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Density Calculation

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Can you please provide the equations and reference that GWB uses to calculate the density of a solution from TDS and temperature? I'm trying to understand how GWB includes these variables in the calculation. Additionally, does the calculation change if the solution is not dominantly Na-Cl, but is, say, dominantly Ca-SO4 or Mg-SO4?





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Hi Morgan,


Density is calculated from a correlation developed by Phillips et al. 1981 for NaCl solutions. The correlation uses the temperature, pressure (which corresponds to the principal temperatures in the thermo dataset), and salinity of the fluid.


The program normally figures density as that of an NaCl solution with the same TDS (which it calculates by adding the masses of solutes) as the fluid in question, at the temperature of interest. With the command “density = chlorinity” you can tell the program to instead use the density of an NaCl solution of equivalent chlorinity. Please see 5.15, density, in the GWB Reference Manual for more information.


Phillips, S. L., A. Igbene, J. A. Fair and H. Ozbek, 1981, A technical databook for geothermal energy utilization. Lawrence Berkeley Laboratory Report LBL-12810, 46 p.
Hope this helps,
Brian Farrell
Aqueous Solutions LLC

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