Arapahoe County weighs earlier water reviews as transit-area growth plans advance
A proposed Water Supply Element would require earlier documentation of supplies, provider connections and aquifer-specific limits for future development, but it has not been adopted.
Arapahoe County is considering requiring developers to document water supplies earlier in the development-review process as the county weighs transit-area zoning changes that could accommodate tens of thousands of additional homes.
The proposed Water Supply Element would add a chapter to the county’s 2018 Comprehensive Plan. The Planning Commission agenda lists the measure, Case LR26-002, as a study-session item for Sept. 15, not as an action item. The element and the transit-area maps remain proposals rather than adopted policy or zoning.
The draft responds to Colorado Senate Bill 24-174, which requires counties to adopt water-supply elements by Dec. 31, 2026. The county staff report and draft element project that Arapahoe County’s population could reach 900,000 to 960,000 by 2050. Annual water demand could range from 115,996 to 124,769 acre-feet without conservation, or from 101,490 to 108,497 acre-feet with modeled conservation measures.
The draft estimates countywide developed water supplies of 195,039 acre-feet per year by 2050, but says individual providers, projects and water sources would still need review. The county’s 2024 Water Supply Study identified projected gaps for some providers and specific supply issues for future development.
Under the proposed policies, applicants for rezonings, planned-unit developments, subdivisions and special-use permits would provide water-supply information earlier in the review process. The draft favors connections to existing public water providers and renewable supplies, calls for standardized documentation of adequate supplies, and encourages conservation, water reuse and efficient landscaping and building standards. It also proposes limits on isolated rural systems and new rural water districts in some circumstances.
The staff report projects shortfalls for Englewood and Inverness Water and Sanitation District under some 2050 demand scenarios. It says Englewood’s efficiency and demand-management measures are expected to address its projected gap. For Inverness, the report identifies expanded Denver Water allocations, direct agreements and regional arrangements as possible options.
The draft would also change how groundwater-dependent applications are evaluated. It proposes aquifer-specific production factors based on three-dimensional modeling rather than relying only on the state’s 100-year groundwater allocation formula. The proposed factors are 0.60 for the Denver aquifer, 0.42 for the Upper Arapahoe, 0.27 for the Lower Arapahoe and 0.71 for the Laramie-Fox Hills aquifer.
Those factors would reduce the groundwater counted as physically available in some development analyses. The draft describes Denver Basin aquifers as largely nonrenewable, with limited natural recharge, and says the Laramie-Fox Hills aquifer contains most of the basin’s potential supply but is more costly to develop.
The report also says only the first phase of Prosper Farms, involving 900 homes and about 180 acre-feet of annual demand, has been approved. Later phases would need to document additional renewable supplies and reuse before proceeding, according to the county.
The water proposal is proceeding alongside proposed transit-area rezoning. County staff previously estimated that maps covering Federal Enclave, Dry Creek/Inverness, Four Square Mile and Belleview could accommodate about 36,765 homes, compared with a county-reported goal of roughly 19,000. The estimates remain preliminary, and future projects would still face site-plan, traffic, drainage, water and sanitation review.
The county is seeking comments on the draft by Oct. 1. A Planning Commission public hearing is scheduled for Oct. 20, followed by a Board of County Commissioners hearing scheduled for Nov. 24. If adopted, the draft would be reviewed every five years, with the first full update planned before the end of 2031.