This child page contains 34 csv files, site_qw_ions, which contain observations of chloride (cl), sulfate (sul), total dissolved solids (tds), or total suspended solids (tss) for each site. Each file includes date of observation, measured value of water-quality constituent, remark code for the measured value, and site name. Availability of observations of water-quality constituents depended upon collecting agency and varied by site and constituent. Not all sites had observations for all constituents. The format of the csv file (date format and column headings) is designed to meet the specific requirements of file format for R–QWTREND. If csv files are opened directly in excel, the format of the data can change. To ensure the data are in the proper format for R–QWTREND, files should be opened in a text editor. The "site" in site_qw_ions can be cross-referenced to the main report by downloading the zipped folder RRTrend from child page, "Scripts to run R-QWTREND models and produce results" and navigating to the file siteinfo_appendix.txt.