Duck River Watershed Plan FINAL WATERSHED ASSESSMENT U.S. Army Corps of Engineers, Nashville District May 2018 Executive Summary This Watershed Plan is a Final Watershed Assessment (FWA) of the Duck River watershed, located in south-central Tennessee. This assessment was prepared under the authority of Section 729 of the Water Resource Development Act of 1986, as amended, which authorizes the U.S. Army Corps of Engineers to undertake watershed planning. This Watershed Plan identifies existing conditions within the watershed, details the major water resources problems and opportunities in the watershed, and provides specific recommendations for implementation. This study was undertaken with collaboration and input from four non-federal sponsors: The Duck River Development Agency (DRWA), The Nature Conservancy (TNC), Tennessee Department of Environment and Conservation (TDEC), and the Buffalo/Duck Resource Conservation and Development Council. The Duck River is considered one of the most biologically diverse rivers in North America and is an outstanding national resource. It has an almost unsurpassed variety of freshwater animal life and is one of three most diverse streams for fish and mussel diversity in the world. The Duck River basin provides habitat for 35 species listed as federally endangered, threatened, candidate or species of concern. The developed landscape ranges from small cities and towns to sparsely populated rural areas with the upper part of the watershed experiencing rapid urbanization and population growth. More than 250,000 middle Tennessee residents rely on the Duck River as their sole source of water. The watershed’s ecosystem is under stress from rapid urban development, land use changes, incompatible agricultural practices, wastewater management and water supply practices, and resource extraction activities. Many communities in the watershed are experiencing periodic flooding which is only expected to worsen as development continues. The major resource issues identified in this FWA are water quality and water supply. Water quality problems stem from riparian buffer alteration, bank erosion, sedimentation, nutrient loading, low dissolved oxygen, and land management and agricultural practices. Water supply problems are controversial because a high quality and quantity water flow is essential for both supporting rare aquatic species and meeting the basin’s growing municipal water demands. DISCLAIMER: The information presented in this report is to provide a strategic framework of potential options to address problems within the watershed. Options identified will follow normal authorization and budgetary processes of the appropriate agencies. Costs presented were rough-order- magnitude estimates used for screening purposes only. Table of Contents Executive Summary ........................................................................................................................... i 1.0 Introduction ............................................................................................................................... 1 1.1 Study Authority ...................................................................................................................... 1 1.2 Background ............................................................................................................................ 3 1.3 Sponsors ................................................................................................................................. 3 2.0 Study Purpose and Scope .......................................................................................................... 3 2.1 Goals and Objectives.............................................................................................................. 3 2.2 Stakeholder Involvement ....................................................................................................... 3 2.3 Vision Statement .................................................................................................................... 5 3.0 Study Area ................................................................................................................................. 5 3.1 Location of Watershed........................................................................................................... 5 3.2 Congressional Districts ........................................................................................................... 7 4.0 Existing Conditions .................................................................................................................... 8 4.1 Hydrologic Features ............................................................................................................... 8 4.2 Ecoregions .............................................................................................................................. 8 4.3 Climate ................................................................................................................................. 10 4.3.1 Regional Climate Change Assessment........................................................................... 11 4.4 Population and Land Use ..................................................................................................... 11 4.5 Aquatic Life .......................................................................................................................... 12 4.6 Terrestrial Life ...................................................................................................................... 13 4.7 Federally Listed Species ....................................................................................................... 13 4.8 Wetlands .............................................................................................................................. 14 4.9 Erosion ................................................................................................................................. 15 4.10 Riparian Buffers ................................................................................................................. 16 4.11 Water quality ..................................................................................................................... 16 4.11.1 Sediment Loading ........................................................................................................ 16 4.11.2 Bacteria Counts and Nutrient Loading ........................................................................ 16 4.11.3 Dissolved Oxygen ........................................................................................................ 17 4.11.4 Phosphates .................................................................................................................. 18 PAGE I 4.11.5 Mining Activities .......................................................................................................... 19 4.12 Water Supply and Low Water Flows .................................................................................. 19 4.13 Flooding and Floodplains ................................................................................................... 19 4.14 Recreation ............................................................................................................................ 1 4.15 Cultural Resources ............................................................................................................... 3 4.16 Sub-Watershed Data and Characteristics ............................................................................ 4 4.16.1 Upper Duck Rivet Watershed ........................................................................................ 4 4.16.2 Lower Duck River Watershed ........................................................................................ 4 4.16.3 Buffalo River Watershed ............................................................................................... 5 5.0 Problems and Opportunities ..................................................................................................... 5 5.1 Water Quality ......................................................................................................................... 6 5.2 Water Supply ......................................................................................................................... 7 5.3 Ecosystem degradation .......................................................................................................... 7 5.4 Land Use Change .................................................................................................................... 7 5.5 Flood Risk Management ........................................................................................................ 8 5.6 General Watershed-Scale ...................................................................................................... 8 5.9 Opportunities ......................................................................................................................... 8 6.0 Objectives and Constraints ...................................................................................................... 10 6.1 Objectives ............................................................................................................................ 10 6.2 Constraints ........................................................................................................................... 10 7.0 Future Conditions ...................................................................................................................