Hedging our water bets

Las Vegas in 2007 bet on declining reservoir levels in the Colorado River. The bet is now paying off. Municipal water providers in Colorado have started tightening the spigot for landscaping. That move is also wise — but overdue?

by Allen Best

Lake Mead’s receding waters have exposed sunken boats, dead bodies and more. But the wisdom of a bet placed in 2005 by Las Vegas has also been revealed.

The Southern Nevada Water Authority draws 90% of its water for a population of 2.3 million from Lake Mead. It had two intake pipes, one higher and one lower in the reservoir. Reservoir levels have dropped precipitously since 2002 when the Colorado River delivered just 3.8 million acre-feet of flows. The 1922 compact among Colorado and the seven other basin states assumes more than 20 million in annual flows.

Las Vegas bored a third tunnel, this one coming up from the bottom of the reservoir. The far-sightedness of that and other investments totaling $1.3 billion was revealed in April when reservoir levels dipped below what was needed for the highest intake pipe. Depending upon the Colorado River, Las Vegas had wisely hedged its bet.

Steamboat Springs city hall, xeriscaping

The front of the Steamboat Springs municipal building has been xeriscaped to consume less water. Top photo, Lake Mead floats boats below the now-infamous bathtub ring in December 2021. Photos/+Allen Best

Drought combined with the aridification produced by warming temperatures have upset the cart in the Colorado River Basin. Apples are rolling everywhere. The easy, visual way of telling that story is of the widening bathtub rings in the giant reservoirs of the Colorado River. Mead and Powell are respectively 73% and 74% empty.

But the most important story will be in how demand gets cut in Colorado and the six other basin states. The onus is on California, Arizona, and Nevada —particularly California, which for years into the drought to slurp too generously given the emerging climate realities.

Colorado and other upper basin states have lived within their compact-apportioned means. But here, too, changes are underway, because the water just is not there. Farms and ranches, which still consume upward 85% of water in Colorado, will have to be part of the story. So will the still- growing towns and cities.

Changes can be seen most prominently in those places on the edge, including Denver’s fast-growing suburbs of Aurora and Castle Rock. They’re redefining acceptable landscapes in the semi-arid West. Sprawling lawns resembling those of the rain-soaked eastern states are on their way out.

In Aurora, Colorado’s third largest city at nearly 400,000 residents, the city council last week approved regulations sharply limiting turf grasses on golf courses and new homes. Residential lots will be limited to 45% or 500 square feet of the yard, whichever is less, for grass. Within that limit are other limits. No more Kentucky blue-grass. Other varieties use less water

Elected officials in Castle Rock, a city of 80,000 people that expects to fully fill out its britches at 142,000 people, in early September review similar regulations. “Coloradoscape” is what Castle Rock calls its recommended landscapes. For homes, 500 square feet is tiny, smaller than some bedrooms. For new yards, it will be the max. Mark Marlow, director of Castle Rock Water, says city leaders began meeting with stakeholders, including homebuilders, in November.

Commerce City, ornamental grasses, xeriscaping

Landscape architects will be crucial to creating landscapes that are still pleasing but less reliance on water, as along this street in the Denver suburb of Commerce City seen in October 2021. Photo /Allen Best

Denver has a goal of a 30% reduction in “non-functional turf.” It will start with medians, tree lawns and non-residential areas. “Purely ornamental grass should be replaced with trees and plants that can cool, shade, pollinate, manage rainwater and survive extended dry periods,” explains Denver Water’s Todd Hartman.

Most surprising may be the actions by the water provider for Vail and Beaver Creek and associated areas. Even here, at the headwaters of the Colorado River, in a state that produces more than half of the river’s annual flows, the Eagle River Water and Sanitation District has been clamping down on outdoor water use.

Aesthetics still matter. Saving water should not mean having a front yard that looks like a gravel pit along the South Platte River. The draft revised Colorado Water Plan emphasizes the role of landscaping contractors in creating new useful and pleasing yards with minimal water use.

Take away three key messages from this, though. If all Colorado’s towns and cities ceased use of Colorado River water, Mead and its upper-basin sibling, Powell, will not fill up. The lower-basin states have a reckoning.

Also to be remembered is that if this drought ends, there will still be a warmer and almost certainly drier climate. A 2017 study found that only 50% of the reduced precipitation can be attributed to drought. Even in a very good snow year in Steamboat Springs, for example, the Yampa River can still have meager flows by August.

One final thing. Las Vegas, in addition to sinking a third tunnel into Mead, has also been wringing its towel through its own demand-side management programs. The Bellagio’s fountains will remain, but those bloated backyard swimming pool – good bye to that illusion of plenty.