There are five datasets included in this collection. One dataset (SiteInventoryunique.shp) provides metadata for sampling stations associated with estuarine water quality data focused on chlorophyll measurements from 1984 to 2021 and with ancillary data parameters added. Water quality data compiled by US EPA from multiple sources are provided in a separate .csv file (surfchl_withSiteInvID.csv) also downloadable from EPA's Estuary Data Mapper (EDM; www.epa.gov/edm). Chlorophyll data were collected as part of a project to refine algorithms for chlorophyll a and harmful algae using Sentinel 2 remote sensing data. Water quality data observations can be matched to the station file using the SiteInvID variable. A station inventory (Sentinel2matchedsets_surface_uniqstns_NAD83.shp) and two additional datasets (also in EDM) are available with matched chlorophyll - remote sensing Sentinel 2 Level 2A data (Sent2matchsurfchl_wStnIndex.csv) and with matched chlorophyll - Sentinel 2 Level 1C data (....csv).