India is among the countries that uses a significant fraction of available water for irrigation. Irrigated area in India has increased substantially after the Green revolution and both surface and groundwater have been extensively used. Under warming climate projections, irrigation frequency may increase leading to increased irrigation water demands. Water resources planning and management in agriculture need spatially-explicit irrigated area information for different crops and different crop growing seasons. However, annual, high-resolution irrigated area maps for India for an extended historical record that can be used for water resources planning and management are unavailable. Using 250 m normalized difference vegetation index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS) and 56 m land use/land cover data, high-resolution irrigated area maps are developed for all the agroecological zones in India for the period of 2000–2015. The irrigated area maps were evaluated using the agricultural statistics data from ground surveys and were compared with the previously developed irrigation maps. High resolution (250 m) irrigated area maps showed satisfactory accuracy (R2=0.95) and can be used to understand interannual variability in irrigated area at various spatial scales.
Compound extremes of soil moisture (SM) drought and high vapor pressure deficit (atmospheric aridity) are disastrous for natural and social systems. Despite a significant expansion in irrigated area in India, the role of irrigation on SM and atmospheric aridity is not examined. We used observations, reanalysis datasets, and high-resolution simulations from the Weather Research and Forecasting (WRF) model to show that irrigation significantly modulates SM and atmospheric aridity in India. The Indo-Gangetic Plain, which is one of the most intensively irrigated regions in the world, experienced significant (P-value = 0.03) cooling (∼0.8 °C) and an increase in solar-induced chlorophyll fluorescence during the crop growing season (November–February). Atmospheric aridity has significantly (P-value = 0.0002) declined (−1.38 kPa) while SM (1.6 m3 m−3) and relative humidity (RH) (2.0%) have increased over the Indo-Gangetic Plain during 1979–2018. We conducted high-resolution simulations using the WRF model to examine the role of irrigation on atmospheric aridity. Irrigation strongly modulates SM drought and atmospheric aridity by increasing latent heat and RH and reducing sensible heat. Our findings have implications as irrigation can influence compound extremes of SM drought and atmospheric aridity. Climate models need to incorporate the influence of irrigation for reliable projections in the intensively irrigated regions.
Irrigated area in India has significantly increased after the green revolution. However, quantification of irrigation influence on vegetation health and land surface temperature (LST) remains limited. Here, we develop a high‐resolution (250 m) remotely sensed data of enhanced vegetation index (EVI) and LST from Moderate Resolution Imaging Spectroradiometer for 2000–2017 at the 8‐day temporal resolution for India to quantify the role of irrigation in the modulation of EVI, LST, and vegetation health. We show that irrigation‐dominated regions have significantly (p value < 0.05) higher EVI and cooler (1–2 K) LST during the crop‐growing season in the Indo‐Gangetic Plain. Vegetation health in highly irrigated areas is poorly correlated with meteorological drought primarily due to irrigation. Moreover, vegetation health is negatively correlated with groundwater storage anomalies in the highly irrigated Indo‐Gangetic Plain. Irrigation in Indo‐Gangetic Plain modulated EVI, LST, and vegetation health and resulted in groundwater depletion during 2002–2016.
Compound extremes of low soil moisture and high vapor pressure deficit (VPD) have implications on terrestrial carbon sequestration, vegetation growth, and net primary productivity (NPP). Yet, the role of irrigation on the occurrence of compound extremes remains unexplored in India. Here, we use satellite observations, reanalysis data sets, and high‐resolution simulations from the Weather Research and Forecasting (WRF) model to show that irrigation significantly reduces the frequency of compound extremes of low soil moisture and high VPD in India. The Indo‐Gangetic plain witnessed a significant (p < 0.05) increase in mean annual soil moisture while a substantial reduction in VPD during 1979–2018. Moreover, irrigation caused considerable cooling over the Indo‐Gangetic plain during 1982–2018. The increase in soil moisture and the decline in VPD partly contributed to a substantial rise in Normalized Difference Vegetation Index (NDVI) and NPP. We conducted high‐resolution simulations using the WRF model to examine the role of irrigation in modulating the frequency of compound extremes during 1979–2018. The WRF simulations under the irrigation‐on show a considerably reduced frequency of the compound extremes compared to the irrigation‐off (control) simulations. Irrigation modulates compound extremes by changing the land surface energy budget and planetary boundary layer height. Therefore, there is a need to consider irrigation for reliable projections of compound extremes under a warming climate in intensively irrigated regions.
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