Water Quality Concentrations and Discharge in the Lower Boise River and Select Tributaries, Southwestern Idaho, Water Years 1994-2023

This dataset describes (a) concentrations of nutrients and related constituents, and (b) discharge in the lower Boise River (Idaho) and its primary tributaries for Water Years 1994 through 2023 and 1969 through 2024, respectively. Constituents include water column concentrations of suspended sediment, total phosphorus, dissolved phosphorus, orthophosphate as phosphorus, total nitrogen, nitrite and nitrate as nitrogen, ammonia and ammonium as nitrogen, Escherichia coli (E. coli) bacteria, and total coliform bacteria; and concentrations of periphyton biomass and chlorophyll a on submerged rocks. Sites with water quality and periphyton results include five mainstem Boise River locations (at Eckert Road, Glenwood Bridge, Middleton, Caldwell, and Parma) and nine tributary locations (Conway Gulch, Dixie Drain, Fivemile Creek, Tenmile Creek, Fifteenmile Creek, Indian Creek at its mouth and upstream at Caldwell, Mason Creek, and Mill Slough. Data are also reported for Sand Hollow Creek, which is not a tributary to the Boise River but is generally considered to be part of the lower Boise River system. Discrete and daily mean discharge data are also provided, when available. This dataset is a compilation of water quality and discharge data from different entities including the U.S. Geological Survey, U.S. Bureau of Reclamation, Idaho Department of Water Resources, City of Boise, and Idaho Power Company. The sampling agency and collection and analysis methods are described in the Processing Steps section of the metadata.