Windy Gap Firming Project Recreation Resources Technical Report July 2008 U.S. Department of the Interior Bureau of Reclamation Great Plains Region Recreation Resources Technical Report Windy Gap Firming Project prepared for: U.S. Bureau of Reclamation Eastern Area Office Loveland, Colorado prepared by: ERO Resources Corporation 1842 Clarkson Street Denver, Colorado 80218 CONTENTS 1.0 Introduction.................................................................................................................1 2.0 Alternatives.................................................................................................................1 3.0 Study Area ..................................................................................................................2 4.0 Objectives ...................................................................................................................4 5.0 Methods.......................................................................................................................4 5.1. Data Sources and Analysis.................................................................................4 5.2. Assumptions.......................................................................................................5 6.0 Affected Environment.................................................................................................5 6.1. West Slope Recreation .......................................................................................5 6.1.1. Recreation at Existing Reservoirs..........................................................5 6.1.2. Three Lakes Recreation Activities and Uses .........................................7 6.1.3. Recreation at Potential New Reservoir Sites .........................................9 6.1.4. Colorado River Recreation ....................................................................9 6.2. East Slope Recreation ......................................................................................17 6.2.1. Recreation at Existing Reservoirs........................................................17 6.2.2. Recreation at Potential Reservoir Sites ................................................22 6.2.3. River Recreation ..................................................................................23 7.0 Environmental Consequences ...................................................................................26 7.1. Methods............................................................................................................26 7.1.1. Recreation Seasons ..............................................................................27 7.2. West Slope Reservoirs .....................................................................................27 7.2.1. Grand Lake and Shadow Mountain Reservoir .....................................27 7.2.2. Willow Creek Reservoir ......................................................................28 7.2.3. Granby Reservoir .................................................................................28 7.2.4. Potential New West Slope Reservoirs .................................................31 7.3. East Slope Reservoirs ......................................................................................31 7.3.1. Ralph Price Reservoir ..........................................................................31 7.3.2. Carter Lake...........................................................................................32 7.3.3. Horsetooth Reservoir ...........................................................................34 7.3.4. Potential New East Slope Reservoirs...................................................37 7.4. West Slope River Recreation...........................................................................38 7.4.1. Colorado River .....................................................................................38 7.4.2. Willow Creek .......................................................................................51 7.5. East Slope River Recreation ............................................................................51 7.5.1. Big Thompson River ............................................................................51 7.5.2. North St. Vrain Creek and St. Vrain Creek .........................................53 7.5.3. Other East Slope Streams.....................................................................54 i 8.0 Cumulative Effects....................................................................................................55 8.1. Methods............................................................................................................55 8.2. West Slope Reservoirs .....................................................................................55 8.2.1. Grand Lake and Shadow Mountain Reservoir .....................................55 8.2.2. Willow Creek Reservoir ......................................................................56 8.2.3. Granby Reservoir .................................................................................56 8.2.4. Potential New West Slope Reservoirs .................................................59 8.3. East Slope Reservoirs ......................................................................................59 8.3.1. Ralph Price Reservoir ..........................................................................59 8.3.2. Carter Lake...........................................................................................59 8.3.3. Potential New East Slope Reservoirs...................................................63 8.4. West Slope River Recreation...........................................................................64 8.4.1. Colorado River .....................................................................................64 8.4.2. Willow Creek .......................................................................................79 8.5. East Slope River Recreation ............................................................................80 8.5.1. Big Thompson River ............................................................................80 8.5.2. North St. Vrain Creek and St. Vrain Creek .........................................81 8.5.3. Other East Slope Streams.....................................................................82 9.0 References.................................................................................................................83 TABLES Table 1. Three Lakes Boating Facilities. ............................................................................7 Table 2. Boat Ramp Elevations at Three Lakes..................................................................7 Table 3. Campgrounds and Campsites at Three Lakes. ......................................................9 Table 4. Upper Colorado Campgrounds and Associated Recreation Facilities................13 Table 5. Colorado River Boating Flows for Gore Canyon and Pumphouse.....................15 Table 6. Total Annual Commercial Boating and Fishing Visitor Days (1999­ 2005) in the Pumphouse and Gore Canyon section of the Colorado River. ..............16 Table 7. Average Monthly Changes in Granby Reservoir Water Levels and Surface Area in Average Conditions. ........................................................................28 Table 8. Average Monthly Changes in Granby Reservoir Water Levels and Surface Area in Wet Years. .......................................................................................29 Table 9. Average Monthly Changes in Granby Reservoir Water Levels and Surface Area in Dry Years.........................................................................................29 Table 10. Average Monthly Changes in Carter Lake Elevation and Surface Area in Average Conditions. ..............................................................................................32 Table 11. Average Monthly Changes in Carter Lake Elevation and Surface Area in Wet Years. .............................................................................................................33 Table 12. Average Monthly Changes in Carter Lake Elevation and Surface Area in Dry Years...............................................................................................................33 Table 13. Average Monthly Changes in Horsetooth Reservoir Elevation and Surface Area in Average Conditions. ........................................................................34 ii Table 14. Average Monthly Changes in Horsetooth Reservoir Elevation and Surface Area in Wet Years. .......................................................................................35 Table 15. Average Monthly Changes in Horsetooth Reservoir Elevation and Surface Area in Dry Years.........................................................................................35 Table 16. Estimated Average Monthly Changes to Colorado River Flow above Windy Gap Reservoir in Average Conditions. ..........................................................38 Table 17. Estimated Average Monthly Changes to Colorado River Flow above Windy Gap Reservoir in Wet Years. .........................................................................39 Table 18. Estimated Average Monthly Changes to Colorado River Flow at Hot Sulphur Springs in Average Conditions. ...................................................................40 Table 19. Estimated Average Monthly Changes to Colorado River Flow at Hot Sulphur Springs in Wet Years....................................................................................40