Water-quality data for stream and hyporheic zone samples altered by injection of sodium bromide tracer during a synoptic-sampling study, Leavenworth Creek, Clear Creek County, Colorado, 2012

Leavenworth Creek, a tributary of South Clear Creek and Clear Creek near Georgetown, Colorado contains copper, lead, and zinc concentrations that are near to or exceed aquatic life standards. The creek drains the Argentine mining district where mining was active primarily in the early 1900s. In the summer of 2012, the U.S. Geological Survey (USGS) conducted a metal-loading study using tracer dilution and spatially detailed synoptic sampling to assess the location and magnitude of copper, lead, manganese, and zinc sources to Leavenworth Creek. Sodium bromide solution was injected into the stream to facilitate calculation of streamflow at all stream sites using the principles of tracer dilution. Consequently, concentrations of tracer (total and filtered sodium and filtered bromide) and specific conductance measured in the stream do not represent true environmental conditions because they have been altered by injection of the tracer into the stream. As a result, these data are stored in the U.S. Geological Survey?s National Water Information System database but are not accessible to the public. This data release contains values for total and filtered sodium and filtered bromide concentrations, where available, and specific conductance measeurements for (1) stream sites sampled during the synoptic sampling event, (2) three hyporheic sniffer samplers installed in the shallow streambed, and (3) one inflow to the stream that likely represented a side channel of the mainstem. Four stream sites have additional bromide concentrations collected after synoptic sampling occurred at 1200 on August 30, 2012. In addition, automatic samplers installed at three stream sites collected samples on approximately an hourly basis for varying periods from August 27 through 30, 2012. Concentrations of filtered sodium (where available) and bromide are reported for these samples. Methods of sampling and analysis are available in Walton-Day and others (2019).