Water quality change in dam reservoir and shallow aquifer: analysis on trend, seasonal variability and data reduction.

Change of water quality in dam reservoir and aquifer complicates safe drinking water supply. Few parameters are monitored to control water quality in these sources. Adequate knowledge on the correlation structure, interaction effect, trends and seasonal variability of these parameters is essential to control water quality. This study applied time series and multivariate analyses on 15 water quality parameters, collected from the King Fahd dam reservoir (L1) and aquifer (L2) in Saudi Arabia during April 2010 to February 2012. Moderate to strong correlations were observed between sulfate, hardness, fluoride, chloride, magnesium, conductivity, turbidity and total dissolved solids (TDS), while separate clusters were visible for TDS-chloride-magnesium-conductivity; fluoride-turbidity; chloride-hardness; ammonia-nitrate; and calcium-magnesium-hardness. Four major principal components explained 81.1% and 83.2% of the overall variances in L1 and L2, respectively. The factor analysis showed that 53% and 67% of the data were necessary to explain 81.3% and 83.2% of total variances for L1 and L2, respectively, indicating the possibility of data reduction. Possible degradation of water quality in these sources was highlighted, while such degradation may require enhanced treatment for producing drinking water in future.