Rueter–Hess Reservoir

Other locations had been considered for the reservoir and dam prior to a final determination. By December, 1991 after further water studies, PWSD determined, "...that the Castlewood Canyon site [south of Parker] was the most favorable location for upstream water storage and, therefore, the two additional sites were dropped from the Water Court application. Therefore, PWSD continued with plans for building the dam and 600-acre (2.4 km²) reservoir at Castlewood Canyon State Park (Ciruli and Associates, 1999)." The reservoir "would flood much of the state park and the cattle operations on historic ranches nearby (McKibben, 1991)."

In early 1993, PWSD and the town of Parker became involved as plaintiffs in a civil court action to appropriate the state land comprising the Castlewood Canyon State Park needed for the dam and reservoir. The town and PWSD had petitioned to condemn certain property owned by the state in order to determine the feasibility of recreation and a water storage project on the state park land. The District Court of Douglas County had found for the state dismissing the petition from PWSD on the grounds that the town and district did not have authority to condemn state-owned lands. The town and PWSD appealed. On March 11, 1993, the Colorado Court of Appeals issued a decision in Town of Parker & Parker Water and Sanitation District v. The Colorado Division of Parks and Outdoor Recreation. No. 92CA0494. The appellate court also found for the state.

The town of Parker and PWSD decided they would continue with their legal options to the Colorado Supreme Court. Consequently, in June, 1993, PWSD filed a motion in Division 1 Water Court to add two alternate sites for the dam and reservoir in the event that any further civil actions remained unsuccessful in the attempt to condemn state land for the state park site. One alternate site was located on a tributary of Cherry Creek just upstream of Castlewood Canyon State Park; the other, to be located in Newlin Gulch southwest of Parker. This second alternate site was to eventually become the site of the Rueter–Hess dam and reservoir.

On November 1, 1993, the Supreme Court of Colorado upheld the decision of the district and appellate courts in Town of Parker & Parker Water and Sanitation District v. The Colorado Division of Parks and Outdoor Recreation. No. 93SC301. The high court had once again found for the state.

The Newlin Gulch site was the home of several long time ranchers, including the Rueter and Hess families. The Parker Water & Sanitation District needed to purchase Ms. Rosie (Rueter) Hess's property. One of her conditions of sale was the naming of the reservoir after both her married and maiden names.[7]

Ground was broken for a 17,000 acre feet project 2004. The entire project was planned to be completed in late 2007 at a cost of over $120 million. When initial construction was nearly complete, other water districts joined the project and funded expansion to 72,000 acre feet (75,000 as built). Final completion was in 2012 at a total cost of around $170 million not including land, capitalized interest and other per-construction costs.

A moist 2013, 2014 and first half 2015 in Colorado resulted in a free stream much of the time since then. Free stream conditions combined with return flows resulted in routine 25 to 30 acre feet of water a day being pumped to the reservoir by the three megawatt pumping station at Cherry Creek.

As of July 2017, the reservoir was about 38% full, containing over 27,600 acre feet of water, more than three times the current annual demand of PWSD. Considering that PWSD operates a Reuse paradigm, in reality this represents enough water for the district for nearly 6 years.