TRENDS OF DROUGHT IN THE NORTHERN NIGERIA (1907-2006)

Abstract

A quantitative assessment of drought characteristics and in the Northern Nigeria was carried out with 100 year CRU rainfall data. The specific objectives of the study were to; validate CRU rainfall data with NIMET’s surface rainfall data; examine the drought variability over northern Nigeria using SPI; examine the drought trends; and determine the frequency of occurrence of drought in the 100 years of study. Monthly rainfall data for Yelwa, Sokoto, Kaduna, Katsina, Gombe, Maiduguri, Kano, Yola, Abuja, Minna, Dutse, Gusau, Bauchi, Nguru, Jos, and Ibi, which span a period of 100years (1907-2006) collected from the Climate Research Unit (CRU) database were used. The resolution of the data is 0.5 by 0.5 in grids. The CRU data was validated using NIMET surface data. The data validation was done using a simple linear regression model. 30 years surface monthly rainfall data (1971 – 2000) was obtained from the archives of the Nigerian Meteorological Agency, Lagos Nigeria (NIMET) which was used along side with 30 year CRU rainfall data. The long term rainfall records were analyzed for drought using standardized precipitation index (SPI). The 100 years of Study was subdivided into 10 decades. Using Ilwis GIS software, the SPI results were presented on a spatial digitized map of northern Nigeria. The results of the regression model shows there is an agreement between CRU rainfall data and NIMET’s surface rainfall data. The frequency of occurrence of mild drought (near normal dry) was the highest across all stations within the 100 years of study, followed by moderate drought, severe drought and extreme drought. The results of SPI analysis revealed that there were several drought years in the study period. 30 years of persistent drought occurrences was noted within decade 7 to decade 9 (i.e. 1967 – 1976, 1977 – 1986. 1987 – 1996) in Sahel, Sudan and Guinea ecological zones of northern Nigeria. The results revealed that the north eastern part of Nigeria is more susceptible to moderate drought on a decadal basis. The study concluded that the northern Nigeria experienced mild, moderate, severe and extreme drought conditions during the study period.