COMPARATIVE ANALYSIS OF DIRECT AND FOUR INDIRECT METHODS FOR DETERMINATION OF EVAPOTRANSPIRATION OF WATERLEAF (TALINUM TRIANGULARE)

C.P. Obioma, C.D. Okereke, Kevin Nnanya Nwaigwe

Abstract: This study focused on comparative analysis of five widely used methods for determining evapotranspiration, namely, Weighing lysimeter, Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods. Each of the five methods was used to estimate crop evapotranspiration of waterleaf (Talinum triangulare) in Umudike, Southeast Nigeria. The efficacy of these evapotranspiration methods is evaluated by comparing them with the Weighing lysimeter(direct method), which provides the most reasonable estimation of evapotranspiration and is one of the most reliable methods. The crop was irrigated daily and the daily data generated from the lysimeter were used to calculate the crop evapotranspiration (ETc) between the months of November/ December, 2013. Climatic data obtained for the same period were used to determine the crop evapotranspiration (ETc) using the Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods. The total crop evapotranspiration from the Lysimeter between November and December was 148.69 mm, while that of Pan Evapotranspiration (PE), Blaney – Morin Nigeria (BMN), Blaney – Criddle (BC) and Modified Hargreaves – Samani (MHS) were 152.42 mm, 151.22 mm, 147.76 mm and 135.58 mm, respectively. Test of hypothesis using z-Test indicates that there was no significant difference between the mean of the ET by lysimeter and that of each of the other four methods (Blaney - Criddle, Pan Evapotranspiration, Modified Hargreaves - Samani and Blaney - Morin Nigeria) as z-cal < z-critical at 5% level of significance for the crop growth period of 8 th November to 12th December, 2013.

Keywords: Comparative analysis, Evapotranspiration methods, Crop evapotranspiration, Hydrologic cycle, Lysimeter

DOI: https://doi.org/10.15623/ijret.2015.0402031