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United States Department of Agriculture

Agricultural Research Service

Title: Phosphorus Criteria and Ozark Streams: An Oklahoma Case Study

Author
item Haggard, Brian

Submitted to: Conference on Watershed Management to Meet Emerging TMDL Environmental Regulations
Publication Type: Proceedings
Publication Acceptance Date: October 1, 2003
Publication Date: November 8, 2003
Citation: Haggard, B.E. 2003. Phosphorus criteria and ozark streams: An oklahoma case study. Conference on Watershed Management to Meet Emerging TMDL Environmental Regulations. p. 123-128.

Interpretive Summary: The development of numeric P criteria in Ozark streams of Oklahoma is inevitable, and in some Ozark streams (i.e., Oklahoma's Scenic Rivers) a TP criterion has already been established. This paper discusses the distribution of median total phosphorus concentrations in Oklahoma streams and relevance to factors contributing to eutrophication of Oklahoma streams. The percentile distribution of median TP concentrations in Oklahoma streams varied across the state, particularly between the Ozark Highlands and Ouachita Mountains. The 25th percentile of median TP concentrations in Ozarks streams was generally greater than Oklahoma's Scenic River TP criterion, except in smaller headwater streams. It may be possible to relate SRP concentrations in Ozark streams to a simple measure of trophic state (LETSI) and determine SRP concentrations which may limit the potential for algal growth in Ozark streams. However, much consideration must be given to physical factors, particularly discharge, limiting the production of stream algae or affecting water-quality monitoring strategies.

Technical Abstract: Nutrient and chlorophyll a concentrations are generally the basis for trophic state classification because of the strong relation between the two, particularly in lakes. However, this relation is often much weaker in streams because the effect of physical factors on the production and composition of algae. The occurrence of eutrophic conditions in stream is most often related to nuisance algal biomass and excessive nutrient concentrations; the impairment of the beneficial uses of streams from these factors is protected by narrative or numeric criteria. Recently, a guidance document has been released on the development of numeric nutrient criteria in streams, and this approach considers the statistical distribution of nutrient concentrations in streams. We use recently published investigations on stream nutrient concentration and limitation in Oklahoma streams to present potential scenarios in the development of total phosphorus (TP) criteria and compare these investigations with recently promulgated TP criterion in Oklahoma's Scenic Rivers. The percentile distribution of median TP concentrations in Oklahoma streams varied across the state, particularly between the Ozark Highlands and Ouachita Mountains. The 25th percentile of median TP concentrations in Ozarks streams was generally greater than Oklahoma's Scenic River TP criterion, except in smaller headwater streams. It may be possible to relate soluble P concentrations in Ozark streams to a simple measure of trophic state and determine soluble P concentrations which may limit the potential for algal growth in Ozark streams.

Last Modified: 10/22/2014
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