Rainfall and Meteorological Drought Characteristics in Maiduguri, Nigeria

Abstract

Information and data on drought in Nigeria are lacking and critical issues, which 
require urgent attention. In this paper, meteorological drought, Maiduguri is the 
subject. Rainfall data measured in Maiduguri; Nigeria was collected. Rainfall data 
were used as input to assess the values of SPI (Standardized Precipitation Index), 
and PNI (Percent Normal Index), and determined the historical meteorological 
drought duration, magnitude, intensity, severity and frequency for individual and 
grouped years of 1915 – 1924, 1925 – 1934, 1935 – 1944, 1945 – 1954, 1955 – 
1964, 1965 – 1974, 1975 – 1984, 1985 – 1994, 1995 – 2004, 2005 – 2014 and 2015 – 2018. Constants in Gamma distribution for the rainfall and SPI were determined 
using Microsoft Excel Solver (MES). Drought parameters and drought forecast were 
presented for SPI based on the drought frequency and returned period. Analysis of 
Variance (ANOVA) was conducted to ascertain the significance and effects of all the 
selected parameters. Entropies of annual rainfall and SPI were computed using 
standard equation and Gamma distribution parameters. The study revealed that 
the yearly maximum and minimum recorded rainfalls were 1406 and 64.8 mm, 
respectively. It was shown that there was very high rainfall variability that ranged 
in the monthly mean (between 5.4 and 93.8 mm), maximum (between 39.2 and 
641.5 mm), median (between 0.0 and 42.2 mm), standard deviation (between 12.0 
and 192.2) and coefficient of variation (between 118.2 % and 237.4 %). The total 
drought duration was 53 years with a total magnitude of -37.13, average intensity 
of -0.71 and 0.505 mean frequency. drought magnitude was in the range of -0.33 
to -8.73, frequency was between 0.009 and 0.065, and return period was between 
15 and 107 years with drought intensity in the range of -0.33 to 1.25. The mean SPI 
was 0.687 and the values of parameters for Gamma distribution were α (0.867) and 
β (1.264). It was concluded that Maiduguri is prone to drought based on indices, 
drought indices explained the drought characteristics as mainly low drought 
(73.58%), moderate drought (16.98%), severe drought (1.89%) and extreme 
drought (7.55%).