PATTERN OF RAINFALL ANOMALIES AND RURAL WATER SUPPLY IN THE SUDANO-SAHELIAN REGION OF NIGERIA.

Umar, A.T. and Gada, M.A.*

The pattern of rainfall anomalies have been largely neglected in the literature on climatology in Nigeria in spite of their significance to rural water supply. This paper examined the pattern of rainfall anomalies from 1961-2010 with a view to understanding its causal factors and possible implications for rural water supply. Monthly rainfall data for five meteorological stations located in the Sudano-Sahelian region of Nigeria were obtained from the Nigerian Meteorological Agency. Other category of data used for the study included monthly Sea Surface Temperatures (SSTs) of the Atlantic and Pacific oceans and Southern Oscillation Index (SOI) obtained from the Climatic Prediction Center (CPC), U.S.A. Stepwise multiple regression model and simple linear regression analysis were used for data analyses. Simulations were run with Water Simulation Model (WaSim) for the stated period using daily rainfall and atmospheric temperature to predict the rate of recharge to groundwater table in response to rainfall anomalies in the region. The result showed that the El-Nino/Southern Oscillation (ENSO) and Sea Surface Temperature (SST) anomalies over the tropical oceans together deprive the Sudano-Sahelian region of Nigeria the copious moisture required for abundant rainfall in the region. It was also found that the annual and seasonal rainfall amounts in the region exhibited a downward trend over the period of study. Recharge to the groundwater table is found to be highly sensitive to annual rainfall anomalies in the region and this significantly affects the rural water supply. The paper recommends that the ENSO and SSTs factors should be considered for forecasting of rainfall anomalies in the region. The conjunctive use of surface and ground water sources should also be adopted in order to mitigate the adverse effects of rainfall anomalies on rural water supply in the region.

Key words: Rainfall anomalies, Sea surface temperatures, Sudano-Sahelian, Water simulation Model.