Locating inflows and springs discharging into Mineral Creek, CO, prior to conducting a tracer test. Tracer tests are used to assess the relative magnitude of metal loading from inflows along a stream reach.

A site of continuous water-quality sampling during a tracer test conducted on the North Fork of the Animas River, CO.

View of a data logger used to control a pump that injects a tracer solution into a stream during a stream tracer test.

USGS equipment trailer -- bringing tracer tests to Rocky Mountain streams.

Spacing sampling points along a stream prior to a tracer test on Mineral Creek, CO.

Filling a holding tank with a tracer solution prior to the start of a stream tracer study, Upper Animas River Watershed, CO.

View of the setup of a NaCl tracer test that was designed to determine natural attenuation of metals in Pinal Creek, AZ.

Downstream view of Pinal Creek, AZ, where a tracer solution was injected into the stream during a tracer test. Water-quality sampling crews can be seen in the distance.