Analysis of Rainfall Distribution, Temporal Trends, and Rates of Change in the Savannah Zones of Nigeria.

Abstract

The impact of climate is often demonstrated by rainfall and its attributes. Consequently this study analyzes rainfall concentration a temporal trends, and rates of change in the savannah zones of Nigeria. Rainfall data were acquired from the archives of the Environmental Management Programme Federal University Technology Minna, for 13 synoptic stations at annual, seasonal, and monthly time scales for the the 1970-2016 period. The precipitation concentration index (PCI), Mann-Kendall trend test, Theil-Sen s slope estimator (β) and relative percentage change methods were adopted for data analysis. The findings reveal that PCI calculated on an annual scale falls into three categories 11-15. 16-20, and PCI>20. Two distinct patterns patterns emerged from the calculated PCI indicating that stations in the Guinea savannah zone (Bida, Yola, Minna, Jos, Bauchi, and Kaduna have moderate, irregular, and strongly irregular rainfall concentrations whereas stations in the Sudano-Sahelian savannah zone Kano, Gusau. Maiduguri, Yelwa. Nguru. Sokoto and Katsina) have irregular gular rainfall concentrations. The Mann-Kendall analysis of the PCI values reveals that 8 of the 13 stations (62%) experienced downward trends. This implies that rainfall is sliding toward a moderate to uniform distribution the trends and consequently the variability in the annual and seasonal rainfall, reveal that, with the exception of Yola and Jos stations, where the trends were downward, the overall rainfall was increasing some areas and insignificantly in others. The magnitude of the significant found to be 3.59 mm yr-1 at Yelwa station. 9.84 mm yr 1 at Bauch, station, 17.13 mm yr -1 at Kano station, 3.98mm yr-1 at Sokoto station and 3 11 mm yr-1 at Katsina station. It is understood that the changes in rainfall distribution and trends have positive effects on water availability for crops, and this should facilitate enhanced productivity in rain-fed farming.