There already are six projects being pursued in the South Platte Basin to extend the water supply. These are not included in the recent South Platte Storage Survey, but have been considered and under way for some time:
Northern Integrated Supply Project (NISP) map July 27, 2016 via Northern Water.
• The NISP/Glade project — The Northern Integrated Supply Project is a proposed water storage and distribution project that will supply 15 Northern Front Range water partners with 40,000 acre-feet of new, reliable water supplies.
Map from Northern Water via the Fort Collins Coloradan.
• Chimney Hollow Reservoir — A 360-foot high dam that will hold 90,000 acre feet to help supply the thirsty Thompson Valley urban area. The water will come from the Windy Gap Project, a diversion dam and pumping station completed in 1985 to provide extra irrigation and municipal water out of the Colorado River. The water originally was stored in Grand Lake, but when that is full, the water cannot be stored. Chimney Hollow, also known as the Windy Gap Firming Project, solves that problem.
Reservoirs NW of Fort Collins
• Halligan reservoir enlargements — Halligan Reservoir near Fort Collins is about 100 years old. Its capacity is about 6,400 acre feet of water and the City of Fort Collins wants to add 8,125 acre feet to the reservoir by raising its dam about 25 feet.
• Milton Seaman Reservoir enlargement — Greeley originally had wanted to expand Seaman Reservoir in conjunction with Halligan, but because of diverging goals Greeley withdrew from the joint project. The expansion of Seamon now is targeted for design in 2028 and construction by 2030.
Gross Dam enlargement concept graphic via Denver Water
• Gross Reservoir enlargement — Gross Reservoir is one of 11 reservoirs supplying water to the City of Denver and surrounding urban areas. It is on the city’s Moffat System, which diverts water from the Western Slope to the metro area. Denver Water has proposed raising the dam height by 131 feet, which will allow the capacity of the reservoir to increase by 77,000 acre feet.
Proposed reallocation pool — Graphic/USACE
• Chatfield Reallocation Plan — The U.S. Army Corps of Engineers has determined that Chatfield Reservoir, built primarily for flood control after the 1965 South Platte River flood, can accommodate an additional 20,600 acre feet of water storage for water supply without compromising its flood control function. This additional storage space will be used by municipal and agricultural water providers to help meet the diverse needs of the state. No actual construction is required, but the legal, environmental, and engineering concerns of allowing the reservoir to hold more water all have to be satisfied.
