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Oregon District Completed Projects

PN364 Nutrient-Metabolism Relations in a Periphyton-Dominated Stream Community

(Shaded Study Area Map) Study area

PROJECT CHIEF: Dwight Q. Tanner

LOCATION: Douglas County

PROJECT EXTENT: South Umpqua River Basin

TOTAL AREA IN SQUARE MILES: 176

BACKGROUND

Excessive growth of periphytic algae in the South Umpqua River in Oregon becomes a problem each summer during low-flow periods. This growth results from excessive inputs of nutrients, primarily from point sources. In several river reaches, the primary productivity and respiration of the periphyton- dominated community results in pH values and dissolved oxygen concentrations that do not comply with Oregon State standards. Because of continued water- quality violations in the South Umpqua River (and 10 other rivers), courts in Oregon have mandated that TMDLs (total maximum daily loads) be promulgated statewide for all water-quality limited streams. Oregon is the first State where the TMDL requirement of the Clean Water Act is being enforced. Establishing appropriate and defensible TMDL's for nutrients in periphyton- dominated streams is difficult because of the complex (and poorly understood) relations between nutrient loads and the metabolism of the stream community.

OBJECTIVE

The objectives of this study were to:
  1. Quantify the metabolism (primary productivity and respiration) of the South Umpqua River during the summer low-flow periods
  2. Relate metabolism rates to levels of nutrient enrichment and physical properties of the stream (such as velocity, depth, substrate type, and light intensity) and
  3. Quantify these relations to determine the effectiveness of establishing TMDL's for controlling stream pH and dissolved- oxygen concentrations.

APPROACH

Data collection included three levels of effort:
  1. Synoptic surveys of water quality throughout the basin to identify sources and sinks of water, nutrients, carbon, and other constituents,
  2. A fixed-station sampling program for determining seasonal water-quality patterns, and
  3. Diel inflow/outflow sampling of six river reaches to determine short-term (hours) water-quality patterns over a range of different nutrient concentrations, channel morphologies, and light intensities. Diel data were used to study primary production and respiration rates as they relate to physical, chemical, and biological characteristics of the river.

REPORTS

OFR 94-40. Water-quality data for the South Umpqua River Basin, Oregon, 1990-92, by Chauncey W. Anderson, Dwight Q. Tanner, and Douglas B. Lee.

WRIR 96-4082. Assessment of water quality, nutrients, algal productivity, and management alternatives for low-flow conditions, South Umpqua River Basin, Oregon, 1990-92, by Dwight Q. Tanner and Chauncey W. Anderson. [Abstract]

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http://oregon.usgs.gov/projs_dir/pn364/pn364.html
Last modified: Tue Oct 13 16:43:00 1998