How do nutrient concentrations in streams and groundwater relate to land use?
Nutrient concentrations in streams and groundwater are directly related to land use and nutrient inputs in the upstream watershed or the area overlying the aquifer, along with natural features and management practices that influence the amount and timing of transport over the land and to the groundwater system. Concentrations of total nitrogen were highest in agricultural streams compared to concentrations in streams draining urban, mixed, or undeveloped land use, with a median concentration of about 4 milligrams per liter, about 6 times greater than background levels. Concentrations of total phosphorus were elevated in streams in both agricultural and urban areas, with a median concentration of about 0.25 mg/L (about 6 times greater than background levels). Elevated concentrations of phosphorus in agricultural streams are associated with relatively high applications of fertilizer and manure. Urban sources may include treated wastewater effluent and runoff of fertilizers from residenti
