National Water-Quality Assessment Program Water-Quality Assessment of the Ozark Plateaus Study Unit, Arkansas, Kansas, Missouri, and Oklahoma—Nutrients, Bacteria, Organic Carbon, and Suspended Sediment in Surface Water, 1993–95 Water-Resources Investigations Report 98–4164 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior U.S. Geological Survey National Water-Quality Assessment Program Water-Quality Assessment of the Ozark Plateaus Study Unit, Arkansas, Kansas, Missouri, and Oklahoma—Nutrients, Bacteria, Organic Carbon, and Suspended Sediment in Surface Water, 1993–95 By JERRI V. DAVIS and RICHARD W. BELL Water-Resources Investigations Report 98–4164 Little Rock, Arkansas 1998 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Thomas J. Casadevall, Acting Director 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 401 Hardin Road Box 25286 Little Rock, Arkansas 72211 Denver, CO 80225-0286 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: <URL:http://wwwrvares.er.usgs.gov/nawqa_home.html> FOREWORD The mission of the U.S. Geological Survey • Improve understanding of the primary natural (USGS) is to assess the quantity and quality of the and human factors that affect water-quality earth resources of the Nation and to provide informa- conditions. tion that will assist resource managers and policymak- This information will help support the develop- ers at Federal, State, and local levels in making sound ment and evaluation of management, regulatory, and decisions. Assessment of water-quality conditions and monitoring decisions by other Federal, State, and local trends is an important part of this overall mission. agencies to protect, use, and enhance water resources. One of the greatest challenges faced by water- The goals of the NAWQA Program are being resources scientists is acquiring reliable information achieved through ongoing and proposed investigations that will guide the use and protection of the Nation’s of 60 of the Nation’s most important river basins and water resources. That challenge is being addressed by aquifer systems, which are referred to as study units. Federal, State, interstate, and local water-resource These study units are distributed throughout the agencies and by many academic institutions. These Nation and cover a diversity of hydrogeologic settings. organizations are collecting water-quality data for a More than two-thirds of the Nation’s freshwater use host of purposes that include: compliance with permits occurs within the 60 study units and more than two- and water-supply standards; development of remedia- thirds of the people served by public water-supply sys- tion plans for a specific contamination problem; oper- tems live within their boundaries. ational decisions on industrial, wastewater, or water- National synthesis of data analysis, based on supply facilities; and research on factors that affect aggregation of comparable information obtained from water quality. An additional need for water-quality the study units, is a major component of the program. information is to provide a basis on which regional This effort focuses on selected water-quality topics and national-level policy decisions can be based. Wise using nationally consistent information. Comparative decisions must be based on sound information. As a studies will explain differences and similarities in society we need to know whether certain types of observed water-quality conditions among study areas water-quality problems are isolated or ubiquitous, and will identify changes and trends and their causes. whether there are significant differences in conditions The first topics addressed by the national synthesis are among regions, whether the conditions are changing pesticides, nutrients, volatile organic compounds, and over time, and why these conditions change from aquatic biology. Discussions on these and other water- place to place and over time. The information can be quality topics will be published in periodic summaries used to help determine the efficacy of existing water- of the quality of the Nation’s ground and surface water quality policies and to help analysts determine the as the information becomes available. need for and likely consequences of new policies. This report is an element of the comprehensive To address these needs, the Congress appropri- body of information developed as part of the NAWQA ated funds in 1986 for the USGS to begin a pilot pro- Program. The program depends heavily on the advice, gram in seven project areas to develop and refine the cooperation, and information from many Federal, National Water-Quality Assessment (NAWQA) Pro- State, interstate, Tribal, and local agencies and the gram. In 1991, the USGS began full implementation public. The assistance and suggestions of all are of the program. The NAWQA Program builds upon an greatly appreciated. existing base of water-quality studies of the USGS, as well as those of other Federal, State, and local agen- cies. The objectives of the NAWQA Program are to: • Describe current water-quality conditions for a large part of the Nation’s freshwater streams, Robert M. Hirsch rivers, and aquifers. Chief Hydrologist • Describe how water quality is changing over time. Foreword III CONTENTS Abstract.................................................................................................................................................................................. 1 Introduction ........................................................................................................................................................................... 2 Description of the Ozark Plateaus Study Unit....................................................................................................................... 2 Hydrology.................................................................................................................................................................... 4 Climate, Population, Land Use, and Water Use .......................................................................................................... 4 Nitrogen and Phosphorus Fertilizer Use...................................................................................................................... 6 Animal and Municipal Sources of Nutrients ............................................................................................................... 7 Description of Surface-Water-Quality Sampling Network.................................................................................................... 10 Basic-Fixed and Intensive-Fixed Sites ........................................................................................................................ 10 Synoptic Sites .............................................................................................................................................................. 11 Assessment of Conditions ..................................................................................................................................................... 15 Study Approach ........................................................................................................................................................... 15 Nutrients ...................................................................................................................................................................... 16 Dissolved Nitrite Plus Nitrate............................................................................................................................ 18 Total Phosphorus ............................................................................................................................................... 24 Fecal Indicator Bacteria............................................................................................................................................... 25 Organic Carbon............................................................................................................................................................ 31 Suspended Sediment.................................................................................................................................................... 35 Summary................................................................................................................................................................................ 37 Selected References............................................................................................................................................................... 39 Contents V FIGURES 1.–4. Maps showing: 1. Location of Ozark Plateaus study unit, major river basins, and physiographic areas................................... 3 2. Land use in the Ozark Plateaus study unit .................................................................................................... 5 3. Municipal sewage-treatment plant point-source discharges greater than 0.5 million gallons per day ......... 9 4. Location of sampling sites comprising the surface-water sampling network ............................................... 11 5. Graphs showing