This child page contains a zipped folder which contains all files necessary to run trend models and produce results. The file structure is organized to track data provenance by clearly denoting how files that were input to the analysis generate the output files. Upon downloading the folder, there are two subdirectories: "01_input", which contains the input total selenium concentration and streamflow data for the models and "02_protocol", which contains the scripts required to run the R–QWTREND analysis tool. Results in the "04_product" folder can be produced by running the "02_protocol/QWTREND_runs.RMD" file, and the user should start with this file and follow instructions on how to run the trend models. By running this script, two additional subdirectories will be created: "03_incremental", which contains all model results for each site regardless of whether those models were included in the journal article associated with this data release, and "04_product", which only contains model results that were included in the article ("final" models). The model results files are briefly described in the "02_protocol/QWTREND_runs.RMD" file, follow the format of files exported by the R–QWTREND software, and are further described in the R-QWTREND documentation (Vecchia and Nustad, 2020). R–QWTREND is a software package for analyzing trends in stream-water quality, and files associated with this package are in "02_protocol/QWTREND2018V4." The package is a collection of functions written in R (R Core Team, 2019), an open source language and a general environment for statistical computing and graphics. The following system requirements are necessary for using R–QWTREND: • Windows 10 operating system • R (version 3.4 or later; 64 bit recommended) • RStudio (version 1.1.456 or later). A report (Vecchia and Nustad, 2020) serves as the formal documentation for R–QWTREND.