SPATIAL VARIATION OF RAINFALL IN GALMA, KADUNA CENTRAL AND MADA CATCHMENT AREAS OF KADUNA STATE, NIGERIA

Abstract

The rainfall data for Galma, Kaduna central and Mada catchment areas for the period 1984- 2014 which is further projected to 2030 were used in this study to analyse the spatial variation of rainfall in the three catchment areas with a forecast to 2030 in Kaduna State. The rainfall data was obtained from Global Weather Data for SWAT (Soil Water Assessment Tools) since other studies have utilized rainfall data from the Nigerian Meteorological management agency (NIMET). Rainfall data were only available in SWAT platform till the end of 2014. The Data were collected from twelve (12) remotely sensed stations around Kaduna State. 10 years non-overlapping mean, Cramer's test and Auto-Regressive Integrated Moving Average (ARIMA) time series modeller fit the data used to achieve this aim. The results revealed that the mean annual rainfall of the study area decreased from 1733.4mm in Mada catchment area to 1203.5 mm in Galma and 1032.3 mm in Kaduna central catchment areas respectively. The annual rainfall shows that Mada catchment area (460.56mm) has the highest rate of increase in rainfall for the period under study. This is followed by the Galma catchment area (236.09 mm)with the least- Kaduna central catchment area (78.22mm). The annual increase in rainfall for Mada catchment area occur substantially in the months ofJuly to September respectively while the increase in Galma catchment area happens in August. Findings from the 10 years non-overlapping sub-period analysis of both the monthly and annual rainfall revealed an upward increase in the last three decades for Mada and Galma catchment areas. The result further revealed that Mada and Galma catchment areas were significantly wet in the last 30 years while Kaduna central catchment area had a normal condition. The forecast rainfall indicated that Mada has returned values (336.84mm), followed by Kaduna central (309.74mm) and Galma catchment area (320.05mm) as the minimum and best model performance index. It is recommended that agricultural planning, water resources management and government policies in Kaduna State should be based on recent rainfall trends.