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Denver Water’s reservoir system tops out at 92% after the spring runoff

After below-average snowpack, wise water use needed to help maintain water storage levels.

Denver Water’s reservoir system hit its peak storage level for the year on July 10, reaching 92% in the reservoirs critical for storing water for 1.5 million people in the Denver metro area. 

The storage level fell short of reaching 100%, due in part to last winter’s below-normal snowpack.

“We always hope to reach 100% storage capacity during the spring runoff, as that’s the water we rely on for the next 12 months and we also need it to help build our water supplies for future years,” said Nathan Elder, Denver Water’s manager of water supply. 

“The good news is that we got lucky with some late-spring snowstorms. Without them, we likely would have peaked below 90% this year.”

Dillon Reservoir in Summit County reached 96% capacity on July 1. Dillon is Denver Water’s largest reservoir. Photo credit: Denver Water.

Denver Water collects water from the snow and rain that falls in the mountains and foothills west of Denver. Snow provides the majority of the water when it melts in the spring, then flows into rivers and streams that feed the utility’s reservoirs.

Water flows down Tenmile Creek in Frisco on June 21 during the mountain snow runoff. Tenmile Creek is one of three main water sources for Dillon Reservoir. Photo credit: Denver Water.

Water storage in Colorado follows an annual cycle, peaking in early summer then slowly falling over the rest of the year until the spring runoff begins again. In early May 2022 — right before this year's runoff season began — Denver Water’s reservoir storage hit its low point for the year at 78%. 

One of the reasons Denver Water was able to climb back up to 92% storage in its reservoir system, after a below-average snow year, was because of ongoing efforts by customers to use water efficiently.

“Managing water supply is like managing money, and this year our spring runoff paycheck came in a bit low,” Elder said. “Looking forward to next year, we don’t know what the runoff will bring or how full our reservoirs will get, so it’s important to save now for the future. That’s how customers can help.”

See how a Denver Water employee gradually transformed his landscape with a patio and water-wise plants. 

That’s why in both wet and dry years, Denver Water is always asking customers to be smart with their water use, which means following the annual summer watering rules, switching to water efficient indoor and outdoor fixtures and fixing leaks.

Another reason the reservoir system didn’t reach full capacity this year is due to construction work in Denver Water’s North System.

To provide more reliability in its storage system, Denver Water has embarked on the Gross Reservoir Expansion Project, which will nearly triple the water storage capacity of the reservoir.

And, as with any major construction project on a working system, the project creates some short-term challenges. For safety reasons, during the project the reservoir can only be filled to about 60% of its normal capacity through 2027. 

But Denver's water planners say this short-term issue of not being able to reach full reservoir capacity is worth the long-term gain of additional storage capacity. 

Denver Water is raising the height of Gross Dam in Boulder County to nearly triple the water storage capacity of the reservoir. During construction, the reservoir will only be able to store about 60% of its capacity. Photo credit: Denver Water.

According to Elder, increasing storage capacity in Gross Reservoir will help balance the amount of storage Denver Water has between its north and south collection systems, making the entire system more resilient and flexible as weather patterns of the future veer from those of the past. 

For example, in a year when the southern part of the collection system doesn’t receive as much snow, or if there is an emergency like a wildfire, the utility can lean on water supplies from the north side of its system and vice versa.

Having a robust and balanced storage system is critical in Colorado because it can ensure drinking water is available — especially when there is lackluster snowpack or in times of drought. 

Customers play a key role as well.

“In Colorado, water is a scarce resource, and our customers play a critical part of managing our water supply,” Elder said. 

“The amount of water we use indoors and outdoors has a direct impact on reservoir levels, so it’s crucial to pay attention to lawn watering and limit use where possible.”

Watering by hand using a hose with a shut-off nozzle is using water wisely. Photo credit: Denver Water.

Despite not reaching full reservoir storage capacity in 2022, Elder says that at this time, Denver Water does not expect to issue additional watering restrictions beyond its annual summer watering rules

However, water managers will closely monitor reservoir levels, weather conditions and water demand from customers throughout the summer to see if further restrictions are needed.