A BASELINE QUANTIFICATION OF AGRICULTURAL WATER USE EFFICIENCY OVER INDIAN REGION USING GEO-LEO SATELLITES
The agricultural water use efficiency (AWUE) over India was evaluated during 2009–2014 through three steps e.g. productivity mapping using MODIS GPP; consumptive water use (CWU) mapping in terms of evapotranspiration (ET) partioned into green (CWUg; ET streaming from rainfall) and blue (CWUb; ET streaming from irrigation) water; AWUE mapping i.e. the ratio of the seasonal sum of GPP and CWU in terms of green (AWUFg) and blue (AWUFb) water. The CWU was estimated from seasonal sum of crop ET (ETc). ETc was obtained from composite crop co-efficient from INSAT and corresponding reference ET (ET0), where daily ET0 was estimated using daily solar insolation (Kalpana-1VHRR) and metrological data from Weather Research and Forecasting (WRF) variables through data fusion in FAO-56 framework. Monthly effective rainfall (ER) was estimated from daily NOAA CPC rainfall data using USDA SCS method. Actual ET (ETa) was estimated using single-source surface energy balance framework with thermal observations from MODIS and MERRA reanalysis data. The CWUg at seasonal scale was determined using ER, ETa and CWU, whereas CWUb was estimated as the difference between ETa and CWUg followed by estimation of AWUEg and AWUEb. The average AWUEg and AWUEb during kharif and rabi seasons were found to be 1.13 kg Cm−3 and 1.25 kg Cm−3 respectively with highest share goes to Indo-gangetic plains due to high crop intensification. The arid and semiarid tract showed low AWUE. The baseline assessment of satellite based AWUE at country scale providesa scope for better management of agricultural water with respect to food security.