A Colorado water court has granted junior water rights for a pipeline and reservoir project that will eventually carry new water from northeastern Colorado to Castle Rock and Parker.
What the water court approved
In October 2026, the water court granted junior water rights decrees for the Platte Valley Water Partnership, a project between Parker Water & Sanitation District, the Lower South Platte Water Conservancy District and Castle Rock Water. The decrees came after the three partners settled with other South Platte River water users and the State of Colorado, per a joint announcement from Parker Water on October 8.
It's the first major legal milestone for the partnership since it formally launched in 2021. Castle Rock Water signed on as a participant in October 2024, according to Parker Water.
"This adjudication moves an important regional partnership forward," said Mark Marlowe, director of Castle Rock Water, in the joint announcement. "Working with agricultural partners and neighboring providers helps us diversify Castle Rock's water portfolio, invest in renewable supplies and build long-term resilience for our community while supporting the agricultural economy that is a vital part of Colorado's future."
What Castle Rock gets
Per Parker Water's own project page, the plan calls for a 125-mile pipeline, plus a new reservoir and diversion structures built in northeastern Colorado, to capture South Platte River water, mostly spring runoff and storm flows that currently leave the state unused, and move some of it south to the Denver metro area.
Parker Water's share would be 22,000 acre-feet of that water a year. Castle Rock Water's share is 3,000 acre-feet a year, per Parker Water. An acre-foot is roughly enough water to supply one to two households for a year.
What we couldn't confirm at the source
The Colorado Sun (Fresh Water News) reported the full project at $1.1 billion, with Parker Water paying 52% of the cost, the Lower South Platte district 27% and Castle Rock 20%, citing Parker Water General Manager Ron Redd, and reported a 2040 target for delivering water to cities. Parker Water's own project page currently puts the estimate lower, at approximately $780 million for the entire project, with $560 million "built into PWSD's long-term planning and rate structure" to cover the first phase. It doesn't list a city-delivery date. We could not independently confirm the $1.1 billion figure, the cost-share percentages or the 2040 timeline at a primary source, so treat those as the Colorado Sun's reporting, not confirmed numbers.
What's next
With the water rights decreed, the partnership moves on to engineering, permitting and property acquisition. Castle Rock's own Proposed 2027 Budget lists the Platte Valley Water Partnership among the projects it's funding to "secure our water future," alongside the Chatfield Reallocation project and an expansion of the Plum Creek Water Purification Facility.
Sources: Parker Water & Sanitation District, "Platte Valley Water Partnership Granted Junior Water Rights Decrees," Oct. 8, 2026, and its Platte Valley Water Partnership project page; Lower South Platte Water Conservancy District, Platte Valley Water Partnership; Town of Castle Rock, Proposed 2027 Budget Message, Sept. 15, 2026; The Colorado Sun / Fresh Water News, "Pipeline to share water between Parker, Castle Rock and northeastern Colorado farms OK'd in water court," Oct. 30, 2026.