Effects of irrigation and canal networks on groundwater–land surface interactions in the middle Heihe River Basin, China

Heihe River Basin, a typical endorheic river basin in northwest China. Agriculture is the highest water-consuming sector, utilizing approximately 70 % of available water resources, predominantly for irrigation purposes. However, limited studies have explicitly diagnosed the role of agriculture managements (such as irrigation and canal networks) on the water–energy cycles of the agriculture system. This study presents a suite of numerical experiments to analyze the effects of irrigation and canal networks on groundwater–land surface interactions using a 3D, fully integrated hydrologic model. The model has been validated against both observations and spatially distributed products, confirming its reliability in simulating regional hydrologic dynamics. The findings reveal that irrigation expanded the shallow water table depths (WTD) zone by 30 % and increased summer and fall streamflow by approximately 10 %. Additionally, irrigation substantially reduced soil temperature at WTD of 0.01–10 m (i.e., cooling effect), altering the strong correlations between water table depth and latent heat flux. Moreover, irrigation canals heightened streamflow peaks, and increased spatial variability in surface heat flux differences, particularly in sensible heat flux, even causing localized reversals. This study provides scientific evidence in understanding the role of agriculture activities in local water resources management. • A high resolution integrated hydrologic model was constructed. • Simulated hydrological variables agree well with the in-situ observations. • Irrigation altered the strong correlation between water table and latent heat flux. • Irrigation substantially reduced soil temperature at water table depth of 0.01–10 m. • Canals shifted the surface heat flux patterns.