Estimation of crop water requirement, effective rainfall and irrigation water requirement for vegetable crops using CROPWAT

Abstract

Land and water resources are the basic needs of agriculture and for the economic\rdevelopment of any country. As water becomes increasing scare and increasing demand for\rirrigation water, everywhere, has now focused national attention and public interest on utilization\rof existing water supplies, integrated irrigation water conservation and management policy and\rpractices. Accurate quantification of evapotranspiration is crucial for better management and\rallocation of water resources. It is important that the water requirements of crops are known at\rdifferent management levels within the irrigated area to accomplish effective irrigation management.\rEstimation of the evapotranspiration and effective rainfall are extremely useful for operation planning\rand management issues. CROPWAT is a computer model, was used to estimate the reference\revapotranspiration, effective rainfall, crop water requirement and irrigation water requirement for\rthe Bapatla region in Andhra Pradesh state, India. Daily meteorological data including rainfall,\rmaximum and minimum temperatures, relative humidity, wind speed and sunshine hours were\rcollected for the period of 2009 to 2013 and used as input data for CROPWAT. Average peak\rmonthly ET0 was observed to be 8.09 mm/day for the month of June and followed by the 7.55 mm/\rday for the month of May. Whereas average minimum ET0 were observed as 3.85 and 3.92 mm/day\rin the months of December and January, respectively. The average effective rainfall was estimated\rfor the study area as 769.3 mm out of 1060.3 mm annual rainfall. The crop water requirement (ETc)\rand irrigation water requirement were estimated for vegetable crops during Rabi season in the\rstudy area (Bapatla) as 516.3 mm and 470.4 mm, respectively.