Three synoptic sampling campaigns were conducted on upper Cement Creek, near Gladstone, Colorado, under low-flow conditions. The first campaign, conducted October 2012, was part of a larger campaign to characterize low-flow water quality in the entire Cement Creek watershed. The second campaign, conducted in September 2019, was designed to quantify metal loading and identify sources of contamination along a 2.5-kilometer study reach. The third campaign, conducted in September 2020, was designed to quantify loads and sources along the same 2.5-kilometer study reach during a test closure of a bulkhead on the Red and Bonita Mine, one of the primary sources of metals within the watershed. Streamflow measurements during the 2012 campaign were conducted using Acoustic Doppler Velocimetry. A continuous, instream injection of a sodium bromide tracer was initiated at the head of the study reach two days prior to the 2019 synoptic sampling campaign and maintained throughout the duration of the campaign. Bromide concentrations were subsequently used to determine streamflow using the tracer-dilution method. Streamflow estimates for the 2020 campaign were developed using a series of sodium chloride slug additions, wherein specific conductivity readings were used as a surrogate for chloride concentration. This data release includes concentration data (inorganic cations and anions), estimated streamflow, and calculated loads for the three sampling campaigns. Tracer data for the continuous tracer injection (2019) and slug additions (2020) are also included. Calculated loads may be used to compare low flow conditions with and without contributions from the Gold King Mine (2012 versus 2019) as well as before and after closure of the Red and Bonita bulkhead (2019 versus 2020). The data release consists of a kmz file showing site locations and the following 9 tables: Table 1, Locations of sampling sites Table 2, Synoptic sampling results, October 3, 2012 Table 3, Synoptic sampling results, September 5, 2019 Table 4, Synoptic sampling results, September 19, 2020 Table 5, Iron speciation results, September 7, 2019 Table 6, Bromide timeseries, September 3-5, 2019 Table 7, Slug addition chloride data, September 19, 2020 Table 8, Slug addition results, September 19, 2020 Table 9, Spatial profiles of streamflow and metal load

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

The American Tunnel, the Black Hawk mine, the Gold King mine, the Mogul mine, and the Red and Bonita mine are located in the Cement Creek watershed, tributary to the upper Animas River near Silverton, Colorado. All five sites have tunnels that drain groundwater from abandoned underground mine workings to the surface. This draining water has elevated concentrations of metals and degrades water quality in Cement Creek. Water quality (pH, and dissolved copper, manganese, and zinc concentrations) and discharge data were compiled from multiple sources to examine changes in these parameters through time. Copper, manganese, and zinc loads calculated from these data are included in the data files. Data are reported for the American Tunnel (November 1988 through July 2015), the Black Hawk mine (September 1991 through September 2005), the Gold King mine (August 1993 through July 2015), the Mogul mine (July 1992 through July 2015), and the Red and Bonita mine (June 1997 through July 2015).

The American Tunnel, the Black Hawk mine, the Gold King mine, the Mogul mine, and the Red and Bonita mine are located in the Cement Creek watershed, tributary to the upper Animas River near Silverton, Colorado. All five sites have tunnels that drain groundwater from abandoned underground mine workings to the surface. This draining water has elevated concentrations of metals and degrades water quality in Cement Creek. Water quality (pH, and dissolved copper, manganese, and zinc concentrations) and discharge data were compiled from multiple sources to examine changes in these parameters through time. Copper, manganese, and zinc loads calculated from these data are included in the data files. Data are reported for the American Tunnel (November 1988 through July 2015), the Black Hawk mine (September 1991 through September 2005), the Gold King mine (August 1993 through July 2015), the Mogul mine (July 1992 through July 2015), and the Red and Bonita mine (June 1997 through July 2015).

This U.S. Geological Survey (USGS) data release contains stream water chemistry and streamflow data collected in late August and early September, 2021 from 28 sites located throughout Colorado, USA. The sampled streams all drain high-elevation mountain watersheds in areas where the bedrock is hydrothermally altered and contains abundant sulfide minerals. Most sampled streams are therefore affected by natural acid-rock drainage. All sites had been sampled in prior years so that the 2021 data could be used to evaluate potential changes in stream water chemistry in recent decades. Streamflow was also quantified at most sites using data from a sodium chloride slug addition wherein specific conductivity readings were used as a surrogate for the tracer concentration.

This U.S. Geological Survey (USGS) data release contains stream water chemistry and streamflow data collected in late August and early September, 2021 from 28 sites located throughout Colorado, USA. The sampled streams all drain high-elevation mountain watersheds in areas where the bedrock is hydrothermally altered and contains abundant sulfide minerals. Most sampled streams are therefore affected by natural acid-rock drainage. All sites had been sampled in prior years so that the 2021 data could be used to evaluate potential changes in stream water chemistry in recent decades. Streamflow was also quantified at most sites using data from a sodium chloride slug addition wherein specific conductivity readings were used as a surrogate for the tracer concentration.

Two synoptic sampling campaigns were conducted near Breckenridge, Colorado, to quantify metal loading to Illinois Gulch, a tributary of the Blue River. The first campaign, conducted in August 2016, was designed to determine the degree to which Illinois Gulch loses water to the underlying mine workings, and to determine the effect of these losses on observed metal loads. The second campaign, conducted in September 2017, was designed to evaluate metal loading within Iron Springs, a subwatershed that was responsible for the majority of the metal loading observed in 2016. A continuous, instream injection of a sodium bromide (NaBr) tracer was initiated at the head of the respective study reaches several days prior to both synoptic sampling campaigns and maintained throughout the duration of each study. Bromide concentrations were subsequently used to determine streamflow in gaining stream reaches using the tracer-dilution method, and as an indicator of hydrologic connections between the Illinois Gulch and subsurface mine workings. Streamflow losses to the mine workings were quantified using a series of magnesium chloride slug additions conducted in August 2016, wherein specific conductivity readings were used as a surrogate for the tracer concentration. Study results indicate that Illinois Gulch loses water in the vicinity of the Puzzle Extension Shaft, and that water leaving the stream enters the subsurface mine workings. These losses are evidenced by the results of the slug additions and the elevated bromide concentrations observed at a collapsed mine portal in the Iron Springs subwatershed (Willard Adit 1). The primary sources of metal loading to the overall Illinois Gulch study reach include diffuse springs and groundwater near the toe of the Iron Springs mine dump and Willard Adit 1. This data release consists of 8 tables: Table 1, Locations of sampling sites for the 2016 and 2017 campaigns Table 2, Synoptic sampling results, August 18, 2016 Table 3, Synoptic sampling results, September 7, 2017 Table 4, Streamflow measurements, August 2016 Table 5, Bromide time series, August 2016 and September 2017 Table 6, Slug addition conductivity data, August 2016 Table 7, Slug addition results, August 2016 Table 8, Spatial profiles of streamflow and metal load, August 2016 and September 2017

Two synoptic sampling campaigns were conducted near Breckenridge, Colorado, to quantify metal loading to Illinois Gulch, a tributary of the Blue River. The first campaign, conducted in August 2016, was designed to determine the degree to which Illinois Gulch loses water to the underlying mine workings, and to determine the effect of these losses on observed metal loads. The second campaign, conducted in September 2017, was designed to evaluate metal loading within Iron Springs, a subwatershed that was responsible for the majority of the metal loading observed in 2016. A continuous, instream injection of a sodium bromide (NaBr) tracer was initiated at the head of the respective study reaches several days prior to both synoptic sampling campaigns and maintained throughout the duration of each study. Bromide concentrations were subsequently used to determine streamflow in gaining stream reaches using the tracer-dilution method, and as an indicator of hydrologic connections between the Illinois Gulch and subsurface mine workings. Streamflow losses to the mine workings were quantified using a series of magnesium chloride slug additions conducted in August 2016, wherein specific conductivity readings were used as a surrogate for the tracer concentration. Study results indicate that Illinois Gulch loses water in the vicinity of the Puzzle Extension Shaft, and that water leaving the stream enters the subsurface mine workings. These losses are evidenced by the results of the slug additions and the elevated bromide concentrations observed at a collapsed mine portal in the Iron Springs subwatershed (Willard Adit 1). The primary sources of metal loading to the overall Illinois Gulch study reach include diffuse springs and groundwater near the toe of the Iron Springs mine dump and Willard Adit 1. This data release consists of 8 tables: Table 1, Locations of sampling sites for the 2016 and 2017 campaigns Table 2, Synoptic sampling results, August 18, 2016 Table 3, Synoptic sampling results, September 7, 2017 Table 4, Streamflow measurements, August 2016 Table 5, Bromide time series, August 2016 and September 2017 Table 6, Slug addition conductivity data, August 2016 Table 7, Slug addition results, August 2016 Table 8, Spatial profiles of streamflow and metal load, August 2016 and September 2017

This data release contains five comma separated value (csv) files that describe the location and water-quality data for wells, springs, and streams compiled for the U.S. Geological Survey (USGS) and Oregon Water Resources Department (OWRD) investigation of the groundwater resources of the Harney Basin, Oregon. The data included are site IDs, various site location information, well-construction details and hydrostratigraphy, monitoring status, spring elevation, summarized historic spring discharge, date of each spring discharge measurement, source of the discharge measurement, and results of geochemical analyses for sites sampled as part of the associated USGS Scientific Investigations Report. Some of the data presented here references sections of the the larger work which can be found here: Gingerich, S.B., Johnson, H.M., Boschmann, D.E., Grondin, G.H., and Garcia, C.A., 2022, Groundwater resources of the Harney Basin, southeastern Oregon: U.S. Geological Survey Scientific Investigations Report 2021–5103, 118 p., https://doi.org/10.3133/sir20215103.