Water-Quality, Bed-Sediment, and Invertebrate Tissue Trace-Element Concentrations for the Clark Fork River and Tributaries in the Upper Clark Fork Basin, Montana, October 2020-September 2021

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana (MT), as part of a long-term monitoring program within the Upper Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Upper Clark Fork Basin and monitor trace elements associated with historical mining and smelting activities. Sampling sites were on the Clark Fork River and a subset of its tributaries. Water samples were collected periodically at 21 sites from October 2020 through September 2021. Bed-sediment and tissue samples were collected once at 13 sites in July 2021. Water-quality data included water-quality properties, concentrations of major ions, dissolved organic carbon, nitrogen (nitrate plus nitrite), trace elements, and suspended sediment. Bed-sediment data included trace element concentrations measured in the fine grained (less than 0.063 millimeter) fraction. Biological data included trace-element concentrations in whole-body tissue of selected aquatic benthic invertebrates. Water-quality, bed-sediment, and invertebrate tissue trace element data for sites in the Upper Clark Fork Basin were provided between October 2020 through September 2021.