Text Size

Site Search

Public Lands

HW Winter2018 FINAL2cover

Colorado's public lands are faced with new challenges but water and land management depend on working together. Read about the relationship between water and land in Colorado and how Coloradans are converging to restore Colorado's public lands in the Spring 2018 issue of Headwaters magazine.

Browse articles and find a flipbook of the magazine here.

Connecting the Drops

connectingdropslogo4.1Bringing you the reporting you crave over the radio airways with extras and archives on our website. Visit the audio archives or listen to the latest story on the connection between Colorado's forests, watersheds, and forest fires:

IMG 20180402 101801web

Water Education Colorado

Denver Basin Aquifers in Decline

In the Denver Basin, deep bedrock aquifers store water in the pores of rocks more than 50 million years old. Studies show it takes tens of thousands of years to recharge the aquifers, and in places we are drawing it down rapidly. Some wells located along the western flank of the basin can already feel the effects of the aquifer's declining artesian pressure.

‘My well has an estimated 20 years of life left, but that's not going to happen,’ says Jack McCormick, a 20-year resident of Plum Valley Heights, a 29-home neighborhood tucked in the foothills between Sedalia and Highlands Ranch. ‘I don't think it'll go more than 10.’

McCormick and his neighbors rely on an aquifer in a marginal zone scientists predicted would be the first to show signs of the vast underground reserve's limits. How quickly wells in other areas of the basin will drop, and how long it will be economically feasible to pump this resource is debatable.

Understanding What's Underground
The Denver Basin is a geologic formation that stretches from Greeley south to Colorado Springs and from Limon west to Jefferson County. Four aquifers—the Dawson, Denver, Arapahoe and Laramie-Fox Hills—hold its water reserves.

They're stacked and tilted like bowls.

While in some areas the aquifer can be recharged—surface water can seep back into tiny pore spaces within or between rocks—it may take thousands of years. That makes this resource, while immense, essentially nonrenewable.

Each year, groundwater measurements from select wells in the Denver Basin are published by the Colorado Division of Water Resources. The validity of these data is sometimes questioned. The wells measured are not dedicated to monitoring and vary significantly in age and how they are pumped, among other things.

Consistent annual trends indicate that depending on the location of the well, water levels in the Denver Basin aquifers are either relatively stable, declining, or even rising. It all depends on the aquifer and the location of the measurement well.

In the aquifers used predominately by the high-volume wells necessary for municipalities, specifically the Arapahoe and Laramie-Fox Hills, water level declines are significant.

Between 1990 and 2000, groundwater levels in the Arapahoe aquifer declined from 100 to almost 300 feet. Municipalities relying almost exclusively on groundwater, such as Castle Rock or Parker, are concerned about how the aquifer will react and how long it will last, as pumping increases.

Rural water users with private domestic wells are also concerned. If their water supply fails, they do not have the water utility managers or paid water brokers readily-available to help them find other sources of water.

The issue becomes more complex as economics, water rights, legislation and advances in technology and science are stirred into the mix. And then there's growth: State projections forecast an additional 1.7 million people will call Colorado home by 2015 and more than 80 percent will live along the Front Range. They'll need water.

Location, Location, Location
Although south metro municipal providers can anticipate decreased well production, this isn't the case throughout the entire basin—a fact some well experts and water entrepreneurs like to reiterate.

Much of the problem with dropping Denver Basin aquifers depends on location. Water tightly held in sandstone does not move very far, and if it does, it may take thousands of years. In locations where demand is modest and the resource large, such as the eastern plains, these aquifers should provide many years of adequate supply. Private domestic wells tapping the Denver Basin in these areas may have little to worry about.

Similarly, the shallower Dawson and Denver aquifers which are more easily recharged by irrigation and precipitation, remain steady or show water level increases in some areas. Homeowners with wells in those locations may not observe any decrease in well production for years, if ever.

But the situation is very different for areas in Douglas County where high volume pumping from the Arapahoe aquifer has caused dramatic declines. In some areas, 40 feet drops per year have been recorded and it is anticipated well flow rates will diminish during the next decade.

An Exhaustible Resource?
Concern over the amount of water being pumped from deep nonrenewable aquifers started decades ago. After a variety of groundwater-related legislation in the 1950s and 1960s, in 1973 Senate Bill 213 set out to allocate who could use Denver Basin groundwater, and in what quantity. The act determined that the Denver Basin aquifers could be pumped at rates that might allow, based on the best available data, a minimum 100-year life. Landowners overlying the Denver Basin groundwater would have the right to withdraw that water at the rate of 1 percent per year.

Yet by the early 1980s, the population of south-Denver communities was growing at a startling rate, accompanied by a spike in speculative groundwater claims. Developers were keen to pump the readily-available groundwater. Many people wanted to take advantage of the high-quality Denver Basin aquifers, but the state needed more guidance to ensure that the resource would be meted out fairly.

In 1985, complex legislation commonly known as Senate Bill 5 developed specific rules and a basic legal framework of how Denver Basin groundwater should be allocated.

By enacting this legislation, the Colorado legislature agreed that it was acceptable to mine—or take out more water than is replaced—the Denver Basin aquifers. They knowingly allowed this even though, over time, some wells might be impaired.

Boulder attorneys Mike Shimmin and David Harrison were on the blue ribbon panel then-Gov. Richard Lamm appointed to map out a set of recommendations that would later form the basis for Senate Bill 5.

While imperfect, both agreed that the bill made a good attempt given the science and the political will at the time. But it does have its limitations. ‘I do not think Senate Bill 5 was intended as a groundwater management act,’ said Harrison in a May 2006 interview. ‘It is a groundwater allocation act. There is no management of the Denver Basin right now.’

‘Somewhere along the line,’ says Harrison, ‘we will make an economic decision not to use it (nonrenewable groundwater) very much anymore, except in emergency situations…So we'll come in for a soft landing, somewhere above exhausted, and the remainder will (be) for (emergencies). But that soft landing assumes that you can find some surface water to substitute—and how that will be done is still really, really unresolved right now.’

Preparing for Change
Water resource managers have known for years a shortage of groundwater wouldn't slow growth, and they have been studying their options.

Recently, Elbert, Adams, Weld and El Paso counties have started requiring that new developments show they can provide sufficient water supply to last at least 300 years.

Some groundwater-dependent cities are shouldering the expense of drilling deeper, higher-production wells. Others are preparing themselves to relinquish their dependence on groundwater almost entirely.

Castle Rock, for instance, has already embarked on plans to convert its water supplies to more than 75 percent renewable surface water sources by 2032. The central Douglas County town estimates that at build out, it will need 18,000 acre-feet of surface water each year to wean itself from the aquifer.

‘It's late in the game and we know it's going to cost,’ says Ron Redd, Castle Rock's water utilities director. ‘We're collecting the fees now so we can get there.’

Among Castle Rock's options—buying river water from Sterling, 150 miles to the north and east; drawing it from the Arkansas River; forming a partnership with East Cherry Creek; or buying into Denver Water's Green Mountain pumpback plan—each scenario is estimated to cost around $300 million. ‘We're considering two dozen alternatives for renewable sources,’ says Redd.

But plans like Castle Rock's aren't going to help places like Plum Valley, the small cluster of homes dependent on the Denver Basin aquifers. As predicted, the Denver Basin's west rim, over which Plum Valley sits, was the first to drop as pumping increased.

Plum Valley resident Jack McCormick's first well was drilled 408 feet into the shallow Dawson aquifer. It initially produced 5 gallons a minute, but finally dropped to a point where it was no longer useful. Next, McCormick drilled a new well into the lower Arapahoe aquifer. Since 1987, the well's static level has dropped 7-10 feet a year. Four times since then the pump's been lowered, chasing the dropping water table. He estimates the well's life may be only 10-15 more years, depending on technology.

‘Less than a half mile away, one of my neighbors has his pump as low as it can go,’ McCormick says. ‘These folks up here,’ he says pointing to a small enclave north of his property. ‘They've been hauling water for years.

‘One of the things we need for certain is a remedy. I'd be hard pressed to prove Highlands Ranch is pumping our water. We need legislation that adequately defines injury.’

McCormick and his neighbors have been ‘working the issue.’

They aren't rookies. The residents of Plum Valley and the surrounding communities have been talking to county commissioners, lobbying for legislation, searching for renewable water sources in conjunction with new developers, and teaming up with their rural neighbors in Louviers, Chatfield Basin and Meridian to bring in a surface water supply.
Plum Valley, McCormick says, is hanging some hopes on developers who are mulling plans for Sterling Ranch, a 2,000-acre tract immediately to the west. If the area is developed for housing, Plum Valley and its neighbors could tap into its infrastructure for surface water. They're already saving money for the possibility.

‘We're not looking for others to solve our problems,’ McCormick says. ‘We want to come to the table and participate.’

In its latest publication, a Citizen's Guide to the Denver Basin Aquifers, the Colorado Foundation for Water Education delves into the conflicting stories about this contested resource. Authors Ralf Topper with the Colorado Geological Survey, and Bob Raynolds with the Denver Museum of Nature and Science, provide fresh analysis of the water level data from the Denver Basin, and summarize it into concepts accessible to non-geologists.

Social Media

Stay in touch and connect through:

FB-fLogo-Blue-broadcast-2 Twitter Logo White On Blue instagram    

Sign Up for our e-newsletter

learn more3learn more

 And view the latest issue of Headwaters Pulse, Water Education Colorado's monthly e-newsletter, here.


Click the icons below for videos about climate change, ranching and more; or audio from Water Education Colorado's Connecting the Drops radio series.

filmicon   headphonesicon

1750 Humboldt Street, Suite 200
Denver, CO 80218