ESTIMATION OF REFERENCE EVAPOTRANSPIRATION IN SELECTED AREAS IN NIGER STATE, NIGERIA

Abstract

ABSTRACT There is need for adequate information on reference evapotranspiration (RET) due to its importance on irrigated agriculture and water resources management. In view of this, the study determined reference evapotranspiration and its trends in Niger State, Nigeria. The meteorological parameters used were derived from National Aeronautics and Space Administration (NASA) and Environmentally Responsible Aviation (ERA) between 1982 and 2020. Daily climatic data and other parameters obtained were available on a 0.5° x 0.5° latitude and longitude global grid. Penman-Monteith formula was used to determine reference evapotranspiration. The trend of reference evapotranspiration was computed using Mann-Kendall. Minna, Shiroro and Bida has maximum RET values of 7.49, 9.22 and 6.03 in 2000 (February) with minimum values of 1.4, 1.36 and 1.57 in 1994 (August), respectively. The results obtained show a statistically significant increasing RET trend in Minna, Shiroro and Bida. In Minna April, July, and September also have the same trend as January in Shiroro which indicated the same level of significant, though have different values. RET trends in May, June, July, and August are similar to January and February in Bida. The implication is that the water required for the crop in September (Minna), April, July, September (Shiroro) and May, June and August (Bida) were the same as February and January. The aerodynamic and net radiation changes the trend of RET in Minna, Shiroro and Bida. The study concluded that Shiroro had the highest maximum RET followed by Minna and Bida in February, 2000