TREND OF RAINFALL CYCLE AND ITS IMPLICATION FOR AGRICULTURAL AND HYDROLOGICAL PLANNING IN THE GUINEA ECOLOGICAL ZONE, NIGERIA

Abstract

T h e im p a c t o f r ain f all o n m a n in t h e G uin e a E c olo gic al Z o n e , Nig e ria ( G E Z N ) is g r e a t because it c o n t r ols g r e a t e r p a r t o f his e c o n o mic a c tivitie s e s p e cially a g ric ult u r e and hydrology /water resources . This study aimed at assessing the trend of rainfall c ycle over the GEZN and its implication on agriculture and hydrology/water resources . D aily rainf all for the period of thirty five (35) years ( 1981 - 2015 ) fo r the nine (9) synoptic stations within the study area were obtained from Nigerian Me teorological Agency and analysed. The data were analysed using various programs written in MATLAB (and named prepNN1.m, prep NN2.m, plot _ Y e a r . m , r u n nin g 1 . m , periodogram ) a n d o t h e r s t a tis tic al m e t h o d s . R e s ult s w e r e presented in figures and table. Part of the results showed that the highest cycle per year of 0 . 2 w a s o b s e r v e d o v e r J o s , w hile t h e lo w e s t o f 0 . 0 8 9 8 w a s observed over Lafia. The conclusion revealed an inter - annual variability in rainfall across the data collection points , number of cycles within the study period is between 3 - 5, highe st number of years per cycle was 12.8 years, while the lowest was 5 years, year wit h highest rainfall before a trough r a n g e s b e t w e e n 2 0 1 3 - 2 0 1 5 , w hile y e a r wit h t h e lo w e s t r ain f all b e f o r e a p e a k ranges between 2011 - 2015. The peak year of rainfall ranges between 2017 and 2019, while the drop year rang es between 2016 and 2019 . The peak rate of rainfall ranges between 36. 2 mm and 82.1 mm, while the trough rate range s between 26.8 mm and 73.6 mm. R ainfall a m o u n t f o r t h e p e a k y e a r r a n g e s b e t w e e n 1 2 3 2 . 2 m m a n d 1 5 5 5 . 7 m m , w h ile r ain f all amount for the trough year ranges between 104 0 mm and 189 3.3 mm. R ecommendations focused on the need for frequent rainfall forecast, irrigation, hybrid cropping, construction of more water reservoirs and dams in the study area.