An evaluation of the impact of irrigation and groundwater pumping on regional climate using an improved Earth-System model

Irrigation is one of the crucial Nature-Human interactions and also an anthropogenic forcing in the Earth system. The literature has shown that artificial water supply to soil for example water exploitation from groundwater for irrigation can alter water and heat budgets at the land surface, resulting in changes in regional climate and hydrological cycles. Due to the expected increase in irrigation to meet growing food demand, the impact of irrigation is likely to increase further in the future. Therefore, it is essential to consider to better understand the irrigation-induced changes in the various components of the Earth system, today and in the future.

Our research aims to advance the quantitative understanding of the impact of irrigation and groundwater exploitation as anthropogenic drivers of regional climate and environmental changes. We developed an earth system modeling framework coupling the updated Earth system model, MIROC-ES2L (Model for Interdisciplinary Research on Climate, Earth System version 2 for Long-term simulations) and newly implemented hydrological human activity modules. This modeling framework enables to simulate a fully coupled Nature-Human system including water cycle dynamics related to irrigation.

Our preliminary results show notable differences between simulations with and without the irrigation process. Here, we show the hydrological variables affected by irrigation and identify the regions and timings of significant impact. Further, we estimate the individual contribution of groundwater and surface water use to such impacts by irrigation.