Biogeochemical processes are key drivers of chemical solubility and mobilization. Understanding these processes will lead to improved predictive capabilities and may aid with watershed management decisions. This data release presents results from the Boulder Creek, Colorado watershed, including analyses of water and sediment. From April to August 2019, water samples were collected weekly at 2 sites along Boulder Creek and 4 tributary sites draining into Boulder Creek. In August 2022, water samples were collected every 2 hours for 34 hours at 2 sites on Boulder Creek (upstream and downstream of the city of Boulder). Samples for both studies were analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, alkalinity, trace metals, water isotopes, and field parameters including dissolved oxygen, pH, water temperature, and specific conductance. In August 2022, bed sediment (0-3 cm depth) samples were collected at 8 sites along Boulder Creek. The sediment was dried, sieved, pulverized, digested, and then analyzed for metals, total carbon, sulfur, and carbonate. In 2021 and 2022, laboratory incubations of sediment and stream water were conducted to assess how different oxidation-reduction conditions affect metal and nutrient concentrations. Sediment cores (0-5 cm and 5-10 cm depth) and surface water were collected from Boulder Creek at three sites upstream, within, and downstream of the city of Boulder. Samples were collected from incubation reactors over time and analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, trace metals, total arsenic, pH, and specific conductance. Sediments used for the incubations were further characterized by sequential extractions with hydroxylamine and dithionite and analyzed for major cations and trace metals. Site information, soil characterization details, incubation preparation and biogeochemical nutrient data, sediment sequential extraction data, and water-quality data are presented in this data release as ten comma-separated values (.csv) formatted tables. A data dictionary file describes the data found in the .csv files. Method details and references are located in the metadata file “Boulder Creek Watershed Data (2019-2023).xml.”

In 2019, soil samples were collected at selected sediment-retention ponds in the Gunnison Gorge National Conservation Area, near Delta, Colorado. This dataset includes pond location, pond characteristics, soil-moisture data, soil-chemistry data, and geophysical data. Pond locations were surveyed using real-time kinematic Global Navigation Satellite Systems (RTK-GNSS) methods and incorporated as a single shapefile in Ponds.zip. Pond characteristics were assessed, and observations were made for assigned surficial-geologic unit, vegetation, check-dam condition, check-dam height, water holding capacity, and stream condition entering and exiting the pond. Pond-characteristic data are incorporated as a single comma-separated values (.csv) file (PondInventory.csv). Soil moisture and chemistry data characterize soil moisture, specific conductance, pH, total dissolved solids, and chloride at selected depths in the soil profile. Soil moisture and chemistry data are presented in a .csv file (SoilData.csv). Geophysical surveys were conducted using a Geophex GEM-2, a hand-held multi-frequency electromagnetic induction sensor. The geophysical surveys were conducted to evaluate soil conductivity differences in and around pond locations and are presented as the unprocessed data from the instrument as a .csv file in GEM-2 data.zip.

In 2019, soil samples were collected at selected sediment-retention ponds in the Gunnison Gorge National Conservation Area, near Delta, Colorado. This dataset includes pond location, pond characteristics, soil-moisture data, soil-chemistry data, and geophysical data. Pond locations were surveyed using real-time kinematic Global Navigation Satellite Systems (RTK-GNSS) methods and incorporated as a single shapefile in Ponds.zip. Pond characteristics were assessed, and observations were made for assigned surficial-geologic unit, vegetation, check-dam condition, check-dam height, water holding capacity, and stream condition entering and exiting the pond. Pond-characteristic data are incorporated as a single comma-separated values (.csv) file (PondInventory.csv). Soil moisture and chemistry data characterize soil moisture, specific conductance, pH, total dissolved solids, and chloride at selected depths in the soil profile. Soil moisture and chemistry data are presented in a .csv file (SoilData.csv). Geophysical surveys were conducted using a Geophex GEM-2, a hand-held multi-frequency electromagnetic induction sensor. The geophysical surveys were conducted to evaluate soil conductivity differences in and around pond locations and are presented as the unprocessed data from the instrument as a .csv file in GEM-2 data.zip.

This dataset includes field measurements and laboratory analyses of surface water, bottom water (sediment-water interface), surficial (0-2 cm) sediment, pore water (0-2 cm), and biota collected in Lake Combie, California, from September 2017 through August 2021. The study area includes six sites within the reservoir where discrete samples of surface water, bottom water, sediment, and pore water were taken along the length of the reservoir at the following distances from the spillway: 0.07 miles, 0.5 miles, 0.9 miles, 1.2 miles, 1.3 miles, and 1.4 miles. The within-reservoir sites were sampled during September 2017, February 2018, and May 2018, prior to a large sediment removal operation, and again during September 2019, February 2020, and June 2020 following the removal operation. Zooplankton samples were collected at four of the six sites during the sampling period. Fish were collected from within two regions of the lake: in the Wooley Creek arm of the lower reservoir, and in the upper reservoir near the targeted area for sediment removal operations. Vertical profiles of water quality were measured with a multi-parameter sonde during water collection events and during one zooplankton event. Thirty-six surface water and thirty-six bottom water samples were collected at each site and analyzed for total mercury (filtered and particulate), methylmercury (filtered and particulate), total suspended solids, sulfate, chloride, selected dissolved nutrients, particulate 13-C/12-C and 15-N/14-N isotopic ratios, total particulate carbon and nitrogen, particulate carbon to nitrogen molar ratio, dissolved organic carbon, and dissolved organic-matter properties (absorption and fluorescence). Thirty-six bed-sediment samples were analyzed for total mercury, methylmercury, total reduced sulfur, and organic content. Pore water extracted from bed sediment was analyzed for filtered total mercury, filtered methylmercury, sulfate, chloride, selected dissolved nutrients, and dissolved organic carbon. Surface water, bottom water, and sediment collections included an additional four field replicates each for analysis - pore water had six replicates. One hundred six zooplankton samples and twenty-three replicates were analyzed for total mercury, methylmercury, 13-C/12-C isotopic ratio, and 15-N/14-N isotopic ratio. Two hundred ninety fish samples were analyzed for total mercury, methylmercury, 13-C/12-C isotopic ratio, 15-N/14-N isotopic ratio, and total mass carbon and nitrogen. Water-quality field measurements made with a multi-parameter sonde included water temperature, barometric pressure, specific conductance, dissolved oxygen, pH, and turbidity. The within-reservoir data includes seven data tables given as both machine readable tab-delimited text (*.txt) and Excel formats (*.xlsx): 1) DataDictionary_LCR17-21, the data dictionary, which provides definitions and details related to the six other data tables, and includes citations of analytical methods; 2) SurfWater_Field-Lab_LCR17-20, the surface water and bottom water data table; 3) Sediment_LCR17-20; 4) PoreWater_LCR17-20; 5) Zooplankton_LCR17-20; 6) Fish_LCR18-21; and 7) SurfWater_Profiles_LCR17-20.

This dataset includes field measurements and laboratory analyses of surface water, bottom water (sediment-water interface), surficial (0-2 cm) sediment, pore water (0-2 cm), and biota collected in Lake Combie, California, from September 2017 through August 2021. The study area includes six sites within the reservoir where discrete samples of surface water, bottom water, sediment, and pore water were taken along the length of the reservoir at the following distances from the spillway: 0.07 miles, 0.5 miles, 0.9 miles, 1.2 miles, 1.3 miles, and 1.4 miles. The within-reservoir sites were sampled during September 2017, February 2018, and May 2018, prior to a large sediment removal operation, and again during September 2019, February 2020, and June 2020 following the removal operation. Zooplankton samples were collected at four of the six sites during the sampling period. Fish were collected from within two regions of the lake: in the Wooley Creek arm of the lower reservoir, and in the upper reservoir near the targeted area for sediment removal operations. Vertical profiles of water quality were measured with a multi-parameter sonde during water collection events and during one zooplankton event. Thirty-six surface water and thirty-six bottom water samples were collected at each site and analyzed for total mercury (filtered and particulate), methylmercury (filtered and particulate), total suspended solids, sulfate, chloride, selected dissolved nutrients, particulate 13-C/12-C and 15-N/14-N isotopic ratios, total particulate carbon and nitrogen, particulate carbon to nitrogen molar ratio, dissolved organic carbon, and dissolved organic-matter properties (absorption and fluorescence). Thirty-six bed-sediment samples were analyzed for total mercury, methylmercury, total reduced sulfur, and organic content. Pore water extracted from bed sediment was analyzed for filtered total mercury, filtered methylmercury, sulfate, chloride, selected dissolved nutrients, and dissolved organic carbon. Surface water, bottom water, and sediment collections included an additional four field replicates each for analysis - pore water had six replicates. One hundred six zooplankton samples and twenty-three replicates were analyzed for total mercury, methylmercury, 13-C/12-C isotopic ratio, and 15-N/14-N isotopic ratio. Two hundred ninety fish samples were analyzed for total mercury, methylmercury, 13-C/12-C isotopic ratio, 15-N/14-N isotopic ratio, and total mass carbon and nitrogen. Water-quality field measurements made with a multi-parameter sonde included water temperature, barometric pressure, specific conductance, dissolved oxygen, pH, and turbidity. The within-reservoir data includes seven data tables given as both machine readable tab-delimited text (*.txt) and Excel formats (*.xlsx): 1) DataDictionary_LCR17-21, the data dictionary, which provides definitions and details related to the six other data tables, and includes citations of analytical methods; 2) SurfWater_Field-Lab_LCR17-20, the surface water and bottom water data table; 3) Sediment_LCR17-20; 4) PoreWater_LCR17-20; 5) Zooplankton_LCR17-20; 6) Fish_LCR18-21; and 7) SurfWater_Profiles_LCR17-20.

This dataset includes data for water, sediment, and biota samples collected at 250 locations in the northwestern Sierra Nevada and the Trinity Mountains during 1999–2012. The locations were chosen to assess potential effects from historical mining, with a focus primarily on mercury contamination associated with placer gold mines in the Sierra Nevada and the Trinity Mountains, and a hard-rock mercury mine in the Trinity Mountains. Trace elements and major elements were analyzed in selected samples. All analyses of mercury, methylmercury, and (or) trace and major elements in water and sediment were performed by U.S. Geological Survey laboratories. Biota samples (invertebrates, fish, and frogs) were analyzed for mercury, methylmercury and (or) trace elements at the Trace Element Research Laboratory in College Station, Texas.

This dataset includes data for water, sediment, and biota samples collected at 250 locations in the northwestern Sierra Nevada and the Trinity Mountains during 1999–2012. The locations were chosen to assess potential effects from historical mining, with a focus primarily on mercury contamination associated with placer gold mines in the Sierra Nevada and the Trinity Mountains, and a hard-rock mercury mine in the Trinity Mountains. Trace elements and major elements were analyzed in selected samples. All analyses of mercury, methylmercury, and (or) trace and major elements in water and sediment were performed by U.S. Geological Survey laboratories. Biota samples (invertebrates, fish, and frogs) were analyzed for mercury, methylmercury and (or) trace elements at the Trace Element Research Laboratory in College Station, Texas.

These data have been collected as part of a cooperative project in between the U.S. Geological Survey Colorado Water Science Center, Colorado Springs Utility, and Colorado Springs Engineering. This project began in 2005 and has collected macroinvertebrate samples from Fountain Creek and its tributaries to monitor the biological condition of this watershed. Provided in this data release are Multimetric Index (MMI) values of aquatic macroinvertebrate assemblages using four different sampling methods. There are two subsets of these data included: (1) MMI values of macroinvertebrate data collected from 2010 to 2012 at 15 sites as part of an invertebrate sample method comparison Scientific Investigations Report (SIR) titled “Comparability among Four Invertebrate Sampling Methods and the Recalibrated Multimetric Index Values, Fountain Creek Basin, Colorado, 2010 – 2012”, and (2) all the MMI values from macroinvertebrate data collected at 34 sites from 2005 to 2016. This USGS data release contains all the data and files to reproduce results of the SIR. Data preparation of these data files is fully described in the SIR.

These data have been collected as part of a cooperative project in between the U.S. Geological Survey Colorado Water Science Center, Colorado Springs Utility, and Colorado Springs Engineering. This project began in 2005 and has collected macroinvertebrate samples from Fountain Creek and its tributaries to monitor the biological condition of this watershed. Provided in this data release are Multimetric Index (MMI) values of aquatic macroinvertebrate assemblages using four different sampling methods. There are two subsets of these data included: (1) MMI values of macroinvertebrate data collected from 2010 to 2012 at 15 sites as part of an invertebrate sample method comparison Scientific Investigations Report (SIR) titled “Comparability among Four Invertebrate Sampling Methods and the Recalibrated Multimetric Index Values, Fountain Creek Basin, Colorado, 2010 – 2012”, and (2) all the MMI values from macroinvertebrate data collected at 34 sites from 2005 to 2016. This USGS data release contains all the data and files to reproduce results of the SIR. Data preparation of these data files is fully described in the SIR.

This data release includes sampling location data, field-collected water chemistry data, cation and anion concentration data for water and tissues of submerged aquatic vegetation, aquatic insect larvae, adult aquatic insects and riparian spiders from 35 first- and second-order sub-alpine streams that ranged over several orders of magnitude in metal concentrations but were similar in elevation, geology, and stream morphology. Sampling was completed in late summer, after snowmelt runoff was complete and as the streams approached baseflow conditions.