Using Water Quality Index for Assessing of Physicochemical Quality of Quaternary Groundwater in the Southern Part of Abidjan District (Côte d’Ivoire)

Abstract

In this study, fourteen physicochemical parameters were monitored at 61 groundwater sampling points located in the southern part of Abidjan District. Each water sampling location was sampled in March and July 2007, representing respectively the long dry season and the long wet season. Groundwater evaluation index and statistical methods were used to assess Quaternary groundwater physicochemical quality in term of drinking and irrigation purposes. The groundwater samples irrespective of seasons fell in mixed K-Na-HCO 3 and K-Na-Cl types. Groundwater quality index values varied from 14.01 to 593.44 and from 20.88 to 567.44, in dry and rainy seasons, respectively. In both seasons, 9.83% exhibited poor water quality and 3.27% indicated unsuitable water for drinking purposes. The studied water wells were heavily contaminated with nitrate, nitrite and ammonium in the strongly urbanized areas at Treichville, Koumassi, Marcory, Port-Bouët and Grand-Bassam. The degree of correlation between physicochemical parameters suggested that groundwater quality was mainly related to geogenic (rock-water interaction) and anthropogenic sources (domestic sewage), and intrusion of marine and lagoon waters in the study area. Sodium adsorption ratio was generally low during study period, indicating most groundwater sampled was suitable for irrigation purposes.