Lake Powell Pipeline Draft Study Report 18 Surface Water Resources March 2011 Lake Powell Pipeline 3/10/11 Draft Surface Water Resources Study Report Utah Board of Water Resources Table of Contents Page Executive Summary ES-1 Introduction ...................................................................................................................... ES-1 ES-2 Methodology .................................................................................................................... ES-1 ES-3 Key Results of the Wetlands and Riparian Resources Impact Analyses ......................... ES-1 Chapter 1 – Introduction 1.1 Introduction ............................................................................................................................ 1-1 1.2 Summary Description of Alignment Alternatives.................................................................. 1-1 1.2.1 South Alternative ................................................................................................ 1-1 1.2.2 Existing Highway Alternative ............................................................................ 1-8 1.2.3 Southeast Corner Alternative .............................................................................. 1-8 1.2.4 Transmission Line Alternatives ........................................................................ 1-10 1.3 Summary Description of No Lake Powell Water Alternative ............................................. 1-17 1.3.1 WCWCD No Lake Powell Water Alternative .................................................. 1-17 1.3.2 CICWCD No Lake Powell Water Alternative .................................................. 1-18 1.3.3 KCWCD No Lake Powell Water Alternative ................................................... 1-18 1.4 Summary Description of the No Action Alternative............................................................ 1-18 1.4.1 WCWCD No Action Alternative ...................................................................... 1-19 1.4.2 CICWCD No Action Alternative ...................................................................... 1-19 1.4.3 KCWCD No Action Alternative ....................................................................... 1-19 1.5 Impact Topics....................................................................................................................... 1-20 Chapter 2 – Methodology 2.1 Study Area ............................................................................................................................. 2-1 2.2 Streams ................................................................................................................................... 2-3 2.2.1 Existing Conditions............................................................................................. 2-3 2.2.2 Direct Effects ...................................................................................................... 2-3 2.2.2.1 Virgin River Daily Simulation Model ................................................ 2-3 2.2.2.1.1 Virgin River Daily Simulation Model Scenarios ............... 2-4 2.2.2.2 Lower Colorado River and Lake Powell Model ................................. 2-5 2.3 Reservoirs .............................................................................................................................. 2-6 2.4 Peak Flows ............................................................................................................................. 2-6 2.5 Geomorphology ..................................................................................................................... 2-7 2.6 Cumulative Effects................................................................................................................. 2-7 2.7 Study Period ........................................................................................................................... 2-7 Chapter 3 – Affected Environment 3.1 Water Regulation ................................................................................................................... 3-1 3.2 Streams ................................................................................................................................... 3-1 3.2.1 Colorado River .................................................................................................... 3-1 3.2.2 Virgin River Drainages ....................................................................................... 3-8 3.2.2.1 Virgin River at Virgin, UT ............................................................... 3-12 3.2.2.2 Virgin River Near St. George, UT ................................................... 3-15 3.2.2.3 Virgin River at Littlefield, AZ .......................................................... 3-19 3.2.2.4 Santa Clara River at St. George ........................................................ 3-22 3.2.2.5 Ash Creek ......................................................................................... 3-25 Lake Powell Pipeline TOC-i 3/10/11 Draft Surface Water Resources Study Report Utah Board of Water Resources Table of Contents (continued) Figure Number Figure Title Page 3.2.2.6 LaVerkin Creek ................................................................................ 3-26 3.2.2.7 Other Potential Affected Streams ..................................................... 3-26 3.2.3 Kane, Mohave and Coconino County Drainages .............................................. 3-26 3.2.3.1 Kanab Creek ..................................................................................... 3-28 3.2.3.2 Paria River ........................................................................................ 3-31 3.2.4 Iron County Drainages ...................................................................................... 3-33 3.2.4.1 Coal Creek Near Cedar City ............................................................. 3-35 3.3 Return Flows ........................................................................................................................ 3-38 3.4 Reservoirs ............................................................................................................................ 3-40 3.4.1 Lake Powell ...................................................................................................... 3-40 3.4.2 Quail Creek Reservoir ...................................................................................... 3-42 3.4.3 Sand Hollow Reservoir ..................................................................................... 3-44 3.4.4 Rush Lake and Quichapa Lake ......................................................................... 3-45 3.5 Peak Flows ........................................................................................................................... 3-45 3.6 Geomorphic conditions ........................................................................................................ 3-47 3.6.1 Colorado River .................................................................................................. 3-47 3.6.2 Remaining Study Area Streams ........................................................................ 3-47 3.6.2.1 Virgin River Stability........................................................................................ 3-48 3.6.2.2 Santa Clara River Stability ............................................................................... 3-48 Chapter 4 – Environmental Consequences 4.1 Significance Criteria .............................................................................................................. 4-1 4.2 Potential Impacts Eliminated From Further Analysis ............................................................ 4-1 4.3 Streams and Return Flows ..................................................................................................... 4-1 4.3.1 Colorado River .................................................................................................... 4-1 4.3.1.1 Final Planning Study (FPS) ................................................................ 4-2 4.3.1.1.1 Direct Natural Flow (DNF), ISM Results .......................... 4-4 4.3.1.1.2 Nonparametric Paleo-Conditioned (NPC) Results ............. 4-5 4.3.1.2 No Additional Depletions ................................................................... 4-5 4.3.1.2.1 Direct Natural Flow (DNF), ISM Results .......................... 4-7 4.3.1.2.2 Nonparametric Paleo-Conditioned (NPC) Results ............. 4-8 4.3.2 Virgin River Drainages ....................................................................................... 4-8 4.3.2.1 Stream Crossings .............................................................................. 4-16 4.3.3 Kane, Mohave, and Coconino County Drainages ............................................. 4-16 4.3.3.1 Return Flows .................................................................................... 4-16 4.3.3.2 Stream Crossings .............................................................................. 4-17 4.3.4 Iron County Drainages ...................................................................................... 4-18 4.4 Reservoirs ............................................................................................................................ 4-19 4.4.1 Lake Powell ...................................................................................................... 4-19 4.4.1.1 Final Planning Study (FPS) .............................................................. 4-19 4.4.1.1.1