NITROGEN AND PHOSPHORUS CONCENTRATIONS AND FLUXES OF STREAMS IN THE MISSISSIPPI EMBAYMENT STUDY UNIT, 1996-98 _ National Water-Quality Assessment Study Units U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 01-4024 Mississippi Embayment Study Unit ,/.- ..,~·· /~ICKSBURG National Water-Quality Assessment Program NITROGEN AND PHOSPHORUS CONCENTRATIONS AND FLUXES OF STREAMS IN THE MISSISSIPPI EMBAYMENT STUDY UNIT, 1996-98 by R.H. Coupe U.S. Geologica-l Survey Water-Resources Investigations Report 01-4024 National Water-Quality Assessment Program Pearl, Mississippi 2002 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of trade, product, or firm names is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. For additional information Copies of this report can be write to: purchased from: District Chief U.S. Geological Survey U.S. Geological Survey, WRD Branch of Information Services 308 South Airport Road Box 25286 Jackson, Mississippi 39208-6649 Denver, Colorado 80225 Information regarding the National Water-Quality Assessment (NAWQA) Program is available on the Internet via the World Wide Web. You may connect to the NAWQA Home Page using the Universal Resource Locator (URL) at: http://water.usgs.gov/nawqa/ FOREWORD The U.S. Geological Survey (USGS) is commit­ resources, and agricultural, urban, and natural sources ted to serve the Nation with accurate and timely scien­ · of contamination. tific information that helps enhance and protect the Each assessment is guided by a nationally con­ overall quality of life, and facilitates effective manage­ sistent study design and methods of sampling and anal­ ment of water, biological, energy, and mineral ysis. The assessments thereby build local knowledge resources. Information on the quality of the Nation's about water-quality issues and trends in a particular water resources is of critical interest to the USGS stream or aquifer while providing an understanding of because it is so integrally linke.d to the long-term avail­ how and why water quality varies regionally and ability of water that is clean and safe for drinking and nationally. The consistent, multi-scale approach helps recreation and that is suitable for industry, irrigation, to determine if certain types of water-quality issues are and habitat for fish and wildlife. Escalating population isolated or pervasive, and allows direct comparisons of growth and increasing demands for the multiple water how human activities and natural processes affect uses make water availability, now measured in terms of water quality and ecological health in the Nation's quantity and quality, even more critical to the.lorig­ diverse geographic and environmental settings. Com­ term sustainability of our communities and ecosys­ prehensive assessments on pesticides, nutrients, vola­ tems. tile organic compounds, trace metals, and aquatic The USGS implemented the National Water­ ecology are developed at the national scale through Quality Assessment (NAWQA) Program to support comparative analysis of the Study-Unit findings. national, regional, and local information needs and The USGS places high value on the communica­ decisions related to water-quality management and pol­ tion and dissemination of credible, timely, and relevant .icy. Shaped by and coordinated with ongoing efforts of science so that the most recent and available knowl­ other Federal, State, and local agencies, the NAWQA edge about water resources can be applied in manage­ Program is designed to answer: What is the condition ment and policy decisions. We hope this NAWQA of our Nation's streams and ground water? How are the publication will provide you the needed insights and conditions changing over time? How do natural fea­ information to meet your needs, and thereby foster tures and human activities affect the quality of streams increased awareness and involvement in the protection and ground water, and where are those effects most and restoration of our Nation's waters. pronounced? By combining information on water The NAWQA Program recognizes that a national chemistry, physical characteristics, stream habitat, and assessment by a single program cannot address all aquatic life, the NAWQA Program aims to provide sci­ water-resource issues of interest. External coordination ence-based insights for current and emerging water at all levels is critical for a fully integrated understand­ issues. NAWQA results can contribute to informed ing of watersheds and for cost-effective management, decisions that result in practical and effective ~ater­ regulation, and conservation of our Nation's water resource management and strategies that protect and resources. The Program, therefore, depends exten­ restore wate·r quality. sively on the advice, cooperation, and information from other Federal, State, interstate, Tribal, and local Since 1991, the NAWQA Program has imple­ agencies, non-government organizations, industry, aca­ mented interdisciplinary assessments in more than 50 demia, and other stakeholder groups. The assistance of the Nation's most important river basins and aqui­ and suggestions of all are greatly appreciated. fers, referred to as Study Units. Collectively, these Study Units account for more than 60 percent of the overall water use and population served by public water supply, and are representative of the Nation's Robert M. Hirsch major hydrologic landscapes, priority ecological Associate Director for Water iii iv CONTENTS Abstract.................................................................................................................................................. 1 Introduction............................................................................................................................................ 1 Description of Study Unit ....................................................................................................·.......... 3 Climate ............................................... ;. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3 Physiography......................................................................................................................... 4 Land Use ................................................................................................................................. 4 Surface-Water Hydrology ..................................................................................................... 5 Description of Sampling Sites·················:······················································································ 5 St. Francis River Basin, Arkansas and Missouri .................................... ~.............................. 5 White River Basin, Arkansas................................................................................................ 8 Wolf River Basin, Mississippi and Tennessee....................................................................... 11 Yazoo River Basin, Mississippi ............................ :................................................................ 13 Tensas River Basin, Arkansas and Louisiana ........................................................................ 15 Mississippi River Alluvial Plain Sampling Sites .................................................................. 15 Methods ..... ~ ................................................................................................................................... 17 Sampling Frequency, Collection, Processing, and Laboratory Procedures........................... 17 Data-Analysis Procedures ..................................................................................................... 18 Quality-Control Data ............................................................................................................. 19 Flux Calculations ................................................................................................................. : 21 Sources of Nitrogen and Phosphorus..................................................................................................... 21 Point Sources . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 22 Non-point Sources ......................................................................................................................... 22 Concentrations of Nitrogen and Phosphorus .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 24 Nitrogen ..................· ........................................................ :.............................................................. 24 Phosphorus . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. 26 Spatial Variability ......................................................................................... :................................. 31 Fluxes of Nitrogen and Phosphorus....................................................................................................... 34 Summary .............................................., ...... ,................................................................... :................ ~······· 42 References............................................................................................................................................... 43 Appendix I --Summary