Water quality Reliabilty

[GIS1]

Hi friends
I am working in my thesis with water quality reliability .I have three parameters I want to study water age ,chlorine residuals and mixing various sources .I Know how to calculate hydraulic reliability but I need help from you If any one did that or if you have any code to calculate the water quality reliability .
I must to come with Water quality Reliability Index.
I hope to help me with materials or ideas .Thanks in advance