Crews work on excavating Antero Dam this past October as part of the rehabilitation project that began in 2013.
Draining Antero Reservoir: Where will all that water go?
And 9 more facts about rehabbing Denver Water’s 100-year-old Antero Dam
This summer, Denver Water will empty Antero Reservoir to clear the way for significant repairs to the 100-year-old dam. Draining Antero is a major undertaking; the reservoir holds about 20,000 acre-feet of water, enough to supply approximately 50,000 households for one year in the Denver metro area. And such a project is bound to raise questions about the dam, the water supply and the impact on recreational fishing. Here are the answers to questions we thought Coloradans might ask:
1. So what’s wrong with the dam?
Antero Dam is fully operational, but it’s old. The dam has been in service for 100 years, and this rehab project will help ensure that it can operate for another 100 years. That means bringing the dam more in line with current standards of engineering and safety. It’s a big job, but a necessary one, at a cost of $17 to $20 million over several years.
2. How long will the reservoir be empty?
That depends. While the entire dam rehab project is tentatively scheduled to be completed in 2018, we expect to complete the phase that requires the reservoir to be drained by the end of 2015. Barring any weather or construction delays, refilling could begin as soon as spring of 2016. Generally, it takes from one to four years to refill the reservoir, depending on the amount of snowfall and timing of snowmelt. While it may be sooner, the safe bet is that the reservoir will return to its normal operation by late 2018, when construction ends.
3. When you drain the reservoir, where does all the water go?
We will recapture and store the water drained from Antero reservoir in several reservoirs along the South Platte River system, such as Cheesman, Marston and Chatfield.
4. Will draining the reservoir cause flooding or other safety concerns?
Denver Water has opted to draw down the reservoir in a planned and managed way before construction to minimize, if not completely eliminate, any flooding or safety concerns. It will take approximately two months to empty the reservoir. We believe this to be a much safer course of action than allowing water to remain in the reservoir and risking the need for an emergency unplanned release during construction.
Recreationists fish off of a boat at Antero Reservoir in 2009. There are many other similarly accessible and productive fishing locations in Park County for anglers, water enthusiasts and other outdoor lovers to enjoy for the duration of the project.
5. Have you drained the reservoir before?
Antero Reservoir was drained in the late 1990s to complete some repairs to the outlet works of the dam. It also was drained during the 2002 drought. Due to its shallow depth, Antero Reservoir has the highest evaporation rate of any of Denver Water’s reservoirs. In times of low water supply, moving the water to other reservoirs in Denver Water’s system reduces evaporation losses and makes the water available to customers.
6. What if we go into drought while the reservoir is empty?
We’re not losing the water from the Antero Reservoir. It will be stored in other reservoirs, where it can still serve as a reserve water supply.
7. If we have enough water in our system to drain a reservoir, why do you stress the need to conserve every year?
We plan to store the water drained from Antero Reservoir in other reservoirs throughout our collection system. Antero Reservoir is a reserve water supply that Denver Water maintains for use when our water supplies run low. Regardless of conditions, it is important that we all use water efficiently.
8. Will we still be able to use the park during construction?
Once we begin to drain the reservoir, the park will be closed to the public for the duration of the project. The park will re-open for recreation once the reservoir has been refilled and recreational opportunities, like fishing, bird-watching and camping, have been restored.
9. Will fishing be better after the project?
While there are no guarantees, we expect the rehabilitation project to provide a long-term benefit to the fishery by allowing us to return the reservoir to a depth of 18 feet (except during drought periods). The reservoir has been operating at a reduced capacity since May 2011, when we lowered the reservoir by 2 feet to investigate the condition of the dam.
10. What effect will this have on fishing at Antero and in other reservoirs in Park County?
Colorado Parks and Wildlife will be increasing the bag and possession limit to eight fish, with no size restrictions, effective Saturday, Jan. 10. Additional information about the bag limit can be found here. Questions regarding fishing at Antero can be directed to Colorado Parks and Wildlife at 303-291-7227.
Once Antero Reservoir closes this summer, there will remain many other similarly accessible and productive fishing locations in Park County for anglers, water enthusiasts and other outdoor lovers to enjoy. We encourage everyone to take advantage of those areas while Antero Reservoir is unavailable. Additionally, fish from Antero Reservoir will be relocated within the county, which may even improve fishing at some of these other locations.