Hydrologie : recherche actuelle

Analysis of Precipitation Concentration Index (PCI) for Awka Urban Area, Nigeria

Abstract

Ezenwaji EE, Nzoiwu CP and Chima GN

Causes and consequences of climate variability of which the fluctuation in rainfall amounts over time represent an important indicator is indeed an area that has continued to generate research attention. The aim of this paper is, therefore, to evaluate the concentration and variability of rainfall in time using Precipitation Concentration Index (PCI) based on monthly precipitation over 38 years period (1976–2013) and its implications for flooding and water supply in the town. Data for the study were collected from NIMET, Lagos. The PCI was calculated for annual, seasonal and decadal scales using annual, wet and dry season equations. Result shows that annual PCI value range from the lowest of 12 in 1976 to the highest of 20 in 1987. About 78% of the years were characterized by PCI values that fall within moderate range, an indication of moderate precipitation distribution within the 38-year period, while 24% of the years recorded annual value within the irregular range indicating an irregular rainfall distribution and concentration across the months. Again, the fact that many months have PCI values within ≥ 16.7 is a further manifestation that almost 90% of the rainfall occurred in 6 months. These results show that the area is having reasonable floods with consequent pollution of the surface water bodies as well as soil erosion as observed in the town. It is, therefore, recommended that the Awka Capital Territory Development Authority (ACTDA) should take cognizance of this result in the planning of the new layouts and redevelopment of the old areas of the town.