Rueter-Hess Reservoir, Protected water reservoir in Douglas County, Colorado.

Rueter-Hess Reservoir is a water storage facility behind Frank Jaeger Dam in Newlin Gulch, southwest of Parker and east of Castle Pines North in Douglas County, Colorado. The reservoir, expanded to 75,000 acre-feet, is visible looking east from I-25 south of the Castle Pines Parkway/Hess Road exit.

The Parker Water and Sanitation District secured a Cherry Creek water right on March 20, 1985, and later chose Newlin Gulch after courts blocked a Castlewood Canyon site. Ground was broken in 2004 for a 17,000 acre-foot project; other districts joined and funded expansion to 75,000 acre-feet as built. Final completion came in 2012 at about $170 million.

The reservoir is named for Rosie (Rueter) Hess, who sold her Newlin Gulch ranch land on the condition that both her married and maiden names be used. The Rueter and Hess families were among the long-time ranchers in the gulch before the dam was built.

Reservations are required to take part in activities like fishing with artificial lures, paddling, or hiking, which run from April through October. Planning ahead is a good idea, as available spots can fill up quickly.

The reservoir actively protects the Denver Basin aquifer system through its daily operations, going well beyond simple water storage. This function is invisible to visitors on the trails, but it is a key reason why access is carefully managed.