Estimation of water requirement of wheat using multispectral vegetation indices

Abstract

Estimation of crop coefficient (Kc) and crop evapotranspiration (ETc) using remote sensing data is essential for planning irrigation water use in arid and semiarid regions. The study was conducted to test the suitability of remotely sensed Vegetation Indices (VIs) for modeling spatial crop coefficient, choosing most appropriate vegetation index among them for modeling and applying this model to estimate water requirement of wheat. The study area consisted of wheat growing five districts situated in central Maharashtra. Images of IRS-P6, AWiFS sensor were used to generate multi temporal vegetation indices RVI, NDVI, TNDVI, SAVI and MSAVI2. The week-wise VIs were correlated with week-wise recommended wheat crop coefficients which resulted in linear relationships/models. Simple linear regression analysis showed NDVI as a superior index for predicting crop coefficients of wheat. NDVI-Kc model showed highest R² and D values of 0.895 and 0.980 respectively with lowest values of SE, RMSE and PD of 0.120, 0.113 and 4.64 respectively. The crop coefficients (Kc), obtained by this NDVI-Kc model and reference evapotranspiration (ETo), estimated by Penman- Monteith equation, were used to compute wheat crop evapotranspiration (ETc) which represents the water requirement of wheat and found varying from 378.34 mm to 439.10 mm in the study area.

Keywords

• Wheat
• vegetation indices
• evapotranspiration,
• water requirement
• AWiFS
• Maharashtra