Decadal and Trend Analysis of Potential Evapotranspiration in Oluyole, LGA, Oyo State Nigeria

Abstract

Variability of potential evapotranspiration due to climate change is presently causing alterations in the global hydrological cycle with devastating effect on the water requirements of crops. This study evaluated the trend and decadal variability of the potential evapotranspiration in Oluyole Local Government Area for one climatic period ranging between 1991 and 2020. Meteorological data, which include the maximum and minimum temperature, were obtained from the NASA Langley Research Center POWER Project portal. These data were applied to estimate the potential evapotranspiration of the study area using the Thornthwaite equation. Thereafter normality test was performed using a coefficient of skewness and kurtosis, trend assessment was performed using the Mann Kendal method, while the significance of decadal variability was assessed using the One-sample t-test and Analysis of Variance (ANOVA). The results reveal that the annual trend of potential evapotranspiration for the period of 1991 and 2020 was accepted as indicative of normality at 95% confidence level, while a positive non-significant (p > 0.05) trend was observed during the study period. The study further unravelled that potential evapotranspiration in the first decade was lesser than the long-term mean average of 1498.64 mm, while the proceeding decades recorded slightly higher average values. The t-test and ANOVA revealed that the variations from the long-term average were not statistically significant in the study period. There is the need to pay critical attention to these alterations in order to satisfy crop water requirements.