DRAFT EPA/600/R-11/098B DO NOT CITE OR QUOTE September 2013 External Review Draft Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence NOTICE THIS DOCUMENT IS A PRELIMINARY DRAFT. It has not been formally released by the U.S. Environmental Protection Agency and should not be construed to represent Agency policy. It is being circulated for comment on its technical accuracy and policy implications. Office of Research and Development U.S. Environmental Protection Agency Washington, DC DISCLAIMER This document is distributed solely for the purpose of predissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This document is a draft for review purposes only and does not constitute Agency policy. 9/10/2013 ii DRAFT―DO NOT CITE OR QUOTE CONTENTS LIST OF TABLES ....................................................................................................................... viii LIST OF FIGURES ....................................................................................................................... ix LIST OF ACRONYMS AND ABBREVIATIONS .................................................................... xiv LIST OF UNITS ............................................................................................................................xv PREFACE .................................................................................................................................... xvi AUTHORS AND REVIEWERS ................................................................................................ xvii ACKNOWLEDGMENTS ........................................................................................................... xxi 1. EXECUTIVE SUMMARY ..................................................................................................... 1-1 1.1. BACKGROUND ...................................................................................................... 1-1 1.2. SUMMARY OF MAJOR CONCLUSIONS ............................................................ 1-3 1.3. CONCEPTUAL FRAMEWORK OVERVIEW ....................................................... 1-4 1.4. DISCUSSION OF MAJOR CONCLUSIONS ......................................................... 1-6 1.4.1. Conclusion (1): Streams ............................................................................. 1-6 1.4.2. Conclusion (2): Riparian/Floodplain Waters ............................................. 1-9 1.4.3. Conclusion (3): Unidirectional Wetlands ................................................ 1-10 1.5. CLOSING COMMENTS........................................................................................ 1-13 2. INTRODUCTION ................................................................................................................... 2-1 2.1. PURPOSE AND SCOPE .......................................................................................... 2-1 2.2. APPROACH ............................................................................................................. 2-1 3. EFFECTS OF STREAMS AND WETLANDS ON DOWNSTREAM WATERS: A CONCEPTUAL FRAMEWORK .................................................................................... 3-1 3.1. INTRODUCTION .................................................................................................... 3-1 3.2. AN INTRODUCTION TO RIVER SYSTEMS ....................................................... 3-1 3.2.1. River System Components ......................................................................... 3-1 3.2.2. River System Hydrology............................................................................ 3-9 3.2.3. River Network Expansion and Contraction ............................................. 3-16 3.3. INFLUENCE OF STREAMS AND WETLANDS ON DOWNSTREAM WATERS ........................................................................................................... 3-23 3.3.1. Effects of Streams and Wetlands on Material Fluxes .............................. 3-25 3.3.2. Connectivity and Transport of Materials to and from Streams and Wetlands ................................................................................................ 3-28 3.3.2.1. Connectivity and Isolation ........................................................ 3-28 3.3.2.2. Spatial and Temporal Variability of Connectivity .................... 3-31 3.4. FACTORS INFLUENCING CONNECTIVITY .................................................... 3-33 3.4.1. Climate-Watershed Characteristics .......................................................... 3-33 3.4.2. Spatial Distribution Patterns .................................................................... 3-41 3.4.3. Biota ......................................................................................................... 3-47 3.4.4. Human Activities and Alterations ............................................................ 3-47 3.4.5. Interactions Among Factors ..................................................................... 3-50 This document is a draft for review purposes only and does not constitute Agency policy. 9/10/2013 iii DRAFT―DO NOT CITE OR QUOTE CONTENTS (continued) 4. STREAMS: PHYSICAL, CHEMICAL, AND BIOLOGICAL CONNECTIONS TO RIVERS ........................................................................................................................... 4-1 4.1. ABSTRACT .............................................................................................................. 4-1 4.2. INTRODUCTION .................................................................................................... 4-1 4.3. PHYSICAL CONNECTIONS .................................................................................. 4-3 4.3.1. Water .......................................................................................................... 4-3 4.3.2. Sediment .................................................................................................... 4-9 4.3.3. Wood ........................................................................................................ 4-11 4.3.4. Temperature (Heat Energy) ..................................................................... 4-13 4.4. CHEMICAL CONNECTIONS .............................................................................. 4-15 4.4.1. Nutrients ................................................................................................... 4-16 4.4.2. Dissolved and Particulate Organic Matter ............................................... 4-21 4.4.3. Ions ........................................................................................................... 4-25 4.4.4. Contaminants ........................................................................................... 4-26 4.5. BIOLOGICAL CONNECTIONS ........................................................................... 4-29 4.5.1. Invertebrates ............................................................................................. 4-29 4.5.2. Fishes ....................................................................................................... 4-31 4.5.3. Genes........................................................................................................ 4-33 4.6. STREAMS: SYNTHESIS AND IMPLICATIONS................................................ 4-35 4.7. CASE STUDY: PRAIRIE STREAMS ................................................................... 4-38 4.7.1. Abstract .................................................................................................... 4-38 4.7.2. Introduction .............................................................................................. 4-38 4.7.2.1. Geography and Climate ............................................................ 4-38 4.7.2.2. Hydrology and Geomorphology ............................................... 4-40 4.7.2.3. Physicochemistry ...................................................................... 4-42 4.7.2.4. Ecology ..................................................................................... 4-43 4.7.2.5. Human Alterations .................................................................... 4-44 4.7.3. Evidence ................................................................................................... 4-45 4.7.3.1. Physical Connections ................................................................ 4-45 4.7.3.2. Chemical Connections .............................................................. 4-49 4.7.3.3. Biological Connections ............................................................. 4-52 4.7.4. Prairie Streams: Synthesis and Implications ............................................ 4-55 4.8. CASE STUDY: SOUTHWESTERN INTERMITTENT AND EPHEMERAL STREAMS ......................................................................................................... 4-56 4.8.1. Abstract .................................................................................................... 4-56 4.8.2. Introduction .............................................................................................. 4-56 4.8.3. Southwestern Rivers ................................................................................ 4-57 4.8.4. San Pedro River ......................................................................................