COMPARATIVE ANALYSIS OF RAINFALL AND TEMPERATURE ACROSS THE EIGHT HYDROLOGICAL AREAS OF NIGERIA

Abstract

A comparative analysis of rainfall and temperature across Nigeria’s eight Hydrological Areas (HAs) was conducted. The HAs include Hydrological Area I (Niger North), II (Niger Central), III (Upper Benue), IV (Lower Benue), V (Niger South), VI (West Lithoral), VII (East Lithoral) and VIII (Lake Chad). A 100 yr rainfall and temperature data were collected from University of East Anglia’s Climate Research Unit (CRU) archive. The data was subjected to descriptive and standard parametric trend analyses. Change point years were estimated using Cumulative Sum Technique, Drought Episodes and Frequencies were estimated using the Standard Precipitation Index (SPI) methods. The highest mean annual rainfall of 2826.8 mm/year was observed at HA VII while the lowest rainfall of 386.8 mm/year occurred at HA VIII. The rainfall coefficient of variation (CV) varied from 11.5-20.4% at Northern HAs (I – V & VIII) and 10.4-11.2% at Hydrological Areas VI and VII. The change point in rainfall decreased in all the HAs with the highest change of -202.8 mm/yr at East Lithoral, -133.4 mm/yr at Niger South, -126.6 mm/yr at North Central and -122.8 mm/yr at Lake Chad during the century. Temperature was found to increase in all the HAs with 0.33oC in HA II, 0.39oC in HA V and 0.49oC in HA VII at 0.05% level of significance. The outlook on hydrological drought index showed varied degrees of SPI across different HAs, with HA II recording the maximum SPI value of 3.03 and HA IV recording minimum SPI value of 1.83. Also, HA V recorded minimum SPI value of -3.17 and HA I recording maximum SPI value of -2.02. The findings of the study are useful in agricultural water use and water resources management.