WY2000 – WY2015 C-BT East Slope North End Water Quality Report March 17, 2017 Prepared by: Judith A. Billica, P.E., Ph.D. Northern Colorado Water Conservancy District Berthoud, Colorado WY2000-WY2015 East Slope - North End Water Quality Report 03/17/17 This page intentionally left blank. ii WY2000-WY2015 East Slope - North End Water Quality Report 03/17/17 TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................ III LIST OF TABLES .................................................................................................................... VII LIST OF FIGURES ................................................................................................................... IX ACRONYMS AND ABBREVIATIONS ....................................................................................... XV EXECUTIVE SUMMARY ................................................................................................. XVII 1. INTRODUCTION .......................................................................................................... 1 1.1 COLORADO-BIG THOMPSON PROJECT & WINDY GAP PROJECT OVERVIEW ....................................................... 1 1.2 BASELINE WATER QUALITY MONITORING PROGRAM OVERVIEW ..................................................................... 2 1.2.1 Purpose of Baseline Monitoring Program ................................................................... 3 1.2.2 Scope of Baseline Monitoring Program ....................................................................... 4 1.2.3 Quality Assurance/Quality Control (QA/QC) ....................................................................... 6 1.3 BASELINE MONITORING PROGRAM: EAST SLOPE – NORTH END SITES .............................................................. 6 1.3.1 Sampling Sites ..................................................................................................................... 6 1.3.2 Parameters & Frequency .................................................................................................. 14 1.3.3 Sample Collection and Laboratory Analysis ...................................................................... 16 1.4 COLLABORATIVE ROUTINE MONITORING .................................................................................................. 20 1.4.1 Monitoring of the Big Thompson River: Big Thompson Watershed Forum ..................... 20 1.4.2 City of Fort Collins Cooperative Monitoring of Horsetooth Reservoir ............................... 20 1.5 REPORT OBJECTIVES AND SCOPE ............................................................................................................. 21 2. METHODS FOR DATA ANALYSIS ................................................................................ 23 2.1 HANDLING OF NON-DETECT DATA .......................................................................................................... 23 2.2 DATA REVIEW AND ANALYSIS TOOLS ........................................................................................................ 23 2.2.1 Graphical Analyses ............................................................................................................ 24 2.2.2 Statistical Analysis ............................................................................................................ 28 2.3 DATA LIMITATIONS AND EXCLUDED DATA ................................................................................................. 31 3. WATERSHED DESCRIPTION, SIGNIFICANT EVENTS, WATER QUALITY CONCERNS & SPECIAL STUDIES ...................................................................................................... 33 3.1 OVERVIEW OF WATERSHEDS .................................................................................................................. 33 3.2 DESCRIPTION OF HORSETOOTH RESERVOIR ............................................................................................... 36 3.3 SIGNIFICANT EVENTS ............................................................................................................................ 38 3.3.1 Pine Beetle Epidemic ......................................................................................................... 38 3.3.2 Wildfires ............................................................................................................................ 40 3.3.3 2013 Flood ........................................................................................................................ 42 3.4 WATER QUALITY CONCERNS .................................................................................................................. 44 3.4.1 303(d) List of Impaired Waters ......................................................................................... 44 3.4.2 Copper ............................................................................................................................... 45 3.4.3 Drinking Water Treatment Concerns ................................................................................ 45 iii 03/17/17 WY2000-WY2015 East Slope - North End Water Quality Report 3.4.4 Other Horsetooth Reservoir Issues .................................................................................... 46 3.5 OTHER RELATED WATER QUALITY STUDIES & REPORTS ............................................................................... 47 3.5.1 Emerging Contaminants Cooperative Monitoring Program ............................................. 47 3.5.2 Big Thompson Watershed Forum 2015 State of the Watershed Report ........................... 48 3.5.3 City of Fort Collins 2013 Horsetooth Res Water Quality Monitoring Program Reports .... 49 3.5.4 2013 CE-QUAL-W2 Horsetooth Reservoir Modeling Report ............................................. 49 4. HYDROLOGY & OPERATIONS .................................................................................... 51 4.1 OVERVIEW OF WEST SLOPE COLLECTION & EAST SLOPE DISTRIBUTION SYSTEMS ............................................. 51 4.2 WY2000-WY2015 EAST SLOPE – NORTH END FLOWING SITES HYDROLOGY ................................................ 53 4.3 HORSETOOTH RESERVOIR HYDROLOGY & OPERATIONS ....................................................................... 55 5. FIELD PARAMETERS .................................................................................................. 59 5.1 TEMPERATURE ..................................................................................................................................... 59 5.1.1 Flowing Sites ..................................................................................................................... 60 5.1.2 Horsetooth Reservoir Profiles ........................................................................................... 61 5.2 DISSOLVED OXYGEN (D.O.) ................................................................................................................... 66 5.2.1 Flowing Sites ..................................................................................................................... 66 5.2.2 Horsetooth Reservoir Profiles ........................................................................................... 67 5.3 SPECIFIC CONDUCTANCE ........................................................................................................................ 70 5.3.1 Flowing Sites ..................................................................................................................... 70 5.3.2 Horsetooth Reservoir Profiles ........................................................................................... 71 5.4 PH .................................................................................................................................................... 72 5.4.1 Flowing Sites ..................................................................................................................... 72 5.4.2 Horsetooth Reservoir Profiles ........................................................................................... 73 5.5 HORSETOOTH RESERVOIR SECCHI DISK DATA............................................................................................. 74 6. GENERAL CHEMISTRY ............................................................................................... 77 6.1 MAJOR IONS AND ALKALINITY................................................................................................................. 77 6.2 FLOWING SITES TOTAL ORGANIC CARBON (TOC) ....................................................................................... 81 6.3 HORSETOOTH RESERVOIR TOC, DOC, UVA & SUVA ................................................................................ 84 6.4 TOTAL SUSPENDED SOLIDS (TSS) ............................................................................................................ 88 6.5 TIME TREND ANALYSIS RESULTS FOR TOC & MAJOR IONS ........................................................................... 91 7. NUTRIENTS ............................................................................................................... 93 7.1 PHOSPHORUS ...................................................................................................................................... 94 7.2 NITROGEN .......................................................................................................................................... 98 7.3 HORSETOOTH RES