Uncompahgre River Basin Natural Heritage Assessment
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A Natural Heritage Assessment of Wetlands and Riparian Areas in the Uncompahgre River Basin Eastern Montrose and Ouray Counties Volume II Colorado Natural Heritage Program Colorado State University College of Natural Resources 254 General Services Building Ft. Collins, Colorado 80523 May 1999 A Natural Heritage Assessment of Wetlands and Riparian Areas in the Uncompahgre River Basin Eastern Montrose and Ouray Counties Volume II Prepared for: Colorado Department of Natural Resources 1313 Sherman Street Room 718 Denver, Colorado 80203 Prepared by: Thomas Stephens, Denise Culver, Jennifer Zoerner, and Peggy Lyon May 1999 Colorado Natural Heritage Program College of Natural Resources 254 General Services Building Colorado State University Fort Collins, Colorado 80523 i USER’S GUIDE The Uncompahgre River Basin Natural Heritage Assessment conducted by the Colorado Natural Heritage Program consists of two essentially distinct projects that are highly integrated with respect to methodology and fieldwork. This report reflects the separate nature of the projects by being organized in a two-volume set. Both projects utilized the same Natural Heritage methodology that is used throughout North America, and both searched for and assessed the plants, animals, and plant communities on the Colorado Natural Heritage Program’s List of rare and imperiled elements of biodiversity. Each volume prioritizes potential conservation sites based on the relative significance of the biodiversity they support and the urgency for protection of the site. All information explaining Natural Heritage methodology and ranks is repeated in each volume, so that each volume can stand alone and be used independently of the other. Volume I presents all potential conservation sites identified in the Uncompahgre River Basin that support rare and imperiled plants, animals, and significant plant communities, including wetland and riparian areas. Volume II focuses exclusively on wetland and riparian areas. Volume II also presents “locally significant areas.” These are sites that are among the most important wetlands in the Uncompahgre River Basin, but they did not support animals, plants or plant communities that are unique from a national or statewide perspective, therefore these sites did not receive a Biodiversity Rank. Additionally, Volume II presents an assessment of the wetland functions performed by each site that was surveyed. These functional assessments are intended to provide the user with a more complete picture of the value wetlands and riparian areas provide to Uncompahgre River Basin residents. ii ACKNOWLEDGEMENTS Financial support for this study was provided by a grant from the Environmental Protection Agency (EPA), Region VIII, through the Colorado Department of Natural Resources (CDNR), with in-kind services provided by the Colorado Natural Heritage Program. We greatly appreciate the support and assistance of Doug Robotham and Deborah Mellblom of the CDNR and Sarah Fowler, Jim Louie, and Ed Sterns of the EPA. This project would not have been possible without the help of numerous dedicated individuals. We appreciate the support of the eastern Montrose and Ouray County Commissioners and the assistance that both County Assessors Offices gave us in determining land ownership. We received much help from the Bureau of Land Management, especially Jim Ferguson and Amanda Clements; Colorado Division of Wildlife, especially Rick Sherman, Ken Miller and Jim Garner; the U. S. Forest Service, especially Craig Grother; the Natural Resource Conservation Service, especially Steve Woodis; and the National Park Service, especially Nancy Zaenger and Myron Chase. We appreciate the many landowners that gave us permission to survey their property. In many cases, they imparted to us knowledge that they had gained from many years’ experience in caring for the land. Our staff in Fort Collins, including Mary Klein, Jill Handwerk, Susan Spackman, Kim Fayette, Renee Rondeau, Barry Baker, Amy Lavender, and Mike Wunder all worked with us patiently. iii TABLE OF CONTENTS USER’S GUIDE ............................................................................................................................. ii ACKNOWLEDGEMENTS...........................................................................................................iii LIST OF FIGURES ...................................................................................................................... vii LIST OF TABLES......................................................................................................................... ix EXECUTIVE SUMMARY ............................................................................................................ 1 RECOMMENDATIONS................................................................................................................ 3 PROJECT BACKGROUND AND PURPOSE .............................................................................. 5 STUDY AREA..........................................................................................................................................................6 General Description ..............................................................................................................................................6 Physiography and Geology....................................................................................................................................7 Climate and Vegetation .......................................................................................................................................10 Regional Hydrology.............................................................................................................................................12 Human Impacts on the Ecology of Wetlands and Riparian Areas.......................................................................14 LOWER UNCOMPAHGRE RIVER VALLEY ..................................................................................................................14 THE NATURAL HERITAGE NETWORK AND BIODIVERSITY.......................................... 18 WHAT IS BIOLOGICAL DIVERSITY? ..........................................................................................................................19 COLORADO NATURAL HERITAGE PROGRAM ............................................................................................................20 The Natural Heritage Ranking System ................................................................................................................21 Protection Urgency Ranks...................................................................................................................................23 Management Urgency Ranks...............................................................................................................................23 Element Occurrence Ranking ..............................................................................................................................24 Potential Conservation Areas..............................................................................................................................25 Potential Conservation Planning Boundaries .....................................................................................................25 Off-Site Considerations .......................................................................................................................................26 Ranking of Potential Conservation Areas............................................................................................................27 LEGAL DESIGNATIONS .............................................................................................................................................27 WETLAND DEFINITIONS, REGULATIONS, FUNCTIONAL ASSESSMENTS................... 29 WETLAND DEFINITIONS ...........................................................................................................................................29 WETLAND REGULATION IN COLORADO....................................................................................................................29 WETLAND FUNCTION AND VALUES..........................................................................................................................30 General Wildlife and Fish Habitat ......................................................................................................................32 Flood Attenuation and Storage............................................................................................................................32 Sediment/Nutrient/Toxicant Retention and Removal ...........................................................................................32 Sediment/Shoreline Stabilization .........................................................................................................................33 Production Export/Food Chain Support..............................................................................................................33 Groundwater Discharge/Recharge......................................................................................................................33 Uniqueness ..........................................................................................................................................................34 Recreation/Education Potential...........................................................................................................................34