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Scientific Investigations Report 2007-5279

In cooperation with the U.S. Army Joint Readiness Training Center and Fort Polk

Effects of Hardened Low-Water Crossings on Periphyton and Water Quality in Selected Streams at the Fort Polk Military Reservation, Louisiana, 1998–99 and 2003–04

By Barbara W. Bryan1, C. Frederick Bryan1, John K. Lovelace2, and Roland W. Tollett2

1 Bryan and Associates.
2 U.S. Geological Survey.
Thumbnail of and link to Report PDF (23.2 MB)
Scientific Investigtions Report
2007-5279 PDF (23.2 MB)
Abstract

In 2003, the U.S. Geological Survey (USGS), at the request of the U.S. Army Joint Readiness Training Center and Fort Polk, began a follow-up study to determine whether installation and modification of hardened low-water crossings had short-term (less than 1 year) or long-term (greater than 1 year) effects on periphyton or water quality in five streams at the Fort Polk Military Reservation, Louisiana. Periphyton data were statistically analyzed for possible differences between samples collected at upstream and downstream sites and before and after low-water crossings were modified on three streams, Big Brushy Creek, Tributary to East Fork of Sixmile Creek, and Tributary to Birds Creek, during 2003–04. Periphyton data also were analyzed for possible differences between samples collected at upstream and downstream sites on two streams, Tributary to Big Brushy Creek and Little Brushy Creek, during 1998–99 and 2003. Variations in periphyton communities could not be conclusively attributed to the modifications. Most of the significant changes in percent frequency of occurrence and average cell density of the 10 most frequently occurring periphyton taxa were increases at downstream sites after the hardened low-water crossing installations or modifications. However, these changes in the periphyton community are not necessarily deleterious to the community structure.

Water-quality data collected from upstream and downstream sites on the five streams during 2003–04 were analyzed for possible differences caused by the hardened crossings. Generally, average water-quality values and concentrations were similar at upstream and downstream sites. When average water-quality values or concentrations changed significantly, they almost always changed significantly at both the upstream and downstream sites. It is probable that observed variations in water quality at both upstream and downstream sites are related to differences in rainfall and streamflow during the sample collection periods rather than an effect of the hardened low-water crossing installations or modifications, but additional study is needed.

Version 1.0

Posted May 2008


Suggested citation:

Bryan, B.W., Bryan, C.F., Lovelace, J.K., and Tollett, R.W., 2007, Effects of hardened low-water crossings on periphyton and water quality in selected streams at the Fort Polk Military Reservation, Louisiana, 1998—99 and 2003–04: U.S. Geological Survey Scientific Investigations Report 2007–5279, 36 p.



Contents

Abstract

Introduction

Purpose and Scope

Description of Study Area

Methods

Periphyton

Water Quality

Statistical Analysis

Quality Control and Quality Assurance

Effects of Hardened Low-Water Crossings on Periphyton

Effects of Hardened Low-Water Crossings on Water Quality

Summary

References



For additional information contact:
Director, Louisiana Water Science Center
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Suite 120
Baton Rouge, LA 70816
(225) 298-5481ext. 3117
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Last modified: Thursday, 01-Dec-2016 20:02:06 EST