Nutrient Criteria Project
Portland State University
Center for Lakes and Reservoirs
PO Box 751
Portland OR 97207-0751
Overenrichment of surface waters in the United States has been a
long-standing problem to the extent that approximately half of the
waters reported by the States to be impaired are attributed to excess
nutrients and related biological growth. The EPA has established the
National Nutrient Criteria Program to address this water quality problem.
The surface waters of concern are lakes and reservoirs, streams and
rivers, and estuaries and coastal marine waters, and wetlands. Criteria
representing enrichment conditions of surface waters that are minimally
impacted by human developmental activities will be developed for each
of the regions of the country. These will then become the basis for
States and Tribes of the United States to develop nutrient criteria
to protect the designated uses of those waters.
Nitrogen and phosphorus are the primary causes of overenrichment
and are obfious nutrient criteria variables, but biological response
variables are also important in addressing the consequences of overenrichment
Limnologists and lake managers have developed a general consensus
about freshwater lake responses to nutrient additions, that essentially
an ambient total phosphorus (TP) concentration of greater than about
0.01 mg/L and or a total niroen (TN) of about 0.15 mg/L is likely
to predict blue-green algal bloom problems during the growing season.
Similarly, chronic overenrichment leads to lake quality degradation
manifested in low dissolved oxygen, fish kills, algal blooms, expanded
macropytes, likely increased sediment accumulation rates, and species
shifts of both flora and fauna.
Nutrient criteria development consists of five elements:
- Historical data and other information to provide an overall perspective
on the status of the resource.
- Present reference sites and their
collective reference condition describing the current status.
- Modeling to refine data implications
and analysis above if necessary
- Objective assessment of all the
above information by the States and by the EPA Regional Technical
Assistance Groups (RTAG's), a board of State and Federal specialista
established in each EPA Region to help develop and administer
the National Nutrient Criteria Program, to establish ecoregional
criteria, and to review proposed State or Tribal nutrient criteria.
- Attention to downstream consequences before the criterion is fully
Portland State University is on the RTAG for nutrient criteria development
in the Pacific NW. Data were collected on 12 Oregon and 12 Washington
coastal lakes in 2000 and 2001. The data are being analyzed to determine
patterns in nutrient levels within the region. In 2002 data collection
will concentrate on reservoirs in central and eastern Oregon and Washington
and western Idaho.
Nutrient Criteria Technical Guidance Manual (index of PDF documents).