Comparative Study of Potential Evapotranspiration in Different Geopolitical Zones; A Case Study of Nigeria

The dearth of information on crop water requirements through the evaluation of climatic characteristics cannot be over-emphasized, making water management and crop production a herculean task. This study was designed to estimate the ETo of states in each geopolitical zone of Nigeria using the Penman-Monteith method for proper crop growth and water management. The study also addresses difficulties experienced in sourcing climatological data in different geopolitical zones of Nigeria. The study is limited to comparative analysis of potential evapotranspiration estimates in states such as Southeast (Enugu State), South-south (Cross River State), Southwest (Ogun State), Northcentral (Kogi State) Northeast (Adamawa State) Northwest (Jigawa State). The estimated potential evapotranspiration (ETo) was calculated by applying Penman-Monteith method CROPWAT model. Cumulative daily ETo for the year were 1266mm, 1231.26mm, 1173.87mm, 1360.79mm, 1260.38mm, and 1332.35mm for Enugu, Abeokuta, Calabar, Dutse, Ilorin, and Yola cities, respectively. The results show that crop water consumptive use was higher in the northwest and northeast compared to other parts of the country. Estimated ETo values in the North-central region were similar to values obtained in the southern part. In the southern part, February, March April, and May recorded higher ETo values compared to July and August with the lowest ETo values.