The Town of Castle Rock has signed as a partner in the Platte Valley Water Partnership.

Since 2021, the partnership has been a collaboration between the Lower South Platte Water Conservancy District and the Parker Water & Sanitation District to store South Platte River water.

Castle Rock’s town council voted 6-0 to join the partnership; the Parker district voted 5-0 to the agreement.

Castle Rock’s participation adds economies of scale to the project by sharing overall costs for storage and conveyance, while contributing approximately 3,000 acre-feet of renewable water annually to the Town of Castle Rock, according to a joint statement from Parker and Castle Rock on Thursday.

“We are thrilled to have the trust and support of Castle Rock’s leadership,” said Ron Redd, Parker Water’s district manager. “This partnership between two of the largest water providers in Douglas County is a powerful statement about our commitment to regional collaboration and long-term water sustainability.”

Redd told Colorado Politics the unanimous votes show a lot of support and confidence in the project. 

The partnership, at an estimated cost of $780 million, will boost storage infrastructure along the South Platte in northeastern Colorado.

That includes small storage reservoir, at about 6,500 acre-feet of water, near Iliff; a larger reservoir of up to 72,000 acre-feet near Akron, and a 125-mile pipeline that will transport water to Douglas County’s Rueter-Hess Reservoir. 

While Castle Rock is signing onto the agreement, the town will not use any water allocated either to the Lower South Platte or Parker districts. The town has its own junior water rights on the South Platte.

The statement explained the the project “will benefit the farms and communities in LSPWCD’s service area, as well as PWSD and Castle Rock, by helping them meet long-term water needs without relying on unsustainable buy and dry water practices. The project requires that no new ‘buy and dry’ water may be stored or transported through its infrastructure.”

“This is a win-win for both Castle Rock and the broader region,” said Mark Marlowe, director of Castle Rock Water. “By working together, we’re ensuring that our growing communities have the water they need while protecting agricultural resources across Colorado.”

Parker Water owns 9,000 acre feet of junior water rights near where the Platte Valley project is envisioned. That water has already been adjudicated by the state water court for municipal use, plus another 4,000 acre feet in senior water rights currently used for irrigation. The latter awaits a water court date.