AGGREGATION TECHNIQUES APPLIED IN WATER QUALITY INDICES (WQIS)TALENT DIOTREFE BANDA AND MUTHUKRISHNAVELLAISAMY KUMARASAMYAbstract Since water quality is a prime natural resource, it is then important to conduct regular water quality assessment that describes the degree of pollution and substantiate the healthiness of water resources. And water quality index is an essential tool that can provide an initial quick guide necessary to evaluate water quality status of a given water body. Water quality indices are beneficial for integrating significant physical, chemical and biological constituents of water and provide a simple, but yet scientifically justifiable water quality rating score. Such a valuable and unique rating comprehend the influence of various water quality variables and easily communicate water quality data to non-technical individuals and more importantly the policymakers. In order to obtain a WQI, sub-indices of water quality variables are employed to indicate water quality on a scale most probably from zero (worst quality) to unity (best quality). Furthermore, the sub-indices are aggregated to yield an overall WQI value normally between zero (poor quality) and hundred (excellent quality). In this review paper, various aggregation techniques have been evaluated, outlining their advantages and disadvantages. Conclusions have been drawn about the similarities and dissimilarities existing among different aggregation methods leading to the suggestion of possible methods applicable in the development of a universal water quality index for South African river catchments. |