F Ghayurdoost - MSc student of environmental health engineering, Department of Environmental Health Engineering, Zanjan University of Medical Sciences, Zanjan, Iran.
A Assadi - Associate Professor of environmental health engineering, Department of Environmental Health Engineering, Zanjan University of Medical Sciences, Zanjan, Iran.
J Mohammadi - MSc student of environmental health engineering, Department of Environmental Health Engineering, Zanjan University of Medical Sciences, Zanjan, Iran.

Background & Aim: Supply of safe drinking water are of particular importance, however, human intervention in nature and technology development and production of various pollutants, have negative effects on the quality of drinking water. Every year with the sampling and analysis of surface water and groundwater, much information about the quality parameters such as pH, temperature, turbidity, dissolved solids and other parameters are obtained. Due to the high volume of data and need to useful tool for understanding the lay of water quality is more tangible. Therefore, the purpose of telling the understanding and expression of the results of water quality index (WQI) used.This paper begins by presenting the regulatory interest behind the concerns about drinking water quality. Nowadays, supplying high quality water is important issue in the communities.Search Methods: This is a systematic review. In this study, We were searched with using the key words water quality, surface waters, groundwater, CPI, river waters, water parameters and water quality index by main database include Elsevier, Science direct, Scopus, Google Scholar, Ovid and preQuest. Finally, 125 articles were obtained. After reviewing, 47 studies were selected that published between 1995 to 2015.Finding: Water quality index (WQI) is valuable and unique rating to depict the overall water quality status in a single term that is helpful for the selection of appropriate treatment technique to meet the concerned issues. However, WQI depicts the composite influence of different water quality parameters and communicates water quality information to the public and legislative decision makers. Every year with analyzing surface and ground waters much information about qualitative parameters of water has been obtained. Water quality of any specific area or specific source can be assessed using physical, chemical and biological parameters. There are several water indexes in order to evaluation of water quality. Conclusion: The main conclusion of the paper will be a highlighted and draws attention towards the Water Quality Indices in a simplified format, which may be used at large and could represent the reliable picture of water quality.

Water quality, surface waters, groundwater, water quality index, water parameters