in spring leads to a slight recovery of groundwater and an increase in soil moisture. In summer, the lake surface and the groundwater level are the smallest before the next ecological water delivery (the minimum surface area is about 1 km2, and the maximum groundwater depth of observation sites is 3.6 m). Meanwhile, the surface soil moisture is also the lowest (the minimum soil moisture of observation sites is 0.01 m3/m3), and the groundwater recharges the lake in some areas. The ecological water conveyed in late summer and autumn can act on vegetation recovery and growth in the following year by storing the water in groundwater and soil. Increasing the lake surface area formed by ecological water is helpful in upgrading vegetation coverage (the average correlation coefficient is 0.655). The soil water environment formed by the interaction of surface water-soil-groundwater is the main factor affecting vegetation types, root distribution and water use strategy. It is mainly controlled by the groundwater depth. With the increasing groundwater depth, the vegetation types and root depths increase, and the vegetations tend to use deep soil water. The research results can provide a scientific basis for the restoration of wetland ecosystems and efficient use of water resources in the northwestern inland basins.