Large-scale hydrological modeling in a multi-objective uncertainty framework – Assessing the potential for managed aquifer recharge in the North China Plain

The region studied is the 137.000 km² North China Plain (NCP). A region with high population density and a major agricultural production leading to unsustainable exploitation of groundwater resources. Previous modeling studies in the region have utilized simplified representations of model boundary fluxes, both regarding lateral inflows from surface and groundwater and related to water demands and consumptions. The current study focusses on developing a hydrological modeling framework, with better spatial descriptions of major water balance components regarding water demands, model boundary conditions of surface and groundwater inflows and evaporative losses due to irrigation. Compared to previous efforts, the modeling framework utilizes a novel multi-objective parameter optimization strategy combined with an ensemble modeling approach to illuminate optimization trade-offs and impacts of parameter uncertainty. Groundwater storage declines are estimated to be in the order of 25–55 mm/y for the period 2000–2013. The impacts of water management strategies are explored using the model ensemble and show that this decline can be counterbalanced by approximately 15–20 mm/y by substantial reductions in irrigation (20%) or implementation of planned inter-basin water transfers. Managed aquifer recharge in the form of infiltrating excess river peak flows, can only reduce groundwater storage declines to a limited degree. However, at the local to regional scale storage decline reductions from MAR are in the same order of magnitude as other extensive water management strategies.