A Systematic Review and Meta-Analysis of Water Quality Indices

Water quality indices (WQI) are useful tools for indicating the suitability of water for an expected use. However, they can suffer from some problems. The objective of this paper was to analyze the development of WQI to determine which parameters are used in water quality assessment and to discuss the characteristics of WQI. To screen articles on WQI, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method is applied to include or exclude articles. Four necessary steps are needed to design WQI: parameter selection, standardization, weighting and aggregation. A set of six methods of aggregations of sub-indices are identified: the arithmetic mean, the geometric mean, the root square, the logarithmic function, the fuzzy inference and the minimum operator. The problems encountered for the overall index are different according to the form of aggregation. They are eclipsing, ambiguity, rigidity or flexibility, adaptability and compensation. The chemical parameters (70%) are the most used in the development of WQI with the physical parameters used at 24% and the biological parameters at 6%. Dissolved oxygen (DO, 87%), total coliforms (87%), biological oxygen demand (BOD, 73%), pH (73%), temperature (67%), turbidity (60%), ammonia (53%), ammonium (47%) and total dissolved solids (47%) are the most commonly used parameters for water quality assessment.

Analysis of Water Resources Vulnerability Assessment Tools

Water resources face many pressures and stresses around the world.Assessing the vulnerability of water resources is,therefore,increasingly an essential practice in water resources management.Several studies of water resources vulnerability have been carried out around the world during the last three decades.Thus,the main objective of this study was to analyze water resources vulnerability assessment tools and identify the methodological trend of water resources vulnerability assessment at the local level in existing literature.To achieve this objective,the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)method has been applied to include or exclude articles.Articles on water vulnerability numbering 374 were preselected in the ScienceDirect and the Google Scholar databases.Only 32 out of the 374 articles met the inclusion criteria defined for the analysis.The results show that China(21.9%),U.S.A.(9.4%)and Canada(6.3%)are the most active countries publishing water resources vulnerability assessments.Some 191 vulnerability indicators from the 32 articles were classified into five categories of factors:physical factors(33.5%),socio-economic factors(28.3%),environmental or eco-environmental factors(25.1%),institutions and governance factors(7.3%)and infrastructure factors(5.8%).This study shows that almost half of the studies(47%)considered all five categories of factors,9.4%considered four categories of factors,6.3%considered three categories of factors,28%used two types of factors and 9.4%considered only one category.Researchers have used several methods to assess water resources vulnerability:overlay and index methods(59.4%),process-based models(12.5%),statistical methods(9.4%),overlay and index methods plus process-based model(9.4%),overlay and index methods plus statistical methods(6.3%)and statistical methods plus process-based models(3.1%).Geographic information system(GIS)is an important tool in assessing the vulnerability of water resources with almost 60%of the studies using it at some stage of the assessment.In recent years,there is an increasing trend toward conceptualizing the vulnerability of water resources in a holistic way.