Remote sensing based vegetation indices and crop coefficient relationship for estimation of crop evapotranspiration in Ozat-II canal command

Abstract

The estimation of evapotranspiration is important for the water resource management, water requirement, water use efficiency and resulting crop productivity in canal command. The estimation of irrigation demand is really important for efficient management of water in the canal command area. The real time and spatial information on the area under irrigation and crops in the large command area for effective water management. Remote sensing provide a powerful tool for the identification of crops, crop status, area under crops, crop evapotranspiration, irrigation scheduling, etc. The crop evapotranspiration represents the crop water demand and governed by weather and crop conditions. The Food and Agriculture Organization (FAO) Penman-Monteith empirical calculation is an accepted method for calculating crop water requirements and has been tried and tested worldwide (Monteith, 1965; Allen et al., 1998;Gontia and Tiwari, 2010; Er-Raki et al., 2010; Papadavid et al., 2011). Remotely sensed spectral reflectance may provide an indirect estimate of crop coefficient or basal crop coefficients. Thecrop coefficient (K c) can be estimated from spectral vegetation indices since both of them are related to leaf area index and fractional ground cover. Farg et al. (2012) estimated crop coefficient (K c) and crop evapotranspiration (ET c) using satellite data integrated with the meteorological data and vegetation indices (NDVI, soil adjusted vegetation index (SAVI). Kamble et al. (2013) estimated crop coefficient (K c)-based crop evapotranspiration for irrigation water management using satellite-derived vegetation index. Bandyopadhyay et al. (2005), Gurusamy, et al. (2010), Papadavid et al. (2011) estimated the summer groundnut crop coefficient for the estimation of crop water requirement and irrigation planning.The study was undertaken to investigate the applicability of time-series Landsat-8, NDVI, SAVI data to establish the relationship between the crop coefficients at different growth stages of summer groundnut and remote sensing based vegetation indices for theestimation of crop evapotranspirationin Ozat-II canal command area. The study area comprises the canal command area of Ozat-II dam across river Ozat near Badalpur, Junagadh district, Gujarat, India. The location of the command area lies between latitude 21 0 12'46"N to 21 0 33'04"N and longitude 70 0 25'07"E to 70 0 53'24"E.The total catchment of the dam is 475.24 sq. km. The projected culturable command area is 4918 h. The canal system comprises of 20.60 km long main canal.Four agricultural farms in the canal command area with summer groundnut crops were selected for the study. The location i.e. latitude and longitude of different farms were ;