This child page contains a zipped folder which contains all items necessary to run geochemical models and produce results published in U.S. Geological Scientific Investigations Report 2021–XXXX [Tatge, W.S., Nustad, R.A., and Galloway, J.M., 2021, Evaluation of Salinity and Nutrient Conditions in the Heart River Basin, North Dakota, 1970-2020: U.S. Geological Survey Scientific Investigations Report 2021-XXXX, XX p.]. The main folder contains a readme.txt and a file called allsiteinfo.table.csv that can be used to learn how to use the files and reference sites to the main report. Also the main folder contains two folders Model Zone 1 and 2 which include a .pqi, .pqo, and .txt files that can be used to run the models and reproduce results from the main report. PHREEQC is a publicly available software for geochemical modeling. The software can be downloaded at https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqci/. An accompanying report (Parkhurst and Appelo, 2013) serves as the formal documentation for PHREEQC. Parkhurst, D.L., and Appelo, C.A.J., 2013, Description of input and examples for PHREEQC version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Techniques and Methods, book 6, chap. A43, 497 p., available only at http://pubs.usgs.gov/tm/06/a43/. Copy of the readme.txt is as follows: USING THE PHREEQC INPUT FILES Software needed: PHREEQC Interactive 3.4 or newer to run the models [https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqci/] Text reader Description of the files included: MZX_YYYY_YYYY.pqi <- PHREEQC input file indicating the model zone and range of years MZX_YYYY_YYYY.pqo <- PHREEQC output file indicating the model zone and range of years MZX_YYYY_YYYY_input.txt <- Text document of the input data MZX_YYYY_YYYY_output.txt <- Text document of the output data Run the PHREEQC models 1. Download PHREEQC Interactive 2. Open the .pqi file in PHREEQC Interactive 3. Select the default database for PHREEQC Interactive 4. Press "Run" on the top ribbon 5. Evaluate the output of the model View the PHREEQC output files 1. Download PHREEQC Interactive 2. Open the .pqo file in PHREEQC Interactive 3. View the output file OR 1. Open the _output.txt file with a text reader