TABLE 2.

Recommended USEPA Total Nitrogen (TN) and Total Phosphorus (TP) Criteria for Aggregated Level III Ecoregions in the United States Pacific Northwest

	Nutrient
Aggregated Level III Ecoregion	TN	TP
Willamette and Central Valleys	0.31	0.047
Western Forested Mountains	0.12	0.010
Xeric West	0.38	0.022

Notes: USEPA, U.S. Environmental Protection Agency.

Values are in mg/l. The recommended nutrient criteria are equal to the 25th percentile of all available concentrations for each aggregated level III ecoregion and are intended to represent reference (i.e., minimally impacted) conditions for each ecoregion.