An Analysis of Rainfall Trends in Kafanchan, Kaduna State, Nigeria

Abstract

Rainfall data for 35 years (1974-2008) for Kafanchan located within latitude 9o 3ʹN and longitude 8o 17ʹ E were used in this analysis in order to detect the recent trends in the rainfall regime of the area. The calculated Relative Seasonality Index for the area revealed that rainfall regime is markedly seasonal with a long drier season. In order to identify trends, the rainfall series was divided into 10-year overlapping sub-periods 1974-1983, 1979-1988 through 1999-2008 and the Cramer's test was then used to compare the means of the sub-period with the mean of the whole record period. The results of the test revealed that the sub-period 1974-1983 and 1999-2008 for the months of June and October respectively were significantly drier. The results of the Standardized Anomaly Index revealed that rainfall yield is declining in the study area. The 5-year running mean shows that the declining yield of the annual rainfall started from 1990 to date. The results of the linear trend lines furt her revealed that the decli ne in the annual rainfall yield is predominantly as a res ult of the substantial decline in July, September, and October rainfall, which are the critical months for agricultural production in the area. It is recommended that agricultural planning and government policies in the area should be based on recent rainfall trends.