To: Board of County Commissioners
Through: Ceila Rethamel, Acting Director, Public Works and Development Department
Prepared By:
prepared
Loretta Daniel, Long Range Planning Program Manager, Public Works and Development
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presenter
Presenter: Loretta Daniel, Long Range Planning Program Manager, Public Works and Development
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Subject:
title
2:00 PM *Amendment to the 2018 Arapahoe County Comprehensive Plan to include Chapter V. Water Supply Element
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Purpose and Request:
recommended action
The purpose of the study session is to present a proposed update to the 2018 Arapahoe County Comprehensive Plan specifically incorporating a new water supply element as mandated by recent state law. The proposed amendment builds on recommendations from the 2024 Water Supply Study and if adopted, would meet statutory requirements for a Water Supply Element to the Comprehensive Plan. Staff is seeking Board comments on the proposed Water Supply Element chapter and support for proceeding with the proposed amendment.
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Alignment with Strategic Plan: Sustainable Growth and Infrastructure - Support environmentally responsible development and energy efficiency in county operations.
Background and Discussion: Senate Bill 24-174, Sustainable Affordable Housing Assistance (“the Act”), was passed by the legislature and became effective on May 30, 2024. The Act requires that, by December 31, 2026, local governments include a water supply element in their comprehensive plans, with mandatory updates every five years thereafter. The Colorado Department of Local Affairs (DOLA) oversees, guides, and enforces local government compliance regarding the new water supply element by providing technical assistance and reviewing jurisdictions’ water supply elements for statutory compliance.
The intent underlying the Act is to “encourage smarter land use, prevent sprawl, and ensure alignment between development and available water resources.” The state affords local jurisdictions flexibility in implementation, allowing the water supply element to be integrated throughout existing chapters or formatted as a separate chapter. Since the County accepted the Arapahoe County Water Supply Study in 2024, staff found it most effective to merge all current water references in the Comprehensive Plan and recommendations from the Water Supply Study into a single new chapter: Chapter V. Water Supply Element. The Board accepted the Arapahoe County Water Supply Study on November 12, 2024, and the Board included direction that Planning Commission and staff prepare a Water Supply Element to the Comprehensive Plan and that “…the Water Study be taken into consideration in amendment of the Comprehensive Plan as consistent with the requirements of state statute.” The proposed Water Supply Element amendment to the Comprehensive Plan both follows that Board direction and fulfils the statutory requirements of Sente Bill 24-174.
Arapahoe County Water Supply Study (2024) To better understand the content of the proposed Chapter V, Water Supply Element of the Comprehensive Plan, the following synopsis of the Water Supply Study highlights the planning process and key findings.
The Study was an update of a previous water resources study completed in 2001 prior to the adoption of the 2001 Arapahoe County Comprehensive Plan. That study recommended that the County limit Denver Basin groundwater development to 50 percent of that allowed by the state. The state manages Denver Basin groundwater under a statutory framework from the Colorado Groundwater Management Act known as the 100-Year Rule, or One Percent Rule. Under that rule, the total volume of groundwater stored beneath a property is allocated to be withdrawn at a rate of no more than one percent per year over a 100-year lifetime. The 2018 revised Comprehensive Plan adopted by the Planning Commission recommended basing groundwater supply analyses on a more stringent consumption policy, limiting annual withdrawals to one-third the volume allowed by state statutes, equivalent to a 300-year rule rather than the state’s 100-year rule. Without technical analysis and modeling of water demands and groundwater supply, it would be difficult to determine whether the 300-year rule would effectively safeguard long-term water supply.
The County initiated the Arapahoe County Water Supply Study to provide that technical analysis and to update the water resource goals established in its 2001 and 2018 Comprehensive Plans. The primary objective was to align long-range land-use decisions with sustainable water management, focusing on three core goals: closing future supply-demand gaps, increasing water efficiency, and extending the operational life of the non-renewable Denver Basin aquifer system.
A consultant team with Forsgren Associates, Inc., LRE Water, and Michael Baker International was selected to lead the project, with guidance from two advisory committees comprised of water districts and municipal planning staff. The county was divided into three geographic regions, with Region 1 as the western, urbanized area of the county (with major water providers such as Denver Water and Aurora Water), Region 2 as the central existing rural and agricultural area, but with the greatest potential for development (area reliant on groundwater and with some water districts), and Region 3 as the agricultural and ranching area east of I-70 (with reduced access to groundwater and no water districts).
The Study was developed through an extensive inter-agency and public outreach approach with the following:
Ÿ Advisory Committees: Water provider representatives and planners from the cities and towns in the county met regularly to align growth assumptions and resultant water demand and supply, regulatory processes, and utility capacities.
Ÿ Public Feedback: Over 500 participants provided input through surveys and three community open houses, submitting more than 400 comments. The open houses were also used to refine the draft policy recommendations.
Ÿ Interactive Map: The consultant team built a public online GIS map so residents and planners can easily view aquifer, well permits, and other water data.
To assess water demand to 2050, the County evaluated two growth scenarios from the Colorado Water Plan: a conservative “Business as Usual” scenario (standard, or Low Growth) and a more vibrant “Hot Growth” scenario (rapid population and economic growth, or High Growth). These population and employment numbers were translated to water demand in 2050, with both a No Conservation and a Conservation scenario. The results are summarized below:
*AFY = Acre-Feet per Year (one acre-foot is about 326,000 gallons).
The next step in the Study was to estimate how much Denver Basin groundwater is physically available. A groundwater model (PetraTM) was utilized to analyze extensive well data to define water levels, well yields, aquifer properties and saturated thicknesses within the Denver Basin aquifers. The state uses a 100-Year rule (SB-5 Model) and this was compared to the Study’s model of physically available water volumes for a representative study area in the middle of the county. The result identified a significant gap between the state’s rule and what the model presented as physically available. The table below summarizes the findings for the aquifers:
The Study recommended utilizing the Production Factors rather than the state’s 100-Year rule, or any other rule, such as a 200-year or 300-year rule that some other counties are using. This is a key recommendation of the Study and is carried over to the Water Supply Element in the Comprehensive Plan.
To summarize the important findings from the Study, the key takeaways are:
Ÿ The deep Denver Basin aquifer system holds a potential water supply of over 51,800 acre-feet per year. However, 65 percent of that water is in the deepest layer (the Laramie-Fox Hills aquifer), which is more expensive to drill and pump.
Ÿ The state's standard formula for groundwater overestimates how much water can actually be pumped over time. Advanced computer modeling shows that real-world available groundwater is only about 60 percent of what state rules assume. It is recommended that the County use these realistic numbers to review new development proposals.
Ÿ Total countywide water supply will be sufficient to meet 2050 demand under both growth scenarios.
Ÿ It is expected that water conservation will play a large role in reducing future demand, reducing overall water needs by at least 12 percent. Lawn watering accounts for over a third of potential water savings.
The study outlined two sets of policy recommendations: actions the County will lead directly, including updating code regulations for new development approvals, and joint efforts led by local water providers and special districts with County support.
As part of the Water Supply Study planning process, presentations were made to the Planning Commission at study sessions on November 14, 2023, and September 17, 2024, and to the Board of County Commissioners at study sessions on October 31, 2022, October 31, 2023, and September 24, 2024. The Board accepted the Study on November 12, 2024, and included direction to Planning Commission and staff to use the Water Supply Study to develop an amendment to the Comprehensive Plan that would incorporate a Water Supply Element and be consistent with state statute.
The Water Supply Element: Proposed Chapter V in the Comprehensive Plan
The proposed Chapter V consolidates existing water policies distributed through different sections of the Comprehensive Plan. These existing policies have been updated, combined with findings and recommendations from the Water Supply Study, or deleted if implemented or no longer considered to be relevant.
The Water Supply Element is organized into seven sections, which are outlined below.
1. Introduction and Statutory Compliance
This section introduces the statutory requirements of SB24-174 for the Water Supply Element with the four required components that were described previously in the Background section. The County intends to meet the “High-Tech Pathway” approach developed by the DOLA due to the advanced modeling and GIS integration used for the Study.
An overview of the public engagement activities is also described since outreach and engagement is an important process not only in all County planning activities, but is also a required action identified in SB24-174.
2. Current Water Landscape
This section describes the elements in the Water Supply Study that describe the hydrogeologic conditions in the county, including defining the three regions that were used to analyze existing populations and water demand and supplies. An overview of surface water and groundwater sources and supplies is provided along with an introduction to the four aquifers that comprise the Denver Basin aquifer system. These are the Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers.
3. Growth Scenarios and Projected Water Demand
This section presents two scenarios forecasting population growth to 2050 to provide a population range to assess water demand. To align with the Colorado Water Plan’s 2050 planning horizon, the Water Supply Study evaluated two demographic scenarios to account for future growth uncertainty:
Ÿ Low Growth (Business as Usual): Assumes steady economic growth and historical demographic trends, projecting 900,000 residents and 532,000 jobs by 2050.
Ÿ High Growth (Hot Growth): Assumes accelerated economic expansion and regional in-migration, projecting 960,000 residents and 595,000 jobs by 2050.
With this information, population growth was allocated for each of the water providers along with total water demand under the Low and High Growth scenarios, with both no conservation and assumed conservation practices in place. These numbers were then compared to the available water supply.
This is followed by an explanation summarizing the state’s 100-year rule and the results from the PetraTM modeling. The result is the identification of Production Factors, which is a key recommendation of the Study and of this Water Supply Element, and is described in the previous section describing the Water Supply Study.
4. Goals, Policies, and Strategies
The format for the goals, policies, and strategies section follows the priority hierarchy used in the Comprehensive Plan, and the first sub-section is Water Supply Management and Groundwater Protection. Since this unit has important policies that integrate land use planning with water resource planning, particularly in the development review process, it is placed at the beginning of the Goals, Policies, and Strategies section. Because these policy sections are quite extensive, the following description highlights only the goal statements and briefly describes the overall intent of the policies.
This section includes three goals, seven policies, and 18 strategies. The Goals are:
Ÿ Goal WSM-1 - Ensure Groundwater Sustainability for Existing and Future Development
Ÿ Goal WSM-2 - Ensure Early Water Evaluation in the Development Review Process
Ÿ Goal WSM-3 - Support Regional Infrastructure Integration and Demand Reduction.
The key strategy in this section is the recommendation to adopt the Production Factors in County regulations. In summary, this section establishes policies to protect the Denver Basin aquifers, recommends mandating the Production Factors for development review, requires verification of water availability before development approval, and promotes consolidated utility infrastructure.
5. Water Conservation and Efficiency
Water conservation, often referred to as water management, has become increasingly important to the County, particularly in times of ongoing drought. This section reflects the importance of this topic in the Water Supply Study as well as in the Colorado Water Plan.
This section includes five goals, eight policies, and 21 strategies. The Goals are:
Ÿ Goal WCE-1 - Promote a Water-Efficient Built Environment through Land Use and Design
Ÿ Goal WCE-2 - Promote Water-Wise Landscaping and Public Stewardship
Ÿ Goal WCE-3 - Encourage Water Reuse and System Resiliency
Ÿ Goal WCE-4 - Promote Infrastructure and Utility Best Practices
Ÿ Goal WCE-5 - Collaborative Outreach and Inter-Jurisdictional Alignment.
Overall, this section aligns countywide land-use authority with local utility operations to reduce per-capita demand and build climate resilience by promoting water-efficient site design, landscaping standards, expanding water reuse, and promoting interjurisdictional partnerships.
6. Water Collaborative Policies and Actions
Since water supply policy is often collaborative and requires coordination across various governments and agencies, this section establishes strategies for inter-agency discussions and cooperation.
This section includes 3 goals, 3 policies, and 8 strategies. The Goals are:
Ÿ Goal WCP-1 - Support Watershed Protection and Public Drinking Water Quality
Ÿ Goal WCP-2 - Support Storage Capacity and Infrastructure Reliability
Ÿ Goal WCP-3 - Continue Water Provider and Municipal Planning Partnership.
This section emphasizes the importance of inter-agency partnerships to address water supply and other challenges that go beyond jurisdictional boundaries. To summarize all the strategies, this section encourages establishing formal arrangements, such as forums, Memoranda of Understanding (MOUs), and sharing of information to achieve common goals of protecting drinking water sources, streamlining permitting for major facilities such as reservoirs, and supporting renewable water projects such as the Water, Infrastructure and Supply Efficiency (WISE) project.
7. Water Supply Element Implementation
This concluding section identifies the three key aspects of the ongoing work of water planning in Arapahoe County: integration with the Colorado Water Plan, cooperation with the water providers in the county, and regular review and updating of the Water Supply Element every five years.
Adding Chapter V: Water Supply Element allows the County to integrate key findings from the 2024 Water Supply Study directly into our long-range planning vision and satisfy recent state statutory requirements.
Alternatives: The BOCC could propose alternatives or additional ideas for the goals, policies, or strategies.
Fiscal Impact: There is no fiscal impact at this time.
Alignment with Strategic Implementation Strategies: The attached framework helps Arapahoe County institutionalize values-based, transparent decision-making, documenting how we make decisions and carry out actions to achieve the county’s strategic plan.
Staff Recommendation: Staff recommendation is to incorporate the draft Chapter V. Water Supply Element into the Comprehensive Plan and solicitate BOCC’s comments on the draft. Next step is to go to public hearing for formal adoption, which is tentatively scheduled for Planning Commission on October 20, 2026, and the BOCC on November 24, 2026.
Concurrence: N/A