Colorado’s tale of two seasons
Mother Nature, who brought deep drifts of snow and a lingering ski season to Colorado earlier this year, flipped the switch this summer to hot and dry, and customers’ water use in the Denver area followed the rise in temperatures.
“Water use typically goes down when it’s cold and wet and up when it’s hot and dry,” said Greg Fisher, demand planning manager at Denver Water. “Delivering water is our business, so tracking the connection between weather and customer demand is an important part of ensuring a reliable water supply today and tomorrow.”
Weather patterns have changed considerably in the mountains and plains during 2019.
The year started off with abundant snowpack at higher elevations and wet conditions in the city during the spring.
But on Sept. 19, the U.S. Drought Monitor classified portions of the upper South Platte and the entire upper Colorado river basins as abnormally dry. In August, those two basins received just 39% and 53%, respectively, of the average moisture levels typically seen during that month.
Summer rains are important to Denver Water. The utility collects about 80% of its water from mountain snow and roughly 20% from rain that falls in these two river basins.
East of the Continental Divide, portions of Denver and most of the northern Front Range have also been classified as abnormally dry.
Watching the weather
Over the years, Fisher and his planning team have watched water use by Denver Water customers rise and fall as temperatures and weather patterns change. This year was no different.
For instance, May and June of this year were unusually cool, with the month of May clocking in at the fifth-coolest May since 1949, when Denver Water started tracking temperatures.
And water use among Denver Water customers during those two months also was unusually low this year, nearly 19% lower than the 20-year average for May and June.
But in July, temperatures climbed. And as irrigation for landscapes increased, overall water use rose slightly above average.
Then in August, as the summer’s heat soared into the 90s and the monsoon season failed to bring meaningful moisture to the Front Range, water use rose 8.5% above the 20-year average.
A look at water use on two days in August provides a snapshot of how closely customers keep their eyes on the skies when it comes to watering their yards.
On Aug. 11, Denver hit a high of 85 degrees and saw .23 inches of rain. Customers used 297 million gallons of water that day.
Then on Aug. 19, as temperatures soared to 97 degrees with no precipitation, customers used 371 million gallons. (We did the math and 371 million gallons is enough water to fill 562 Olympic-sized swimming pools.)
It’s a lot, but it’s a far cry from maximum water use days seen in years past.
In 2000, the peak day for water use hit 478 million gallons. And the last time daily water use rose above 400 million gallons was July 21, 2008, when customers used 426 million gallons.
“This summer, water use went up when it turned hot and dry, which was appropriate to keep landscapes healthy,” Fisher said. “Our customers get a lot of credit for paying attention to weather conditions and skipping watering days after rains and when temperatures are cooler.”
Using customer use data
Data about weather and customer use helps inform Denver Water’s operations in a variety of ways, including meeting future demand and planning for emergencies.
“If we had an incident at one of our dams or treatment plants and we couldn’t deliver water from those locations, we would want to know how much water customers would need that day so we could create a backup plan,” Fisher said.
Customer use patterns are help determine how much water Denver Water brings down from its mountain reservoirs to meet anticipated demand.
“If there is a good chance for significant rain in the metro area, we know customers won’t be watering as much, so we won’t bring down as much water compared to a day when the forecast calls for sunny skies,” said Nathan Elder, manager of water supply at Denver Water. “Our goal is to bring down only as much water as we need to meet customer demand.”
Over the long term, water use trends help the organization plan infrastructure improvements, make revenue projections, and prepare for water delivery in an uncertain future due to the impacts of climate change.
Protecting reservoir levels
Despite dry months in July and August, Denver Water’s reservoir levels were 95% full as of Sept. 9, just above average for this time of year.
But shifting weather patterns can have major impacts on water supply, which is why it’s important for customers to use water wisely.
Efficient water use helps keep reservoirs full and is part of Denver Water’s long-term strategy to ensure customers have a safe, reliable, affordable water supply in the future.
The strategy includes finding new ways to reuse water and increasing water storage through projects like the Gross Reservoir expansion.
When the Gross Reservoir Expansion Project — which is in the final stages of approval after 15 years of permitting — is done, Denver Water will have more flexibility throughout its system to react to year-to-year changes in snowpack levels, extreme weather swings and unbalanced conditions across the state.
Using water wisely
Denver Water customers also have made large strides in using water wisely since the drought in the early 2000s. Read, “Efficiency is the new conservation” to learn more about Denver Water’s successful 10-year conservation plan that led to customers meeting the citywide reduction goal of 22%.
Fisher credits the drop in water usage to customers updating their irrigation systems, following Denver Water’s watering rules and implementing best irrigation practices, such as skipping watering after it rains.
“It’s clear to us that most of our customers are paying close attention to the weather and watering when they need too,” Fisher said. “We still expect to see wild swings in the weather, so it’s important to pay attention to your landscape, make watering adjustments throughout the summer, and be sure to water trees during dry spells.”