Estimation of crop water requirement in rice-wheat system from multi-temporal AWIFS satellite data

The present study investigates remote sensing based approach of large-area crop water requirement using vegetation indices as proxy indicator of crop coefficient (Kc). This study is an attempt to estimate the reasonably proper Kc for lowland rice and wheat and subsequently crop evapotranspiration (ETc) in rice-wheat system using multitemporal IRS P6-AWiFS data integrated with meteorological data following FAO-56 approach. Geometrically and radiometrically corrected multi-temporal AWiFS images were classified by rule based classifier to discriminate rice-wheat system from other cropping system. Monthly biophysical parameters viz., fractional canopy cover (f_c) and water scalar factor (Ws) were derived from spectral indices in order to adjust Kc for the different growth stages in rice-wheat system. The results showed that after including Ws with f_c for rice, degree of fit (R²) has been significantly improved from 0.72 to 0.94 for Kc estimation of rice. Satellite derived Kc has captured the effect of phenology and management practices in study area. The estimated crop water requirement was 241.66, 531.34, 440.86 and 192.63 Mha.m for rice and 127.43, 135.77, 305.55, 262.84 and 204.5 Mha.m for wheat at various growth stages.