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Beginners => PHREEQC basics => Topic started by: d_guse on May 04, 2021, 07:05:19 PM

Title: Definition of saturation index SI/ documentation of version 3
Post by: d_guse on May 04, 2021, 07:05:19 PM
Dear all,

I have a question concerning the definition of the saturation index SI respectively concerning its documentation.

According to the documentation of version 2 of PHREEQC, SI is defined according to the attached screenshot (from: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/html/final-11.html).

1. Shouldn't this equation read SI = log(IAP / K_SP) with K_SP defined according to eq. (35)? In my opinion, K_SP^(-1) (or a_m,eq^(-1)) is missing in eq. (36).

2. Is there any equivalent documentation for version 3 of PHREEQC concerning the numerical methods and equation definitions?

Thank you very much!


Kind regards
David
Title: Re: Definition of saturation index SI/ documentation of version 3
Post by: dlparkhurst on May 05, 2021, 01:08:12 AM
Yikes. You are right. There should be another term: -log(Kp) or a divisor of Kp inside the log IAP term.

No, the documentation of the numerical method of version 2 is essentially the same for version 3 and was not repeated in the version 3 manual. What can I say, I got tired of writing documentation. Description of numerical methods of new features, particularly TRANSPORT, were added to a limited extent within the description of input for the keywords in the Version 3 manual.