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.
