Decadal gross level assessment of green and blue consumptive water use over Indian agro-ecosystems

Abstract

ABSTRACT Assessment of consumptive water use (CWU) and water productivity at the regional scale is important to diagnose vulnerable zones to improve water use efficiencies in cropland to achieve the sustainable development goal 6.0 prescribed by the United Nations. The present study was carried out to segregate and quantify CWU into agricultural green (CWUg) and blue (CWUb) water use and water productivity (AWP) on seasonal, annual, and decadal (2009–2018) scales over the Indian region using satellite remote-sensing data from geostationary and polar-orbiting platforms. A logical algorithm was used to determine partitioned water use from a combination of satellite-based estimates of key variables such as agricultural water demand (AWD), actual evapotranspiration (ETa), and effective rainfall (ER). Satellite-based estimates of CWU were evaluated with respect to ground reference that showed underestimation of the order of 15–32% but with a strong Pearson’s correlation coefficient (r = 0.80–0.99) and coefficient of determination (R 2 = 0.64–0.98). The reasons for this difference and uncertainties in satellite-based inputs have been explained. The decadal mean of CWU at annual scale showed wide spatial variation over India with 84% and 16% share of CWUg and CWUb, respectively, in kharif season and 27% and 73%, respectively, in rabi season. A non-significant increasing trend in CWUg,kharif (0.57%) and a decreasing trend in CWUb,kharif (–5.18%), CWUg,rabi (–2.81%), and CWUb,rabi (–1.77%) were observed over 10 years. A decreasing trend in green AWP (AWPg) (–0.18%) in kharif season reveals a lack of sustainable adoption of green water management practices while a significantly increasing trend in AWPb (2.65%) in rabi season reveals sustainable adoption of efficient irrigation management practices over 10 years. These long-term estimates would help in smoothing out trade-offs of water use versus water productivity, reducing the vulnerability and aiding in decision-making for water savings, controlled water allocation, strategic policy formulations for water, and food security especially through sustainable management practices in rainfed agriculture.