A water quality index for use with diatoms in the assessment of rivers

Water quality is commonly reported with respect to the minerals that comprise the total dissolved solids, often together with COD, BOD, pH and other components. For ease of use by consumers, the quality parameters are mostly related to usage, i.e. water quality for domestic use, livestock or irrigation, etc. When diatom populations are used as water quality indicators a different system is necessary because diatoms are mostly good indicators of the total dissolved solids. A system to report water quality as an index or class is proposed using data collected from the Swartkops River system, which has pristine headwaters but which becomes progressively polluted downstream. The data included in the index encompass water quality values that cover more than 90% of the 212 river sites sampled from all the phytogeographical areas of South Africa.