Hello,

Please check the following links, hope it helps!

Bests- FS

http://www.moef.nic.in/sites/default/files/nlcp/B%20-%20Water%20Quality/B-30.pdf

http://shodhganga.inflibnet.ac.in/bitstream/10603/8242/10/10_chapter%204.pdf

 http://pubs.sciepub.com/ajwr/1/3/3/

Dear Raghavan,

There are many parameters to consider, for rainy season, winter season and summer season : pH, electrical conductivity, total dissolved solids, total alkalinity, total hardness, total suspended solids, calcium, magnesium, chlorides, nitrate, sulphate, dissolved oxygen, biological oxygen demand.

The WQI can be calculated by using the standards of drinking water quality recommended by WHO. The weighted arithmetic index method (brown et al.) can be used for the calculation of WQI.  

I enclose in the attached file a simplified calculation example and the mathematical calculation procedure..

With my best regards

Prof. Bachir ACHOUR

Please read the attached paper - a discussion on WQI and its computation.

Regards

Dr. Asit Kr. Batabyal

Please read the attached paper - a discussion on NSFWQI and its computation.

Regards

Please consult Yogendra & Puttaiah (2008) "Determination of water quality index and sustainability of an urban water body....". Another for groundwater WQI you may consider Ramakrishnaiah (2009). Hope these will help to clear your idea how the overall water quality index can be calculated.

There in your equation

Qn = Quality rating of the nth water quality parameter 

Wn= Unit weight of nth parameter=K/Sn

K= Constant for proportionality

Sn= Standard (permissible) value of nth parameter

Please follow the papers provided by Jayanta.

Regards

thanks lot... all are given details it very use full i done this calculation for my research work thanks all prof. 

Dear Raghavan Kuppu, I didn't get the concept of the Water Quality Index. Can you please send me the excell sheet in which you did your calculation related to the Water Quality Index.

Thanks and regards

Balraj Singh

I am explaining the WQI in a simple way for easy understanding.

WQI: It may be defined as a rating reflecting the composite influence of different water quality parameters on the overall quality of water. The main objective of computing of water quality index is to turn the complex water quality data into information which is easily understandable and usable.

Selection of  parameters: First study the Indian Standard (BIS) for drinking water specification. Here,  the physicochemical parameters along with the desirable limits and related health effects are given. A parameter has to be selected based on its impact in the overall quality of water and heath effects. This standard is freely available.

Computation of WQI: The WQI is computed following the three steps.

First step – Assigning of weight (wi) to the selected water parameters (e.g., pH, TDS, TH, HCO3, Cl, SO4, NO3, ……) according to their relative importance in the overall quality of water for drinking purposes (weight may be from 1 to 5).

Second step – Computation of a relative weight (Wi) of the chemical parameter using the following equation:                                                   Wi = wi / ∑  wi ( i = 1 to n) 

where, Wi is the relative weight, wi is the weight of each parameter and 'n' is the number of parameters

Third step - Assigning of a quality rating scale (qi) for each parameter, as below:

qi = (Ci / Si ) x 100                                                                                       

where,  qi is the quality rating, Ci is the concentration of each chemical parameter in each water sample in mg/l, and Si is the guide line value/desirable limit as given in Indian drinking water standard (BIS).

For computing the WQI, the sub index (SI) is first determined for each chemical parameter, as given below:                                                          SIi = Wi x qi     

WQI = ∑ SIi - n                                            

where, SIi is the subindex of ith parameter; Wi is relative weight of ith parameter; qi is the rating based on concentration of ith parameter and 'n' is the number of chemical parameters.

The water may be classified into five types based on computed WQI as given below:

WQI range and water type:

< 50             

Excellent water;

50 - 100           

Good water;

100- 200          

Poor water;

200 – 300         

Very poor water;

> 300                

Water unsuitable for drinking.

For more details, you can consult my paper published in 'Water Environment Research (USA)'. The link is given below:

https://www.researchgate.net/publication/280062602_Hydrogeochemistry_and_Water_Quality_Index_in_the_Assessment_of_Groundwater_Quality_for_Drinking_Uses

Give your feedback. With best wishes

Wonderful explanation

Dr. Asit Kumar Batabyal sir your given excellent explanation thank you sir...

You may also like to see this approach. hope you find this interesting Article Comparative evaluation of water quality zonation within Dwar...

Please read the attached paper Article Water quality index for Al-Gharraf River, southern Iraq

Dear Raghavan Kuppu,

Please have a look at these useful PDF attachments.

Good luck!

There are many Water Quality Indices for different purpose. The WQI mentioned here is NSF WQI. To know more you can read this paper:

Roy R., Majumder M. (2017) Comparison of surface water quality to land use: a case study from Tripura, India. Desalination and Water Treatment, 85, 147-153

There are many water quality indices given in different books and research papers for different purposes. Kindly read the attached paper, here we used weighted arithematic mean water quality index.

Please, How to calculate the weight (wi)

You can use this model in erdas software to analysis the water quality

Rating for irrigation purpose may differing from rating for drinking purpose.

If our pH is less than ideal value of pH(7) say 6...............then do we need to neglect (-)sign from our quality rating value?

The National Sanitation Foundation (NSF) Water Quality Index (wQI) was one of the analytical tools used to summarize the data. Essentially, the WQI converts the concentration data for nine analytes into one offive water quality classes, ranging from ·very bad" to· excellent".https://water-research.net/index.php/water-treatment/water-monitoring/monitoring-the-quality-of-surfacewater

10.35940/ijitee.I1051.0789S219