FAO-CROPWAT Model-Based Estimation of Crop Water Need and Appraisal of Water Resources for Sustainable Water Resource Management:Pilot Study for Kollam District - Humid Tropical Region of Kerala, India

An effort has been made to calculate the water needs for various crops in different agro-ecological units (AEUs) of Kollam district (a humid tropical region of Kerala) using FAO-CROPWAT. The major cultivated crops are rice, coconut, rubber, pepper, banana, brinjal, tomato, tapioca, cardamom, tea, etc. The gross water required for these crops has been computed in various AEUs using meteorological parameters. Using evapotranspiration and effective rainfall in each unit, a water balance has been worked out. An overall water balance of the district has been attempted by considering irrigation, domestic and industrial demand of AEUs, under current scenario and future demand. The gross irrigation demand for the currently irrigated area in the district at 70% efficiency is 1045 mm³, of which 920 mm³ is supplied from surface water sources and 125 mm³ from groundwater sources. The projected future total water demands for irrigation, drinking and industrial purposes will be 2667 mm³. However, the utilizable water resource from all river basins of Kollam is only 1117 mm³. The above data shows a deficit of 1550 mm³ and it will be difficult to arrive at requirements with the existing water resources at a given point of time. We infer that if the total area is brought under irrigation, there will be water scarce years, and hence decreasing irrigation or the command area needs to be adopted to manage this shortfall and sustain production. We have also discussed several options/strategies for better water management under these changing climatic circumstances to provide water to meet the demands of all the users.