USGS

Percentile Distributions of Median Nitrite Plus Nitrate as Nitrogen, Total Nitrogen, and Total Phosphorus Concentrations in Oklahoma Streams, 1973–2001

By B.E. Haggard, J.R. Masoner, and C.J. Becker

Water-Resources Investigations Report 03-4084

 

Prepared in cooperation with the
Oklahoma Water Resources Boad

 

The report is available in PDF format.


ABSTRACT

Nutrients are one of the primary causes of water-quality impairments in streams, lakes, reservoirs, and estuaries in the United States. The U.S. Environmental Protection Agency has developed regional-based nutrient criteria using ecoregions to protect streams in the United States from impairment. However, nutrient criteria were based on nutrient concentrations measured in large aggregated nutrient ecoregions with little relevance to local environmental conditions in states. The Oklahoma Water Resources Board is using a dichotomous process known as Use Support Assessment Protocols to define nutrient criteria in Oklahoma streams. The Oklahoma Water Resources Board is modifying the Use Support Assessment Protocols to reflect nutrient informa-tion and environmental characteristics relevant to Oklahoma streams, while considering nutrient information grouped by geographic regions based on level III ecoregions and state boundaries.

Percentile distributions of median nitrite plus nitrate as nitrogen, total nitrogen, and total phosphorous concentrations were calculated from 563 sites in Oklahoma and 4 sites in Arkansas near the Oklahoma and Arkansas border to facilitate development of nutrient criteria for Oklahoma streams. Sites were grouped into four geographic regions and were categorized into eight stream categories by stream slope and stream order. The 50th percentiles of median nitrite plus nitrate as nitrogen, total nitrogen, and total phosphorus concentrations were greater in the Ozark Highland ecoregion and were less in the Ouachita Mountains ecoregion when compared to other geographic areas used to group sites. The 50th percentiles of median concentrations of nitrite plus nitrate as nitrogen, total nitrogen, and total phosphorus were least in first, second, and third order streams. The 50th percentiles of median nitrite plus nitrate as nitrogen, total nitrogen and total phosphorus concentrations in the Ozark Highland and Ouachita Mountains ecoregions were least in first, second, and third order streams with streams slopes greater than 17 feet per mile.

Nitrite plus nitrate as nitrogen and total nitrogen criteria determined by the U.S. Environmental Protection Agency for the Ozark Highland ecoregion were less than the 25th percentiles of median nitrite plus nitrate as nitrogen, total nitrogen, and total phosphorus concentrations in the Ozark Highland ecoregion calculated for this report. Nitrite plus nitrate as nitrogen and total nitrogen criteria developed by the U.S. Environmental Protection Agency for the Ouachita Mountains ecoregion were similar to the 25th percentiles of median nitrite plus nitrate as nitrogen and total nitrogen concentrations in the Ouachita Mountains ecoregion calculated for this report. Nitrate as nitrogen and total phosphorus concentrations currently (2002) used in the Use Support Assessment Protocols for Oklahoma were greater than the 75th percentiles of median nitrite plus nitrate as nitrogen and total phosphorus concentrations calculated for this report.

CONTENTS

Abstract

Introduction

Purpose and Scope

Acknowledgments

Methods of determining nutrient criteria

U.S. Environmental Protection Agency methods for determining nutrient criteria

Modification of use support assessment protocols for Oklahoma

Geographic regions and stream category determination

Local Setting

Methods Used and Data Sets Considered

Geochemistry of Madison and Minnelusa Aquifers

Stream water-quality data compilation

Statistical distributions

Percentile distributions of median nitrite plus nitrate, total nitrogen, and total phosphorus concentrations

Summary

Selected references

Appendix

Nutrients and Stream Impairment

 


For additional information write to:

 

District Chief

U.S. Geological Survey

Water-Resources Division

202 NW 66 St., Bldg. 7

Oklahoma City, OK 73116

 

Copies of this report can be purchased from:

 

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225


Download the PDF version of the report for high-resolution, printable pages (2.8MB).

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U.S. Department of the Interior, U.S. Geological Survey
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Last modified: Thursday, September 01 2005, 02:03:52 PM
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