Strong linkage between irrigation and land surface cooling in India

A significant increase in irrigated area has been observed in India since the green revolution, however the influence of irrigation on vegetation health, land surface temperature (LST), and vegetation drought remains to be explored in detail. We develop a high-resolution (250m) remotely sensed data of enhanced vegetation index (EVI) and LST from Moderate Resolution Imaging Spectroradiometer (MODIS) at 8-day temporal resolution for the period 2000-2019 for India. We quantify the role of irrigation in the modulation of EVI, LST, and vegetation stress. The results show significantly higher EVI (p-value < 0.05) and cooler LST (1-2 K) in the irrigation dominated regions during the crop-growing season over the Indo-Gangetic Plain. A poor correlation between vegetation and meteorological drought (Standardized Precipitation Evapotranspiration Index-SPEI and Standardized Precipitation Index-SPI) was found in highly irrigated regions due to irrigation. While irrigation resulted in an elevated vegetation growth, it has caused groundwater depletion in Indo-Gangetic Plain. Simulations (with and without irrigation) using Noah land surface model coupled with the weather research and forecasting (WRF) show cooling due to irrigation that is consistent with the observational evidence.