HomeMy WebLinkAboutCOUNCIL - AGENDA ITEM - 03/24/2020 - WATER SUPPLY VULNERABILITY STUDYDATE:
STAFF:
March 24, 2020
Meagan Smith, Water Resources Engineer
Donnie Dustin, Water Resources Manager
Carol Webb, Deputy Director, Utilities
WORK SESSION ITEM
City Council
SUBJECT FOR DISCUSSION
Water Supply Vulnerability Study.
EXECUTIVE SUMMARY
The purpose of this item is to provide Council an overview of the recently completed Water Supply Vulnerability
Study (Study) that investigated the impacts of various risks on the reliability of Fort Collins Utilities’ (Utilities) long-
term water supply. Key findings indicate:
• A warmer/drier climate poses the largest risk to the current long-term planning strategy.
• Adequate storage is crucial to meeting current policy criteria.
• Reductions in available supplies from the Colorado-Big Thompson Project (C-BT) via Horsetooth Reservoir
have significant impacts to system performance.
GENERAL DIRECTION SOUGHT AND SPECIFIC QUESTIONS TO BE ANSWERED
This item is for informational purposes. Direction is not sought on the Study at this time. However, any questions
Council may have regarding the Study are welcomed.
BACKGROUND / DISCUSSION
Utilities operates its water supplies and does long-term water supply planning under the Water Supply & Demand
Management Policy (Policy), last updated in 2012. The Policy provides the framework for water supply and
demand management planning for Utilities’ water supply service area. Related Council-approved plans include:
• Water Supply Shortage Response Plan (to be renamed as Water Shortage Action Plan) - (adopted 2014,
update to be considered on First Reading on April 7, 2020) that establishes conditions and restrictions to
manage Utilities’ water supply in the event of a projected water shortage.
• Water Efficiency Plan - (adopted 2016, update by 2022) that addresses long-term water conservation and
efficiency planning.
The Study was a 2017/18 Budgeting for Outcomes (BFO) Enhancement Offer to investigate the relative impacts
on Utilities’ ability to meet expected future water demands from:
• Changing hydrology due to a warming climate.
• Water supply disruptions, such as infrastructure failures or wildfire impacts.
• Changing demands due to population shifts, land-use changes or altered demand patterns.
The Study will serve as the foundation for a Policy update. Policy revisions are likely to include updated level of
service goals framed by customer experience and adoption of risk-based water supply planning objectives that
embed demand management targets and are based on selected planning futures.
LONG-TERM WATER SUPPLY PLANNING
The current Policy plans for Utilities to develop enough water supplies to meet expected future demands for
Utilities’ water service area through a single, assumed “planning drought,” while keeping 20% of annual demand
in storage as an emergency reserve. This “yield-based planning” calls for the acquisition of supplies that will yield
March 24, 2020 Page 2
an amount of water equal to expected demands through the planning drought. The Policy articulates this through
current level of service goals:
• Meet 100% of demands through the planning drought
• Maintain the emergency reserve 100% of the time through the planning drought
For worse droughts, Utilities’ will use restrictions to close any gap between expected supplies and demands (via
the Water Shortage Action Plan).
Consistent with industry best practice, Utilities intends to move away from yield-based planning toward more
flexible planning that considers, and more accurately analyzes, climate change impacts and other water supply
risks. Other regional water providers (e.g., Denver Water, Colorado Springs Utilities) have already moved in this
direction. The Study provides a basis for a similar evolution of Utilities’ planning.
WATER SUPPLY VULNERABILITY STUDY
The Study had three main components:
• Develop new tools and datasets.
• Identify vulnerabilities (by developing and modeling plausible scenarios).
• Process results and assess key findings.
New Tools and Datasets
All of Utilities’ water supplies are influenced by seasonal and annual weather patterns and highly dependent on
annual snowpack. To test the reliability of Utilities’ supplies in meeting expected future demands under a broad
range of natural climate variability, staff and a consultant team generated new weather combinations based on
the historical observed record (1950-2005) combined with tree-ring studies (1615-1999) for the Cache la Poudre
River. Warming temperatures and changes in precipitation were then layered onto the new weather data to better
understand the potential impacts of climate change. This new weather data was utilized to generate water supply
forecasts.
Staff and the consultant team developed a new water demand forecasting tool that allows estimation of future
demands as a function of historical use, land-use zoning, development densities, economic conditions, and most
importantly, weather. This allowed staff to generate demand forecasts that match the weather-generated supply
forecasts. Water demand forecasts were created across the range of generated weather for two distinct
development trajectories based on the 2019 City Plan.
Vulnerability Scenarios
The overarching purpose of the Study was to identify vulnerabilities that may impact Utilities’ ability to provide a
reliable water supply. Staff held two half-day brainstorming workshops with cross-departmental and multi-
organizational teams. These workshops included subject matter experts from Water Board and Colorado State
University, water resources staff from other water providers in the growth management area (GMA), a large team
from Northern Water, and staff from departments across the City and Utilities.
In total, the workshops identified more than 90 vulnerabilities across five categories:
• Demands
• Operations and Infrastructure
• Climate and Hydrology
• Watershed and Environmental
• Legal and Administrative
Utilities staff developed 11 vulnerability scenarios based on the most likely and impactful individual vulnerabilities
and modeled the scenarios with all combinations of new supply and demand forecasts. More than 45,000 model
March 24, 2020 Page 3
runs were made to assess Utilities’ “system performance,” which is the ability to meet the current Policy’s level of
service goals.
Key assumptions modeled across these scenarios include:
• Forecasted water demands for expected development trajectories in 2070.
• Expected water supply portfolio and built infrastructure in 2070.
o Halligan Reservoir enlargement is built and operational (unless otherwise noted).
Key Findings
Key findings include:
• Warmer/drier climate poses the largest risk to the current long-term planning strategy. A warmer/drier
climate really reduces system performance by both decreasing supplies and increasing demands.
• Adequate storage is crucial to meeting current policy criteria. Without enough storage capacity, Utilities
will not be able to maintain the current policy target of 20% of annual demand in emergency storage based on
expected future demands.
• Reductions in available supplies from C-BT via Horsetooth Reservoir have significant impacts to
system performance. C-BT water meets approximately half of the annual water use by Utilities’ customers.
The Study helps quantify how a long-term reduction in available C-BT water would impact Utilities ability to
meet demands.
This Study was the first of its kind for Utilities, highlighting some of the risks Utilities must plan for in providing
reliable service in the face of an uncertain future.
NEXT STEPS
One of the main drivers of the Study was to lay the groundwork for an update to the Policy. Expected outcomes of
an updated Policy include new level of service goals framed by the customer experience and adoption of risk-
based water supply planning objectives grounded in a range of planning futures.
Staff expects this Policy development to be an iterative process:
1. Determining planning futures will define expected demands and available supplies.
2. Setting service levels will define system performance, describing success or failure of the system.
3. Exploring solutions will quantify options for closing any gap between expected supplies and demands.
4. If solution options do not meet specified triple-bottom line criteria, the process can repeat by revisiting defined
planning futures and/or altering level of service goals.
These Policy level discussions will be discussed in greater detail in a future Work Session.
The full version of Water Supply Vulnerability Study Final Report is available for download at:
fcgov.com/utilities/img/site_specific/uploads/wsvs-final-report.pdf
<https://fcgov.com/utilities/img/site_specific/uploads/wsvs-final-report.pdf>
ATTACHMENTS
1. Water Supply Vulnerability Study Final Report - Executive Summary (PDF)
2. Water Supply and Demand Management Policy (2012) (PDF)
3. Powerpoint presentation (PDF)
Fort Collins Utilities Water Supply
Vulnerability Study DraIt Report
Prepared for: Fort Collins Utilities LQFRRUGLQDWLRQZLWKNorthern Water
Prepared by: Stantec in Association with RTI International
-XQH 2019
ATTACHMENT 1
Fort Collins Water Supply Vulnerability Study
Final Report
June 27, 2019
Prepared for:
Fort Collins Utilities
In coordination with Northern Water
Prepared by:
Stantec Consulting Services, Inc.
In association with RTI International
FORT COLLINS WATER SUPPLY VULNERABILITY STUDY
This document entitled Fort Collins Water Supply Vulnerability Study was prepared by Stantec Consulting
Services Inc. (“Stantec”) for the account of Fort Collins Utilities (the “Client”). Any reliance on this document
by any third party is strictly prohibited. The material in it reflects Stantec’s professional judgment in light of the
scope, schedule and other limitations stated in the document and in the contract between Stantec and the
Client. The opinions in the document are based on conditions and information existing at the time the
document was published and do not take into account any subsequent changes. In preparing the document,
Stantec did not verify information supplied to it by others. Any use which a third party makes of this document
is the responsibility of such third party. Such third party agrees that Stantec shall not be responsible for costs
or damages of any kind, if any, suffered by it or any other third party as a result of decisions made or actions
taken based on this document.
Prepared by
Lisa Fardal, PE, Samantha Dyche, EIT, Neil Stewart, PE, Enrique Triana, PE
Reviewed by
Chip Paulson, PE, Terry McEnany, PE
Approved by
Chip Paulson, PE
ES-1
Executive Summary
Introduction
The City of Fort Collins is located 65 miles north of Denver in Larimer County, between the Rocky
Mountains foothills and the Eastern Plains of Colorado. Fort Collins Utilities (FCU) currently serves about
75% of Fort Collins’ residents and businesses. The FCU service area boundary for water, which does not
coincide with Fort Collins city limits, is landlocked by neighboring water districts. Current estimates for the
FCU service area show an increase in population to about 178,000 by 2065. Fort Collins is home to
Colorado State University and a few large commercial enterprises.
The Fort Collins Water Supply Vulnerability Study (WSVS) was performed to investigate the ability of the
FCU water supply system to meet future demands under current policy criteria and level of service goals
when subjected to alternative hydrologies and various risks and uncertainties. The WSVS compiled
alternative hydrologies, demands, and infrastructure risks and uncertainties into risk scenarios, resulting
in a broad range of potential future conditions. The performance of the Fort Collins system under these
risk scenarios was evaluated to inform under what future conditions the FCU water rights portfolio, raw
water infrastructure and water supply policy and planning efforts are most vulnerable.
This project was performed by Stantec Consulting Services, Inc. under a contract with the City of Fort
Collins. RTI International was a subconsultant to Stantec for hydrologic analyses and demand tool
development.
Water Resources System Model
The WSVS involved risk-based water resources planning analyses that required a robust modeling
platform to simulate the performance of FCU’s raw water system under a wide range of possible future
conditions. The modeling system used for the WSVS consists of three separate models: the Colorado-Big
Thompson Quota Model (CBTQ), the Poudre Basin Network Model (PBN) and the Fort Collins System
Model (FCSys).
x The CBTQ Model was developed by Northern Water to estimate annual quotas of C-BT and
Windy Gap water for its allottees based on hydrology and current operations.
x The PBN Model is a MODSIM model that simulates water supply infrastructure and operations by
municipal, industrial, and agricultural entities in the Poudre River basin and the lower South Platte
River basin below the Poudre River confluence near Greeley. It was originally developed by
Resource Consultants in 1985 for the Fort Collins Drought Study, but has been enhanced by Fort
Collins, Northern Water and Greeley over the years to serve a number of purposes.
x The FCSys is a MODSIM model developed by FCU that simulates the FCU water supply system
under various water demand, water rights, infrastructure and operational scenarios. The FCSys
simulates city water deliveries, deliveries to large contractual users (LCU), return flow obligations
ES-2
from the use of converted agricultural water rights and various other operations of the FCU water
supply system.
These models were run in sequence through a Data Management System as shown in Figure ES-1. The
system is semi-automated and includes the ability to export FCSys output as PBN inputs and vice versa.
Figure ES-1 FCU Modeling System Overview
Fort Collins and other agencies have used previous versions of the PBN and FCSys models for past
water resources planning and decision-making. The WSVS modeling system was not developed to re-
evaluate any previous planning studies and it does not simulate flows in streams that could be affected by
water development projects in the Poudre River basin. This modeling system was developed to identify
and prioritize future risks for which FCU should be planning.
The WSVS used the FCU modeling system to evaluate FCU water supply system performance. “System
performance” is defined as the ability to meet customer demands and satisfy adopted water supply
planning policy criteria. For FCU, the Water Supply and Demand Management Policy (WSDMP)
establishes an objective of:
x meeting demands calculated using a per capita use factor of 150 gallons per capita per day,
x through the 1-in-50-year drought,
x with no shortages or water restrictions,
x while maintaining a minimum of 20 percent of annual demand in reservoir storage at all times
(storage reserve factor).
As part of the WSVS, the performance of the FCU water supply system was quantified using measurable
parameters (metrics) with target values based on the criteria defined in the WSDMP (level of service
goals). The performance metrics and level of service goals were identified and calculated as part of the
modeling system outputs. Risk-based water supply planning commonly considers three categories of
performance metrics: reliability metrics (i.e., measures of how often certain conditions occur), resilience
metrics (i.e., how long certain conditions occur) and vulnerability metrics (i.e., how severe certain
conditions area). Many specific reliability, resilience and vulnerability performance metrics were identified
ES-3
to help quantify the impacts of risks and uncertainties to the FCU water supply system. As the WSVS
progressed, FCU staff found that the following four performance metrics were most useful for identifying
the impactful risks.
x Average annual total demand shortage in years when shortages occur
x Reliability (i.e., frequency) of maintaining 20% of annual demand in storage (storage reserve
factor)
x Percentage of time in any level of water use restrictions based on the current planning policy
criteria
x Reliability of meeting indoor demand
Hydrology
Synthetic sets of potential future hydrologic model inputs that include natural variability and large-scale
shifts in precipitation and temperature trends due to potential climate change were generated for use in
the Fort Collins Modeling System.
Figure ES-2 provides an overview of the process used to generate hydrologic datasets for the WSVS.
Application of this process resulted in 20 sets of 100 sequences of natural hydrologic variability (referred
to as a “trace”), with each set representing a particular future climate condition. Future climates were
described by the offset of temperature and precipitation from historical conditions. Based on review of
previous climate change studies for the Front Range region, the temperature offset ranged from 0 to plus
8 degrees F compared to average annual 1981 to 2010 observed temperature, and the precipitation
offset ranged from -10% to +15% of average annual 1981 to 2010 observed precipitation.
Figure ES-2 Overview of Hydrologic Analysis Process
Note: JVRCCVS = Joint Front Range Climate Change Vulnerability Study
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Temperature and precipitation changes in the range adopted for the WSVS were found to have significant
effects on streamflow contributing to FCU water supply. The hottest/driest climate condition (T=+8,
P=-10%) reduced the Poudre River at the Canyon Mouth mean annual streamflow by an average of 30%
for the 100 hydrologic traces, compared to the non-climate adjusted traces. The coolest/wettest climate
condition (T=0, P=+15%) increased the Poudre River mean annual streamflow by an average of 39% for
the 100 hydrologic traces, compared to the non-climate adjusted traces. This is shown in Figure ES-3.
In the past, FCU has used a 6-year critical period within the 86-year model simulation period to determine
the 1-in-50-year drought for water supply planning. Hydrologic inflows were based on synthetic runoff
data. This 6-year critical period for the Poudre River at the Canyon Mouth has an average annual runoff
of 196,090 acre-feet per year (AFY). The 100 hydrologic traces in the WSVS hydrologic dataset for the
unaltered historical climate conditions (T=0, P=0%) have an average 6-year critical period flow at this
location of 191,343 AFY, which is a 2% reduction. The hottest/driest climate condition (T=+8, P=-10%)
produces an average 6-year critical period annual streamflow that is 31% less than the critical period
streamflow currently used for planning. The coolest/wettest climate condition (T=0, P=+15%) produces an
average 6-year critical period annual streamflow that is 38% more than the critical period streamflow
currently used for planning. This is important when interpreting the vulnerability study results relative to
current water supply policy criteria that are based on the 6 year long, 1-in-50-year drought in the synthetic
runoff data. When considering the full set of 100 hydrologies times 20 climate scenarios generated for
the WSVS, there are traces which capture more severe and more frequent critical periods than the
historical 6-year critical period used in previous water supply planning to represent the 1-in-50 year
drought. Additionally, there are traces in the WSVS that do not see critical periods as severe as the
historical.
Figure ES-3 Average Annual Flow Volume for Hydrologic Traces for All Climate
Conditions
Note: Each cell shows the mean of the average annual flows for the 100 traces with the corresponding T/P
combination expressed in AFY and as a percentage of the average annual flow for the T=0, P=0 combination.
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Water Demands
Future water demands for general residential and commercial customers in the FCU service area were
estimated using a new Demand Estimation Tool developed for this project. The Demand Estimation Tool
consists of individual linear regression models, each developed for the following groups of water
customers: single family and duplex, multifamily, commercial small, commercial medium, and commercial
large customers. It was developed using processed historical customer-level water use data from 2001-
2016.
Three demand scenarios were developed
by FCU for use in the WSVS: City Plan 2,
City Plan 3 and City Plan 3 plus 20%.
The first two demand scenarios are
based on the most likely proposed future
development scenarios for 2070
developed as part of the Fort Collins City
Plan update. The median average annual
water demand in 2070 under City Plan 2
assumptions, including the effects of
climate change, is 37,700 AFY. The more
aggressive growth assumptions in the
City Plan 3 scenario result in a median
total water demand of 39,200 AFY, for an
increase of 4% compared to City Plan 2.
The City Plan 3 Plus 20% scenario
increased both the general residential
and commercial portion of the total
demand and a portion of the Large Contractual User demand by 20%. This resulted in a median total
water demand of about 45,200 AFY. Figure ES-4 compares the total annual demands for these three
scenarios. The average annual demand for 2065 developed from previous FCU planning studies is
40,629 AFY; this is referred to as the “baseline demand” in this study.
Risks and Uncertainties
The purpose of the WSVS is to identify the vulnerability of the FCU water supply system to a range of
risks or threats that could occur in the future and factors that cannot be accurately forecasted. Risks and
uncertainties that could affect the future performance of the FCU water supply system were brainstormed
in workshops held at Fort Collins Utilities and Northern Water. Identified risks and uncertainties were
organized in the following categories that span the various aspects of the FCU water supply system.
x Climate and Hydrology risks relate to weather variability and other hydrologic factors, both
short- and long-term, that can impact the potential yields from a watershed.
x Watershed risks relate to physical watershed conditions that can impact the yields available to
FCU.
Figure ES- 4 Total Annual Demand in 2070 Including
Climate Change (Median of All 2,000
Traces for Each Development
Scenario)
Note: Average Baseline demand = 40,629 AFY
ES-6
x Operational and Infrastructure risks relate to how FCU delivers physically and legally available
water to its treatment facilities.
x Administrative and Legal risks relate to conditions, regulations, or policies that could impact the
legal allocation or availability of water supplies.
x Demand risks relate to changes in required volume, timing, and quality of water that will need to
be delivered to water treatment facilities to meet customer needs.
Some risks are long-term, or chronic, and would persist indefinitely and affect all future years. Other risks
are short-term, or acute, and would only occur for a short period of time (e.g., several months or a few
years). Although long-term and short-term risks could have very different impacts on the FCU raw water
system performance, both types of risks were assessed together in the WSVS.
The identified risks were rated as part of the prioritization process. Individual risks were rated by
assigning a 1 to 5 score for both likelihood (possibility of the risk or uncertainty occurring) and impact
(consequences to the FCU/C-BT water supply system if the risk or uncertainty were to occur). The
composite score was calculated by multiplying the likelihood score by the impact score and was then
used to prioritize risks. The prioritized risks and uncertainties were organized into five major threat groups
that span the various risk categories. These threat groups are: climate change, demands, critical outages,
enhanced environmental stressors and shared infrastructure (i.e. risks or uncertainties due to lack of
infrastructure ownership by FCU). The risks and uncertainties selected for analysis in the WSVS are
shown in Table ES-1.
Table ES-1. List of Key Risks and Uncertainties Prioritized for Simulation
ID Risk or Uncertainty Name Threat
Group
Description
O1 Outage - 24 Pipeline CO Short term outage due to flooding, landslides, wildfire, etc.
O2 Outage - 27 Pipeline CO Short term outage due to flooding, landslides, wildfire, etc.
O3 Algal Blooms EES Algal blooms in storage reservoirs and rivers increases
water quality issues and potential treatment problems.
C1 Longer duration droughts CC Multi-year and/or more severe droughts occur in the future
that are not captured in the observed record.
A1 New Regulations EES New regulations (either federal or state) impact availability
of yields from existing water rights.
W1 Wildfires EES Wildfires occur, causing a variety of impacts on water
quality, runoff and threats to infrastructure.
C3 Change in precipitation type -
Hydrology
CC More precipitation falls as rain instead of snow during the
Fall and Spring.
C4 Changes in frequency/ magnitude
of precip events - Hydrology
CC Precipitation events, particularly summer rainstorms,
become less frequent and more intense.
C2 Changes in runoff timing CC Early higher runoff and lower late-season baseflow
reduces yield from volumetric decrees that list specific
diversion dates.
W2 Forest Health Degradation EES Forested area health decreases due to beetle kill,
pollution, warming climate, etc.
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ID Risk or Uncertainty Name Threat
Group
Description
A4 Changing state administration CC Policies around state water administration change,
impacting yields from water rights
D3 Development Uncertainty D The composition of development in service area (e.g.
density, type, outdoor area) is different that past.
A2 Increased Basin Demands D Higher demands across the entire Poudre River basin
(due to climate change/population growth) impact use of
water rights.
O5 Outage - Horsetooth Reservoir
Intake
CO Short term outage of reservoir outlet and intake to WTP;
higher risk due to lack of redundancy.
O4 Outage - Michigan Ditch CO Short term outage due to flooding, landslides, wildfire, etc.
D2 Water Use Changes D Decrease in per capita use continues and how water is
used (e.g. indoor vs. outdoor) changes.
D1 Service area growth and
Regionalization
D Ft. Collins expands its service area or enters into
agreements to provide water to regional entities.
A9 Elimination or Interruption of
Reuse Plan
SI Platte River Power Authority decommissions Rawhide
Energy Station, effectively eliminating the need for the
Reuse Plan. In multi-year droughts, water from the Reuse
Plan is reduced or unavailable.
D8 Change in precipitation type -
Demands
CC More precipitation falls as rain instead of snow during the
Fall and Spring.
D9 Changes in frequency/ magnitude
of precip events - Demands
CC Precipitation events become less frequent and more
intense.
A3 Changes to Northern Water C-BT
Operations
SI Allocation of C-BT water through setting of the quota and
ways in which C-BT water can be managed, changes in
the future.
W3 Development in Watersheds EES Land development in watersheds (recreation, residential,
O&G, mining) increases risk of water quality
contamination.
D6 Hotter summer changes irrigation D A warmer climate increases the length of the irrigation
season and hotter days increase demand during the
summer.
O6 Outage - Chambers Reservoir CO Short term outage due to flooding, landslides, wildfire, etc.
O8 Outage - Joe Wright Reservoir CO Short term outage due to flooding, landslides, wildfire, etc
O11 Outage - Pleasant Valley Pipeline CO Short term outage due to flooding, landslides, wildfire, etc.
Note: Threat Group ID definitions: CC = Climate Change, D = Demands, CO = Critical Outages, EES = Enhanced
Environmental Stressors, SI = Shared Infrastructure
Risk Scenarios
Risk scenarios were developed by FCU to represent combinations of future conditions for which a
vulnerability analysis was desired. Scenarios are comprised of single or multiple risks and are designed to
allow FCU to understand how its water resources system would behave under a range of future stressful
conditions.
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In general, a WSVS scenario consists of three parts:
x A climate condition, defined as one of the 20 temperature and precipitation combinations, which
determines 100 hydrologic traces representing climate variability around that climate condition.
x A demand condition, defined as one of the two City Plan demand scenarios or the baseline
planning demand.
x A system risk condition, defined as a combination of one or more of the risks and uncertainties.
The process for creating WSVS scenarios is shown in Figure ES-5.
Figure ES-5. Process of Creating WSVS Scenarios
FCU Staff, in coordination with Northern Water, identified 13 scenarios for simulation, including baseline
conditions. The 12 non-baseline scenarios were selected to represent a range of future conditions
believed to be possible and potentially impactful to the FCU water resources system. They represent both
long-term or chronic conditions (i.e., those that occur over the entire simulation period) and short-term or
acute conditions (i.e., those that occur for only a short period of time). These risk scenarios are described
briefly below.
x Baseline – Future conditions, including current water rights and anticipated acquisitions, current
water supply infrastructure, Halligan Reservoir enlargement and a demand of 40,629 AFY.
x Climate Change Impacts – 20 future climate conditions with constant demand and no other risks.
x Loss of Storage – No Halligan Reservoir enlargement and no C-BT carryover storage in
Horsetooth Reservoir.
x Increased Demands – Two City Plan based demand scenarios and one increased demand
scenario beyond the City Plan development assumptions.
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x No Halligan Enlargement – No enlargement of Halligan Reservoir as currently proposed.
x Poudre River System Acute Outage – Short-term outage of 24-inch and 27-inch delivery pipelines
and Pleasant Valley Pipeline.
x C-BT System Environmental Impacts – Impacts on C-BT quota allocations due to environmental
issues resulting from wildfires in the receiving East Slope watershed or restricted use of
Horsetooth as a water source because of algal blooms.
x Poudre River System Environmental Impacts – Impacts due to algal blooms or environmental
issues resulting from wildfires in source watersheds (e.g. increased sediment deposition) that
would limit FCU’s diversions from the Poudre River.
x C-BT System Acute Outage – Short-term loss of C-BT deliveries due to delivery infrastructure
failures.
x C-BT System Long-Term Reduction - Captures possible effects of a wide range of conditions that
could reduce C-BT deliveries and quotas over a period of 10 years.
x Horsetooth Reservoir Outage – Short-term outage of deliveries from Horsetooth Reservoir due to
infrastructure failures.
x Reuse Plan Changes – Two options: Reuse Plan Change 1 represents 100% elimination of the
Reuse Plan; Reuse Plan Change 2 represents 50% reduction in the Reuse Plan.
Vulnerability Assessment
The impacts of these various risk scenarios on the FCU water supply system were quantified using the
system performance metrics tied to the current water supply planning policy criteria. Vulnerabilities were
investigated in a systematic methodology based on the following steps.
1. Determine the current system’s performance for the baseline demand with no climate or
infrastructure risks.
2. Investigate how potential short-term climate variability and broader climate change could affect
the performance of the baseline system.
3. Assess the impacts of increased demands, generated by the new Demand Estimation Tool in
combination with the climate-adjusted hydrologies.
4. Evaluate the superposition of the risk scenarios with the climate-adjusted hydrologies and each
City Plan based demand scenario.
5. Identify the risk scenarios with the greatest potential to adversely affect the FCU system
performance.
The process for evaluating risks in the WSVS is shown in Figure ES- 6 below.
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Figure ES- 6 Method for Risk Evaluation
Results showed that FCU’s water system and water rights portfolio is well adapted to current climate
conditions. The existing system, which includes the Halligan Reservoir enlargement, meets all demands,
including Reuse Plan demands, with 99.1% reliability. Indoor demands are met 99.8% of the time. The
results also showed that the system maintained the policy guideline of a 20% storage reserve factor in
97.1% of the total simulated months. Note that none of the WSVS simulations include the effects of water
use restrictions.
However, system performance
declines as the climate gets
hotter and drier. The effect of
climate on the reliability of
meeting an annual demand of
40,629 AFY is shown in Figure
ES-7. This figure shows the
average percent of months in
which the target baseline
demand was met across the
100, 86-year traces for each of
the 20 climate conditions.
Comparing these reliability
results to the current water
supply policy of 100% reliability,
under almost all climate futures,
including no change in climate, the FCU system is unable to meet this level of service goal. Uncertain
future hydrology is the biggest threat to FCU’s future water supply, as it is heavily influenced by changing
climate. Even the risk scenarios with the worst performance under current climate conditions were shown
to perform better than a scenario with no system risks and an increase in temperature and decrease in
precipitation.
Figure ES-7. Average Monthly Reliability of Meeting Total
Demands for All Climate Conditions
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Simulations of increased demands showed the FCU baseline system is only moderately vulnerable to the
City Plan 2 and City Plan 3 scenarios and only for hotter/drier climates. However, the City Plan 3 + 20%
condition has more significant effects and represents a greater threat to FCU system performance.
Figure ES-8 shows the effects of the demand scenarios on the average annual shortage metric. This
metric calculates the average annual shortage across the years when shortages occur. The figure also
shows the number of years when shortages occur for each scenario. The current water supply policy
establishes a level of service goal of no shortages during the 1-in-50-year drought. With the exception of
significantly wetter climates, all demand scenarios have a shortage, showing the FCU system is unable
satisfy this level of service goal, even for traces where the critical drought period is less than the historic
1-in-50-year drought used in previous water supply planning.
Figure ES-8 Average Annual Total Demand Shortage for Increasing Demand Scenarios
and All Climate Conditions
Notes:
a) Poorer performance is indicated by greater shortage volume towards the top of the graph.
b) Current water supply planning policy goal is no shortages for the 1-in-50-year drought.
ES-12
Besides climate change and increased demands, the risks found to have the largest impact on the Fort
Collins system performance relative to the current water supply planning policy criteria are:
x loss of storage, including no Halligan Reservoir enlargement;
x Reuse Plan changes, including elimination or 50% reduction;
x increase in demands above the expected City Plan 3 levels;
x and a long-term reduction in C-BT quota due to constrained C-BT supply or other factors.
Over the four metrics analyzed in this report, those risks and risk scenarios show the poorest
performance for current climate conditions and their performance is significantly reduced for the warmer
and drier climates.
ES-13
Figure ES-9 shows the storage reserve metric for all risk scenarios as a function of climate. The storage
reserve metric measures the ability to maintain a minimum of 20% of total annual demand in reservoir
storage. The water supply policy establishes a level of service of 100% for the storage reserve factor.
Under any risk, the FCU system cannot satisfy this LOS goal at most climate futures however the Loss of
Storage and No Halligan Enlargement risks have the most significant cumulative impact on maintaining
20% of total annual demand in storage.
Figure ES-9 Storage Reserve Metric for All Risk Scenarios and All Climate Conditions
Notes:
a) Poorer performance is indicated by lower reliability towards the bottom of the graph.
b) Current FCU policy establishes a goal of 100% for the storage reserve factor during the 1-in-50-year
drought.
ES-14
The risk scenario simulations demonstrated the fundamental difference between long-term or chronic
risks and short-term or acute risks. All the most impactful risks based on the metrics used in the WSVS
are long-term risks. This is biased by the metrics themselves which, with the exception of the annual
demand storage metric, are always calculated over the entire 86-year simulation period. Thus, long-term
risks that adversely affect system performance over the entire simulation period or for many years within
the simulation period affect metric values more than short-term risks that occur for only a few months or
years. Short-term risks such as an outage of the Poudre River pipelines or C-BT facilities can have
extreme impacts on system performance for a short period but are masked by climate shifts that cause
significant long-term impacts to performance. The effects of long-term risks are not as easily masked by
the shifts in climate, as their impacts are also significant over several years or the entire simulation.
ES-15
Figure ES- 10 highlights the storage reserve metric for the five short-term risks simulated for the WSVS.
This figure shows that most of the short-term risk scenarios have very similar performance when
measured by the WSVS metrics. Additional investigation may be warranted to develop different metrics
that are useful in comparing performance of short-term risks to each other. Many of these short-term risks
received relatively high composite scores (likelihood multiplied by impact) at the risk identification
workshops, meaning they are of high concern to FCU staff and should be further assessed.
Figure ES- 10 Reliability of Retaining 20% Storage Reserve for Short Term Risks
Compared to Long Term Risks
ES-16
Conclusions
FCU plans to use the results and conclusions of the WSVS as the foundation for updating its Water
Supply and Demand Management Policy and its long-range water resources strategy. The following
findings from the WSVS may be important as FCU contemplates the coming planning process.
x Climate change is the most important vulnerability faced by the FCU system. Future climate
conditions may be more impactful to FCU’s ability to meet its water supply planning policy criteria
than the occurrence of any particular infrastructure outage or environmental condition simulated
by the WSVS risk scenarios. However, climate change is the most difficult risk to track. Long-term
trends are difficult to measure and are obscured by the natural variability in wet and dry years.
Participating in or keeping informed of state and federal climate change studies will help FCU
understand the trajectory of climate change in the region.
x Water demands higher than those forecast in the City Plan 3 scenario represent a significant
vulnerability to the current FCU system. This points out the importance of FCU maintaining its
water conservation program, and working with City Planning Department to closely monitor
population and development density trends to see how they are tracking with City Plan
assumptions. An increase in 2070 demands by 20% significantly increases shortages and
incidence of failures to meet current water supply policy requiring 20% of average annual demand
in storage through a 1-in-50-year drought.
x The risk scenarios found to have the largest impact on the FCU system performance across the
range of performance metrics are listed below.
o Loss of storage, including no Halligan Reservoir enlargement; the FCU system is
storage-limited, therefore loss of any existing or proposed storage capacity has
significant adverse effects.
o Reuse Plan changes, including elimination or 50% reduction in the amount of water
incorporated in the Plan; the Reuse Plan is a water supply agreement with other Northern
Colorado entities that results in additional water supplies for FCU in most years. Losing
all or part of the supplies generated from this agreement has compounding effects on
FCU water supply.
o A long-term reduction in C-BT quotas due to C-BT supply or delivery infrastructure
issues; C-BT supply is a critical part of FCU’s water supply portfolio and reduction in that
source over several years significantly impacts FCU’s ability to meet its water supply
planning policies.
x For most risk scenarios, shortages for climate conditions that are wetter than the current climate
would occur most often in late summer and early fall. For warmer and drier climate conditions,
shortages would occur throughout the year except in the peak runoff months of May and June.
This shows the challenge of maintaining a resilient water resources system in the face of a
warmer and drier climate with the limited amount of storage in the FCU raw water system.
ES-17
x Without the proposed Halligan Reservoir enlargement of 8,125 AF, FCU system performance
would be significantly impacted and current water supply planning policy criteria could not be met
under most future climate and demand conditions.
x The WSVS highlights the importance of storage in the FCU system and the significant
vulnerability posed by the inability to implement the proposed Halligan Reservoir enlargement or
a similar storage project as a strategy to mitigate effects of climate change and other risks.
x The WSVS validates that FCU is highly reliant on the C-BT system and is particularly susceptible
to extended periods of low quotas and loss of the carryover storage program. FCU should
monitor conditions that could trigger either of those risks.
x Results of the WSVS are biased toward long-term risks, but a number of short-term risks were
identified that could severely impact FCU operations for a few weeks or months. These conditions
will require further study and may involve a different management strategy in the future water
supply plan.
x The WSVS analysis was performed without simulating the effects of demand management
measures that FCU could adopt under the City’s current Water Supply Shortage Response Plan.
Investigating benefits of the current shortage response policy should be a key aspect of the water
supply plan update.
x FCU now has a water supply modeling tool that can be used to conduct more detailed analyses
of the WSVS risk scenarios or explore a broader range of uncertainties or operating conditions if
desired. It can also be used to measure and compare the effectiveness of alternative water
supply system improvements.
ATTACHMENT 2
1
City of Fort Collins
Water Supply and Demand Management Policy
The City of Fort Collins’ Water Supply and Demand Management Policy provides a
foundational framework for water supply and demand management decisions concerning the
City’s water supply system. Operational and management actions and decisions by the Water
Utility will be consistent with the provisions of this policy.
Objective
To provide a sustainable and integrated approach to 1) ensuring an adequate, safe and reliable
supply of water for the beneficial use by customers and the community and 2) managing the level
of demand and the efficient use of a scarce and valuable resource consistent with the preferences
of Water Utility customers and in recognition of the region’s semi-arid climate.
This objective aligns with the 2010 Plan Fort Collins that provides a comprehensive 25-year
vision for the future development of Fort Collins. Policy ENV 21.2 of Plan Fort Collins states,
“Abide by Water Supply and Demand Management Policy: Provide for an integrated approach to
providing a reliable water supply to meet the beneficial needs of customers and the community
while promoting the efficient and wise use of water.”
This Water Supply and Demand Management Policy calls for a “sustainable and integrated
approach” to water demand and water resources management. Sustainability is defined within
the context of the triple-bottom-line decision making in Plan Fort Collins as, “To systematically,
creatively, and thoughtfully utilize environmental, human, and economic resources to meet our
present needs and those of future generations without compromising the ecosystems upon which
we depend.” Aligning with Plan Fort Collins, the Water Utility will take a leadership role by
incorporating the triple-bottom-line in its management of water supply and demand. When this
core value is applied to the use and development of our valuable water resources, the Utility will
strive to:
Avoid, minimize or offset impacts to our environment
Consider the social benefits and impacts of having a reliable and high quality water supply
Analyze the economic cost to provide such supplies, while also considering the effects it has
to our local and regional economies
The Utility will continue to provide a culture of innovation that finds proactive and creative
solutions in managing its water supplies and demands, which is a dynamic process that evolves
along with changes in data management and technology, legal and political environments,
economic development and water innovation, and as the State’s population continues to increase.
Given these factors, it is important to maintain an up-to-date effective policy that is based on
current data. The policy’s terms and conditions should be reviewed and updated by 2020, or
sooner if desired by the City Council or the Utilities Executive Director.
2
1.0 WATER USE EFFICIENCY AND DEMAND MANAGEMENT
The City views its water use efficiency program as an important proactive response to supply
variability and climate change. Elements of the City’s conservation program include reducing
indoor demand through improved technology, leak reduction and behavior change and reducing
outdoor demand through improved irrigation efficiency and reasonable changes in landscaping.
The City believes water use efficiency is of vital importance for many reasons, including to:
Foster a conservation ethic and eliminate waste
Demonstrate a commitment to sustainability
Provide water for multiple beneficial purposes
Reduce the need for capital expansion projects and certain operational costs
Encourage and promote innovation in water demand management
Prepare for potential impacts of climate change
1.1 Water Use Efficiency Goals for Treated Water Use
The City’s 2009 Water Conservation Plan1 established a goal of reducing the City’s treated water
use to 140 gallons per capita per day (gpcd)2 by the year 20203. The City will utilize water use
efficiency measures and programs with the aim of reducing its water use to an average of 140
gpcd, subject to 1) continuing study of the water requirements of the City’s urban landscaping, 2)
impacts on water demand due to changes in land use policies, building codes and housing trends,
3) additional studies on climate change, and 4) changes in the water use goal as may be adjusted
by any subsequent water conservation plans. This water use goal is subject to change as
discussed above and is intended as a goal that can be met while sustaining reasonable indoor and
outdoor values of the City.
The per capita peak daily demand4 will be reduced or maintained to be no more than 350 gpcd by
the year 2020, but may be adjusted by any subsequent water conservation plans.
1.2 Water Use Efficiency Program
Policy ENV 21.2 of Plan Fort Collins states, “Conservation measures should be implemented in
accordance with the Water Conservation Plan and periodically adjusted to reflect new and
effective conservation measures.” The City will optimize water use efficiency through the
programs and measures specified in its Water Conservation Plan. These programs and measures
include educational programs, incentive programs, regulatory measures and operational
1 State guidelines are changing the terminology of Water Conservation Plans to Water Use Efficiency Plans, and
likewise conservation is being changed to water use efficiency. For purposes of this policy, water use efficiency is
referred to as water conservation; however, the terminology may be used interchangeably.
2 Gallon per capita per day (gpcd) calculations are based on the total treated water produced at the Water Treatment
Facility for use by Water Utility customers (minus large contractual customers and other sales or exchange
arrangements) divided by the estimated population of the Water Utility’s service area.
3 This goal represents an 8.5% reduction in water use compared to Fort Collins’ 2006-2010 average daily water use
of 153 gpcd. It represents a 29% reduction in water use compared to Fort Collins’ pre-drought (1992-2001) average
daily water use of 197 gpcd.
4 The peak daily demand is 2.5 times the average daily use water conservation goal and is based on historic ratios of
average to peak daily use.
3
measures. Specific measures and programs are outlined in the Water Conservation Plan.
The overall effectiveness of these measures and programs will be evaluated on a regular basis
and if necessary, modifications will be made to increase effectiveness or to modify the City’s
water use goal. An annual water conservation report will be prepared to describe the status and
results of the various measures and programs. The Water Conservation Plan will be updated at a
minimum of every seven years, as currently required by the State of Colorado.
1.3 Water Rate Structures
The City will have stable water rate structures with transparent accountability for all classes of
customers. The water rate structures will provide an economic incentive to use water efficiently
while also providing sufficient revenue for operational and maintenance purposes. Examples of
structures that may be utilized include 1) tiered rates with increasing prices as water use
increases, 2) seasonal blocks with higher rates during the irrigation season, and 3) water budget
approaches based on appropriate targets for individual customers.
The City will annually review the effectiveness of its water rate structures as part of its financial
analyses regarding Water Utility revenue, expenses and rates. Specific studies or changes to the
rate structure may be made upon identification of the need to revise it. Any changes to the rate
structure will require City Council approval.
1.4 Population Growth
Population growth is an important factor in determining the City’s water supply needs, since
increases in population generally increase the need for additional supplies. Population growth
projections and associated water demand are mostly a function of land use planning,
development densities, annexation and other growth related issues that can be affected by City
Council decisions. The Water Utility will continue to work closely with the Current Planning
Department, which provides population projections that may be effected by changes in City
policies related to growth.
2.0 WATER SUPPLY RELIABILITY
The City needs to meet future water demands in an efficient and reliable manner. Policy ENV
21.2 of Plan Fort Collins states, “Water supply reliability criteria will take into consideration
potential effects of climate change and other vulnerabilities. Water supplies and related facilities
shall be acquired or developed after careful consideration of social, economic and environmental
factors.” One of the Water Utility’s primary objectives is to provide an adequate and reliable
supply of water to its customers and other water users. Key principles that need to be considered
when addressing water supply for municipal use include:
Providing water supply system reliability and flexibility
Considering a broad portfolio of resources that do not overly depend on any one source
Maintaining a water storage reserve for unforeseen circumstances
Maintaining water supply infrastructure and system security
Being a steward of the City’s water resources, which includes watershed management
Collaboration with the City’s regional water providers and users
4
Maintaining awareness of state, national and worldwide trends and adapting as needed to
meet our customer needs
Promoting education, awareness and a culture of innovation among the Water Utility and
others to enable creative responses to future water supply uncertainties
2.1 Water Supply Planning Criteria
An integral component of the City’s water supply planning efforts is to maintain computer
models that estimate the yield of its existing and future water supplies. The following water
supply planning criteria are key parameters used in these models that provide a foundation for
planning future supplies.
2.1.1 Planning Demand Level
The reliability of the City’s water supply should be maintained to meet an average per capita
demand level of 150 gpcd5,6. This planning level provides a value that is higher than the water
use goal to address uncertainties inherent in water supply planning.
It is important to have a planning number that can be used for development of long-range water
supply facilities. Because water supply system infrastructure may take many years to permit and
construct, it is desirable to use conservative assumptions to size facilities that may be needed for
the long-term. A planning demand level should be larger than the water use goal, primarily
because of the uncertainties related to projected water demands, yields from specific water
rights, climate change and other unanticipated effects.
2.1.2 Drought Criterion
The reliability and capacity of the City’s water supply system should be maintained to meet the
planning level demand during at least a l-in-50 year drought event in the Cache la Poudre River
Basin. Water rights should be acquired and facilities (including storage capacity) should be
planned and constructed sufficiently ahead of the time to maintain the 1-in-50 year drought
criterion, considering the time required to obtain water court decrees and permit and construct
diversion, conveyance and/or storage facilities. In using this criterion, the City seeks to provide a
balance among water supply reliability, the financial investment necessary to secure such
reliability and the environmental impacts associated with water storage and diversions.
2.1.3 Storage Reserve Factor
The City’s water supply planning criteria will include a storage reserve factor that equates to
20% of annual demand in storage through a 1-in-50 year drought7,8. This factor provides an
5 The 150 gpcd value is based upon the normalized 2006-2011 average daily use.
6 The average per capita demand planning level is used for facility planning purposes. Gallons per capita per day
(gpcd) calculations are based on the total treated water produced at the Water Treatment Facility for use by Water
Utility customers (minus large contractual customers and other sales or exchange arrangements) divided by the
estimated population of the Water Utility’s service area. This number is multiplied by population projections
developed by the City’s Planning Department to calculate future water demands.
7 For the Water Utility, 20% of annual demand is equivalent to around 3.7 months of average winter demand and
about 1.5 months of average July demand.
5
additional layer of protection intended to address dimensions of risk outside of the other
reliability criteria, including emergency situations (i.e. pipeline failure) and droughts that exceed
a 1-in-50 year drought.
2.2 Climate Change
Climate change could significantly impact the reliability of the City’s supplies and/or the amount
of water required to maintain existing landscapes9; however, there is a great deal of uncertainty
related to current climate change projections along the Colorado Front Range and its impact on
municipal demands and water supply systems. The City’s planning criteria and assumptions are
conservative in part to account for climate change based on the information to date. The City will
continue to monitor climate change information and, if necessary, will revise its water supply
planning criteria and assumptions to ensure future water supply reliability.
2.3 Water Supply Shortage Response Plan
The City will maintain a plan for responding to situations where there are projected water supply
shortages, either because of severe drought conditions (i.e., greater than a 1-in-50 year drought)
or because of disruptions in the raw water delivery system. When needed, the Water Supply
Shortage Response Plan will be activated based on the projected water supply shortage.
This plan will include measures to temporarily reduce water use through media campaigns,
regulations, restrictions, rate adjustments and other measures. The plan may also include
provisions to temporarily supplement the supply through interruptible water supply contracts,
leases, exchanges and operational measures. Reducing the City’s water use during supply short
situations may lessen adverse impacts to irrigated agriculture and flows in the Poudre River. The
plan will be reviewed periodically and, if necessary, updated to reflect changes in the City’s
water use and its water supply system.
2.4 Additional Supplies and Facilities
In order to meet projected growth within the Water Utility’s service area, as well as maintain
system reliability and operational flexibility, the City will need to increase the firm yield of its
current water supply system. The following policy elements address ways of meeting these
needs.
8 In meeting this factor, it is assumed that the City cannot rely on the existing Colorado-Big Thompson Project
(CBT) carryover program. This program currently allows each CBT unit holder to carry over up to 20% of its CBT
unit ownership in CBT reservoirs for use in the following year. However, this program has varied over the years and
there is no guarantee that it will be continued in the future.
9 Current research indicates that changes in precipitation in this area are uncertain but that temperatures will increase
and therefore it is likely that runoff will come earlier and in a shorter amount of time, precipitation may more often
come as rain, and higher temperatures will increase outdoor demands and change growing seasons for existing
landscapes.
6
2.4.1 Raw Water Requirements for New Development
The City shall require developers to turn over water rights as approved by the City, or cash in-
lieu-of water rights, such that supplies can be made available to meet or exceed the demands of
the Water Utility’s treated water customers during a l-in-50 year drought.
Cash collected shall be used to increase the firm yield and long-term reliability of the City’s
supply system. Potential uses of cash include acquiring additional water rights, entering into
water sharing arrangements with agricultural entities, purchasing or developing storage facilities
and pursuing other actions toward developing a reliable water supply system. Consideration will
be given to providing a diversified system that can withstand the annual variability inherent in
both water demands and supplies. The balance between water rights being turned over and cash
received by developers should be monitored and adjusted as needed to develop a reliable and
effective system.
2.4.2 Acquisition and/or Sharing of Agricultural Water Supplies
The City currently owns and will acquire additional water rights that are decreed only for
agricultural use. The City will periodically need to change these water rights from agricultural
use to municipal use to meet its water supply needs. The City will change those rights that come
from areas upon which the City is growing, or from areas where the irrigation has ceased, when
needed. For water rights that were derived from irrigated agricultural lands that remain in viable
agricultural areas, the City will refrain from converting agricultural decrees to municipal use as
long as other water supply options are available or other factors make it prudent to do so. The
City will also work towards water sharing arrangements that provide water for municipal uses
when critically needed and that allow for continued agricultural use of water at other times, in a
manner that preserves irrigated agricultural lands over the long-term.
2.4.3 Facilities
The City will pursue the acquisition or development of facilities that are needed to manage the
City’s water rights in an efficient and effective manner and enhance the City’s ability to meet
demands through at least a 1-in-50 year drought. These facilities may include storage capacity,
diversion structures, pipelines or other conveyances, pumping equipment, or other facilities that
increase the firm yield of the City’s supply system.
Additional storage will be acquired or constructed considering 1) the City’s return flow
obligations incurred from changes of water rights, 2) the City’s need to carryover water from wet
years to dry years in order to meet its drought criteria, 3) operational flexibility, redundancy and
reliability of the City’s water supply system, and 4) potential multiple-use benefits (i.e.,
environmental flows, recreational uses, etc.). The City will analyze the potential environmental
impacts of developing storage along with other associated costs and benefits, and will develop
that storage in a manner that avoids, minimizes or offsets the effects to the environment. Storage
capacity options include the enlargement of Halligan Reservoir, the development of local gravel
pits into storage ponds, the acquisition of storage capacity in new or existing reservoirs, the
development of aquifer storage, or some combination of the above.
7
3.0 TREATED AND RAW WATER QUALITY
Policy ENV 21.1 of Plan Fort Collins states, “Develop and adhere to drinking water quality
standards, treatment practices, and procedures that provide the highest level of health protection
that can be realistically achieved.” In addition, the City will take an active role in protecting the
quality of water in the various watersheds from which the City’s raw water is derived and
maintaining the taste and quality of the City’s treated water. This may include mixing of the
City’s source waters to maintain high water quality and require collaboration with private,
county, state and federal land owners and managers. The acquisition, development, and
management of the City’s raw and treated water will be consistent with the City’s Drinking
Water Quality Policy and other applicable policies related to watershed protection and water
treatment.
4.0 USE OF SURPLUS RAW WATER
The City will use its existing supplies to meet municipal obligations with the following priorities:
1) to meet water demands by the City’s treated water customers, and 2) to meet the City’s raw
water needs as well as other City raw water obligations. Raw water needs include use for such
purposes as irrigation of City parks, golf courses, cemeteries and other greenbelt areas.
Additional raw water obligations include primarily water transfers to other entities because of
agreements or exchanges made to manage the water supply system more effectively.
Water not needed for the above purposes is referred to as surplus water and may be made
available to others in accordance with decrees and other applicable policies. Since the City plans
its water supply system using a 1-in-50 year drought criterion, it typically has significant
quantities of surplus raw water in many years. This surplus water may be available on a year-to-
year basis or through multi-year arrangements that do not significantly impair the City’s ability
to meet municipal demands. The City will continue to rent its surplus supplies at a fair market
price that helps offset the cost of owning such supplies and benefits the Water Utility ratepayers.
4.1 Commitment to Other Beneficial Purposes
Acknowledging that the City’s use of its valuable water resources has impacts to the
environment and the region, the City will commit to using its surplus supplies for other
beneficial purposes such as supporting irrigated agriculture, supplementing flows in the Poudre
River or providing other regional benefits. The City’s surplus supplies come from a variety of
sources, each of which has unique characteristics. These sources include CBT water and shares
in several irrigation companies. Some sources are more suitable and available than others to meet
beneficial purposes. Whether the surplus raw water can be used for these other purposes is
dependent upon a number of factors, including the type of water, place of use and other decree
limitations. Any potential use of these supplies should consider, and will likely require
coordination with, other water users, state agencies and other groups. Some uses of the surplus
supplies, such as maintaining an instream flow according to the State’s Instream Flow Program,
may require a change of water rights through the water court process. The City will engage in a
thorough evaluation of these issues as part of assessing the use of its surplus supplies for these
beneficial purposes.
8
Utilities will evaluate implementing a program to allow voluntary contributions from its
ratepayers (i.e., Utility bill “check-off box”) for programs that are designed to support the
following purposes: preserving local agriculture, supplementing flows in the Poudre River, or
meeting other beneficial purposes that our community may desire.
4.1.1 Agriculture and Open Space
Policy SW 3.2 of Plan Fort Collins states, “Participate in and follow the Northern Colorado
Regional Food System Assessment project and other Larimer County agricultural efforts, and
implement their recommendations at a local level, if appropriate.” In addition, Policy LIV 44.1
of Plan Fort Collins states, “Maintain a system of publicly-owned open lands to protect the
integrity of wildlife habitat and conservation sites, protect corridors between natural areas,
conserve outstanding examples of Fort Collins' diverse natural heritage, and provide a broad
range of opportunities for educational, interpretive, and recreational programs to meet
community needs.” To the extent that surplus water is available, the City will continue to support
the local agricultural economy and help preserve the associated open spaces by renting surplus
agricultural water back to irrigators under the respective irrigation companies.
The City will explore long-term rental and sharing arrangements with irrigators10 in order to
support the regional food system, encourage agricultural open space and other benefits provided
by irrigated agriculture, as well as benefit the Water Utility ratepayers.
4.1.2 Instream Flows
Policy ENV 24.5 of Plan Fort Collins states, “Work to quantify and provide adequate instream
flows to maintain the ecological functionality, and recreational and scenic values of the Cache la
Poudre River through Fort Collins.” Recognizing that its water use depletes natural streamflows,
the City will seek innovative opportunities to improve, beyond any associated minimum
regulatory requirements, the ecological function of the streams and rivers affected by its
diversions. The Water Utility will take a leadership role in working with other City departments,
local and regional groups and agencies towards the following objectives in accordance with
Colorado water law and the administration of water rights in Colorado: 1) encourage flows in
local streams to protect the ecosystem, 2) pursue the operation of its water supplies and facilities
in a manner that avoids, minimizes or offsets the effects to the environment while meeting
customer demands, and 3) explore projects or measures that would provide flows in streams and
water in reservoirs for recreational and aesthetic purposes.
4.1.3 Other Arrangements
The City will consider and participate in other surplus water supply arrangements with other
entities that provide mutual benefits and support the region. These may include other rental
agreements, augmentation plans and other cooperative arrangements with regional partners.
These types of arrangements should be limited to unique opportunities that are mutually
10 The City’s largest irrigation company ownership interest is in the North Poudre Irrigation Company, which still
has substantial lands in irrigated agricultural production and has a unique mix of native water and CBT water that
lends itself to these types of partnership arrangements.
9
beneficial to the parties and provide significant social, economic or environmental benefits to the
region.
5.0 REGIONAL COOPERATION
The City recognizes the importance in maintaining good relationships with regional entities and
coordinating efforts to achieve mutual goals. The City also recognizes that growing Colorado
municipalities are currently struggling to define a way to meet future water supply needs in a
manner that minimizes negative impacts to agricultural economies and river ecosystems. The
Water Utility will endeavor to be a leader in demonstrating how water supply can be provided in
a manner that respects other interests and provides a culture of innovation.
5.1 Working with Other Municipal Providers
The City will continue to work with the water suppliers throughout the northern Colorado Front
Range to assure that adequate supplies are maintained in the region. When benefits are identified,
the City will cooperate with area entities in studying, building, sharing capacity and operating
water transmission lines, distribution systems and storage reservoirs for greater mutual benefit.
The City has common interests and the potential to cooperate with regional entities including the
water districts around Fort Collins, the City of Greeley and the Northern Colorado Water
Conservancy District, as well as other Colorado water providers. In particular, the City should
work closely with water districts that serve Fort Collins residents to encourage similar policies
regarding drought protection, conservation and to provide mutual assistance during emergencies.
5.2 Working with Local Irrigation Companies
The City will continue to cooperate with local irrigation companies regarding the use, exchange
and transfer of water in the Cache la Poudre River Basin. As a major shareholder in many of the
local irrigation companies, it is necessary and desirable that the City work closely with these
companies. Much of the water supply available to the City is through the ownership of shares in
local irrigation companies.
5.3 Working with Others
City Departments will work together and also cooperate with local, state and federal agencies,
civic organizations, environmental groups and other non-governmental organizations when
common goals would benefit City residents and the surrounding community. Examples of goals
that may involve City water supplies and be worthy of collaborative efforts include support for
existing and development of new local food sources, promoting open space, improving river
flows and supporting the local economy. Such efforts should identify appropriate entities and
sources of revenue for specific goals or projects.
1
Water Supply Vulnerability Study
Meagan Smith, Donnie Dustin, Carol Webb
March 24, 2020
ATTACHMENT 3
2
WHY ARE WE HERE TODAY?
Water Supply
Vulnerability
Study
Increasing
Uncertainties
Regional
Resource
City Council Update
This presentation is for informational purposes. Direction is not sought
on the Water Supply Vulnerability Study at this time.
However, any questions Council may have regarding the Study
are welcomed.
3
Strategic Alignment
4
ENV 4.6
Provide a reliable, high-quality
water supply
ENV 4.5
Develop strategies to improve
community climate resilience
Source: Resource Central
5
Water Supply &
Demand Management
Policy
Water
Efficiency
Plan Water Shortage
Action Plan
Water
Supply
Vulnerability
Study
Water Resources Division
6
MANAGE
raw water supplies
PROTECT & DEVELOP
water rights
PLAN
for future water supply needs
Current Long-Term Planning
7
Present Future
• Yield-based
• Single-future
• Future demand
• Single planning drought
• Emergency reserve
Cylinder of Certainty
8
Why
Change?
01
02
03
Changing Climate
Assess Other Vulnerabilities
Industry Best Practice
Future Direction of Long-Term Planning
9
• Risk-based planning
• Scenario planning
• Embrace uncertainty
Graphic source: Denver Water
New Tools and Data
10
Water Supply Forecasts
• Observed historical record
• Tree-ring data
• Climate change
Water Demand Forecasts
• Zoning and development density, weather,
economic conditions and historical use
• Two future development scenarios
Snowpack on Cameron Pass, 2011
11
Water
Board
City
Depts.
Identifying
Vulnerabilities
Northern
CSU Water
Water
Districts
Vulnerabilities and Scenarios
12
Climate and Hydrology
Operations and Infrastructure
Demands
Watershed and Environmental
Legal and Administrative
11 Vulnerability
Scenarios
Performance Metrics
• Reliability:
HOW OFTEN
conditions occur
• Resilience:
HOW LONG
conditions persist
• Vulnerability:
HOW SEVERE
conditions are
13
Chart source: Colorado Springs Utilities
Percent of Years on Restrictions
14
0% 100%
Current Planning
• Expected future demands
• Halligan expansion in place
0% 100% 0% 100%
No Halligan Expansion
• Expected future
demands
Colorado-Big Thompson
Long-Term Reduction
• Expected future demands
• Halligan expansion in place
+5 °F +5 °F +5 °F
10%
30%
99%
19%
36%
Some Key Findings – Most Impactful
Warmer / drier climate poses largest risk
to long-term planning
Adequate storage is crucial to meet current
policy criteria
Long-term reduction in Colorado-Big Thompson
supplies impacts ability to meet demands
15
Next Steps – Policy Update
16
22
44
Planning Futures
Explore Solutions
11 Needs/Impacts Identification
33 Service Levels
17
Next Steps – Policy Update
Iterative
Process
Solutions
Service Levels
Planning Futures
City Council Update
18
This presentation is for informational purposes. Direction is not sought
on the Water Supply Vulnerability Study at this time.
However, any questions Council may have regarding the Study
are welcomed.
19
Meagan Smith
mesmith@fcgov.com
970.221.6336
20
Temperature and Precipitation Offsets used to develop
climate impacted hydrology compared to range of
selected GCMs
-12% -8% -4% 0% 4% 8% 12% 16% 20% 24% 28% 32%
Precipitation Change
+10
+8
+6
+4
+2
0
Temperature Change (deg F)
• RCP4.5
• RCP8.5
• Climate Offsets
Reliability of Meeting Total Demands
21
100% 80%
Current Planning
• Expected future demands
• Halligan expansion in place
100% 80% 100% 80%
No Halligan Expansion
• Expected future
demands
CBT Long-Term Reduction
• Expected future demands
• Halligan expansion in place
+5°F +5°F +5°F
98%
91%
95%
93%
84%
85%
Percent of Years on Restrictions
22
0% 100%
Current Planning
• Expected future demands
• Halligan expansion in place
0% 100% 0% 100%
No Halligan Expansion
• Expected future
demands
CBT Long-Term Reduction
• Expected future demands
• Halligan expansion in place
+8°F +8°F +8°F
10%
46%
99%
19%
50%
Percent of Years on Restrictions
23
0% 100%
Current Planning
• Expected future demands
• Halligan expansion in place
0% 100% 0% 100%
No Halligan Expansion
• Expected future
demands
CBT Long-Term Reduction
• Expected future demands
• Halligan expansion in place
+5°F & 5%
reduction
+5°F & 5%
reduction
+5°F & 5%
reduction
10%
60%
99%
19%
63%
Reliability of Meeting Total Demands
24
• Climate impacts only
Deg F
• Climate impacts, Without Halligan
Deg F
With / Without Halligan
Deg F
• Climate impacts, Without Halligan
Reliability of Maintaining 20% SRF
25
• Climate impacts only
Deg F
With / Without Halligan
Restrictions – Percent of Years Simulated
26
• With Halligan, Higher Demands
Deg F
With / Without Halligan
• Without Halligan, Higher Demands
Deg F
Reliability of Meeting Total Demands
27
• Climate impacts only
Deg F
• Climate impacts, C-BT System Long-
Term Reduction
Deg F
C-BT System Long-Term Reduction
Deg F
Reliability of Maintaining 20% SRF
28
• Climate impacts only • Climate impacts, C-BT System Long-
term Reduction
Deg F
C-BT System Long-Term Reduction
Current Planning
Meet All Water Demands – 100% Reliability
• Expected future population X 150 gpcd
Through One Planning Drought
• 1-in-50 year drought
Storage Reserve Factor – 100% Reliability
• 20% of Annual Demand
Restrictions
29
Vulnerability Scenarios
• Increased Demands – Additional demand scenario, 20% increase
• No Halligan Expansion – No Halligan expansion
• Loss of Storage – No Halligan expansion, No C-BT Carryover
• Poudre River System Acute Outage – 12-month outage, all 3 pipelines
• Poudre River System Env Impacts – HT algal bloom, Poudre wildfire
• CBT System Acute Outage – Adams Tunnel outage
• CBT System Env Impacts – HT algal bloom, East Slope wildfire
• CBT System Long-Term Reduction – Compact call
• Horsetooth Reservoir Outage – HT outage for nine months
• Reuse Plan Change 1 – Elimination of Reuse Plan operation
• Reuse Plan Change 2 – 50% reduction in existing Reuse Plan operations
30
All Vulnerability Scenarios
31
Historical C-BT Quotas
32
Total Annual Quota
~30% of Quotas less than 70%
No Quotas less than 50%
-12% -8% -4% 0% 4% 8% 12% 16% 20% 24% 28% 32%
Precipitation Change
+10
+8
+6
+4
+2
0
Temperature Change (deg F)
• RCP4.5
• RCP8.5
• Climate Offsets
33
~30% of Quotas less than 70%
~10% of Quotas less than 50%
~40% of Quotas less than 70%
~15% of Quotas less than 50%
~60% of Quotas less than 70%
~30% of Quotas less than 50%
Climate Impacts – C-BT Quotas
Temp and Precip offset: 0 deg F, 0% P
Temp and Precip offset: +5 deg F, -5% P
Temp and Precip offset: +5 deg F, 0% P
34
Demand Forecasting
35
Percent of Years on Restrictions
36
0% 100%
Current Planning
• Expected future demands
• Halligan expansion in place
0% 100% 0% 100%
No Halligan Expansion
• Expected future
demands
Colorado-Big Thompson
Long-Term Reduction
• Expected future demands
• Halligan expansion in place
10%
99%
19%
Percent of Years on Restrictions
37
0% 100%
Current Planning
• Expected future demands
• Halligan expansion in place
0% 100% 0% 100%
No Halligan Expansion
• Expected future
demands
Colorado-Big Thompson
Long-Term Reduction
• Expected future demands
• Halligan expansion in place
+5 °F +5 °F +5 °F
10%
30%
99%
19%
36%