Site map of the transboundary Kootenay River Basin and Columbia River Basin

(A) Site map of the transboundary Kootenay River Basin and Columbia River Basin. (B) Selected Canada–British Columbia Water Quality Monitoring Program long-term monitoring sites, locations of reported industrial sources, and areas of the Elk River Mines (ERMs). (C) Flow-normalized trends in total Se concentrations with significant trends (p value < 0.001) noted with a solid line. (D) 5-year (2013–2017) mean annual total Se loads at each monitoring site and reported industrial sources noted in B with black lines representing the standard deviation over the 5-year period and with distance downstream from ERMs (the town of Sparwood, Canada). Note that the Kootenay near Fenwick site is not upstream of ERMs but depicted on D as a reference site (“Ref”) located in a neighboring watershed to the ERMs. Six kilometers were added to the Elk River below Sparwood so that this site could be distinguished from the reported load from ERMs along the x axis.