Evaluation of Four ETo Models for IITA Stations in Ibadan, Onne and Kano, Nigeria

Abstract

Records of climatic variables (Solar radiation, Maximum and Minimum Temperature, Maximum and Minimum Relative Humidity and Wind speed) were collected from three International Institute of Tropical Agriculture (IITA) Stations namely Ibadan, Kano and Onne in Nigeria. For Ibadan, a 36-year (1973 – 2008) record was obtained, for Kano, a 29-year (1980 - 2008) record was obtained and for Onne, a 31-year (1977 - 2006) record was obtained. Evapotranspiration rates for each of the stations were estimated using the FAO-56 approach. The performance of four ET models (Blaney-Morin-Nigeria (BMN), Hargreaves-Samani, Priestly-Taylor and Jensen- Haise models) were evaluated with reference to FAO 56 Model making use of ET estimated from these models. The BMN model was found out to be the best model that can be applied to estimate ET in each of these stations because it has a high correlation value with the values obtained from FAO56-PM model along with favourable statistic values and it requires a considerably less number of variables for its estimation with correlation (r) values of 0.7, 0.77 and 0.75 respectively for Ibadan, Onne and Kano.

Key words: Evapotranspiration, FAO-56 Penman-Monteith, Blaney-Morin Nigeria