Analysis of Rainfall Trend in Sokoto State, Nigeria (1987-2016)

Rainfall is an important climatic parameter. The study examined the nature of trend in annual rainfall amount and rainfall attributes such as onset, cessation dates and hydrological growing season. This study was carried out to determine if there was any significant change in rainfall in the study area. Walter’s 1967 formula was used to determine the onset, cessation and hydrological growing season. The results obtained were then subjected to a time-series analysis. The findings showed that annual rainfall in Sokoto from 1987 to 2016 is on the increase, Onset dates showed early onset of recent. The rains stopped late thereby increasing the hydrological growing season. The latest onset date occurred on 4th July in the years 1995 and 2016 and the earliest onset date on 12th April in the year 2015. The earliest cessation date was recorded on 22nd August in the year 1987 and the latest on 18th October in the years 2009 and 2010. The Hydrological growing season was longest (162 days) in 2015, this was seen to be a result of the onset dates of rainfall occurring earlier and cessation dates later. Despite the upward trend rainfall is variable and unreliable and insufficient to meet the water needs of the plants, and this has a great implication resulting in cases of seasonal drought occurrences and reduced agricultural yield. The government policies as related to agriculture and water resources development should be based on recent rainfall parameters.