From the Denver Water Gross Reservoir Recreation Management Plan:
When full to the spillway crest, Gross Reservoir stores 40,990 acre-feet of water. The surface
area of the reservoir covers 418 acres, creating 10.9 miles of shoreline. The water reaches a depth
of 280 feet near the dam.
The depth of the reservoir results in cool water temperatures throughout the year. Summer water
temperatures only reach 18 degrees Celsius (64 F) on the surface. Temperatures cool 2 degrees C
(3.6 F) per foot below the surface, down to 6 feet. Below 6 feet, water temperatures are generally
in the 6 (42 F) to 8 (46 F) degree C range. According to the U.S. Coast Guard, survival times for
victims in water of this temperatures range from 1 to 3 hours depending upon environmental
factors and the person?s physical condition.
Studies by the Colorado Department of Wildlife show that rainbow trout is the predominant fish
species found in Gross Reservoir. Other less populous species include lake trout, tiger muskie,
longnose sucker, and white sucker. CDOW stocks the reservoir with rainbow trout to maintain
the population, because there is minimal natural reproduction. The white sucker and longnose
sucker populations are not maintained by stocking but reproduce naturally in the reservoir.
Assessment of rainbow trout habitat potential for Gross Reservoir rated low to medium,
supporting about 15 rainbow trout per acre. Low trout productivity is due to water depth, cool
reservoir temperatures, and fluctuating reservoir water levels (Gross Reservoir EA 1998).