[A-HW21] Surface and subsurface hydrologic models: Technical advances and applications for water management

[AHW21-06] Extraction of recharge in integrated surface and subsurface hydrologic models

*Chengcheng Gong^1,2, Peter G. Cook³, René Therrien⁴, Philip Brunner² (1.Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Chang’an University, Ministry of Education, P. R. China, 2.Center for Hydrogeology and Geothermics (CHYN), University of Neuchâtel, Switzerland, 3.National Centre for Groundwater Research and Training & College of Science and Engineering, Flinders University, Adelaide, SA, Australia, 4.Department of Geology and Geological Engineering, Université Laval, Québec, QC, Canada)

Keywords:Groundwater recharge, Integrated surface and subsurface hydrologic models, Water resources management, Definitions, HydroGeoSphere

Integrated surface and subsurface hydrological models simulate surface water flows as well as unsaturated and saturated zone flows, as well as the interactions between these zones. They are therefore very useful for supporting decision-making in the context of sustainable water management. In the context of sustainable water resources management, quantification of groundwater recharge is sometimes considered important. However, since integrated models simulate the flux between the unsaturated and saturated zones, they do not require recharge as an input. It is nevertheless often expected that recharge can be reliably extracted from them. In this study, we implemented commonly used definitions of groundwater recharge in an integrated model (HydroGeoSphere). The results show that the commonly used definitions of groundwater recharge implemented in such models do not yield meaningful results. The problems arise because of the storage dynamics in the capillary fringe above the water table. However, since recharge is not of direct interest for water resource management, the difficulty in accurately quantifying recharge in integrated models is not of concern. Rather, since the models simulate both surface water, unsaturated and saturated zone flows, they are able accurately to predict groundwater declines arising from land surface activities and climate change. They, therefore, are ideally suited to addressing water resource problems.