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Integrated Science Assessment for the Upper Muddy River, Clark County, Nevada Wetland downstream of the Muddy River & California Wash junction. Photo: Louis Provencher, 2003 Annual Report to the Clark County MSHCP, February, 2004 by Louis Provencher1 The Nature Conservancy, One East First Street, Suite 1007, Reno, NV 89509 [email protected] Rob Andress Otis Bay Riverine Consultants, 1049 South 475 West, Farmington, UT 84025 [email protected] Contract #: 2003-TNC-1-A 1 Citation: Provencher, L. and R. Andress. 2004. Integrated Science Assessment for the Upper Muddy River, Clark County, Nevada. Annual report to the Clark County MSHCP, Nevada. The Nature Conservancy, Reno, Nevada. Annual Report: Integrated Science Assessment for the Upper Muddy River Table of Contents 1. EXECUTIVE SUMMARY ...................................................................................................................... 1 2. INTRODUCTION .................................................................................................................................... 4 2.1. STUDY AREA AND CONSERVATION SIGNIFICANCE............................................................................... 4 2.2. OBJECTIVES.......................................................................................................................................... 4 3. BACKGROUND INFORMATION ........................................................................................................ 6 3.1 SCIENTIFIC LITERATURE REVIEW.......................................................................................................... 6 Ownership and Land Use ....................................................................................................................... 7 Hydrogeology ......................................................................................................................................... 7 Hydrology............................................................................................................................................... 8 River Alterations................................................................................................................................... 12 Biogeography and Ecological Systems................................................................................................. 12 3.2. BASIN AND SUB-BASIN CHARACTERIZATION ...................................................................................... 15 3.3. EXPERT ASSESSMENT OF THE CONDITION OF ECOLOGICAL COMMUNITIES AND PRIORITY SPECIES...... 18 3.4. KEY RESEARCH AND MANAGEMENT QUESTIONS................................................................................. 20 3.5. HYDROLOGIC MODELING (HEC-RAS) AND PREDICTED FLOWS.......................................................... 23 4. PRELIMINARY ASSESSMENT OF RESTORATION OPTIONS PER RIVER SEGMENT ...... 25 5. CONCLUSIONS..................................................................................................................................... 28 6. ACKNOWLEDGMENTS...................................................................................................................... 30 7. LITERATURE CITED.......................................................................................................................... 30 8. APPENDIX I. MILESTONE #1 BY OTIS BAY, INC—SCIENTIFIC LITERATURE REVIEW 33 9. APPENDIX II. MILESTONES #2 & 3 BY OTIS BAY, INC—HISTORY OF WATER DEVELOPMENTS AND BASIN AND SUB-BASIN CHARACTERIZATION .................................110 10. APPENDIX III. ATTENDEES OF THE UPPER MUDDY RIVER INTEGRATED SCIENCE PLAN WORKSHOP, 17-19 JULY 2002, LAS VEGAS, NV. LISTED BY ALPHABETIC ORDER. SOME ATTENDEES MAY HAVE NOT SIGNED THE ATTENDANCE SHEET...........................154 11. APPENDIX IV. EXPERT FACT SHEETS FROM THE UPPER MUDDY RIVER INTEGRATED SCIENCE PLAN WORKSHOP, 17-19 JULY 2002, LAS VEGAS, NV. ..................155 12. APPENDIX V. ORIGINAL PRIORITY RESEARCH AND MANAGEMENT QUESTIONS IDENTIFIED DURING THE UPPER MUDDY RIVER INTEGRATED SCIENCE PLAN WORKSHOP, 17-19 JULY 2002, LAS VEGAS, NV. ............................................................................278 13. APPENDIX VI. MILESTONES #4 & 5 BY OTIS BAY, INC—HEC-RAS MODELING AND PRELIMINARY RESTORATION RECOMMENDATIONS ..............................................................281 i Annual Report: Integrated Science Assessment for the Upper Muddy River 1. EXECUTIVE SUMMARY The Muddy River is one of the Mojave Desert’s most important areas of biodiversity, providing habitat for 4 rare and endemic fish species, 7 species of rare invertebrates, 76 breeding bird species, and a unique assemblage of Mojave Desert riparian vegetation. Of particular concern is the endangered Moapa dace (Moapa coriacea), which only inhabits the warm headwaters of this river system. The Nature Conservancy was contracted to develop and write a comprehensive upper Muddy River watershed assessment that will address restoration and land management issues on the Moapa Valley National Wildlife Refuge and elsewhere on the upper Muddy River. The contract, which is for two years, has two components—a geomorphic assessment and an integrated science plan. Although the final outcome of the contract is to propose a set of conservation alternatives based on scientific and social considerations and a list of research needs, the first year objectives are to; 1) review the scientific literature; 2) document the history of water developments; 3) characterize basins and sub- basins; 4) summarize physical and ecological information about the upper Muddy River’s priority systems; 5) identify priority research and management questions that limit restoration on the upper Muddy River; 6) present modeled (HEC-RAS software) flow results for the current channel shape; and 7) list preliminary restoration options. Because this document was conceived as a progress report, each section contains information synthesized from deliverables received from the Conservancy’s contractor, Otis Bay Inc, as well as information amassed by the Conservancy during a technical workshop process. Therefore, a large body of technical material is presented in the appendices. The scientific literature review revealed many interesting facts, but the following have more immediate and practical implications: • Spring discharge is decreasing steadily because of water withdrawals from the (regional) carbonate aquifer. The Moapa dace and other thermal endemics are predicted to be directly affected by this reduced discharge; • The floodplain has been disconnected from the upper Muddy River for at least a century due to deep entrenchment and straightening; • Non-native invasive plant and animal species occupy most ecological communities; • Riverine restoration options are greatly limited by land ownership patterns; • On the more hopeful side, a rich diversity of animal species of concern is still supported in primarily four areas retaining remnant plant communities upstream of Interstate 15; • The limited length of the upper watershed spatially bounds exotic species control within the realm of (long-term) feasibility; • Exotic species removal and land acquisition for conservation are on-going activities laying down the fundamental actions for future restoration; • Many species of concern have common ecological requirements that could be met with generalized restoration and management approaches; and, • A core of local stakeholders have demonstrated success and interest in the conservation of the upper muddy River. 1 Annual Report: Integrated Science Assessment for the Upper Muddy River The scientific literature review also identified issues where species of concern depend on human-caused habitat features that could be affected by riverine restoration: • Vermilion Flycatchers require open water and, as a result, utilize the irrigation ditches adjacent to mesquite bosques, riparian shrublands, and open riparian forests; • Although tamarisk removal is desirable, its wholesale removal may result in the temporary loss of all habitat structure for bird species unless some thought is given to the rate and shape of removal (the current rate of removal is small) and native plant revegetation; and, • The only population of yellow bat (Lasiurus xanthinus) in Nevada is found exclusively in fan palms of the upper Muddy River, including at the Moapa Valley National Wildlife Refuge. While this species is more common south of Nevada, a subset of stakeholders value the presence of a disjunct occurrence of the species and wish to manage it for long term viability. To facilitate the formulation of future conservation alternatives, the upper Muddy River was divided into nine segments representing sufficiently homogeneous river reaches based on channel pattern, valley confinement, and sinuosity. HEC-RAS modeled flow results using 2, 5, 10, 25, 50, and 100-year flood recurrence intervals within the current surveyed channel morphology per segment showed that all but the largest flood events (100 and 50-year) never exceeded the banks of river. A synthesized list of 30 ranked priority research and management questions (from 101 original ones) were developed by experts during a July 2002 technical workshop. These questions identified the critical information needed by the public and members of the CCMSHCP Implementation and Monitoring Committee to justify future applied research, management actions, and associated spending for the upper Muddy River. Presentation of hydrologic and

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