Effectiveness of Early Warning Methodology and Standardized Precipitation Index for Drought Monitoring Over Guinea Savanna Zone, Nigeria

Abstract

Rain-fed agriculture remains the most important economic activity in Nigeria, and a key barrier to its success has remained largely the irregular rainfall regime. The response to this variability motivated the development of drought monitoring early warning methodology scheme for determining these phases of the rainfall regime. This study confirmed the efficacy of the scheme by comparing its result with Standardized Precipitation Index. Daily rainfall data from 6 synoptic stations in the Guinea Savanna zone, Nigeria were collected for a period 47 years (1970-2016). The Intra-seasonal Rainfall Monitoring Index (IRMI) and Standardized Precipitation Index (SPI) methods were adopted for data analysis. The results indicate variability in onset of rain as well as the wet and drought periods. The onset phase detected twelve (12) seasons and 12 years that warranted issuance of early warning statements. The SPI captured nine (9) seasons and 9 years as a drought episode which represents 75% efficacy. It also confirmed the effectiveness of early warning methodology scheme as a tool for drought monitoring in the study area. Recommendations include similar studies in other ecological zones in the country for total coverage and adapting the tools for drought monitoring