Spatio-temporal calibration of Hargreaves\u2013Samani model in the Northern Region of Nigeria

Akinwale Temitope Ogunrinde,Taiwo Adedayo Ajayi,Quoc Bao Pham,Mike A Enaboifo,Israel Emmanuel

doi:10.1007/s00704-021-03897-2

Abstract

One of the significant components of the hydrological cycle is evapotranspiration. Monthly meteorological parameters of 35 years from 19 meteorological stations across the Northern Region of Nigeria (NRN) were obtained and utilized for the calibration of Hargreaves–Samani (HS) model by comparing between potential evapotranspiration (ETo) values estimated from the original HS and the Penman–Monteith (FAO-56 PM) models. The calibrated HS equation was assessed using trend patterns and some statistical indices. The average value of root mean square error (RMSE) and the mean absolute error (MAE) decreased by 37.1 and 40%, respectively, after the calibration of the model. Also, the correlation coefficients (R) of stations that had values > 0.8 increased from 6 to 11 and the minimum R value increased by 12% above that of the original HS equation. The trend and spatial map of the statistical tests conducted also indicate better performance in most climatic regions after calibration. The precision of the HS equation improved significantly after calibration for semi-arid, humid, and sub-humid regions. However, few stations in the semi-arid, humid, and sub-humid regions did not show drastic improvement due to the peculiarity of the location and high variations in the wind speed and relative humidity parameters.

Highlights

The necessity to efficiently manage the water resources and the agricultural sectors in a developing country where subsistence farming is the most available job is very important and must be given priority in order to avert serious economic and environmental challenges
The issue of climate change which has led to more drought occurrences in many parts of the earth, most significantly in the Sahel region of West Africa, in recent decades calls for efficient management of available water resources (Ibebuchi 2021; Dong and Sutton 2015; Lele and Lamb 2010; Dai et al 2004; Sultan and Janicot 2000)
Some notable studies carried out in Nigeria as regards the estimation of ETo include, e.g., Akpootu and Iliyasu (2017), Ejieji (2011), and Adeboye et al (2009). All these studies succeeded in comparing many ETo models with the FAOPM 56 without calibrating or developing a localized ETo for any region in Nigeria. To compensate for this and other identified gaps, the aims of this study are (1) to evaluate the performance of the original Hargreaves–Samani model against FAO-56 PM, (2) to calibrate the Hargreaves–Samani equation for Northern Region of Nigeria (NRN) based on FAO-56 PM model for estimating E To, and (3) to assess the efficiency of ETo estimated by the calibrated HS equation during the testing phase

Summary

Introduction

The necessity to efficiently manage the water resources and the agricultural sectors in a developing country where subsistence farming is the most available job is very important and must be given priority in order to avert serious economic and environmental challenges. It is even more pertinent if the area under consideration is classified under arid or semi-arid regions (Jerin et al 2021; Salam and Islam 2020).

Objectives

Methods

Results

Conclusion