ATTACHMENT C - WATER QUALITY REPORT.pdf

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM i

W A T E R Q U A L I T Y T R E N D S R E P O R T 2 0 0 8 – 2 0 2 2

Upper Cache la Poudre Watershed Collaborative Water Quality Monitoring Program

June 1, 2023

PREPARED FOR:

City of Fort Collins Utilities City of Greeley City of Thornton Soldier Canyon Water Treatment Authority

PREPARED BY:

Jared Heath, Senior Watershed Specialist Richard Thorp, Watershed Program Manager

City of Fort Collins Utilities Water Quality Services Division

A T T A C H M E N T C ii UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM iii

TABLE OF CONTENTS

LIST OF FIGURES ...................................................................................................................................................................... V

LIST OF TABLES ...................................................................................................................................................................... VII

LIST OF ABBREVIATIONS & ACRONYMS ............................................................................................................................... IX

EXECUTIVE SUMMARY............................................................................................................................................................ XI

Background ............................................................................................................................................................................. xi

Scope of The 2022 Water Quality Trends Report ................................................................................................................... xi

Upper Cache la Poudre Watershed Impacts & Trends ........................................................................................................... xi

1.0 INTRODUCTION

1.1 Background

1.2 Watershed Description and Sampling Locations

1.3 Sampling Plan and Parameters

1.4 Sample Collection and Analysis

1.5 Scope of Five-Year Report

2.0 WATERSHED IMPACTS & ISSUES OF CONCERN

2.1 Climate Change

2.2 Drought

2.3 Wildfire

2.4 Forest Health

2.5 Air Pollution

3.0 WATERSHED HYDROLOGY AND CLIMATE

3.1 Air Temperature

3.2 Precipitation

3.3 Streamflow

4.0 TRENDS IN WATER QUALITY

4.1 Physical Parameters

4.2 General Parameters

4.3 Total Organic Carbon

4.4 Nutrients

4.5 Microorganisms

4.6 Macroinvertebrates

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5.0 SUMMARY & IMPLICATIONS

5.1 Watershed Impacts & Issues of Concern

5.2 Climate & Watershed Hydrology Trends

5.3 Water Quality Trends

5.4 Implications to Water Treatment

6.0 REFERENCES

ATTACHMENT 1

ATTACHMENT 2

ATTACHMENT 3

ATTACHMENT 4

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM v

LIST OF FIGURES

Figure 1.1 – Map of the Upper CLP collaborative water quality monitoring network

Figure 2.1 – Drought conditions in Larimer County, Colorado from 2008 through 2022 (https://www.drought.gov/states/colorado)

Figure 2.2 – Recent wildfire history (2008 – 2022) in the Cache la Poudre Watershed

Figure 2.3 – Ammonia ion wet deposition has increased throughout the United States since the NADP began in 1985 (Source:

http://nadp.slh.wisc.edu/)

Figure 3.1 – Mean baseline and current air temperatures (top), and monthly mean air temperature over the baseline and current periods of record (bottom) reveal similar air temperature between the two periods

Figure 3.2 – Monthly mean precipitation totals for the baseline period compared to the recent five-year period (top) and seasonal distribution of precipitation for the baseline period and current period (bottom)

Figure 3.3 – Current five-year precipitation totals, and peak snow water equivalent measured at the Joe Wright SNOTEL compared to baseline

Figure 3.4 – Monthly average streamflow for the baseline period compared to the recent five-year period (top) and seasonal distribution of streamflow for the baseline period and current period (bottom)

Figure 4.1 – Smoothed time-series plots for water temperature at NBH and NFG

Figure 4.2 – Smoothed time-series plots for pH at monitoring locations on Mainstem and North Fork CLP Rivers that had significant trends over the 2008 to 2022 long-term period of record

Figure 4.3 – Annual median turbidity values in the Mainstem CLP River over the five-year period of record compared to the baseline period of record

Figure 4.4 – Smoothed time-series plots for long-term trends in turbidity detected in the North Fork CLP River at NBH and

NRC

Figure 4.5 – Annual median specific conductivity levels in the Mainstem CLP River over the five-year period of record compared to median specific conductivity measured over baseline period of record (left) and smoothed time-series plots displaying long-term trends detected in specific conductivity in the Mainstem CLP River (right)

Figure 4.6 – Annual median alkalinity values in the Mainstem CLP River over the five-year period of record compared to the baseline period of record

Figure 4.7 – Smoothed time-series plots indicating long-term trends in hardness concentrations in the Mainstem CLP River (left, and annual median hardness concentrations measured in the North Fork over the five-year period of record compared to baseline (right)

Figure 4.8 – Smoothed time-series plots indicating long-term trends in total dissolved solids concentrations in the Mainstem CLP River (left), and annual median total dissolved solids concentrations measured in in the Mainstem CLP River over the five-year period of record compared to baseline (right) vi UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM

Figure 4.9 – Smoothed time-series plot displaying long-term trends in total organic carbon in the North Fork below Halligan and Seaman Reservoirs (NBH and NFG)

Figure 4.10 – Annual median nitrate concentrations in the Mainstem CLP River over the five-year period of record compared to median nitrate concentrations measured over baseline period of record (left) and annual median total kjeldahal nitrogen concentrations in the Mainstem CLP River over the five-year period of record compared to median total kjeldahal nitrogen concentrations measured over baseline period of record (left). The red line indicates the water quality laboratory’s report limit.

Figure 4.11 – Smoothed time-series plot displaying long-term trends in nitrate concentrations in the Mainstem above Joe Wright Creek (PJW), below Rustic (PBR) and below the South Fork (PSF). Note that the rate of change is less than the water quality laboratory’s reporting limit (<40 µg/L); therefore, it is not displayed above

Figure 4.12 – Median total phosphorus concentrations in the Mainstem CLP River (left) and median orthophosphate concentrations in the North Fork CLP River (right) over the recent five-year period compared to baseline. The red line indicates the City of Fort Collins Water Quality Laboratory’s reporting limit

Figure 4.13 – Smoothed time-series plot displaying long-term trends in E. coli counts in the Poudre below Rustic (PBR) and in the North Fork below Seaman Reservoirs (NFG)

Figure 5.1 – Turbidity measured in the Poudre River at the Manners Bridge real-time water quality instruments. Several rain events over the Cameron Peak burn scar caused turbidity in the river to increase rapidly over a short amount of time and remain elevated for several hours before returning to normal. Note: These data are preliminary and subject to change and some outlier data may be present

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM vii

LIST OF TABLES

Table 1 – Land use comparison between Upper North Fork and Mainstem CLP watersheds. Areas were calculated using US Geological Survey Seamless Geographic Information System data sets

Table 2 – Potential raw and finished water quality impacts related to drought. Adopted from Water Research Foundation Web Report #4324

Table 3 – Potential raw and finished water quality impacts related to wildfire. Adopted from Water Research Foundation Web Report #4324

Table 4 – Summary of statistically significant climatological variables detected in the Upper CLP watershed

Table 5 – Total organic carbon removal requirements for water treatment facilities based on source water alkalinity and total organic carbon concentrations

Table 6 – Routine 2022 macroinvertebrate community metrics from key study locations along the Mainstem CLP. Data from 2022 were compared to baseline data (average of 2019 and 2020 data, shown in parentheses) and notable negative and positive percentage departures (20% or more) are indicated in using red and blue, respectively. Metrics were also compared between 2021 and 2022 to determine whether there were notable (20% or more) positive (green, upward arrow) or negative (red, downward arrow) trends between years

Table 7 – Summary of water quality trends detected throughout the Upper CLP watershed viii UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM ix

LIST OF ABBREVIATIONS & ACRONYMS

% percent BMD Barnes Meadow Reservoir below Dam (routine monitoring site) cfs cubic feet per second CHD Joe Wright Creek below Chambers Lake Dam (routine monitoring site) CLAFTCCO Cache la Poudre at Canyon Mouth Near Fort Collins Stream gage CLP Cache la Poudre River cfu/100 mL colony forming units per 100 milliliters DBP Disinfection By-Product EPA Environmental Protection Agency JWC Joe Wright Creek above the Poudre River (routine monitoring site) LRT Laramie River Tunnel (routine monitoring site) m meter mg/L milligrams per liter NADP National Atmospheric Deposition Program NBH North Fork of the Poudre River below Halligan Reservoir (routine monitoring site) NDC North Fork of the Poudre River above Dale Creek Confluence (routine monitoring site) NFG North Fork of the Poudre River below Seaman Reservoir (routine monitoring site) NFL North Fork of the Poudre River at Livermore (routine monitoring site) ng/L nanograms per liter NTU Nephelometric Turbidity Units oC degrees Celsius PBD Poudre River at the Bellvue Diversion (routine monitoring site) PBR Poudre River below Rustic (routine monitoring site) PCM Pine Creek Mouth (routine monitoring site) PJW Poudre River above the confluence with Joe Wright Creek PNF Poudre River above the North Fork (routine monitoring site) RCM Rabbit Creek Mouth (routine monitoring site) SCM Stonewall Creek Mouth (routine monitoring site) SFC South Fork above confluence with the Mainstem (routine monitoring site) SFM South Fork of the Poudre River above the Mainstem (routine monitoring site) SMKT Seasonal Mann-Kendall Test SNOTEL Snow telemetry network SWE Snow water equivalent TOC Total Organic Carbon µg/L micrograms per liter µS/cm microSeimens per centimeter USGS United States Geological Survey x UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM

UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM xi

EXECUTIVE

SUMMARY

BACKGROUND

The Upper Cache la Poudre (CLP) Watershed Collaborative Water Quality Monitoring Program is designed to assist the cities of Fort Collins, Greeley and Thornton, and the Soldier Canyon Water Treatment Authority in meeting current and future drinking water treatment goals by reporting current water quality conditions and trends within the Upper CLP watershed and summarizing issues that potentially impact watershed health. Annual trend reports have been published in 2008 through 2011, 2013 through 2016, and 2018 through 2021.

Five-year water quality trend analyses reports were published in 2012 and 2017.

SCOPE OF THE 2022 WATER QUALITY

TRENDS REPORT

This five-year water quality trend report analyzes the hydrology, climate, and water quality of the Upper CLP watershed over the last 15 years. Water quality data collected throughout the Upper CLP watershed were analyzed for short and long-term trends to determine if concentrations increased, decreased, or stayed the same over the five-year period of record from 2018 to 2022 and the long-term period of record from 2008 to 2022, respectively. This report documents 1) watershed impacts and issues of concern; 2) significant trends in climate, hydrology, and water quality in the Upper CLP watershed;

3) potential sources of pollution and/or watershed disturbances influencing water quality trends; and 4) a summary of significant findings and implications to water treatment.

UPPER CACHE LA POUDRE WATERSHED

IMPACTS & TRENDS

Watershed Impacts & Issues of Concern Over the past 15 years the Upper CLP watershed has experienced periods of wet and dry water years influencing both streamflow and water quality conditions in the Upper CLP watershed. Exceptionally hot and dry conditions in

2020 led to extreme drought and a major wildfire in the watershed called the Cameron Peak Fire. Post-fire impacts to water quality have been particularly extreme over the past two years and it is expected that these impacts will continue to impact the Poudre River water supply for years to come.

Forest insects and diseases have impacted the Upper CLP watershed over the past several decades. Recent surveys show the mountain pine beetle and spruce beetle epidemics are declining; however, isolated outbreaks of these insects throughout Colorado suggest that forested watersheds continue to be susceptible to forest insects and disease.

Watershed impacts caused by climate change and atmospheric deposition are less clear, but remain a major threat to future watershed processes, water availability, and water quality. Unlike extreme weather driven disturbances, the watershed response from climate change and atmospheric deposition impacts may be subtle, emphasizing the importance of continued monitoring in the Upper CLP watershed.

Climate & Hydrology Trends Air temperature significantly increased at higher elevations in the Upper CLP watershed over the last 15 years.

Precipitation volume and the maximum amount of water contained within the snowpack did not change. No trends were measured in the magnitude or timing of streamflow;

however, recent data suggest that snowmelt runoff is occurring earlier in the year and lasting for a shorter amount of time.

Trends in Water Quality Short and long-term trends were identified in the Upper CLP watershed. Long-term trends were identified as gradual, continuous changes (increasing or decreasing) in the data over time and short-term trends were recognized as shifts (up or down) in the data over the past five years.

Step-trends, an abrupt shift in data, were measured for several water quality parameters at monitoring sites throughout the Mainstem CLP river over the last two years (2021 and 2022). These trends occurred in response to the dramatic landcover change in the Mainstem CLP watershed caused by the 2020 Cameron Peak Wildfire.

The water quality constituents that exhibited step-trends as a response to post-fire water quality impacts were all highly correlated with increased watershed erosion.

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Trends were detected at varying scales. Both site-specific and watershed-wide trends were detected in the Upper CLP watershed. Site-specific trends capture impacts to a specific site, while watershed-wide trends imply a large disturbance that impacted the entire basin or large areas of the basin influencing water quality at multiple monitoring locations.

Most trends detected in the Mainstem CLP watershed were associated with increased watershed erosion caused by wildfires that have impacted the watershed over the last 15 years. Water quality impacts from the Cameron Peak Fire have been particularly evident in the first two years following the fire (2021 and 2022). It is anticipated that water quality impacts from the recent wildfire will continue for many years as the watershed responds to and recovers from this unprecedented disturbance. Climate change impacts, specifically increasing air temperature, flooding and drought, and streamflow alterations are likely the main drivers of water quality trends in the North Fork CLP River.

Implications to Water Treatment Short and long-term trends in certain water quality constituents may pose issues to water treatment processes in the future. Water quality changes were detected for the following parameters near the City of Fort Collins’, City of Greeley’s, and Soldier Canyon Water Treatment Authority’s raw water intakes:

• Temperature & pH

• Alkalinity & hardness

• Total dissolved solids & specific conductivity

• Nutrients

In general, the water treatment facilities should continue to closely monitor key water quality parameters and may be required to adjust blending ratios and chemical additions to meet current water treatment goals. The Watershed Program should continue to work with partners across the watershed to collaborate on source water protection projects that protect and restore human-constructed infrastructure and natural ecosystems in the Upper CLP watershed. Routine water quality monitoring throughout the Upper CLP watershed will allow the Upper CLP Collaborative Water Quality Monitoring Program to continue to sustain a long-term data record providing program partners with valuable information on short and long-term trends that may arise in the future.

UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 1

1.0 INTRODUCTION

1.1 BACKGROUND

The Upper Cache la Poudre (CLP) River is an important source of high-quality drinking water supplies for communities served by the City of Fort Collins Water Treatment Facility, the City of Greeley-Bellvue Water Treatment Plant, and the Soldier Canyon Water Treatment Authority’s Soldier Canyon Filter Plant. In the shared interest of sustaining this high-quality water supply, the City of Fort Collins, the City of Greeley, and Soldier Canyon Water Treatment Authority partnered in 2007 to design the Upper CLP Collaborative Water Quality Monitoring Program. The Program was subsequently implemented in spring 2008. The City of Thornton was added as a partner in 2022. The goal of this collaborative monitoring program is to assist the participants in meeting current and future drinking water treatment goals by providing up-to-date information about water quality and trends within the Upper CLP watershed.

Raw CLP River water quality parameters that have historically had the most impact on water treatment include:

• turbidity

• total organic carbon (TOC)

• pH

• alkalinity

• temperature

• pathogens (Giardia and Cryptosporidium),

• taste and odor (T&O) compounds

Seasonal updates, annual water quality reports, and five-year trend reports for the monitoring program are prepared by City of Fort Collins’ Watershed Program staff to keep participants informed of current issues and trends in water quality in the Upper CLP watershed. Seasonal updates are provided in the spring, summer, and fall. These updates include a summary of precipitation, streamflow, and water quality conditions. The purpose of annual reports is to summarize hydrologic and water quality information for the current year, provide a comparison of water quality data to historic baseline conditions, describe notable events and issues, and summarize the results of special studies. The five-year report provides a more in-depth analysis of short and long-term trends in watershed hydrology, climate, and water quality. Upper CLP updates and reports are available on the City of Fort Collins Utilities’ Source Water Monitoring website.

1.2 WATERSHED DESCRIPTION AND

SAMPLING LOCATIONS

Sampling efforts are divided between the Mainstem CLP River watershed (including Joe Wright Creek, the Big South, and the Little South Fork CLP River) and North Fork CLP River watershed (including Rabbit Creek, Stonewall Creek, and Lone Pine Creek). Collectively these watersheds encompass approximately 645,500 acres of forest, other natural land types, and agricultural land (Table 1). An additional 4,700 acres, representing less than 1% of land surface, is developed for commercial, industrial, utility, urban or residential purposes.

Table 1 – Land use comparison between Upper North Fork and Mainstem CLP watersheds. Areas were calculated using US Geological Survey Seamless Geographic Information System data sets.

Land Use Comparison North Fork (acres) North Fork (%) Mainstem

(acres) Mainstem (%) Developed land (commercial, industrial, residential, urban, and utilities) 2,817 0.8 1,945 0.7

Agricultural use and grassland (cropland, pasture, other agriculture, scrub, and grasses) 183,719 52.3 54,765 18.3

Forest (forest and brush) 154,654 44.1 213,879 71.5

Natural lands (exposed rock, bare ground, wetlands, tundra, lakes) 9,926 2.8 28,473 9.5

Total 351,116 100 299,062 100 https://www.fcgov.com/utilities/what-we-do/water/water-quality/source-water-monitoring/water-quality-reports https://www.fcgov.com/utilities/what-we-do/water/water-quality/source-water-monitoring/water-quality-reports

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When initially established in 2008, the monitoring network consisted of 20 water quality monitoring locations selected to characterize the headwaters, major tributaries, and downstream locations of the Upper CLP River near raw water intake structures.

In 2014, an additional monitoring location was included on the South Fork (SFC) approximately 500 feet upstream of the confluence with the Mainstem CLP River. This monitoring location was added to the monitoring network to capture the full extent of the South Fork drainage following the 2012 High Park Fire. The South Fork above Mainstem (SFM) site was discontinued in 2015 because analyses between SFC and SFM revealed similar water quality conditions. In 2020, SFC was discontinued because the special use permit issued by the Forest Service expired.

Water quality sampling in the South Fork CLP River was re-established at SFM. The sampling locations in Joe Wright Creek below Chambers Lake (CHR) and Barnes Meadow outfall (BMR) were moved in 2019 due to access issues at the original sites and are now formally known as Joe Wright Creek below Chambers Dam (CHD) and Barnes Meadow outfall below Dam (BMD). The Seaman Reservoir (SER) monitoring locations were also discontinued from the Upper CLP monitoring program in 2015.

The current monitoring network consists of 18 monitoring locations (Figure 1.1). A full list of monitoring sites, abbreviations and descriptions is available in Attachment 1.

Figure 1.1 – Map of the Upper CLP collaborative water quality monitoring network.

UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 3

1.3 SAMPLING PLAN AND

PARAMETERS

The sampling frequency for the Program is based on both statistical performance and cost considerations.

Parameters were selected based on analyses of historical data and aim to provide the best information possible within current budgetary constraints. Complete discussions of parameter selection and sampling frequency are provided in Sections 5.3 and 5.4, respectively, of the Program design document by Billica, Loftis and Moore (2008). The annual sampling schedule is provided in Attachment 3 of this report and the full list of water quality parameters is provided in Attachment 2.

1.4 SAMPLE COLLECTION AND

ANALYSIS

Field sampling is conducted by staff members from the City of Fort Collins’ Watershed Program, City of Greeley, and Timberline Aquatics, Inc. Sampling methods, including those for the collection of physical field measurements for temperature, pH, conductivity, turbidity, and dissolved oxygen are documented in the Program’s Standard Operating Procedures. All water samples are analyzed by the City of Fort Collins Water Quality Lab. The analytical methods and detection limits for the City of Fort Collins Water Quality Lab parameters are included in Attachment 4.

Consistent with the quality assurance guidelines outlined in Section 5.5 of Billica, Loftis and Moore (2008), field blanks and field duplicates are collected alongside at least ten percent of samples for a subset of parameters, which are identified in the Annual Operating Plan (Attachment 3).

1.5 SCOPE OF FIVE-YEAR REPORT

Seasonal, annual, and five-year reports for the Program are prepared by the City of Fort Collins’ Watershed Program to keep participants informed about current issues and trends in water quality of the Upper CLP watershed. The purpose of annual reports is to summarize hydrologic and water quality information for the current year. Annual reports highlight significant events, issues of concern, the results of special studies, and provide a comparison of current water quality data to water quality data from the baseline period of record (2008-2012).

Five-year reports provide an in-depth analysis of short-term and long-term trends in the climate, hydrology, and water quality of the Upper CLP watershed. Water quality data collected throughout the Upper CLP watershed were analyzed for short-term trends by comparing the recent five-year period of record from 2018 to 2022 to the baseline period of record from 2008 to 2012. Long-term trends were also evaluated to determine if constituent concentrations increased, decreased, or stayed the same over the 15-year period of record from 2008 to 2022. This report documents

1) watershed impacts and issues of concern; 2) significant trends in climate, hydrology, and water quality in the Upper CLP watershed; 3) potential sources of pollution and/or watershed disturbances influencing water quality trends;

and 4) a summary of significant findings and implications to water treatment. Five-year water quality trend analyses reports are available for the years 2008-2012 (Oropeza and Heath, 2013) and 2013-2017 (Heath and Thorp, 2018).

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UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 5

2.0 WATERSHED

IMPACTS & ISSUES

OF CONCERN

2.1 CLIMATE CHANGE

Climate change is one of the most critical issues related to watersheds and the quality and availability of water supplies of the Colorado Front Range. It is predicted that warmer temperatures will result in changes to the water cycle, which will influence the watersheds that collect, store, and deliver clean water for consumptive and non-consumptive uses. The most serious consequences of climate change to watersheds in Colorado include:

• Changes in precipitation patterns, timing, and type.

• Shifts in timing and intensity of runoff and streamflow.

• Increases in severity and frequency of droughts and wildfires.

• Increases in frequency and intensity of forest insect infestations.

Colorado’s water resources are limited, in high demand and are extremely vulnerable to increasing extremes due to climate change. Many of the consequences of climate change will directly impact drinking water quantity and quality. Precipitation patterns in Colorado vary widely over space and time. Climate-related changes in precipitation patterns, timing, and type may result in periods of extended drought, as well as periods of intense precipitation events and flooding. These patterns result in extreme variability from year to year. Most of Colorado’s precipitation occurs during the winter months. Shifts in the timing of precipitation, in addition to more precipitation falling as rain than snow, will add to the uncertainty in the timing and intensity of runoff and streamflow. The onset of streamflow from melting snow is projected to occur earlier in the spring, resulting in reduced runoff in the late summer. These climate-driven changes to the water cycle present many challenges to water managers, including making it difficult to predict the quantity and quality of water that will be available to meet current and future water needs.

In combination with changes to water quantity, changes to water quality may also occur because of climate change-driven impacts to Colorado watersheds. The increase in the severity, frequency, and intensity of droughts, wildfires, and insect infestations can result in dramatic changes to the land cover of Colorado’s watersheds, directly impacting water quality. Droughts are the leading cause of wildfires, and the occurrence of prolonged droughts has led to an increased frequency of wildfires. Wildfires impact watershed hydrology by changing vegetation and soils and increasing pollution to drinking water supplies.

2.2 DROUGHT

Drought is a deficit in precipitation measured over an extended period that leads to drier than normal conditions for an area of land. Drought is part of the normal climate variability in Colorado and can vary over space and time (days, months, or years) depending on local and regional precipitation patterns. Extended periods of drought not only lead to impacts to the availability of water but can also influence water quality due to changes in streamflow and related disturbances such as wildfire. Potential impacts of drought on raw and treated water quality are summarized in Table 2.

Raw Water Quality Finished Water Quality Increased nutrients, algae, cyanobacteria, MIB, geosmin

Taste and odor Potential for cyanotoxins

Increased water temperature

Increased water temperatures in distribution system Color and turbidity Color and turbidity

Increased microbial contamination

Cryptosporidium and giardia in treated water

Iron and manganese Manganese, color Increased TOC DBPs (THMs and HAAs) Decreased DO

Increased hardness Low alkalinity Corroded pipes

Increased concentrations of contaminants

Higher risk to public health

Table 2 – Potential raw and finished water quality impacts related to drought. Adopted from Water Research Foundation Web Report #4324.

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The United States Drought Monitor tracks drought conditions across the United States and releases weekly maps showing parts of the U.S. that are in drought. Drought conditions are rated from D0 (abnormally dry; yellow) to D4 (exceptional drought; dark red) using the best available data and local observations. Over the last 15 years, from 2008 to 2022, drought conditions in the CLP watershed, as illustrated by drought conditions in Larimer County, have varied in intensity and duration. Over the baseline period of record (2008 – 2012), short periods of low intensity drought (D0 – D1) were observed, but in general, normal drought and precipitation patterns were observed. An extend period of higher intensity (D2 – D3) drought was observed from 2012 to fall-2013, which led to the Hewlett Gulch and High Park Wildfires. Very minimal drought conditions occurred from fall-2013 through summer of 2016 due to an extended period of wet conditions throughout the watershed. In September of 2013, the Colorado Front Range and adjacent foothills experienced a period of intense rainfall leading to severe flooding in streams and rivers throughout much of the South Platte and Arkansas River Basins. Intense rainfall was observed over a 7-day period from September 9th to September 16th with some areas receiving up to 18 inches of water. Several impacted areas measured record rainfall amounts that were greater than average annual precipitation totals. Variable drought conditions returned over the summer of 2016 through 2017.

Over the past five years (2018-2022), drought conditions have been variable both in duration and intensity. Severe and extreme drought (D2 – D3) impacted the watershed from the summer of 2020 through the winter of 2021, contributing to the occurrence of the Cameron Peak Wildfire. Drought continued to persist to varying degrees through 2022.

2.3 WILDFIRE

Several large wildfires have impacted the CLP watershed over the last 15 years (Figure 2.2). The exceptionally hot and dry conditions in 2012 (Figure 2.1) lead to extreme wildfire conditions throughout Colorado. The Upper CLP watershed was impacted by two major wildfires in 2012.

The Hewlett Gulch Fire (May 14- 22) burned 7,685 acres in dense Ponderosa Pine Forest stands on north-facing slopes, as well as shrubs and grasslands that occupied much of the south-facing aspects. The burned area includes sub-watersheds that drain both to the Mainstem and into Seaman Reservoir on the North Fork.

The High Park Fire (June 9 - July 2) burned 87,415 acres of primarily forested land characterized by Ponderosa and Lodgepole Pine at the lower elevations and mixed conifer species at the upper elevations. To a lesser degree, shrublands, grasslands and riparian areas were also impacted. The burned area includes numerous sub-drainages that are tributaries to the Mainstem and South Fork CLP Rivers.

Figure 2.1 – Drought conditions in Larimer County, Colorado from 2008 through 2022 (https://www.drought.gov/states/colorado).

https://www.drought.gov/states/colorado

UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 7

In 2020, the Cameron Peak Fire (August 13 – December 2) burned 208,663 acres of mixed conifer forest in the mid and upper elevations of the watershed. The burned area includes numerous sub-drainages that are tributaries to the Mainstem and the South Fork CLP Rivers as well as several high elevation water storage reservoirs that deliver water into the Mainstem CLP River.

The 2012 and 2020 wildfires caused dramatic changes to land cover within the Upper CLP watershed that had an immediate effect on watershed hydrology and water quality within and downstream of the burn scars. The disturbance caused an increase in streamflow and sediment erosion into streams draining burned sub-basins specifically during and following high-intensity storm events. The loss of vegetative cover altered the cycling of water, carbon, nutrients, and other elements, directly impacting water quality in the CLP River. Potential impacts on raw and treated water quality from wildfires are summarized in Table 3.

Real-time water quality monitoring instruments were installed at two locations upstream of the Poudre supply. The Poudre at Indian Meadows site is located one mile downstream of the Town of Rustic and the Manners Bridge site is located approximately one mile upstream of the City of Fort Collins’ raw water intake (Figure 2.2). This monitoring system provides water treatment operations near real-time water quality data to quickly respond to changes in Poudre River water quality that result from runoff from wildfire burn scars and other upstream events.

Figure 2.2 – Recent wildfire history (2008 – 2022) in the Cache la Poudre Watershed.

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2.4 FOREST HEALTH

Native forest insects and diseases are common in Colorado’s forests and play an important role in forest ecology and maintaining healthy, resilient forests that provide clean water to lakes, streams, and rivers. Over the past two decades several forest insects and diseases have impacted Colorado’s forests. Drought continues to influence forest health across much of the Upper CLP watershed.

The mountain pine beetle, a native bark beetle that infests all pine species, impacted several million acres of Colorado’s forest over the past two decades. Nearly 80% of Colorado’s pine forests were impacted by pine beetle as of 2014. The impact of pine beetle on Colorado’s forests since 2014 has been low; however, impacted acres over the past two years have been on the rise indicating an increase in pine beetle populations and the potential for isolated pine beetle outbreaks on any remaining live pine trees (Colorado State Forest Service, 2022).

The spruce beetle has destroyed millions of acres of forest since 1996 and has been Colorado’s most common forest insect impacting high-elevation Engelmann spruce forests throughout Colorado. Over the past 22 years, spruce beetle has impacted nearly 2 million acres in Colorado. The highest spruce beetle-caused tree mortality was observed in 2014 at over 400,000 acres. State-wide tree morality has been on the decline since 2014 (Colorado State Forest Service, 2017). In 2017, the Colorado State Forest Service identified significant infestations in Larimer County and noted the potential for expanding outbreaks in susceptible Engelmann spruce forests in the northern portion of the state suggesting the potential for future infestations and tree mortality in the Upper CLP watershed.

2.5 AIR POLLUTION

Air pollution along Colorado’s Front Range and from other areas may impact water quality in the Upper CLP watershed through a process called atmospheric deposition. Atmospheric deposition occurs when pollutants emitted into the air are deposited on land and in water with precipitation (wet deposition) or as dry particles and gases (dry depositions). Acidic deposition has been the most widely studied form of atmospheric deposition, which has led to acidification of surface waters from acid compounds (sulfur and nitrogen) and other chemicals. The main source of sulfur dioxide to the atmosphere is large power plants and the source of nitrogen oxide and ammonium emissions include vehicle emissions, oil and gas development, and agricultural practices.

The National Atmospheric Deposition Program (NADP;

http://nadp.slh.wisc.edu/) is a cooperative effort between private, governmental and non-profit agencies that measures precipitation chemistry (wet deposition) throughout the United States with the goal of monitoring the

Table 3 – Potential raw and finished water quality impacts related to wildfire. Adopted from Water Research Foundation Web Report #4324.

Raw Water Quality Finished Water Quality Increased nutrients, algae, cyanobacteria, MIB, geosmin

Taste and odor Potential for cyanotoxins

Color and turbidity Color and turbidity Increased metals Manganese, color Increased TOC DBPs (THMs and HAAs) Decreased DO

Increased hardness Increased alkalinity DBPs (THMs and HAAs)

Figure 2.3 – Ammonia ion wet deposition has increased throughout the United States since the NADP began in 1985 (Source: http://nadp.slh.wisc.edu/).

http://nadp.slh.wisc.edu/ http://nadp.slh.wisc.edu/

UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 9

chemistry of precipitation to determine changes over time.

Atmospheric deposition has been monitored near the headwaters of the Cache la Poudre River in Rocky Mountain National Park since the early 1980s through the National Atmospheric Deposition Program.

Long-term records from monitoring stations in Rocky Mountain National Park and throughout Colorado show decreasing trends in sulfate since the early 1990s because of efforts to reduce emissions established under 1990 Clean Air Act amendments. The reduction in sulfur dioxide emissions has lessened the amount of sulfuric acid in the atmosphere and lead to declines in precipitation acidity and acidic deposition into Colorado’s watersheds (Mast, 2011).

In contrast, trends in nitrogen species (nitrate and ammonium) have been less sensitive to emission reductions and voluntary management strategies aimed at limiting nitrogen to the atmosphere. Increasing trends were observed in ammonium with the largest increase near agricultural and urban areas in eastern Colorado (Mast, 2011; Figure 2.3). It is expected that these trends will continue in the future because of projected population growth along the Colorado Front Range and increasing oil and gas production in Colorado.

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UPPER CACHE LA POUDRE RIVER COLLABORATIVE WATER QUALITY MONITORING PROGRAM 11

3.0 WATERSHED

HYDROLOGY AND

CLIMATE

The hydrology of the Upper CLP plays an important role in regulating water quantity and quality. Precipitation and snowmelt runoff largely control the quantity and timing of deliveries of material to the river, and the amount of water in the system at a given time influences the concentration of most water quality constituents. Changes to the timing, magnitude, and duration of snowmelt runoff and the effects on water quality have implications to water treatment operations that may need to be addressed in the future to continue to maintain high-quality drinking water.

Evaluating Short-Term and Long-Term Data Trends

Short-term trends are presented for the most recent five years of data from 2018 to 2022 (current) and compared to baseline data from 2008 to 2012 (baseline). Annual and monthly mean air temperature, precipitation, and streamflow were calculated for the current period of record and compared to the baseline period of record.

Long-term trends are presented for the combined 15-year period of record from 2008 to 2022. The Seasonal Mann- Kendall test (SMKT) was used to evaluate long-term trends in air temperature, precipitation, and streamflow. The SMKT was performed on 1) monthly average minimum, maximum and mean air temperature calculated from daily average minimum, maximum and mean air temperatures;

2) monthly cumulative precipitation calculated from daily precipitation; and 3) monthly mean streamflow calculated from daily average streamflow. The Mann-Kendall test was used to evaluate annual and seasonal trends.

Seasons were defined as winter (December – February), spring (March – May), summer (June – August), and fall (September – November).

Statistical significance was determined to the 95% confidence level (p ≤ 0.05), while notable trends were identified to the 90% confidence level (p ≤ 0.10).

Hydrologic and Climatic Data Sources

The snow telemetry (SNOTEL) network, managed by the Natural Resource Conservation Service, includes approximately 600 automated monitoring sites located in remote mountain watersheds throughout the United States that measure snow water equivalent (SWE), accumulated precipitation, and air temperature. Joe Wright SNOTEL, located at an elevation of 10,120 feet, contains the longest record of continuous measurements in the Cache la Poudre Watershed, dating back to 1978 (https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=551).

The Cache la Poudre at Canyon Mouth near Fort Collins (CLAFTCCO) streamflow monitoring station managed by the Colorado Department of Water Resources (http://www.dwr.state.co.us/) contains the longest record of continuous streamflow in the Upper CLP watershed, dating back to 1883. CLAFTCCO is located at the Canyon Mouth and includes streamflow contributions from both the Mainstem and North Fork watersheds.

3.1 AIR TEMPERATURE

The annual mean air temperature measured at Joe Wright SNOTEL over the last five years was slightly warmer than baseline conditions. The mean temperature over the current five-year period was 35.4 degrees Fahrenheit (°F) (1.9 degrees Celsius (°C)) compared to a mean baseline temperature of 34.8°F (1.5°C) (Figure 3.1). Monthly mean air temperatures in the Upper CLP watershed were slightly warmer in most months over the current five-year period compared to baseline. Monthly mean temperature over the five-year period exceeded baseline monthly mean temperature in all months except February, March, October, and November. The most notable departure from baseline was observed in the month of September.

Monthly mean temperature in September measured 2.8°F (1.6°C) warmer than baseline (Figure 3.1).

Air temperature significantly increased at higher elevations in the Upper CLP watershed over the long-term period of record. A significantly increasing trend was detected in both the average monthly mean and average monthly minimum air temperatures. Average monthly mean temperatures increased at a rate of 0.08°F (0.04°C) per year, while average monthly minimum temperatures increased at a slightly greater rate of 0.11°F (0.06°C) per year (Table 4). These trends were also observed over the previous long-term period of record from 2008-2017 as documented by Heath and Thorp (2018), although the rate of change over the current period was lower.

Seasonal trend analyses detected significantly increasing average monthly minimum air temperatures during the https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=551 http://www.dwr.state.co.us/

12 UPPER CACHE LA POUDRE WATERSHED COLLABORATIVE WATER QUALITY MONITORING PROGRAM summer season. Over the summer season, average monthly minimum temperatures increased at a rate of 0.15°F (0.08°C) per year (Table 4).

No additional seasonal trends were detected in average monthly air temperatures at the Joe Wright SNOTEL.

Trend analyses of air temperature data collected at the Cache la Poudre at Canyon Mouth near Fort Collins (CLAFTCCO) streamflow monitoring station revealed no discernable trends.

3.2 PRECIPITATION

Mean precipitation measured over the last five years was slightly lower than the baseline. Mean precipitation measured over the five-year period was 95 percent (%) of baseline – 43.0 inches compared to 45.3 inches. A total of 215 inches of precipitation was recorded over the five-year period compared to 227 inches. The highest amount of precipitation was measured in the winter and spring seasons (32.3% and 32.4%, respectively) and the lowest amount was measured in the fall season (14.2%). Higher precipitation was measured over the current winter season compared to baseline. In all other seasons, precipitation over the five-year period was lower than baseline (Figure 3.2). The largest difference in precipitation was observed in the fall season which recorded 3% less precipitation.

Precipitation in all fall months measured below baseline (Figure 3.2).

There were no significant long-term trends in annual, monthly, or seasonal precipitation over the long-term period of record. Total precipitation was variable from year to year.

The highest amount of precipitation was measured in 2022 with a total of 45.4 inches of precipitation (100% of baseline) and the lowest amount of precipitation was measured in 2020 with a total of 36.8 inches of precipitation (81% of baseline).

The maximum amount of water stored in the snowpack, referred to as peak snow water equivalent (SWE), measured 80% of baseline over the five-year period. Peak SWE was lower than baseline in all years (Figure 3.3). The ratio between peak SWE and total annual precipitation

Figure 3.1 – Mean baseline and current air temperatures (top), and monthly mean air temperature over the baseline and current periods of record (bottom) reveal similar air temperature between the two periods.

Figure 3.2 – Monthly mean precipitation totals for the baseline period compared to the recent five-year period (top) and seasonal distribution of precipitation for the baseline period and current period (bottom).

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(peak SWE/total annual precipitation) was lower than baseline in all years, indicating that more precipitation fell as rain compared to snow in current years compared to baseline. More precipitation fell as snow compared to rain in 2020 when the ratio measured higher than baseline (Figure 3.3). There were no significant long-term trends detected in peak SWE or the peak SWE to annual total precipitation ratio over the long-term period of record.

3.3 STREAMFLOW

Mean streamflow measured over the five-year period was 99% of baseline. Streamflow measured 233,941 acre-feet (acre-ft) compared 236,382 acre-ft measured over the baseline period (Figure 3.4). The highest proportion of streamflow was measured in the spring and summer seasons and the lowest was measured in fall and winter seasons. Streamflow measured above baseline in all months, except in June, July, and October (Figure 3.4).

A shift in seasonal flow contributions was observed over the five-year period compared to baseline. The biggest difference in streamflow was observed over the spring and summer seasons. A higher proportion of streamflow was measured over the current spring season compared to baseline, while a smaller proportion of streamflow was measured during the current summer season compared to baseline (Figure 3.4). These seasonal observations suggest that spring snowmelt runoff during the current period occurred earlier in the year and the rate of snowmelt may have occurred faster resulting in a lower contribution of water from snowmelt in the summer months of June and July. In contrast, the proportion of water delivered during the winter and fall seasons was similar compared to baseline conditions. During these seasons, the hydrology of the CLP watershed is largely controlled by water releases from high elevation water storage reservoirs.

Peak streamflow, in cubic feet per second (cfs), observed over the five-year period was like baseline. The average peak streamflow over the current period measured 2,438 cfs compared to 2,436 cfs measured over the baseline period. The highest peak streamflow measured 3,140 cfs in 2022 and the lowest measured 2,210 cfs in 2018. The timing of peak streamflow occurred an average of three days earlier than the baseline (June 9). The latest peak was observed on July 1, 2019, and the earliest peak was observed on May 23, 2014.

There were no significant trends detected in annual streamflow, peak streamflow, or the timing of peak streamflow over the long-term period of record.

Figure 3.3 – Current five-year precipitation totals, and peak snow water equivalent measured at the Joe Wright SNOTEL compared to baseline.

Figure 3.4 – Monthly average streamflow for the baseline period compared to the recent five-year period (top) and seasonal distribution of streamflow for the baseline period and current period (bottom).

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Paramater Test Statistic Season Trend Direction Trend Estimate Significance (p-value)

Temperature

Average Monthly Mean Annual Increasing 0.08°F (0.04°C) per year 0.05

Average Monthly Minimum

Annual Increasing 0.11°F (0.06°C) per year 0.04

Summer Increasing 0.15°F (0.08°C) per year 0.04

Table 4 – Summary of statistically significant climatological variables detected in the Upper CLP watershed.

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