Nutrient concentrations and yields in undeveloped stream basins of the United States

Data from 85 sites across the United States were used to estimate concentra tions and yields of selected nutrients in streams draining relatively undev eloped basins. Flow-weighted concentrations during 1990-1995 were generally low with median basin concentrations of 0.020, 0.087, 0.26, 0.010, and 0.0 22 milligrams per liter (mg/L) for ammonia as N, nitrate as N, total nitrog en, orthophosphate as P, and total phosphorus, respectively. The flow-weigh ted concentration of nitrate exceeded 0.6 mg/L in only three basins. Total nitrogen exceeded 1 mg/L in only four basins, and total phosphorus exceeded 0.1 mg/L in only four basins. The median annual basin yield of ammonia as N, nitrate as N, total nitrogen, orthophosphate as P, and total phosphorus was 8.1, 26, 86, 2.8, and 8.5 kilograms per square kilometer, respectively. Concentrations and yields of nitrate tended to be highest in northeastern and mid-Atlantic coastal states and correlated well with areas of high atmo spheric nitrogen deposition. Concentrations and yields of total nitrogen we re highest in the southeastern part of the nation and in parts of the upper Midwest. In the northeast, nitrate was generally the predominant form of n itrogen, and in the southeast and parts of the upper Midwest, organic nitro gen was the dominant form. Concentrations of total phosphorus were generall y highest in the Rocky Mountain and Central Plain states.