Umudike Journal of Engineering and Technology

Crop evapotranspiration (ET_c) could be determined from reference evapotranspiration (ET_o) if the crop coefficient is known. FAO-56 Penman-Monteith (PM) method  normally gives accurate and consistent ET_o. For a developing country like Nigeria, food sufficiency could only be achieved through irrigation in addition to rainfed agriculture and irrigation requires the detemination of precise crop water requirment or crop evapotranspiration for efficient water utilisation. In this study 10 years, 1996 – 2005,  climatic and meteorological data were obtained from Umudike Meteorological Station, Nigeria, and the data were used in computing ET_o using the FAO – 56 PM method. The average monthly ET_o obtained from January to December were 13.0, 13.1, 10.7, 7.8, 7.2, 6.1, 5.3, 5.0, 5.9, 6.1, 7.3, and 9.8 mm/day, respectively. The results were compared to the studies by other researchers using a lysimeter for crop evapotranspiration at Umudike. The results of ET_o obtained in this study is recommended for computing ET_c for an irrigation project and water management in this area of Nigeria.