Global irrigation cooling benefits: the spatial-temporal patterns and possible mechanisms

Irrigation benefits crop yields directly by providing additional water and indirectly by reducing surface temperature (i.e., irrigation cooling benefit). To date, how irrigation cooling benefit is spatial-temporally distributed remains elusive at the global scale. Here, by synthesizing various datasets and data-driven models, we quantify global irrigation cooling benefits and explore the underlying mechanisms behind its spatial-temporal patterns. Results show that irrigation has exerted a cooling benefit (relative to its total benefit) of 7.76%, 9.43%, 6.92%, 5.0% and 2.82% for the globe, Northeastern China, North China Plain, Southern Great Plain and Northern India, respectively. A greater global-scale benefit of 8.62% is estimated for the year 2010 which is mainly achieved by reducing yield sensitivity to cooling rather than cooling magnitude. Maximum temperature and irrigation properties are found to modulate the spatial pattern of irrigation cooling benefit, while regional characteristics (e.g., the coefficient of variation and mean of irrigation yield increase) control its temporal differences. Additional analysis shows that the grid resolution and the number of maize patches are the main uncertainty sources of the estimated irrigation cooling benefits, suggesting the importance to develop more finer and long-term observational yield datasets under rainfed and irrigated conditions.