Surface water samples were collected from two basins included in the Next Generation Water Observing System network. Six sites were within the Upper Colorado (UCOL) basin, of which three sites (Fraser River at Tabernash, 09027100; Colorado River at Windy Gap, 09034250; Colorado River near Cameo, 09095500) were equipped with Turner Designs C6P fluorometers for continuous fluorescence monitoring. Discrete samples were collected at two additional sites (Colorado River near Colorado-Utah State line, 09163500; Gunnison River near Grand Junction, CO, 09152500) approximately monthly by the Proxies Project to develop proxy models for various contaminants. One additional site (Roan Creek, 391953108130201) was used to evaluate fluorescence characteristics of wildfire-impacted surface waters during a limited number of events. Within the Illinois River Basin (ILRB), samples were collected approximately monthly from two sites (Des Plaines River at Joliet, 05537980; Illinois River at Starved Rock, 05553700) equipped with C6P fluorometers for continuous monitoring. Data contained in this release are compiled into three tables: 1) full absorbance spectra (Proxies_Fixed_Stations_Full_Spectra_Absorbance_Data), 2) full fluorescence spectra in vectorized format (Proxies_Fixed_Stations_Vectorized_Fluorescence_Data), and 3) summary optical measurements (Proxies_Fixed_Stations_Sample_Summary) commonly used in statistical analyses.

Optical spectra reported here are collected from 17 surface water sampling sites within the Fraser River, a headwaters drainage of the Upper Colorado River Basin in the central western United States. The sample collection was conducted as part of the partnership between the United States Geological Survey’s (USGS) Next Generation Water Observation System (NGWOS) and Proxies Project, in coordination with the USGS Colorado Water Science Center and California Water Science Center, and the East Grand Water Quality Board.