Evaluation of Water Quality Indices Adequacy in Characterizing the Physico-Chemical Water Quality of Lakes

Abstract

The accurate and comprehensive characterization/classification of a water system presents a significant challenge. Over the last decades, a number of water quality indices (WQI) has been created and applied towards this goal. In most cases, the WQI is applied in characterizing the overall quality of a water system by integrating all available data, regardless of sampling station and time. This approach may result in misleading interpretation of data and wrong or ineffective policy responses to water quality deterioration. The present study investigates whether this approach is the most appropriate or if it is necessary to take into consideration the water quality of each individual sampling. Two natural lakes in Greece were chosen as case studies and an alternative to National Sanitation Foundation Water Quality Index was applied at each sampling site and at the overall water body. The use of the water quality index presented in this study is proved to be good practice in evaluating and characterizing the water quality of lakes as it can be easily adjusted to local specific conditions. The physico-chemical characterization of an aquatic system by water quality indices is preferable to be made only if the water quality indices, calculated for each individual sampling site, show homogeneity. The identification of the considered critical parameters, which significantly affect the quality of a water body, is of high importance in order to reduce the monitoring cost without influencing the reliability of the final result.