Water Quality Standards


World Health Organization

European Union


Union Health Ministry


What is Water Quality Index(WQI) ?

The Water Quality Index is an attempt to represent overall quality of water collected from pond/lake/river/storage/effluent channel etc.First samples are tested for desired parameters.

Then the purpose of finding WQI is determined.The weightage is given to the parameters according to purpose where most influential/representative parameter for the purpose  is given higher weightage than the less important one.The weighted average of the parameter will give the WQI of that sample for the desired purpose.The purpose will also select the choice of the parameters.

How to apply WQI ?

Say,for example,if the suitability of lake water for drinking is the purpose,important parameters like colliform, pH or acidity, hardness, Iron, Cadmium, Biological Oxygen Demand, Total Suspended Solids, Total Suspended Solid etc. which represent suitability of the collected water for drinking is first determined from literature review or standard reports if available.

Samples are then tested for the selected parameters.The next step will be to select a standard for maximum and minimum permissible limit.Once the results from the sampling is available the weighted average of the values of the parameters are calculated.As mentioned earlier the influential parameter for drinking water is given higher weightage than the other less influential ones.

How to interpret WQI ?

Generally from literature reviews it can be seen that 0-20% represents least quality,21-50% represent a quality better than the least but worse than the WQI of  51 and above.51-70% denotes good quality of water along with 71-90 and 91-100% where latter represents the best quality of the water for the desired purpose(say drinking).WQI may vary with respect to purpose and standards selected.
Application of WQI

In Watershed Pollution

Use of the water quality index and dissolved oxygen deficit as simple indicators of watersheds pollution
Ecological Indicators, Volume 7, Issue 2, April 2007, Pages 315-328
Enrique Sánchez, Manuel F. Colmenarejo, Juan Vicente, Angel Rubio, María G. García, Lissette Travieso, Rafael Borja

Lake and River Water Quality

River quality analysis using fuzzy water quality index: Ribeira do Iguape river watershed, Brazil
Ecological Indicators, Volume 9, Issue 6, November 2009, Pages 1188-1197
André Lermontov, Lídia Yokoyama, Mihail Lermontov, Maria Augusta Soares Machado

Assessing the impact of leather industries on the quality of water discharged into the East China Sea from Wenzhou Watersheds
Journal of Environmental Management, Volume 85, Issue 2, October 2007, Pages 393-403
Mingqin Zhang, Minghua Zhang

A water quality index for lake beaches
Water Research, Volume 16, Issue 6, 1982, Pages 945-948
Normand St-Louis, Pierre Legendre

Urbanization Impact

Surface-water-quality indices for the analysis of data generated by automated sampling networks
TrAC Trends in Analytical Chemistry, Volume 29, Issue 1, January 2010, Pages 40-52
Marta Terrado, Damià Barceló, Romà Tauler, Elena Borrell, Sergio de Campos, Damià Barceló
River Classification

Aquaculture Impact

Water quality index as a simple indicator of aquaculture effects on aquatic bodies
Ecological Indicators, Volume 8, Issue 5, September 2008, Pages 476-484
Fabiano dos Santos Simões, Altair B. Moreira, Márcia Cristina Bisinoti, Sonia M. Nobre Gimenez, Maria Josefa Santos Yabe

Water Supply

An innovative approach of Drinking Water Quality Index—A case study from Southern Tamil Nadu, India
Ecological Indicators, Volume 10, Issue 4, July 2010, Pages 857-868
S. Ramesh, N. Sukumaran, A.G. Murugesan, M.P. Rajan

Water quality evaluation by index in Dalmatia
Water Research, Volume 33, Issue 16, November 1999, Pages 3423-3440
Nives tambuk-Giljanovi

River Classification

Use of water quality index for river classification and zoning of Ganga river
Environmental Pollution Series B, Chemical and Physical, Volume 6, Issue 1, 1983, Pages 51-67
Devendra Swaroop Bhargava

Ground Water

Application of a groundwater quality index as an assessment and communication tool in agro-environmental policies – Two Portuguese case studies
Journal of Hydrology, Volume 327, Issues 3-4, 20 August 2006, Pages 578-591
T.Y. Stigter, L. Ribeiro, A.M.M. Carvalho Dill

Theory of Evidence Concept

Interpreting drinking water quality in the distribution system using Dempster–Shafer theory of evidence
Chemosphere, Volume 59, Issue 2, April 2005, Pages 177-188
Rehan Sadiq, Manuel J. Rodriguez

New Type of WQI

Water quality indicators: Comparison of a probabilistic index and a general quality index. The case of the Confederación Hidrográfica del Júcar (Spain)
Ecological Indicators, Volume 10, Issue 5, September 2010, Pages 1049-1054
Eduardo Beamonte Córdoba, Alejandro Casino Martínez, Ernesto Veres Ferrer

Probability density functions based weights for ordered weighted averaging (OWA) operators: An example of water quality indices
European Journal of Operational Research, Volume 182, Issue 3, 1 November 2007, Pages 1350-1368
Rehan Sadiq, Solomon Tesfamariam

A fuzzy index model for trophic status evaluation of reservoir waters
Water Research, Volume 39, Issue 7, April 2005, Pages 1415-1423
Yi-Ting Liou, Shang-Lien Lo

A proposal for a new method to develop synthetic quality indices for air and water
Journal of Environmental Management, Volume 36, Issue 4, December 1992, Pages 237-252
Giancarlo Barbiroli, Palmira Mazzaracchio, Andrea Raggi, Stefano Alliney

A better water quality indexing system for rivers and streams
Water Research, Volume 24, Issue 10, October 1990, Pages 1237-1244
David G. Smith

Help for the Software

How to open the application ?

Download the .rar file.
Extract it into a folder.
Double Click on Water Quality Index Calculator V2.
A Trial Alert will be generated.
Click OK.
The Calculator window will open automatically.

How to import dataset ?

If you have the data in an excel file then rename the column name according to the field name showing in the calculator.First column must be same as the first field.Save the excel as comma separated value.Go to File,then select Import and select the csv file.Click OK.Then the Final WQI field of the calculator will show the WQI of your entire dataset.

How to export the dataset with calculated WQI ?

Go to file and select Export.Your entire data along with the calculated WQI will be exported to a csv document.

What is WQI1 ?

It is the field which will store the WQI of the parameter you just entered into the calculator.

What is WQI2 ?

WQI2 will show the WQI of the earlier dataset.

What is Final WQI ?

This field will show the actual WQI of the dataset which must be used in  your research works.
W A T E R  Q U A L I T Y  I N D E X  C A L C U L A T O R  V2