Colorado Supreme Court upholds “slow sip” approach to managing underground water supplies

The Colorado Supreme Court, in a ruling that will affect water supplies for millions of Coloradans, said this week that a “slow sip” approach to managing groundwater that helps supply much of the Front Range will remain in place.

The ruling upholds tougher limits on how much nonrenewable groundwater can be pumped from wells over the life of a state permit. The limits date back to 2020.

The ruling comes after Parker and Castle Rock sued the state over new water volume limits included in well permits, saying that the estimates were too imprecise and could undercount how much water might be available in the future. After losing in a special water court, the Douglas County cities took their case to the Colorado Supreme Court.

This Fresh Water News story is a collaboration between The Colorado Sun and Water Education Colorado. It also appears at wateredco.org/fresh-water-news.

Aurora and Greeley sided with the state in the case, and this week, the court sided with the Colorado Division of Water Resources, saying water regulators had acted properly in spelling out explicitly how much water could be pumped over the lifetime of a permit, and that the state’s approach to managing these water resources was critical.

“Given the state’s arid climate and population growth, it would be difficult to overstate the importance of groundwater to Coloradans today,” Supreme Court Justice Maria Berkenkotter wrote in the ruling.

Several aquifer formations underlie Colorado, some of which can be easily recharged via rainfall and snowmelt, and are considered renewable. Others cannot be readily recharged and thus are considered to be nonrenewable. These are known as nontributary aquifers, and wells drilled in them were at the heart of the dispute.

Tracy Kosloff, deputy director of the Colorado Division of Water Resources, said the state was pleased with the decision.

“It affirmed our long-held understanding of the law allocating nontributary groundwater, including in Denver Basin aquifers,” she said via email.

Ron Redd, manager of Parker Water and Sanitation, said he was disappointed in the court’s decision but was still reviewing the ruling. 

Nearly 40 years ago, Colorado lawmakers moved to protect underground water supplies after watching those in Douglas County plunge amid fast growth and heavy use. They enacted a “sip slowly” management process that required communities such as Parker and Castle Rock to pump out just 1% of their estimated share of the aquifers each year in an effort to make the resource last at least 100 years. Those pumping rates were based on estimates of water in the aquifers.

Fast forward to 2020. That year, the state directed well owners to sip even more slowly, explicitly stating how much water their permits entitled them to based on those estimates, and requiring them to stop pumping at the end of that 100-year period if they have fully used all the water they were entitled to when the original well permits were issued.

But Parker and Castle Rock argued that the original volume estimates used to calculate their annual pumping rates were never meant to be formal, total volume limits. Those limits the state had begun using, they argued, were essentially a best guess, based on measuring technology that has changed considerably since then.

State officials said they added the water volumes to ensure wells are regulated in a uniform way and that well owners are informed at the start of that 100-year clock how much actual water they can pump. 

Steve Boand, a former Douglas County commissioner who closely tracks the health of the aquifers, said he agreed with the state Supreme Court’s decision.

“The Supreme Court affirmed what was always the case. You’re entitled to a volume of water, and when it is exhausted, you’re done pumping.”