Well,

the attached pdf explains your question.

Sincerely

Dear Jacky,

Regarding your second step, that is forming equations for the water quality parameter and mapping a rating curve. i was work on particular area and published research paper on "Selection of Suitable Aggregation Function for Estimation of Aggregate Pollution Index for River Ganges in India " highly helpful for solving the problem

2.Transformation of the parameters of different

units and dimensions to a common scale.

The goal is to ensure a general ‘good’ status of the waters

and you need the ecological and the chemical status

an example: in my case we have 4 parameters for defined the ecological status from reservoirs:

chlorophyll a.... it could be any value

IGA (group algae index)... values betwen 0-400

Biovolumen of phytoplankton..... any value

%cyanobacteria............. 0% to 100%

We need to change each value in a scale from 0-1 (0 worse 1 better)

The first step is knowing how far are you values from a better quality momment , we ask this RCE (quality ecological ratio) and you need to defined before for each water mass your paramenters:(THIS NEEDS A WORK BEFORE KNOWING YOUR WATER MASS) assigned values to the good ecological class boundaries for each type .You define for each parameter different qualities boundaries (high/good/ moderate/ poor/bad)

Example using the parameter chl a:

RCE chol a =((1/cl a)/1/(cla a reference condition))

(REFERENCE CONDITION is the GOOD values for this type of water

EXAMPLE: for us for reservoirs type 1, 2 an 3 the good chl a is 2 ,6)

After this you transform your RCE into RCEtrans for having a commons scale for all the parameters you use. ( This are equations ) Then you values are between 0-1 and belongs to a class of quality ( high/good/moderate/poor/bad)

In my example :

For Reservoirs Type 1, 2 and 3 if

RCE>0.21 RCE trans=0.5063 x RCE+0.4937

RCE

Thanks Everyone for the kind reply!

All your contribution has truly guided me through this step! :)

Thanks Jacky wong

Hi Jacky, Formulatio of sub indices is very crucial step. If you failed here it will will mislead the quality of water. I think the attached link will help you to sort out this. Please go through it and let me know further for any information.

https://www.researchgate.net/publication/331009233_Development_of_new_integrated_water_quality_index_IWQI_model_to_evaluate_the_drinking_suitability_of_water

Hello sir, could you kindly send me the full paper if you dont mind? The one here shows the first page image only

Hello my dear friends

Hello Dear Yong Jie Wong

For the calculation of the water quality index (WQI) there are 04 steps

1- At the first stage, each of the 10 parameters (TDS, pH, Ca2+, Mg2+, Na+, HCO3-, K+, Cl-, SO42-, NO3-) has been assigned a weight (wi) according to its relative importance in the overall quality of water intended for drinking purposes.

2- At the second stage, the relative weight (Wi) for each parameter was calculated

3- At the third stage, the relative quality (qi) of each parameter was calculated

4- In the final stage of WQI, SI was determined for each water quality parameter

See the attached file in Pdf For the water quality index (WQI) calculation formulas

Best regards

Fatah BOUTELDJAOUI

I agree with Dr. F. Bouteldjaoui

Index for water quality

Water quality index (WQI) is a mechanism for presenting a cumulatively derived numerical expression defining a certain level of water quality [2]. In other words, WQI summarizes large amounts of water quality data into simple terms (e.g., excellent, good, bad, etc.)