Rainfall Characteristics at Makurdi, North–Central Nigeria II

Abstract

Rainfall characteristics were evaluated in Makurdi in the Guinea Savanna agroclimatic belt of Nigeria. Pluviograhic rainfall data were collected for the period 1985 to 1987. The mean Annual rainfall was 1140mm.The highest rainfall amount per storm event was 71.7mm while the highest six- minute rainfall intensity was 240mmh^-1. The mean monthly Kinetic energy (E) using the Wischmeier and Smith (1978) equation ranged from 2.0 to 84.1MJha^-1 whereas the value ranged from 2.5 to 128.0MJha^-1 using Kowal and Kassam (1976) equation (designated E_k).Conventional rainfall erosivity used for evaluation were the EI₃₀, K.E > 25 and AI_m. The ranges of monthly erosivity based on these indices were 24 to 406 MJ.mmha^-1h^-1, 0.7 to 9.0MJha^-1 and 270 to 4280 mm2h^-1 respectively. Following Obi and Salako (1995) additional indices, namely, E(A), E_kI₃₀, E_kI_m ,E(A)I₃₀ and E_kAI_m were evaluated. Mean monthly erosivity values ranges based on these indices were 18 to 471 MJ.mmha^-1h^-1, 31 to 595 MJ.mmha^-1h^-1, 76 to 1594 MJ.mmha^-1h^-1, 218 to 26992 MJ.mmha^-1h^-1 and 527 to 67293 MJ.mmha^-1h^-1 respectively. The findings enable better understanding of the rainfall effects on soil erosion in the region. The generally high erosivity values are pointers to the compelling need for soil protective covers in particular and the integration of other serious conservation measures as key strategies for sustainable production in the agro-ecological zone.

Keywords: Rainfall, Eosivity, USLE