Analysis of rainfall variability for crop planning in Abeokuta, Nigeria.

Abstract

The study analyzed temporal variability in annual, seasonal, monthly and weekly rainfall in Abeokuta. Daily rainfall data for Abeokuta was obtained from the Nigerian Meteorological Agency Abuja for a period of 21 years. Coefficient of variation was used to analyze the temporal rainfall variability. Markov Chain Model was adopted for drought analysis using the Standard Meteorological week (SMW). The Coefficient of variation of 18.3 per cent indicated that the annual rainfall of Abeokuta has a low variability over the years. The seasonal contribution to annual rainfall was 43.8% and 50.9% for early and late planting (rainy season) and 5.3% for dry season respectively. Within the rainy season, September was the highest rainfall contributing month (16.3%) followed by July (14.3%) and June (14.0%). Mean weekly precipitation amount and its assurance reaches the peak (>50 mm/week) during 18th SMW, 28th SMW, 29th SMW and 39th SMW but lower in other SMW weeks. Onset of rainy season occurred at 14th SMW and runs till the 44th SMW before decline in rainfall for the dry season to set in. There is water availability for rain water harvesting from the month of April to October which can be utilized as crop saving irrigation during the short dry spell period of the rainy season and for irrigation farming during the dry season.