Field experiment designed to compare survival of trout fry (newly hatched fish) exposed to constant versus varying metal concentrations, High Ore Creek, Mont. Water stored in the streamside tanks was used to refresh plastic containers in the stream. Water in the tanks had high, medium, or low metal concentrations. The fourth tank contained metal-free water used as an experimental control

Scientists checking fish held in plastic containers that were exposed to a constant metal concentration as part of a field experiment to compare survival of trout fry (newly hatched fish) exposed to constant versus varying metal concentrations, High Ore Creek, Mont.

Fish held in flow-through containers are exposed to metal concentrations with daily high and low cycles (diel cycles). Scientists conducted a field experiment to compare survival of newly hatched trout (fry) exposed to constant versus varying metal concentrations, High Ore Creek, Mont. The experiment will help scientists understand the effect of diel variations in the concentration of metals on fish in mining effected areas

A field experiment in Mineral Creek, Colo., used 18 drive point wells along a 33-meter study reach to sample for ground-water inflow to the stream of metal-rich water (copper, zinc, and other metals) from abandoned mine sites. Identification of such inflows, when no surface manifestation occurs, is one of the applications of stream-tracer injections

USGS scientists display some of their precautions used to prepare a sodium hydroxide solution. The solution was used for a pH modification experiment in Mineral Creek, Colo. The pH modification experiment was designed to study the changes in geochemical conditions that affect the transport of metals in streams during remediation of acidic mine drainage

Solutions of lithium bromide (right tank) and sodium hydroxide (left tank) used for of a pH-modification experiment in Mineral Creek, CO. The experiment was designed to simulate remediation of acid mine drainage systems that artificially raise the pH of streams

Green ferrous iron hydroxide precipitate forming downstream from the injection of sodium hydroxide base (white tubing in stream) into metal-rich, acidic Mineral Creek, Colo. The injection of the base solution is an analog for mine drainage cleanup programs that use limestone and other materials to raise the pH of streams to conditions that support fish habitat

A field experiment in August 2005 tested the injection of sodium hydroxide base into the metal-rich, acidic (low pH) Mineral Creek, Colo. Green ferrous iron hydroxide precipitate formed downstream from the injection point (white tubing in stream). A reactive solute-transport model, OTEQ, was used to predict the changes that occurred in the acidic stream when the pH is raised by the injection of the high pH solution (basic solution)

Before a pH modification experiment conducted in Mineral Creek, Colo., the pH of the stream was about 3.0, and the streambed was heavily coated with aluminum and iron precipitates. Mineral Creek receives acid mine drainage from abandoned mine lands, and is one of the streams that USGS scientists are studying to understand the factors that influence the transport of metals in acidic streams

During a pH modification experiment conducted in Mineral Creek, Colo., the pH of the stream changed from about 3.0 to about 8.0 (acidic to mildly basic). The change in pH caused the older precipitates in the stream to be covered by a new precipitate (ferrous iron hydroxide). A solution of a base (sodium hydroxide) was injected into the stream to change the pH

USGS scientists collecting water-quality samples from drive point wells along a 30-meter reach of Mineral Creek, Colo. The wells were located near pits along the streambed to characterize the quality of ground water entering the stream

Graph of the increasing number of papers in hydrology journals that reference work by the USGS on the hyporheic zone, transient storage, and/or the solute transport modeling code OTIS