Assessment of rainfall intensity on temporal water quality of Awba Dam, Nigeria

Abstract

Runoff from rainfall can significantly contribute to variation in the quality of surface waters. The effects of rainfall intensity on surface water quality is increasingly becoming a cause for concern because of its indirect impact on the cost of water treatment, and consequently on the quantity of water available for public water supply. Recent hydrological reports in Nigeria indicate significant increase in the average annual rainfall. Hence, this paper investigates the sensitivity of some water quality indicator parameters of Awba dam in South Western Nigeria to temporal variation in rainfall intensity. Representative water samples were collected for a period of five years (2008 – 2012), and analyzed using standard analytical methods. The results showed that Awba dam has a low level of alkalinity. True Colour Units, turbidity and chloride concentrations were initially high, but decreases with increasing rainfall intensity. The pH and iron concentration have minima response to fluctuations in rainfall values. The water quality indicator parameters showed consistent and significantly high correlation with the temporal rainfall intensity during comparatively low rainfall periods and this suggests occurrence of significant influence of the varying rainfall amount on the water quality of Awba dam, though the relationship becomes complex with increasing amount of rainfall.

Keywords: Rainfall runoff, Water quality, Awba dam, Sensitivity, Indicator parameters