Concentration of nutrients in water samples collected from the upper Clark Fork River (Montana, USA) during water years 2017 and 2018 (1 Oct 2016 - 30 Sep 2018)

The LTREB monitoring project is a portion of the 200 million-dollar superfund project for ecological restoration of the Clark Fork River, associated tributaries, and head water streams including Silver Bow and Warm Springs Creek. Restoration along the Clark Fork River includes removal of metal-laden floodplain soils, lowering of the floodplain to its original elevation, and re-vegetation of over 70 km of the river's floodplain closest to contaminant sources. The LTREB monitoring project consists of bi-weekly water quality monitoring across a 200-km restoration gradient contaminated by historic mining practices to monitor inorganic phosphorus and nitrogen concentrations, biotic standing stocks, and heavy metal contamination. The LTREB monitoring project is conducted within the first 200km of the Clark Fork River and associated tributaries located in Western Montana. This LTREB monitoring program began in 2017 and will be completed in the year 2022 with potential for funding extension. Surface water samples represented in this data product are collected from thirteen sites along the mainstem of the upper Clark Fork River. Water samples are collected at each monitoring site in triplicate and filtered with a 0.7 µm glass fiber filter. Nutrient samples are analyzed using a spectrophotometric flow injection analyzer (AP2) for nitrate (N-NO3), soluble reactive phosphorus ((SRP) P-PO4), and ammonium (N-NH4) concentrations reported in mg/L. This data package excludes from the final data product all but three WY2017 NO3N data due to column inefficiency during most measurements. The valid, analysis-ready data of this dataset therefore primarily represent two sets of Quality Assurance and Quality Control (QAQC) processed data from thirteen sites along the mainstem of the upper Clark Fork River: NH4N and SRP concentrations collected in water year 2017 (1 Oct 2016 - 30 Sept 2017) and NH4N, SRP, and NO3N collected in water year 2018 (1 Oct 2017 - 30 Sept 2018).