Irrigation cooling effect reduced by water-saving practices

Irrigation modifies land-atmosphere interactions, cooling land surface and mitigating heat extremes. However, the global shift toward water-saving irrigation technologies raises new questions about the climate regulation capacity of irrigation under constrained water use. Using two decades of high-resolution satellite observations across China, we show that widespread water-saving adoption has substantially weakened irrigation’s biophysical cooling effects, particularly in late summer and early spring. Daytime land surface cooling declined by 0.05 K/decade (15%) nationally and up to 0.20 K/decade (9%) in arid regions, primarily due to reduced soil evaporation and increased sensible heat flux. This trend was absent in semi-arid and semi-humid regions because of enhanced crop transpiration. Conversely, nighttime cooling intensified by 0.04 K per decade, likely driven by lower soil thermal capacity and radiative feedbacks. These findings reveal an emerging trade-off between water-use efficiency and climate mitigation, calling for considering evolving irrigation practices in Earth system models and climate change projections. Water-saving irrigation weakens daytime cooling and enhances nighttime cooling across China; satellite and surface energy balance analyses (2001–2020) link this to reduced soil evaporation, increased sensible heat, and altered land–atmosphere interactions.