WATER QUALITY INDEX (WQI) IN THE MAN-MADE DAM FRANCISCO I. MADERO IN MÉXICO

A water quality index (WQI) is a simple expression showing the quality of water. The objective of this study was to estimate a WQI for the water of the man-made dam Francisco I. Madero in Chihuahua, Mexico. Eight sites were randomly selected in the dam and water samples were collected monthly during the period of March 2011 to February 2012 at three different depths; 0.30 m, 5 m and 10 m. Therefore, a total of 288 water samples were obtained. Eight physicochemical parameters were measured; potential of hydrogen (pH), electrical conductivity (EC), dissolved oxygen (DO), temperature (T), turbidity, total dissolved solids (TDS), total hardness (TH) and chlorides (Cl^-). A statistical analysis was performed to detect the effect of month (Factor A), the effect of depth (Factor B) and the interaction for each variable. The WQI was calculated to each month only for surface sampling (0.30 m) and water was classified into three categories according to the WQI´s result; <2.0 “poor”, 2.0-2.5 “good” and >2.5 “excellent”. The results showed that water quality varies temporally, ranging from “poor water” in the months of rainy seasons to “excellent water” in the months of winter season. It was concluded that, in general, water quality in the dam is “good” and can be used for ecological purposes, but their quality should be continuously assessed, especially during the rainy season.