Modelling the groundwater pumping for agriculture in the Noah-MP model to support sustainable water management over the North China Plain

The intensive irrigation-linked groundwater abstraction in North China Plain (NCP) is dramatically affecting the hydrological processes and regional climate. Impacts from these anthropogenic groundwater withdrawals are evident in the fluctuation of each component in the terrestrial water cycle, the lack of groundwater sustainability, and regional climate extremes. Ensuring future groundwater security within this context will largely depend on how accurately the human activities in the Human-Earth system model were represented. However, to date, most hydrological models and land surface models either ignore the representation of human intervention or realistically model sophisticated human activity processes. In this study, we incorporated two groundwater-fed irrigation schemes in the Noah-MP model and further used realistic irrigation water use results constraining irrigation water withdrawals. We evaluate the influence of the groundwater pumping representation on the simulation of evapotranspiration and groundwater water table depth using Fluxnet-MTE ET data and observational groundwater well data, respectively. The Noah-MP simulation with groundwater-fed irrigation produced ET that matched the magnitude of observations-based Fluxnet-MTE ET values. Observational well-depth anomaly fluctuations can be reproduced in irrigated areas within the groundwater-fed simulation. In addition, the improvement of groundwater pumping also helps to improve terrestrial water storage estimates in higher resolution. We estimated that, over a seasonal cycle, groundwater-fed irrigation in the model can account for 80% of the declining terrestrial water storage trend from 2003 to 2016. Our approach and results reinforce the importance of parameterizing human activities in the Human-Earth system model and better address the water security challenges under climate change and human interventions.