Click the link to read the article on the Denver Water website (Todd Hartman):
August 28, 2025
The dog days of summer have been draining for Dillon Reservoir.
Up until late August, this summer has been particularly dry, both for the Denver region and for the West Slope, the source of half of Denver Water’s supply. And that combination has translated into a heavy workload for the utility’s largest reservoir, the 257,000-acre-foot Dillon Reservoir in Summit County.
A summer largely bereft of the monsoon rains (which bolster our water supply and reduce water use by our water-smart customers) combined with long stretches of days above 90 degrees pushed up demand among the 1.5 million people Denver Water serves.
The dry summer situation also triggered calls for more water from farmers and ranchers who have senior water rights that put them at the front of the line for receiving water from the South Platte River system. Denver Water’s supplies are also constrained on the north side of its system, as ongoing work on the Gross Reservoir Expansion Project requires the utility reduce the amount of water it stores in that reservoir during the project.
Dillon Reservoir provides Denver Water with a supplemental supply to use when the amount of water available from its south system source, the South Platte River, is not enough to meet demands.
That all combined to make Denver Water more heavily reliant on Dillon Reservoir than usual, forcing the utility to push higher volumes from Dillon through the Roberts Tunnel to the Front Range.
“A lot of factors combined to see us lean hard into our Dillon supplies this summer,” said Nathan Elder, manager of supply for Denver Water. “We know this impacts recreation, both what we release into the Blue River below the reservoir and the water levels for the marinas at Dillon Reservoir. We try very hard to maintain good conditions for recreation at Dillon, but this summer posed challenges.”
Adding to the mix: Lower inflows into the reservoir.
Overall, the amount of water flowing into Dillon was at just 70% of normal in the April-through-July stretch. July alone saw just 48% of typical flows into the reservoir — that’s 20,000 acre-feet below average, about the capacity of Antero Reservoir west of Fairplay.
The situation serves as a reminder for Denver Water customers to stay smart about water use.
Especially amid a hot, dry summer, customers should make sure to follow watering rules and skip irrigation during rainy periods. And they should consider landscape changes that replace thirsty turfgrass with plants that need less water.
Yet, despite relentless dry periods covering July and most of August, Denver Water customers did a good job managing irrigation. They used water at a rate of just about 2% above the five-year average, and just 1.6% above the longer term, 2000-2024 average.
But even as Denver Water customers kept demands low by historical standards, the combination of conditions saw water levels in Dillon fall below levels optimal for the marinas at the reservoir by the end of August.
Typically, Denver Water tries to keep the surface of Dillon Reservoir at 9,012 feet in elevation through Labor Day. But this year, levels will fall a few feet below that.
And water volumes flowing out of Dillon into the Blue River — flows important to rafters and anglers — also fell significantly. Since late July, those outflows were about 100 cubic feet per second, about half of normal for this time of year. In August they dropped even further, to 75 cubic feet per second.
The overall picture began to improve slightly in late August, as the state benefited from a cooling trend and bursts of rainfall. The cooler, wetter weather in the metro area cut Denver Water customers’ demand for water in the Denver region, easing the need to pull as much water from Dillon.
Even so, the tough summer means Denver Water will likely enter the new, 12-month water year, which begins Oct. 1, with its reservoirs, including Dillon, at below-average elevations.
That puts the onus on the upcoming winter season to come through with a good snowpack, never a sure thing.
“We’ll hope to see water demands fall in September and then look to a good snowpack in the winter and spring,” Elder said.
“But we’ll be starting from behind. We hope we can make up the gap in reservoir storage with a wet winter and spring. And we’ll need our customers to help us with smart water practices.”
