Data-based global groundwater use for irrigation in CLM5: hotspots and sustainability implications

Abstract

Groundwater withdrawal from confined aquifers is a critical source for irrigation. However, over the past few decades, unsustainable practices have persisted in many large river basins to ensure food security and sustain livelihoods. The current approach to represent the actual groundwater withdrawal in the Community Earth System Model (CESM) is limited, posing challenges to effective groundwater management in irrigation. We integrated global datasets on observed groundwater consumptive use into the CESM coupled with the Community Land Model (CLM5) to address this. These datasets were taken from a published groundwater data inventory for 15,038 national and subnational administrative units globally and reconstructed at a spatial resolution of 0.5° × 0.5°. We evaluated the model’s simulated value against authoritative datasets, including CGWB (for India) and USGS (for the US), to confirm the accuracy of our approach. For instance, in the Central High Plains of the US, the controlled simulation estimated 10 km³ of groundwater use, whereas the experimental setup showed 16.5 km³, and the reported value from the USGS is 18 km³ for 2015. Our global simulation results showed a 28% increase in annual groundwater use for irrigation compared to the controlled irrigation simulation (422.4 km³ vs. 304.5 km³) run for a period of 15 years from 2001 to 2015. Notable cumulative groundwater use differences were observed in 2012 (146 km³), 2011, and 2005 (141 km³ each). Based on the results we identified over 15 major hotspot basins, defined as regions where a majority of grids exhibit a high groundwater abstraction percentage as compared to surface water irrigation. Furthermore, to achieve a sustainable solution we investigated substituting high-water-demand crops with low-water-requirement crops in hotspot regions and simulated groundwater management scenarios for irrigation. Our study provides critical insights into groundwater depletion issues in hotspot basins, highlighting the interconnected dynamics of climate, water resources, and irrigation. These findings contribute to the development of more sustainable water management strategies on a global scale.

Keywords: Irrigation water use, Earth system model, Simulation period, Sustainability

Acknowledgment

This study was supported by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science, ICT, and Future Planning (RS-2024-00456724), and Korea Environment Industry & Technology Institute (KEITI) through the R&D Programs for Innovative Flood Protection Technologies against Climate Crisis, and Water Management Program for Drought funded by the Korean Ministry of Environment (MOE) (RS-2023-00218873 and RS-2023-00231944).