Title: Efficiency of indirect and estimated evapotranspiration methods in South Western Nigeria

Authors: Sunday O. Adesogan; Blessing F. Sasanya

Addresses: Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria ' Department of Crop and Soil Science, University of Port Harcourt, Rivers State, Nigeria

Abstract: Evapotranspiration is the energy which drives the hydrologic cycle. The estimation of evapotranspiration is of utmost importance to irrigation projects as well as water resources, evaluation, planning and management. Various empirical models estimating evapotranspiration suits different basins in various degrees. This study determined the suitability of different evapotranspiration models for South Western Nigeria. These models were compared with measured evapotranspiration. Suitability of the models were determined from correlation coefficients, root mean square errors (RMSEs), efficiency test and volume error. In comparison with measured values, FAO Penman-Montieth had highest correlation coefficient (0.74), lowest RMSE value (27.26 mm/month), highest efficiency test value (0.40) and lowest volume error (0.26). The differences between the evapotranspiration values obtained from the empirical methods and the directly measured values are significant at α0.05. Some of the models overestimated while others underestimated evapotranspiration. This study will facilitate irrigation project planning and water resources management in South Western Nigeria.

Keywords: FAO Penman-Monteith method; class 'A' evaporation pan; Piche evaporimeter; water resources management.

DOI: 10.1504/IJHST.2023.127895

International Journal of Hydrology Science and Technology, 2023 Vol.15 No.1, pp.64 - 77

Received: 27 Jan 2021
Accepted: 23 May 2021
Published online: 21 Dec 2022 *