[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

[AGE28-P10] The dynamic process of river-groundwater conversion and its ecological effects in arid areas

*Wenke Wang^1,2, Zhitong Ma^1,2 (1.Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Changan University, Ministry of Education, P. R. China, 2.School of Water and Environment, Changan University, P. R. China)

Keywords:River-groundwater conversion, Dynamic process, Flow system, Ecological effect, Arid area

River and groundwater conversion is the important component of the terrestrial hydrological cycle, which has a close hydraulic connection and frequent conversion relationship between them in arid regions. However, affected by the influence of natural factors and human activities, the dynamic transition mechanism between rivers and groundwater tends to be complicated which induces a series of negative ecological effects, and the challenges of water resources and ecological environmental protection are highlighted, including the guarantee of high-quality water sources, the development of river ecosystems and their biodiversity, and the improvement of environmental management mechanisms. The interaction of rivers and groundwater has become the core to a series of major contemporary challenges. Based on the field investigation, in situ experiments, dynamic observations, and numerical simulations, this paper focuses on typical watersheds in arid and semi-arid areas and conducts the studies the dynamic process and ecological effects of river and groundwater conversion through the integration of different scales along time series. The following results are obtained in this study: (1) Six typical modes and eight types between rivers and groundwater transformation are proposed in arid areas, and the influencing factors and driving forces of their transformation are analyzed; (2) The complete dynamic process of the evolution of rivers and groundwater from saturated linear connection to unsaturated disconnection is revealed, and important discriminant marks of each hydrodynamic evolution stage of river-groundwater interaction are systematically identified; (3) The nonlinear relationship between the disconnected seepage and river depth, as well as the important scientific law of non-Darcy flow is found, and the analyzed solution of non-linear river infiltration flux is derived; (4) The multi-level nested flow system and its ecological effects under the interaction between rivers and groundwater in typical basins are revealed, and a multi-dimensional critical indicator system for ecological function degradation and crisis in arid basins is established; (5) The interaction between rivers and groundwater in the basin is identified, and the regulation measures and countermeasures to maintain the sustainable development of river ecology are put forward. This study enhances the understanding of the dynamic processes of rivers and groundwater interaction, conversion, and evolution in similar arid areas, and can provide guidance for the rational water resources development, ecological environmental protection and management in the basins.