ABSTRACT
The impacts of climate change are seen throughout every aspect of the world we live in. Trend analysis is a strategy used to make future predictions about changes in climatic and hydrologic time series data such as rainfall based on historical data. It is an attempt to make best decisions based on the results of the analyses. Trend analysis was carried out for eleven (11) meteorological stations namely: Akure, Benin, Calabar, Port-Harcourt, Owerri, Warri, Uyo, Yenagoa, Asaba, Sapele, Umuahia) in the Niger Delta region using rainfall data for a period of thirty-eight (38) years. The main objectives of the study were to; assess the changing trend of rainfall using statistical tests (Mann-Kendall tests and Sen’s Slope test) attributed to monthly, seasonal, and annual rainfall, and map the trend in rainfall using the Mann Kendall test results. The statistical analyses reveals that there is no significant annual and seasonal rainfall pattern in most stations. However, a significant positive trend was identified in Calabar at 95% confidence level with MK-value of 0.286 and a slope of 9.407. The observed rainfall trend indicates that climate change has occurred in the study region. Most stations experienced high rainfall amounts in the months of July (Calabar, Warri, Uyo, Sapele, and Umuahia) and September (Akure, Benin, Port Harcourt, Yenagoa, and Asaba), followed by August as seen in Owerri, while the lowest amount of monthly rainfall is experienced in the months of December, January, and February. The seasonal distribution show that the lowest coefficient of variation, of 14% in April occurred during the wet season months indicates that these months have low variation and have the most reliable rainfall amounts. Also, the highest value of C.V of 53% in November was observed in the dry season months indicating that the year-to-year variation for these months is high. The observed increasing trend in Calabar suggests that Calabar will become wetter in the future. Overall, the result shows a long-wet season of 95% of rainfall from February/March to November and a short dry season from December to January/February with less than 5% of xiii rainfall. There exist the presence of a short dry spell in the middle of the wet season observed in August. The results obtained from the study of rainfall trend and variability is useful for water resource planning, socio-economic activities, and agricultural planning in the region.
