1 Performance of Two Temperature-Based Reference Evapotranspiration Models in the Mkoji Sub-Catchment in Tanzania

Abstract

The performance of two temperature-based empirical models for computing reference evapotranspiration (ETo): the Hargreaves (HG) and the Jensen-Haise (J-H) models, were evaluated for the three: Upper, Middle, and Lower zones of the Mkoji sub-catchment of the Great Ruaha River Basin in Tanzania. Climatic data from the Mbeya, Igurusi, and Kapunga weather stations, representing the Upper, Middle, and Lower Mkoji respectively, were used to compute daily ETo in accordance with the two temperature-based models. A third model: the FAO-Penman-Monteith (F-P-M) model was used as a reference model for assessing the performance of the temperature-based models. The F-P-M model was used as a reference because it has been recommended as a universal model for computing ETo. The daily ETo calculated based on the temperature-based models were compared statistically with those of the F-P-M model. The results showed that daily ETo of the HG and J-H models were significantly different from the F-P-M model at P<0.05 in the three zones. In the Upper Mkoji, the ETo based on the HG and J-H models were significant different (P<0.01) from the F-P-M model for each month of the year. The absolute mean difference between the daily