Estimation of Crop Water Requirement (CWR) and Reference Evapotranspiration of Chickpea Crop Using CROPWAT 8.0 Model for Prayagraj

Abstract

This research evaluates the water requirements of chickpea cultivation in the semi-arid agroclimatic conditions of Prayagraj, Uttar Pradesh, using the CROPWAT model over a climatic baseline period from 1993 to 2023. The study aimed to determine both the crop water requirement (CWR) and irrigation water requirement (IWR) by incorporating monthly reference evapotranspiration (ET₀) and effective rainfall data. Analysis revealed that the annual ET₀ totaled 1727.91 mm, with peak values occurring during the pre-monsoon months—particularly in May. In contrast, effective rainfall was predominantly confined to the monsoon season, offering minimal contribution during the rabi growing season. Chickpea, cultivated primarily between November and February, exhibited a seasonal CWR of 182.12 mm, with the mid-season stage—corresponding to flowering and pod development—demonstrating the highest water demand. Owing to limited winter precipitation, the total IWR was calculated at 153.56 mm, indicating a substantial need for irrigation to support optimal crop performance. These outcomes emphasize the necessity for strategic irrigation management to enhance water-use efficiency and sustain chickpea productivity under rainfed-deficit conditions.