2010 Water Quality Report Flowing Sites Executive Summary

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Jen Stephenson Esther Vincent Jim Loftis

2010

[Type text] Northern Water

2010 Water Quality Report

CONTENTS

CONTENTS ...... I TABLE OF FIGURES ...... 2 ACRONYMS AND ABBREVIATIONS ...... 3 EXECUTIVE SUMMARY ...... 4

COLORADO‐BIG THOMPSON OVERVIEW ...... 4 WATER QUALITY MONITORING PROGRAM OVERVIEW ...... 5 REPORT OBJECTIVES AND SCOPE ...... 8 DATA ANALYSIS AND METHODS ...... 8 CONCLUSIONS AND HIGHLIGHTS ...... 9 Windy Gap Sites ...... 9 Stillwater Creek ...... 9 Arapaho Creek ...... 11 The North Fork of the Colorado River ...... 12 Adams Tunnel and Olympus Tunnel ...... 12 Total Organic Carbon ...... 13 East Slope Canals ...... 14 East Slope Streams ...... 15 Inflows and Outflows to the East slope Reservoirs ...... 16 Specific Conductivity ...... 17

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2010 Water Quality Report

TABLE OF FIGURES

FIGURE 1: MAP OF C-BT SYSTEM ...... 4 FIGURE 2: NORTHERN WATER STAFF COLLECTING WATER QUALITY SAMPLES ...... 5 FIGURE 3: MAP OF MONITORING SITES IN BASELINE MONITORING PROGRAM ...... 6 TABLE 1: LIST OF SAMPLING SITES AND DESCRIPTIONS ...... 7 FIGURE 4: STILLWATER CREEK UPSTREAM OF GRANBY RESERVOIR ...... 9 FIGURE 5: FARR PUMP PLANT ...... 10 FIGURE 6: ORTHO P (MG/L) IN STILLWATER CREEK AND GRANBY PUMP CANAL ...... 11 FIGURE 7: SEASONAL VARIBILITY IN AMMONIA CONCENTRATIONS AT AC-GRU ...... 11 FIGURE 8: ADAMS TUNNEL EAST PORTAL ...... 12 FIGURE 9: TOC CONCETRATIONS OVER TIME ON THE EAST SLOPE ...... 13 FIGURE 10: TOC AT ADAMS TUNNEL, UPPER BIG THOMPSON RIVER AND HANSEN FEEDER CANAL ...... 14 FIGURE 11: SAINT VRAIN SUPPLY CANAL (LEFT) ENTERING SAINT VRAIN CREEK (RIGHT) ...... 14 FIGURE 12: TP AT THE EAST SLOPE STREAM SITES WITH SEASONAL BREAKDOWN ...... 15 FIGURE 13: HORSETOOTH RESERVOIR INLET ...... 16 FIGURE 14: CARTER LAKE ...... 17 TABLE 2: 2007 AND 2009 REPORTED INCREASING TRENDS FOR SPECIFIC CONDUCTANCE ...... 17

2010 Water Quality Report

ACRONYMS AND ABBREVIATIONS

C-BT Colorado-Big Thompson

DO Dissolved Oxygen

DOM Dissolved Organic Matter

Harlan Harlan and Associates, Inc.

MDL Method Detection Limit

N Nitrogen

NH3 Ammonia

NO3 + NO2 Nitrate plus Nitrite

NWFS Northern Water Field Services

NWQL National Water Quality Laboratory (USGS)

Ortho P Orthophosphate

QA/QC Quality Assurance/Quality Control

RL Reporting Limit

RPD Relative Percent Difference

SC Specific Conductance

TKN Total Kjeldahl Nitrogen

TN Total Nitrogen

TOC Total Organic Carbon

TP Total Phosphorus

USBR United States Bureau of Reclamation

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

WQCD Water Quality Control Division

WWTP Waste Water Treatment Plant

WY Water Year

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EXECUTIVE SUMMARY

COLORADO-BIG THOMPSON OVERVIEW Northern Water, a public agency created in 1937, provides water for agricultural, municipal, domestic and industrial uses to an eight-county service area with a population of about 830,000. Northern Water and the U.S. Bureau of Reclamation operate the Colorado-Big Thompson (C-BT) Project, which collects water on the West Slope and delivers it to Northeastern Colorado through a 13-mile tunnel beneath Rocky Mountain National Park.

The C-BT Project annually delivers an average of 213,000 acre feet of water to northeastern Colorado for agricultural, municipal, domestic and industrial uses. Water is provided to Fort Collins, Greeley, Loveland, Longmont, Boulder, Louisville, Lafayette, Broomfield, many smaller communities, rural and domestic water districts and local industries. Water is delivered to approximately 120 ditch, reservoir and irrigation companies serving about 640,000 irrigated acres of farm and ranch land between April and October, the primary growing season.

FIGURE 1: MAP OF C-BT SYSTEM

Runoff from the headwaters of the Colorado River is collected in the Three Lakes system (Granby Reservoir, Shadow Mountain Reservoir and Grand Lake). Granby Reservoir also receives water from Willow Creek Reservoir and Windy Gap Reservoir in addition to the natural runoff from the Three Lakes watershed. When direct runoff to Grand Lake and Shadow Mountain Reservoir is sufficient to meet East Slope water demands, the rest of the flow moves naturally from Grand Lake to Shadow Mountain Reservoir, to the Colorado River and eventually Granby Reservoir. When East Slope demands are greater than the direct runoff to Grand Lake and Shadow Mountain Reservoir, Adams Tunnel deliveries are supplemented with water pumped from Granby

2010 Water Quality Report

Reservoir. Water is pumped from Granby Reservoir to Shadow Mountain Reservoir via the Granby Pump Canal, from where it is gravity fed to Grand Lake before reaching the West Portal of the Adams Tunnel.

Water then travels through the Adams Tunnel, from where it makes its way through a series of tunnels and pipelines to eventually be stored in the East Slope terminal reservoirs (Horsetooth Reservoir, Carter Lake and Boulder Reservoir). It is then distributed to the end-users either directly from the canals, the reservoirs or via deliveries to the South Platte tributaries (Cache La Poudre River, Big Thompson River, Little Thompson River, Saint Vrain Creek, Lefthand Creek and Boulder Creek) used as a conveyance system.

The Windy Gap Project is located just west of the town of Granby on Colorado's West Slope. The project consists of a diversion dam on the Colorado River below the confluence with the Fraser River, a 445-acre-foot reservoir, a pump plant and a six-mile pipeline to Granby Reservoir. The project came online in 1985 to serve municipal water needs and utilizes C-BT infrastructure to move water to the East Slope. The Windy Gap Project delivers an average of 48,000 acre feet of water annually and diverts primarily between April and July. During the spring runoff, water is pumped from Windy Gap Reservoir to Granby Reservoir where it is stored for delivery through the C-BT facilities to water users on the Front Range. The Windy Gap Project introduces water from the Fraser watershed into the Three Lakes system.

WATER QUALITY MONITORING PROGRAM OVERVIEW As the northern Front Range population continues to soar, ownership of C-BT Project water allotment contracts increasingly shifts from the agricultural to the municipal and industrial water users. This trend parallels an increased public awareness of water quality and environmental issues and a strengthening of the regulatory framework both at the Federal and State level. The CB-T Project is a major drinking water supply source for most municipalities it serves, therefore protection of the watersheds associated with the Project has become of particular concern as drinking water treatment requirements are getting tighter.

In response to these developing needs, Northern Water has continuously expanded its water quality related activities over the past twenty years. The backbone of the Water Quality Program is the Baseline Monitoring Program, which started in 1991. As new water quality challenges surface, new monitoring programs are developed to target specific areas of concern and studies are carried out to address identified water quality issues.

The objectives of the Baseline Monitoring Program are to: FIGURE 2: NORTHERN WATER STAFF COLLECTING WATER QUALITY SAMPLES • Monitor trends and changes in water quality in lakes and reservoirs and flowing sites: streams, rivers and canals • Assess potential water quality changes in receiving streams, upstream and downstream of where Colorado-Big Thompson Project and Windy Gap Project water is released • Assess compliance with state water quality standards

The locations of the Baseline Monitoring Program sampling sites are shown in Figure 3 and described in Table 1.

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FIGURE 3: MAP OF MONITORING SITES IN BASELINE MONITORING PROGRAM

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TABLE 1: LIST OF SAMPLING SITES AND DESCRIPTIONS

Station ID Station Location Station Type County Latitude Longitude Watershed Feature in CBT System CR‐SMD Colorado River downstream of Shadow Mountain Reservoir Stream Grand 40.2064 ‐105.8381 Upper Colorado River Colorado River CR‐GRD Colorado River downstream of Lake Granby Stream Grand 40.1442 ‐105.8667 Upper Colorado River Colorado River FR‐WGU Fraser River upstream of confluence with Colorado River Stream Grand 40.0969 ‐105.9719 Fraser River Fraser River CR‐WGU Colorado River above Windy Gap, upstream of confluence with Fraser River Stream Grand 40.1000 ‐105.9725 Windy Gap Colorado River CR‐WGC Colorado River downstream of Windy Gap at the confluence of the bypass and spillway Stream Grand 40.1079 ‐105.9881 Windy Gap Colorado River CR‐WGD Colorado River downstream of Windy Gap Stream Grand 40.1083 ‐106.0036 Windy Gap Colorado River CR‐KRM Colorado River near Kremmling, upstream of Gore Canyon and downstream of the Blue River Stream Grand 40.0367 ‐106.4394 Lower Colorado River Colorado River WG‐Pump Windy Gap discharge chute to Lake Granby Canal Grand 40.1425 ‐105.8886 Three Lakes Pumped Inflows WC‐WCRD Willow Creek directly downstream of Willow Creek Reservoir Dam Stream Grand 40.1457 ‐105.9398 Willow Creek Willow Creek WC‐Pump Willow Creek discharge chute to Lake Granby Canal Grand 40.1425 ‐105.8886 Willow Creek Pumped Inflows ST‐GRU Stillwater Creek upstream of Lake Granby Stream Grand 40.1880 ‐105.8944 Three Lakes Three Lakes Inlets AC‐GRU Arapahoe Creek at Monarch Lake outlet, upstream of Lake Granby Stream Grand 40.1125 ‐105.7492 Three Lakes Three Lakes Inlets RF‐GRU Roarking Fork inlet upstream of Lake Granby Stream Grand 40.1306 ‐105.7674 Three Lakes Three Lakes Inlets GR‐Pump Granby Pump Canal between Lake Granby and Shadow Mountain Reservoir Canal Grand 40.2067 ‐105.8489 Three Lakes Pumped Inflows CR‐SMU North Fork of Colorado River upstream of Shadow Mountain Reservoir Stream Grand 40.2188 ‐105.8569 Three Lakes Three Lakes Inlets NI‐GLU North Inlet upstream of Grand Lake Stream Grand 40.25333 ‐105.8108 Three Lakes Three Lakes Inlets EI‐GLU East Inlet upstream of Grand Lake Stream Grand 40.23639 ‐105.7978 Three Lakes Three Lakes Inlets AT‐EP Adams Tunnel East Portal near Estes Park Canal Larimer 40.3278 ‐105.5775 Big Thompson River Upper Big Thompson River OLY Olympus Tunnel at Lake Estes Canal Larimer 40.3750 ‐105.4869 Big Thompson River Upper Big Thompson River HFC‐FRD Hansen Feeder Canal downstream of Flatiron Reservoir Canal Larimer 40.3747 ‐105.2300 Horsetooth Hansen Feeder Canal HFC‐BT Hansen Feeder Canal at Trifurcation Canal Larimer 40.4194 ‐105.2247 Horsetooth Hansen Feeder Canal HFC‐BTU Big Thompson upstream of Hansen Feeder Canal, at canyon Mouth Stream Larimer 40.4217 ‐105.2261 Big Thompson River Hansen Feeder Canal HFC‐BTD Big Thompson River downstream of Hansen Feeder Canal and Trifurcation Plant Stream Larimer 40.4214 ‐105.2208 Big Thompson River Hansen Feeder Canal HFC‐HT Hansen Feeder Canal at Inlet to Horsetooth Canal Larimer 40.5047 ‐105.1986 Horsetooth Hansen Feeder Canal HSC‐PR Hansen Supply Canal Release to the Cache La Poudre River Canal Larimer 40.6581 ‐105.2092 Horsetooth Hansen Supply Canal HSC‐PRU Cache La Poudre River upstream of Hansen Feeder Canal Stream Larimer 40.6599 ‐105.2094 Cache La Poudre River Hansen Supply Canal HSC‐PRD Cache La Poudre River downstream of Hansen Feeder Canal Stream Larimer 40.6605 ‐105.2031 Cache La Poudre River Hansen Supply Canal SVSC‐CL Carter Lake ouflow to Saint Vrain Supply Canal Canal Larimer 40.3192 ‐105.2061 Carter Lake Saint Vrain Supply Canal SVSC‐LT Saint Vrain Supply Canal feed to Little Thompson River Canal Boulder 40.2561 ‐105.2089 Carter Lake Saint Vrain Supply Canal SVSC‐LTU Little Thompson River upstream of Saint Vrain Supply Canal Stream Boulder 40.2583 ‐105.2089 Little Thompson Saint Vrain Supply Canal SVSC‐LTD Little Thompson River downstream of St Vrain Supply Canal Stream Boulder 40.2606 ‐105.1975 Little Thompson Saint Vrain Supply Canal SVSC‐SV Saint Vrain Supply Canal at Saint Vrain Creek Canal Boulder 40.2167 ‐105.2594 Carter Saint Vrain Supply Canal SVSC‐SVU Saint Vrain Creek upstream of Saint Vrain Supply Canal Stream Boulder 40.2172 ‐105.2594 Saint Vrain Creek Saint Vrain Supply Canal SVSC‐SVD Saint Vrain Creek downstream of Saint Vrain Supply Canal Stream Boulder 40.2167 ‐105.2594 Saint Vrain Creek Saint Vrain Supply Canal BFC Boulder Feeder Canal below cement plant at Hygiene Rd Canal Boulder 40.1889 ‐105.2381 Boulder Boulder Feeder Canal BFC‐LH Boulder Feeder Canal at Left Hand Creek Canal Boulder 40.1036 ‐105.2264 Boulder Boulder Feeder Canal BFC‐LHU Left Hand Creek diversion into Boulder Feeder Canal Stream Boulder 40.1042 ‐105..2283 Lefthand Creek Boulder Feeder Canal BFC‐LHD Left Hand Creek downstream of BFC at golf cart bridge crossing with Left Hand Creek Stream Boulder 40.1036 ‐105.2256 Lefthand Creek Boulder Feeder Canal BFC‐BR Boulder Feeder Canal to Boulder Reservoir Canal Boulder 40.0864 ‐105.2175 Boulder Boulder Feeder Canal BSC‐BR Boulder Reservoir at outlet to Boulder Supply Canal Canal Boulder 40.0781 ‐105.2100 Boulder Boulder Supply Canal BSC‐BC Boulder Supply Canal feed to Boulder Creek at Jay Rd Canal Boulder 40.0531 ‐105.1869 Boulder Boulder Supply Canal BSC‐BCU Boulder Creek upstream Boulder Supply Canal Stream Boulder 40.0506 ‐105.1872 Boulder Creek Boulder Supply Canal BSC‐BCD Boulder Creek downstream of Boulder Supply Canal Stream Boulder 40.0514 ‐105.1781 Boulder Creek Boulder Supply Canal

2010 Water Quality Report

REPORT OBJECTIVES AND SCOPE The purpose of this report is to provide a snapshot of water quality conditions in the C-BT and Windy Gap Projects and to assess any recent changes in water quality. The report focuses on flowing water sites (streams, rivers and canals). Water quality in C-BT lakes and reservoirs will be the subject of a separate report. This report does not focus directly on water quality standards compliance as this is assessed in accordance with the Colorado’s Division of Water Quality 303d data call on a bi-annual basis; however identified impairments are summarized in the report.

Analysis was done on 43 sites in the Baseline Monitoring Program including 14 sites in West Slope rivers and streams, 12 sites in East Slope rivers and streams and 17 sites in the C-BT conveyance/canal system. Reservoir sites are not included in this report and will be the subject of a separate report as reservoir data require significantly different treatment and analytical methods than flowing sites.

Data used for analysis were collected from water year 2000 to water year 2009 (a water year begins in October of the previous year and ends in September). For temporal trend analysis, the entire period of record was used. For the remainder of the analysis, data collected from water year 2005 – water year 2009 were used.

Samples were collected primarily by Northern Water Field Services utilizing protocols guided by the U.S. Geological Survey’s “National Field Manual for the Collection of Water-Quality-Data" (U.S. Geological Survey, variously dated). Samples were also collected by the USGS. USGS certified private laboratories were used for sample analysis. Analytical methods with low level detection limits were used for nutrients and metals in the latter part of the period of record, beginning in 2005 and 2008 respectively.

All samples were subject to thorough quality control to validate laboratory procedures and sampling protocols. Between 5% and 10% of the total number of samples were quality control blanks or replicate samples. Laboratory analysis of quality assurance/quality control samples showed good agreement between replicates and blank samples were generally detected below the reporting limit often at the method detection limit. Any suspect quality assurance/quality control data were investigated and verified; appropriate corrective actions were taken when problems were identified.

The water quality parameters evaluated in this analysis can be classified into four categories: nutrients, metals, general chemistry and field-measured parameters, such as temperature. The list of parameters in this analysis is abbreviated from the list of parameters in the Baseline Monitoring Program and includes: ammonia, nitrate plus nitrite, total nitrogen, orthophosphate, total phosphorus, copper, iron, manganese, alkalinity, total organic carbon, chlorophyll-a, dissolved oxygen, pH, specific conductance and temperature. These parameters represent those of greatest concern in regard to regulatory, environmental and water treatment aspects.

DATA ANALYSIS AND METHODS The study uses basic statistical and graphical procedures to reveal spatial and temporal patterns and trends in the existing data. The statistical procedures used in the study are mostly nonparametric methods (not assuming a normal or any particular distribution shape) and are therefore “robust” or relatively uninfluenced by outliers. These procedures are particularly appropriate for use with environmental data which tend to contain outliers. All ® of the analyses were performed using the Minitab statistical analysis package.

2010 Water Quality Report

Loading calculations were made on nutrients and total organic carbon at sites that are inflows to lakes and reservoirs or are considered ‘key’ canal sites. The load calculation approach relied only on available data and few assumptions resulting in defensible estimates that did not require interpolation of missing data.

CONCLUSIONS AND HIGHLIGHTS This section synthesizes important report findings resulting from the separate analyses performed (seasonal patterns, spatial trends, temporal trends and loading analysis) throughout the report. Therefore, it does not follow the outline of the report but presents highlights based on location or parameter.

In general, water quality in the C-BT system is good. Most parameters have concentrations that are low and in compliance with state regulations. Many sites are not impacted by anthropogenic activities such as wastewater effluent or agriculture, as indicated by the low nutrient concentrations at these sites. This is not to say that nutrients are not of concern in this system. Given the low concentrations and the dynamics of the C-BT system, small changes in concentrations can have a significant effect on overall water quality and ecosystems. Trends in water quality and inputs into the system from areas with higher concentrations should be closely monitored.

The following is a summary of trends and patterns highlighted in the report that warrant discussion and/or further investigation. Further details are included in the report and Appendices.

WINDY GAP SITES The Fraser River has a significant impact on water quality in the Colorado River below Windy Gap Reservoir. This is particularly true for nutrients, chlorophyll-a and pH, which are often elevated in the Fraser River, especially in the late summer. Concentrations in the Fraser River drive concentrations downstream of Windy Gap Reservoir and also in the water pumped from Windy Gap Reservoir into Granby Reservoir, which is a source of nutrient loading into the Three Lakes System. Although there are no current compliance issues for these parameters at these sites, this could become problematic following the adoption of nutrient standards by the Water Quality Control Commission in 2012.

Monitoring at the Windy Gap sites will continue through the Baseline Monitoring Program. This includes weekly monitoring when Windy Gap pump is operating.

STILLWATER CREEK Water quality in Stillwater Creek presents very different characteristics relative to the rest of the C-BT system and more specifically relative to the other inlets to the Three Lakes. Orthophosphate (Ortho P), total phosphorus (TP), iron, alkalinity, total organic carbon and to a lesser extent manganese are remarkably elevated in this watershed in comparison to the rest of the system. Natural occurrences from geologic formations in the watershed are strongly suspected to be the cause. Monitoring performed by the CU Center for Limnology is showing that elevated TP values occur in other parts of the Three Lakes watershed and correlate with phosphorus bearing geological formations FIGURE 4: STILLWATER CREEK UPSTREAM OF that are also present in the Stillwater Creek basin (personal GRANBY RESERVOIR communication with Dr McCutchan, CU Center for Limnology).

2010 Water Quality Report

In terms of quantity, the inputs from Stillwater Creek are relatively small. But, given the magnitude of the concentrations, especially for orthophosphate, the water quality in Stillwater Creek has a non-negligible impact on the Three Lakes system (accounting for about 10% of TP loading into Granby Reservoir according to (Boyer & Hawley, 2010)). The loading analysis and time series data for the Granby Pump canal shows that there is an elevated percentage of orthophosphate in the total phosphorus load as well as elevated orthophosphate concentrations in August and September (Figure 6). FIGURE 5: FARR PUMP PLANT This corresponds with peak concentrations for orthophosphate in Stillwater Creek and indicates that inputs from Stillwater Creek into Granby Reservoir might ‘short circuit’ or get picked up and pumped into the Granby Pump Canal. However, it also corresponds with increases in orthophosphate in the Granby Pump Canal at the same time of year related to sediment releases from the bottom of Granby Reservoir during low dissolved oxygen events at the bottom of the reservoir. Furthermore, total monthly phosphorus load composition shows that there is lower orthophosphate leaving Grand Lake and Shadow Mountain Reservoir through Adams Tunnel in August and September than what is coming in from the Granby Pump Canal. This suggests that orthophosphate is being used up in Grand Lake and Shadow Mountain Reservoir by phytoplankton (floating algae). This is an indication that Stillwater Creek may be a contributor to algal productivity in the Three Lakes System during August and September. This is an indication that Stillwater Creek may be a contributor to algal productivity in the Three Lakes System during August and September. Further analysis is needed to determine how much of a factor this may be relative to internal nutrient loading occurring at the same time.

Targeted monitoring is being pursued in the Stillwater Creek watershed that will help to identify sources of nutrients and contributions from irrigation return flows. Further investigation of the possible short-circuiting of Stillwater Creek flows also needs to be done to understand whether this is a meaningful factor as it relates to Shadow Mountain Reservoir algal productivity and overall nutrient loading.

2010 Water Quality Report

FIGURE 6: ORTHO P (MG/L) IN STILLWATER CREEK AND GRANBY PUMP CANAL

0.14 0.014

0.12 0.012 Ortho GRU

‐

0.10 0.010 P

(mg/L) ST at

0.08 0.008

at 0.06 0.006 GR (mg/L)

‐ 0.04 0.004 Pump Orhto 0.02 0.002

0.00 0.000 07 10 10 06 07 07 07 08 08 08 08 09 09 09 10 10 11 11 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jan Jan Jun Jun Oct Oct Apr Feb Sep Feb Dec Aug Aug Nov Nov Mar May ST‐GRU GR‐Pump

ARAPAHO CREEK Elevated ammonia occurs in Arapaho Creek in April and represents the highest ammonia concentrations in the C- BT system (Figure 7). The source of the ammonia is not clear although this may be related to the amount of organic matter present in Monarch Lake, a very small lake just upstream of the water quality sampling site on Arapaho Creek. Cold temperatures reduce nitrification rates, and if large amounts of organic matter are decaying in Monarch Lake, this could significantly increase the amount of ammonia in Arapaho Creek. It is also possible that low dissolved oxygen occurs under the ice in the winter months causing anoxic conditions and the subsequent release of ammonia from the sediment. There are no winter data for this site but if the elevated concentrations are persistent throughout the winter months, this could have a non-negligible impact on nutrient loading into the Three Lakes System, even at low flows.

FIGURE 7: SEASONAL VARIBILITY IN AMMONIA CONCENTRATIONS AT AC-GRU

Three Lakes Inlets Ammonia 987654 121110 AC-GRU CR-SMU EI-GLU WaterYear 2005 0.08 2006 2007 0.06 2008 2009 0.04

0.02

0.00 NI-GLU RF-GRU ST-GRU

0.08 NH3 as N (mg/L)

0.06

0.04

0.02

0.00 987654 10 11 12 987654 121110 Month

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A more robust baseline of winter data is needed at this site to assess the magnitude of nutrient loading on the Three Lakes system. Winter samples have been collected as part of the Baseline Monitoring Program beginning in water year 2011 and a streamflow gage was installed in 2011. If the nutrient loading is determined to be significant, the exact source will have to be identified. These efforts are underway as part of the Three Lakes Nutrient Study and will be further discussed in the upcoming Lakes and Reservoirs Report.

THE NORTH FORK OF THE COLORADO RIVER The data show an increase in total phosphorus over the past ten years at the North Fork of the Colorado River. The North Fork contains sediment loads that have resulted in a delta forming at the point where the river enters Shadow Mountain Reservoir. Sediments are typically a source of total phosphorus. Sedimentation in the North Fork and the delta formation in Shadow Mountain Reservoir are issues of concern, and alternatives for remediation have been studied, but no feasible solution has been implemented.

There was a breach in the upper segment of the Grand Ditch in the spring of 2003 that resulted in a flush of sediment into the North Fork of the Colorado River, which is most likely a contributing factor to the increase in total phosphorus concentrations. The influx of sediments and debris to the North Fork was most significant in 2003 but has continued in subsequent years to a lesser extent.

The North Fork of the Colorado River will be further investigated as part of the Three Lakes Nutrient Study to better characterize both sediment and nutrient loading associated with this watershed and how they impact water quality in Shadow Mountain Reservoir and Grand Lake.

ADAMS TUNNEL AND OLYMPUS TUNNEL As water moves from the west slope to the Front Range via Adams and Olympus Tunnels, the water quality remains generally good, and concentrations are low, reflecting the water quality of the Three Lakes System. The exceptions are elevated total organic carbon and chlorophyll- a concentrations, which have a direct effect on water quality in the C-BT system on the East Slope, particularly as it pertains to drinking water uses out of Horsetooth Reservoir.

At Adams and Olympus Tunnels, there are elevated chlorophyll-a concentrations in August and September, which coincide with peak algal productivity in Grand Lake and Shadow Mountain Reservoir. Algal productivity in these water bodies and the subsequent movement of water to the East Slope needs to be monitored closely since some species, especially blue-green algae, can cause taste and odor issues in East Slope drinking water supplies and can be related to the potential occurrence of algal toxins.

There is a general decline in water quality as water moves from the Adams

FIGURE 8: ADAMS TUNNEL EAST Tunnel into the Olympus Tunnel. This is due to mixing of trans-mountain PORTAL water with both the native inflows of the Big Thompson River and waste water treatment plant effluent in Lake Estes.

Monitoring at Adams Tunnel and Olympus Tunnel will continue through the Baseline Monitoring Program.

2010 Water Quality Report

TOTAL ORGANIC CARBON Temporal trend analysis shows an increase in total organic carbon from 2000 to 2009 at many East Slope canal sites, particularly in the Hansen Feeder Canal (Figure 9). Temporal trend analyses at the Adams and Olympus Tunnels for the years with total organic carbon data (2005 to 2009) also show an increase in total organic carbon concentration over time. This indicates that West Slope water contributes to the increases in total organic carbon in the Hansen Feeder Canal. The pine beetle epidemic on the West Slope is suspected to be a contributing (although not confirmed) cause of increases in total organic carbon since dead trees provide organic matter inputs into the system. Recent data analysis conducted by the City of Fort Collins indicates that inputs from the Big Thompson River contribute significant total organic carbon into the Hansen Feeder Canal as well (Figure 10).

FIGURE 9: TOC CONCETRATIONS OVER TIME ON THE EAST SLOPE

East Slope Flowing Sites Total Organic Carbon over Time 1/ 1/ 2000 1/ 1/ 2001 1/ 1/ 2002 1/ 1/ 2003 1/ 1/ 2004 1/ 1/ 2005 1/ 1/ 2006 1/ 1/ 2007 1/ 1/ 2008 1/ 1/ 2009 1/ 1/ 2000 1/ 1/ 2001 1/ 1/ 2002 1/ 1/ 2003 1/ 1/ 2004 1/ 1/ 2005 1/ 1/ 2006 1/ 1/ 2007 1/ 1/ 2008 1/ 1/ 2009 HFC-BT HFC-BTU HFC-HT HSC-PR 16

0 HSC-PRU SVSC-CL SVSC-SV SVSC-SVU 16

0 BFC BFC-LH BFC-LHU BSC-BR 16 TOC (mg/L)

0 BSC-BCU 16 1/ 1/ 2000 1/ 1/ 2001 1/ 1/ 2002 1/ 1/ 2003 1/ 1/ 2004 1/ 1/ 2005 1/ 1/ 2006 1/ 1/ 2007 1/ 1/ 2008 1/ 1/ 2009

1/ 1/ 2000 1/ 1/ 2001 1/ 1/ 2002 1/ 1/ 2003 1/ 1/ 2004 1/ 1/ 2005 1/ 1/ 2006 1/ 1/ 2007 1/ 1/ 2008 1/ 1/ 2009

Although the calculated changes in total organic carbon concentrations are all very small from a stream water quality perspective, this should be reevaluated in the next report including new data collected at the Three Lakes Inlet Sites. Increasing total organic carbon concentrations are of significant concern for drinking water treatment plants because higher total organic carbon in raw water results in higher disinfection byproducts (regulated compounds) in finished water.

2010 Water Quality Report

FIGURE 10: TOC AT ADAMS TUNNEL, UPPER BIG THOMPSON RIVER AND HANSEN FEEDER CANAL

Graph from the City of Fort Collins 2010 Horsetooth Reservoir Water Quality Monitoring Program Report (Billica & Oropeza, 2011)

Total organic carbon trends need to continue to be monitored closely. UV254 analysis was added to the Baseline Monitoring Program in 2012 to help characterize sources of total organic carbon in the C-BT system (terrestrial humic sources vs. algal sources). Protection of existing water quality and prevention of any potential degradation should be a consideration as the Three Lakes Nutrient Study and the Grand Lake Clarity Project are progressing (both will be discussed in further detail in the Lakes and Reservoirs Report).

EAST SLOPE CANALS On the Hansen Feeder Canal, inputs of Big Thompson River water at the trifurcation via the Dille Tunnel can degrade the water quality in the canal. This report showed the Big Thompson water to be a source of total nitrogen, orthophosphate, iron, pH and most significantly, chlorophyll-a and total organic carbon. Increased chlorophyll-a concentrations are a concern for FIGURE 11: SAINT VRAIN SUPPLY CANAL (LEFT) ENTERING drinking water providers since chlorophyll-a is SAINT VRAIN CREEK (RIGHT) an indicator of potential problems related to algae, including taste and odor in treated water.

In general, the quality of water is degraded as it moves downstream and through developed areas. Thus one observes degradation as water moves south from Carter Lake toward Boulder Reservoir. The water moving north from Flatiron Reservoir through the Hansen Feeder Canal is less impacted by development and is generally of higher quality. The most obvious indicator of water quality degradation is increasing specific conductance.

Northern Water is pursuing a second pipeline from Carter Lake known as Southern Water Supply Project II. This pipeline will be built on behalf of the City of Boulder, Left Hand Water District, Longs Peak Water District, the

2010 Water Quality Report

Town of Frederick, and Little Thompson Water District. Like the original Southern Water Supply Project, the flow capacity in this project will be owned by those participating entities that will pay for the entire cost of the project. The primary purpose of the project is to provide a year-round supply of high quality C-BT water in a secure conveyance facility. The City of Boulder and Left Hand Water District both presently receive water from the Boulder Feeder Canal. Increased vulnerability concerns along with the inability to take Carter Lake water in the winter is the primary motivation for both of these entities. The project is presently in the Boulder County 1041 permitting process. Following approval, it is anticipated that right-of-way acquisition will commence, followed later by design and construction.

EAST SLOPE STREAMS In general, the canals have better water quality than the South Platte Tributaries, and canal inputs into the streams improve water quality through dilution (as shown for TP in Figure 12). The exception is for copper, which was used as an algaecide in the form of copper sulfate in the canals prior to 2008. During this period, both the canals and the receiving streams were subjected to an influx of copper, which is a significant but not sole factor for most of the stream segments that are listed as impaired for copper. The use of copper sulfate was discontinued in 2008, and since that time there has been a decline in copper concentrations in both the canals and receiving streams. Northern Water is updating its Integrated Pest Management Plan to conform to new Federal NPDES requirements surrounding the application of herbicides and pesticides to or near waters of the U.S. It is Northern Water’s goal to minimize chemical applications to C-BT canals in the future.

FIGURE 12: TP AT THE EAST SLOPE STREAM SITES WITH SEASONAL BREAKDOWN

East Slope Stream Sites Total Phosphorus 2005-2009 0.14 Season Apr-Jul Aug-Oct 0.12 Nov-Mar

0.10

0.08

0.06 P Total (mg/L) P Total

0.04

0.02

0.00 BFC-LHU BFC-LHD HFC-BTU HFC-BTD HSC-PRU HSC-PRD BSC-BCU BSC-BCD SVSC-LTU SVSC-LTD SVSC-SVU SVSC-SVD

There are occurrences of elevated pH in the Saint Vrain River below the Saint Vrain Supply Canal in the late summer. This may be related to periphyton growth. Currently this stream segment is not listed as impaired for pH on the 303d list but pH should be closely monitored in the future as this could become an issue.

2010 Water Quality Report

INFLOWS AND OUTFLOWS TO THE EAST SLOPE RESERVOIRS At all three reservoirs on the East Slope (Horsetooth, Carter and Boulder) there are differences in water quality between the inflows and the releases. For most constituents, concentrations decrease from inflow to outflow indicating that the constituent is accumulating in the sediment or being used by biological processes. Nitrogen may be removed from the system entirely by de-nitrification. In a few cases, concentrations increase from inflow to outflow as a result of additional sources, releases from sediment, or biological processes. Water quality changes within a reservoir are the result of many physical, chemical, and biological processes including flow dynamics, thermal stratification, mixing by wind, turnover, biological oxygen addition and removal, and many others. These processes will be discussed in a separate report that specifically addresses water quality in the lakes and reservoirs of the C-BT system.

The following is a summary of the most obvious and important differences in water quality when comparing the inflows and outflows of the East Slope reservoirs. There is also a summary comparing the difference between Carter Lake and Horsetooth Reservoir.

Horsetooth Reservoir – The primary differences in water quality across Horsetooth Reservoir are nutrient related. There are decreases in ammonia, orthophosphate, total phosphorus and chlorophyll-a concentrations in the water released compared to the water entering the reservoir. There are increases in copper, alkalinity and specific conductance. There is slightly elevated manganese concentrations out of Horsetooth Reservoir compared to the inflow into the reservoir due to the release of manganese from the sediments during periods of low dissolved oxygen at the reservoir bottom.

In the summer of 2009, a new cooperative monitoring program collected data in the metalimnion of Horsetooth Reservoir to help determine the cause of oxygen depletion and the extent of its impact on aquatic life. The new monitoring program forms the basis of a larger Horsetooth Water Quality Study, which includes the development of a water quality model, The Horsetooth Reservoir hydrodynamic water quality model will be used to FIGURE 13: HORSETOOTH RESERVOIR INLET evaluate a range of inter-related water quality issues (dissolved oxygen, total organic carbon, nutrients, and water quality fate and transport) under situations that include interflow from the Hansen Feeder Canal, seasonal thermal stratification and turnover within the reservoir, and variations in C-BT operations. The model will also be used to help evaluate water quality issues related to potential future projects.

Northern Water is also co-sponsoring a 2010 Non-Point Source Project Proposal from Dr. Jesse M. Lepak and Dr. Brett M. Johnson of Colorado State University that will study the relative importance of external mercury loading (primarily atmospheric deposition in the watershed) and internal mercury loading (methylation and uptake by the food web). The Colorado Department of Public Health and Environment is administering the 319 grant and will use the findings to help develop total maximum daily loads for mercury.

Carter Lake – At Carter Lake there are decreases in total phosphorus, iron, chlorophyll-a and temperature in the water released compared to the water entering the reservoir. There are increases in ammonia, orthophosphate, copper, alkalinity, pH and specific conductance. It should be noted that the releases from Carter Lake have elevated ammonia concentrations compared to the other canal sites.

2010 Water Quality Report

Boulder Reservoir – In general, water released from Boulder Reservoir into the Boulder Supply Canal is of poorer water quality than the water entering the reservoir. When compared to the water entering the reservoir, the water released has noticeably higher ammonia, total nitrogen, total phosphorus, alkalinity, chlorophyll-a, specific conductance and temperature. There are decreases in copper, dissolved oxygen and pH.

Carter Lake vs. Horsetooth Reservoir – A comparison of the nutrient levels entering Carter Lake and Horsetooth Reservoir shows that ammonia, orthophosphate and total FIGURE 14: CARTER LAKE phosphorus concentrations to Horsetooth are slightly higher than those into Carter Lake but significantly higher for nitrate plus nitrite. Total nitrogen concentrations are very comparable. Copper concentrations are elevated in the Saint Vrain Supply Canal below Carter Lake compared to the outflows from Horsetooth Reservoir but this is more likely due to inputs of copper sulfate (when copper sulfate was still being used prior to 2008) into the canal than reservoir dynamics. Iron concentrations in the outflows from both Carter Lake and Horsetooth Reservoir are markedly lower than in the inflows but the concentrations are higher in the outflows from Horsetooth Reservoir compared to Carter Lake.

SPECIFIC CONDUCTIVITY There is a continuing trend of increased specific conductivity over time at many of the sites in the C-BT system (Table 2). This trend was discussed in the 2007 Water Quality Report and again in this report. The magnitudes of the trends are small, and there are no impairments to existing uses as a result of current or projected salinity levels. The trends will be monitored and evaluated in future reports.

TABLE 2: 2007 AND 2009 REPORTED INCREASING TRENDS FOR SPECIFIC CONDUCTANCE 2007 WQ 2009 WQ Station Report Report FR‐WGU EE CR‐WGU EE CR‐WGD EE WC‐Pump EE GR‐Pump EE HFC‐BTU EE SVSC‐CL EE SVSC‐SV EE BFC EE BSC‐BCU EE