Hydrology and water quality characteristics of a stressed lotic freshwater system in southwest Nigeria

Abstract

The hydrology and water quality of Aiba stream were investigated from November 2012 to April 2013 on monthly basis. This was with a view to assessing the status of the stream sequel to its last study which indicated a poor physico-chemical water quality. Four sampling stations were established for the study along the longitudinal axis of the stream, covering both the upper and lower reaches. Hydrological input from the upstream reservoir was observed to be considerably low during the dry season, a situation which further exacerbated the water quality as indicated by very low dissolved oxygen concentration, high BOD5, high conductivity value and high ionic concentrations. High nutrient (PO₄^3- and NO₃^-) level recorded in this study indicated a eutrophic freshwater system. Generally, the physico-chemical nature of the water in the dry season indicated that the stream fell short of the standards required for freshwater life. Urgent steps need to be taken to mitigate the impacts of natural and man-induced stresses on the stream in order to safeguard the ecosystem and the surrounding terrestrial ecosystems.

Keywords: channel width, discharge, flow velocity, hydrological characteristics, lotic system, spatio-temporal, stress, water quality