Chemical Modeling of Acid Waters

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March 10, 2011: Version 3.00 Upgrade to WATEQ4F Released 

Incorporates a new method for calculating the electrical conductivity on natural waters.  The method is based on new electrical conductivity data published by McCleskey (2011).  Details of the new method have been submitted for publication and will be included here once published.

May 26, 2004: Version 2.63 Upgrade to WATEQ4F Released 

Writes a banner specifying the version number, development date, and run date and time at the top of the printed output file. 

December 5, 2003: Version 2.62 Upgrade to WATEQ4F Released 

Modifies the spreadsheet output features: Reads lists of output parameters only once per execution (transparent to user). Groups all miscellaneous parameters at the front of the output record. Renames the parameter files to more explanatory names: TABLE5 to MINERALS, TABLE6 to ACTIVITY, TABLE7 to CONCENTR. Adds query for disposition of a pre-existing spreadsheet file (user can choose to overwrite, rename, or append to, the file). Adds a line to the spreadsheet output file labeling the three major groups of output parameters.

  October 28, 2003 : Version 2.61 Upgrade to WATEQ4F Released   

Removes the H4AsO4+ species from the aqueous speciation calculations. The species is now thought not to exist.

  August 28, 2003 : Version 2.60 Upgrade to WATEQ4F Released

Uses a new compiler, Lahey/Fujitsu Fortran 95 Express, Version 5.7.

Implements a new Y2K-compatible date and time function.

Changes the delimiter for the spreadsheet output file to a TAB from a semicolon; this facilitates reading the file into Excel.

Increases the maximum number of aqueous complexes or mineral species that can be chosen for the spreadsheet output file to 250 (the Excel limitation of 237 still applies, however).

V was being input and output as Hg – it is now V.

Lengthens the character string containing the sample description to allow the sample collection date to be appended to it.


  July 24, 2003 : Version 2.49 Upgrade to WATEQ4F Released

Restores the '****' end-of-file flag to correctly terminate execution when reading the .CSV file. WATEQ4F otherwise continued reading blank records.

Adds code to trap and fix lowercase concentration units input. Program now accepts 'mg/l', 'mg/L', 'ppm', 'mmol', and 'mol' units on input.

Fixes a minor error in OUTPCH, wherein values tested for writing to the spreadsheet compatible output file had to be greater than  -100. Values now must be greater than -1000. This error caused charge and conductance imbalances less than -100 to be discarded.

  March 26, 2003 : Version 2.47 Upgrade of WATEQ4F Released

Updates thermodynamic data (Table2 only) for the following Al and Ba aqueous species, based on Nordstrom et al. (1990):

#          Species            log K                delta-H

87        AlSO4+             3.5                   2.29

88        Al(SO4)2-          5.0                   3.11

543      BaSO4 (aq)      2.7                   ---

Adds microcrystalline gibbsite mineral species (index #651).

Removes duplicate input of DOC from the input data. NOTE that earlier datasets are NOT compatible.


  April 29, 2003 : Version 2.48 Upgrade of WATEQ4F Released

Updates thermodynamic data (Table2 only) for the following As species, based on Nordstrom and Archer (2002):

#          Species            log K                delta-H

557      kAs3+/As          12.532             -27.517

488      As2O5              8.228               -7.557

Corrects error in MAIN program: Test of  PRNT parameter before calling RATIO was incorrect.

Corrects error in SUMS: Two U+4-CO3 species were missing from distribution of carbonate species calculations.

October 23, 2002 : Version 2.45 and 2.46 Upgrades of WATEQ4F Released


Add the capability to specify, external to the computer code, the list of minerals, dissolved species activities, and dissolved component concentrations written to the spreadsheet-compatible output file. Modify input files TABLE5, TABLE6, and TABLE7, respectively, to specify the lists. Identity and order can be varied by modifying the files using a plain text editor.   

August 3, 2002 : Version 2.44 Upgrade of WATEQ4F Released


Revises thermodynamic data for arsenic hydrolysis species and oxide and sulfide minerals, and adds two new aqueous thioarsenite species and the mineral phase amorphous orpiment, per Nordstrom and Archer (2002). Source code was modified to add calculations for the three new species and modify the stoichiometry for the arsenolite and claudetite activity product calculations.

Removes capability for WATEQ4F to execute from a network (non‑writable) drive. WATEQ4F now reads from and writes to only the drive and directory from which it is executed.

Changes the name of the default input file to WATEQ4F.CSV from WATEQ4F.DAT.

Changes output to the spreadsheet-compatible file to output trace elements in milligrams per liter, rather than micrograms per liter, to be consistent with other output data.

January 4, 2001 : Version 2.43 Upgrade of WATEQ4F Released  

Adds capability to read and discard an initial data record from the input file. This allows leaving the header record in the .CSV file for easier subsequent data modifications.

Adds equivalents per million cations and equivalents per million anions to the spreadsheet output file.

July 26, 2000 : Version 2.42 Upgrade of WATEQ4F Released

Adds total and speciated ionic strength to the spreadsheet output file.


March 23, 2000 : Version 2.41 Upgrade of WATEQ4F Released

Adds modification of subroutine OUTPCH to generate a file of semicolon-separated plotting parameters suitable for opening by Microsoft Excel.

Removes output of log AP values for minerals, to decrease the size of the file so that it could be accommodated by Excel's maximum of 230 columns.

January 14, 2000 : Version 2.40 Upgrade of WATEQ4F Released

Adds modification of subroutine INPUT to read data saved from an Excel spreadsheet in comma-separated format. A specific spreadsheet format is required, and data items must be in a specific order (See “Creating WATEQ4F Input Files” in the Readme file).

Changes Log K and delta H for jarosite, reaction 205, per Baron and Palmer (1996, GCA 60[185]) as follows:

Log K from -9.21 ±1.1 to -11.0 ±0.3; delta H from -31.28 to -45.0

(Modifications needed for TABLE2 only)

Adds analytical expression for Log K for BaSO4(aq), reaction 543, per Monnin (1999, Chem Geol 153[187]) as follows:

Log K = 2.8243-166.629/T;    at 298.15K: log K = 2.265, delta H = 0.762 kcal mol-1


May 29, 1998 : Version 2.31 Upgrade of WATEQ4F Released


Adds calculation and printing of input versus calculated conductance imbalance.

September 6, 1995 : Version 2.30 Upgrade of WATEQ4F Released  

Adds capability for WATEQ4F to execute from a network (non‑writable) drive. This modification consists of querying the user for a default path to which writing to disk is permitted.  Code was added at all places where writing to disk is possible, to specify the path of a writable disk and directory.

Adds a check for existence of the user's input water analysis data file in the writable path.

  August 10, 1994 : Version 2.22 Upgrade of WATEQ4F Released  

Corrects errors in the activity product calculations for 7 minor minerals.

March 14, 1990 : Version 2.00 Upgrade of WATEQ4F Released

Includes selenium and uranium species, coupled redox reactions, and data base compatible with that of Nordstrom and others (1990). Open‑File Report 91‑183 published July, 1991, describing Version 2.00.



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Created/Maintained: R. Blaine McCleskey;
Last Updated: 03/10/2011