The irrigation releases in canal command areas, in general, are decided on the basis of pre-notified cropping pattern and mean meteorological conditions. Due to changes in crop type, extent and seasonal meteorological conditions, the actual irrigation demands vary from the envisaged. This study attempts to estimate the field level crop water requirement (CWR), using satellite data derived in-season crop information. The spatial crop map generated using in-season satellite data has been used to generate spatially varying crop coefficient (Kc), which later is used to calculate crop water requirement. The crop water requirement, which is the Potential Evapotrasnpiration of the crop (ETc), is estimated by two methods, Hargreaves and Samani method, and Penman Montieth Method. Conventionally irrigation requirement is estimated as the ETc in excess of effective rainfall. The study was conducted for Narayanpur command for the Kharif seasons of 2017 and 2018. Spatial maps of ETc were generated for both the year and it was seen that CWR in the left bank canal is higher. Paddy is the dominant crop in the area commanded by left bank canal whereas when right bank canal command area is dominated by ID crops. The crop water requirement estimated varied with the method adopted. Hargreaves and Samani method estimated infield crop water requirement of 656.73 MCM and 1081.86 MCM for 2017 and 2018 kharif seasons, respectively whereas Penman Montieth method estimated crop water requirement of 879.83 MCM and 1300 MCM for the years under consideration. On validation with the canal release data from the field, it was observed that there was a higher release of water in the year 2018 as compared to 2017, which was similar to the trend of estimated crop water requirement.
Crop Water Requirement, Potential Evapotranspiration, Crop coefficient
