Project No: 16309719

Title: Modeling and quantifying the effect of groundwater exploitation for irrigation on regional climate and hydrological cycle

Principal Investigator: Prof. Eun-Soon IM

Co-Investigator: Prof. Elfatih A. B. ELTAHIR, Prof. Min-Hui LO

Abstract:

The North China Plain has severe groundwater depletion due to intensive irrigation. As summer rainfall is projected to decrease in northern China under global warming, the dependency on groundwater in the North China Plain is expected to increase in the future. While groundwater pumping assures sufficient soil wetness for growing plants, increased soil moisture alters the surface energy partitioning and water cycle through the modulation of heat, moisture, and momentum exchange between the land surface and atmosphere. Therefore, the effects of groundwater overexploitation are not restricted to the region in which groundwater pumping occurs; groundwater overexploitation can also critically affect the hydroclimatology of remote places and the global water budget. However, our knowledge of the broader impacts of pumped groundwater and of the connection between pumped groundwater and the hydrological cycle is quite limited. As a result, the dynamic interactions between the atmosphere, land surface, and subsurface in response to water table fluctuations are not accurately represented in current climate models. The proposed project will be the first attempt to quantify the impact of groundwater pumping on regional climate and hydrological cycle based on a comparative assessment using both a global climate model (GCM) and a regional climate model (RCM) that share the same land surface model (Community Land Model, CLM4.5). To improve the representation of groundwater dynamics, a new module accounting for subgrid heterogeneity in the water table and lateral groundwater flow will be incorporated into the existing groundwater scheme of CLM4.5. A focus will be given to the comparison of the climate responses to groundwater pumping in northern China simulated by GCM and RCM with the same modified CLM4.5. This comparison will help to assess the robustness of the model responses and moderate the model-dependent implications that often refers to a common deficiency embedded in the modeling study. The impact of groundwater pumping on the future climate will then be investigated by dynamically downscaling projections under business-as-usual emission scenario. In addition, the contributions of regional and global groundwater pumping to sea level changes will be quantified, which will help uncover the mechanism determining the fate of pumped groundwater. This project will strengthen our understanding of the nonlinear climate processes that occur when the atmosphere, land surface, and subsurface are perturbed by groundwater pumping, based on an unprecedented level of simulations produced using state-of-the-art GCM and RCM with a new groundwater module.