Spatio‐Temporal Analysis of Rainfall Distribution in Kaduna State, Nigeria

Abstract

Monthly and annual rainfall data for Kafanchan, Kaduna and Zaria for the period 1961-2016 (56 years) were used in this study to analyse the spatio-temporal distribution of rainfall in Kaduna State. 10-year running mean, linear trend line equation, second order polynomial, Cramer’s test and student’s t-test were used to achieve this aim. The results revealed that the mean annual rainfall of the study area decreases from about 1659.44 mm in Kafanchan to about 1245.97 mm and 1016.66 mm in Kaduna and Zaria respectively. The linear trend line equation and the second order polynomial showed an increase in rainfall in recent years, while the 10-year running mean for the annual rainfall was above the long-term mean from the 1990s to 2016. Findings from the 10-year non-overlapping sub-period analysis (Cramer’s test) of both the monthly and annual rainfall revealed an upward trend in the last three decades (1991-2000, 2001-2010 and 2011-2016) for Kafanchan and Zaria Stations and the present decade (2011-2016) for Kaduna. The result of the student’s t-test for the two nonoverlapping sub-periods (1961-1990 and 1991-2016) of each station showed that Kafanchan and Zaria were significantly wetter in the last 26 years (1991‒2016) while Kaduna was having a normal condition. Further findings revealed that the increase in annual rainfall amount in recent years was as a result of increased rainfall in May, July, and September. It is recommended that agricultural planning, water resources management and government policies in Kaduna State should be based on recent rainfall trends.