Concentrations of total nitrogen (TN), nitrate (NO3-N), ammonium (NH4-N), total phosphorus (TP), and phosphate (PO4-P) for 743 stream water samples collected across 155 sample sites on 12 U.S. Forest Service grazing allotments in northern California.

Published estimates of concentrations of general concern for eutrophication of stream water, and estimates of background concentrations for the study area are provided for context.aThe ‘±’ indicates 1 standard error of the mean.bPercentage of samples below minimum analytical detection limit. Limits were 10 µg L−1 for nitrogen and 5 µg L−1 for phosphorous. Observations below detection limit were set to one half detection limit (5 µg L−1 for nitrogen and 2.5 µg L−1 for phosphorus) for calculation of mean and median concentrations.cConcentrations if exceeded indicate potential for eutrophication of streams [38]–[42].dEstimated range of background concentrations for the three U.S. Environmental Protection Agency Level III sub-ecoregions (5, 9, 78) included in the study [43].