American Journal of Water Resources, 2013, Vol. 1, No. 3, 34-38 Available online at http://pubs.sciepub.com/ajwr/1/3/3 © Science and Education Publishing DOI:10.12691/ajwr-1-3-3 Water Quality Assessment in Terms of Water Quality Index Shweta Tyagi 1 , Bhavtosh Sharma 2,* , Prashant Singh 1 , Rajendra Dobhal 2,3 1 Department of Chemistry, DAV Post Graduate College, Dehradun, Uttarakhand, India 2 Uttarakhand Science Education and Research Center, Dehradun, Uttarakhand, India 3 Uttarakhand Council of Science and Technology, Dehradun, Uttarakhand, India *Corresponding author: bhavtoshchem@gmail.com Received July 19, 2013; Revised August 05, 2013; Accepted August 07, 2013 Abstract 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. In spite of absence of a globally accepted composite index of water quality, some countries have used and are using aggregated water quality data in the development of water quality indices. Attempts have been made to review the WQI criteria for the appropriateness of drinking water sources. Besides, the present article also highlights and draws attention towards the development of a new and globally accepted “Water Quality Index” in a simplified format, which may be used at large and could represent the reliable picture of water quality. Keywords: ground water, surface, water quality, water quality index Cite This Article: Shweta Tyagi, Bhavtosh Sharma, Prashant Singh, and Rajendra Dobhal, “Water Quality Assessment in Terms of Water Quality Index.” American Journal of Water Resources 1, no. 3 (2013): 34-38. doi: 10.12691/ajwr-1-3-3. 1. Introduction Water, a prime natural resource and precious national asset, forms the chief constituent of ecosystem. Water sources may be mainly in the form of rivers, lakes, glaciers, rain water, ground water etc. Besides the need of water for drinking, water resources play a vital role in various sectors of economy such as agriculture, livestock production, forestry, industrial activities, hydropower generation, fisheries and other creative activities. The availability and quality of water either surface or ground, have been deteriorated due to some important factors like increasing population, industrialization, urbanization etc. Water quality of any specific area or specific source can be assessed using physical, chemical and biological parameters. The values of these parameters are harmful for human health if they occurred more than defined limits [1,2,3,4]. Therefore, the suitability of water sources for human consumption has been described in terms of Water quality index (WQI), which is one of the most effective ways to describe the quality of water. WQI utilizes the water quality data and helps in the modification of the policies, which are formulated by various environmental monitoring agencies. It has been realized that the use of individual water quality variable in order to describe the water quality for common public is not easily understandable [5,6]. That's why, WQI has the capability to reduce the bulk of the information into a single value to express the data in a simplified and logical form [7]. It takes information from a number of sources and combines them to develop an overall status of a water system [8-25]. They increase the understanding ability of highlighted water quality issues by the policy makers as well as for the general public as users of the water resources [26]. The present study reviews some of the important water quality indices used in water quality assessment and provides their mathematical structure, set of parameters and calculations along with their merits and demerits, which are being used worldwide. 2. Water Quality Index Initially, WQI was developed by Horton (1965) [27] in United States by selecting 10 most commonly used water quality variables like dissolved oxygen (DO), pH, coliforms, specific conductance, alkalinity and chloride etc. and has been widely applied and accepted in European, African and Asian countries. The assigned weight reflected significance of a parameter for a particular use and has considerable impact on the index. Furthermore, a new WQI similar to Horton’s index has also been developed by the group of Brown in 1970 [28], which was based on weights to individual parameter. Recently, many modifications have been considered for WQI concept through various scientists and experts [29,30] . A general WQI approach [31] is based on the most common factors, which are described in the following three steps: