A comparative study of several types of indices for river quality assessment

Abstract

Water is vital for humans, plants, and animals; unfortunately, some anthropogenic activities adversely alter water quality (WQ). Many indicators can be used for WQ assessment; fortunately, extensive data can be simplified by using WQ indices (WQIs). The main difference among WQIs lies in the way of assessing pollution and the number and types of WQ indicators used; therefore, the selection of a reliable WQI should be the first step. This research aimed to compare several types of indices and evaluate their effectiveness. Eighteen sampling sites were monitored, and the selected indices showed different results. Biological indices exhibited a significant statistical correlation and yet different quality results. In addition, biological WQIs showed different outcomes from the physicochemical index. The high concentrations of phosphates, fecal coliforms, and biological oxygen demand, found in most rivers, were responsible for adversely influencing the quality results of the physicochemical index; however, their high concentrations found in some sampling sites had no adverse effect on the macroinvertebrate's existence; therefore, biological WQ assessment showed better quality results than the physicochemical index. The Rapid Bioassessment Protocol index, based on visual habitat observations, proved to be an easy way to classify WQ and an adequate replacement for biological indices. HIGHLIGHTS Different indices lead to dissimilar water quality evaluations.; Biological indices are well correlated and yet show different results.; The lack of correlation among some indices relied on their different indicators used.; The Rapid Bioassessment Protocol index is a visual habitat analysis and very reliable.; High physicochemical indicators content may not affect benthonic life.;

Keywords

• biological
• indices
• macroinvertebrates
• physicochemical
• water quality