After two decades of near-constant drought, Colorado’s water supply is stressed. And there’s not much relief in sight.
Colorado’s cities, industries and farms could face more severe water shortages by 2050, depending on how the state responds to key factors such as warming temperatures, uncertain rainfall and a growing population. Instability in the Colorado River Basin – which provides 40% of Colorado’s water – is just adding to the pressure.
“Warming is going to put more stress on the water resources across the board,” said Russ Schumacher, Colorado’s state climatologist. “Even if precipitation does go up a little bit, that increased stress is still going to be there. Probably the most likely outcome is, on average, a decline in water supply overall.”
So how does Colorado use its water?
This 10-question guide breaks down the basics, explaining Colorado’s water supply, how it gets used and what experts do – and don’t – know about its future.
Where does Colorado’s water come from?
Most of Colorado’s water, about 83%, comes from winter snowfall, spring rain, monsoon showers and more. This precipitation, which collects in Colorado’s rivers, streams, lakes and reservoirs, is known as surface water.
The supply of surface water varies widely across the state and from year to year. This is why water managers are often on pins and needles each winter and spring as they wait to see what the year’s precipitation – and thus the state’s water supply – looks like.
About 80% of the state’s precipitation falls on the western side of the Continental Divide, a continuous ridge of mountain summits that separates river systems and splits the state roughly in half from north to south. However, nearly 90% of Coloradans live on the eastern side of the Divide.
This is a key dynamic. Water managers rely on a network of pumps, reservoirs, tunnels and ditches to store and move water around the state. Cities and towns short on water have looked to the Western Slope as a potential source, which has long been the crux of simmering west-east conflicts over water in Colorado. The Front Range takes over 500,000 acre-feet annually from transmountain diversions.
What is an acre-foot?
An acre-foot is a unit of volume. It equals the amount of water it takes to cover one acre, about the size of a football field, in one foot of water. One acre-foot of water equals about 326,000 gallons.
Water managers have estimated that one acre-foot supplies the indoor and outdoor water needs of about two typical urban households for a year. The comparison depends on factors like the number of people living in a household, the type of landscaping, and the efficiency of a home’s water infrastructure and appliances.
These factors differ geographically and have changed over time. In some communities, one acre-foot can go further than it has in the past. In some areas of California, an acre-foot can supply three or even six households each year.
What is groundwater?
About 17% of Colorado’s water comes from water that collects naturally underground, called groundwater. About 19 of Colorado’s 64 counties rely heavily on groundwater aquifers.
These aquifers occur naturally over time as precipitation seeps through the soil until it collects in the spaces between rock particles and saturates the rocky material. Most groundwater use in Colorado occurs in eastern and central-southern regions of the state.
Colorado water users pump about 2.78 million acre-feet from groundwater aquifers each year, about 85% of which goes to farmers and ranchers for irrigation. About 18% of the state’s population relies on groundwater for their domestic supply.
Groundwater aquifers can be an uncertain water source: They can have water quality issues, and their water storage capacity can fall over time as long-term pumping causes the earth to become more compact. When people are pumping water out of the aquifer faster than it recharges naturally, it’s considered a nonrenewable resource. About 60% of Colorado’s annual groundwater use comes from nonrenewable aquifers.
How much water does Colorado use every year?
Colorado uses about 5.34 million acre-feet of water on average each year. This water is what Coloradans drink, boat, fish, ski and swim in. It nurtures crops and ecosystems, and it keeps industries and cities running.
The agricultural industry is the state’s largest water user. Of that total statewide water use, about 4.84 million acre-feet, or 90%, goes to irrigate farms and ranches, which contribute $47 billion to the state’s economy each year, according to the 2023 Colorado Water Plan.
Cities and towns use just 7%, or about 380,000 acre-feet of water, of the state’s overall use, each year. This water waters urban parks and green spaces, runs through homes for drinking and other household uses and spurts out of sprinklers on lawns and gardens.
Industries use 116,000 acre-feet each year, or 3% of the state’s overall use. Some of this water is used in the energy sector for hydropower production, thermoelectric energy production, steam generation and cooling. It is also used on ski slopes for manufacturing snow.
Streamflows in Colorado support environmental health and a thriving recreation industry which, in 2019, contributed $19 billion to the state’s economy.
Colorado’s water is used over and over as it runs from headwaters to the state’s borders. Delayed return flows from irrigation, for example, help recharge aquifers and streams before the water is used in downstream communities.
Wait, Colorado only uses 40% of the water that lands within its borders?
In total, 13.5 million acre-feet of water originates within Colorado each year, but less than 40% is consumed within the state’s boundaries. The rest, about 60% or 8.18 million acre-feet, is provided to 19 states and Mexico. These water sharing obligations are laid out in dozens of compacts, federal laws, court decisions and decrees, contracts and regulatory guidelines.
Water that falls west of the Continental Divide feeds the Colorado River, which begins in northwestern Colorado. The river supplies water to 40 million people across seven states in the U.S., two states in Mexico and 30 Native American tribes. Four of Colorado’s eight major river basins – the Yampa-White-Green, Colorado, Gunnison and Southwest – are part of the larger Colorado River Basin.
Surface water that falls east of the Continental Divide feeds the state’s other major river basins: the North Platte, South Platte, Arkansas and Rio Grande. These basins make up the Front Range and Eastern Plains. The Platte, Arkansas and Rio Grande rivers run north, east and south out of the state. These major river systems eventually reach the Gulf of Mexico.
How do tribes in Colorado get water?
Both tribes with reservation land in Colorado, the Southern Ute and Ute Mountain Ute Indian tribes, are located within the Colorado River Basin. Colorado is allotted a percentage of the river’s water, and the Southern Ute and Ute Mountain Ute tribes get water out of Colorado’s portion.
Each tribe has a water rights portfolio that includes older, more senior water rights in the San Juan and Dolores river basins. Senior water rights take priority over more recent, or junior, rights when there is not enough water to go around.
The Southern Ute Indian Tribe has rights to divert 128,939 acre-feet of water per year in Colorado, recognized in a 1986 water rights settlement agreement. The act also recognized the Ute Mountain Ute Indian Tribe’s rights to 100,184 acre-feet of water per year in Colorado.
Both tribes have rights to water they currently can’t access in Lake Nighthorse Reservoir near Durango. At its maximum capacity the reservoir can store 123,541 acre-feet of water. Of that total capacity, each tribe is allocated 38,108.5 acre-feet. Neither tribe can currently use that water without costly new water delivery infrastructure projects. The Southern Ute Indian Tribe is working on ways to put that water to use.
How does the agriculture industry use water in Colorado?
Farmers and ranchers irrigate about 3.28 million acres of land statewide and use, on average, 4.84 million acre-feet of water each year. Of that water, about 1.63 million acre-feet is used to grow grass pasture, the state’s predominant crop.
Not only is the agriculture industry Colorado’s largest water user, it supports a multibillion-dollar economy and employs almost 195,000 people. Aside from grass pasture, farmers and ranchers also grow alfalfa, wheat, cereals and grains, vegetables, sugar beets, and oil seed crops like sunflower. On ranches, irrigation helps produce feed for livestock or supports pasture grazing.
Most of the state’s irrigated agriculture, about 44%, takes place in the South Platte Basin, which spans all or parts of 23 counties in northeastern Colorado. The Rio Grande Basin in south-central Colorado and the Arkansas River Basin in eastern Colorado also contain more irrigated acreage than other basins: 16% and 14% of the state total, respectively.
While most of this water comes from the surface, groundwater supplies about 19% of agricultural water, especially in the Arkansas, South Platte/Republican and Rio Grande basins.
Farmers and ranchers are exploring water efficiency tools like technological improvements, different irrigation systems and switching crops. Alfalfa, Colorado’s second biggest crop, has a higher nutritional value as feed for livestock and fetches a better price on the market. But most alfalfa pastures need 4 to 6 acre-feet per acre each season, depending on weather, soil type and many other factors. Some farmers incorporate lower-water-use crops as one way to save water.
Who manages water in Colorado?
Colorado’s water is managed by a matrix of local, regional, state and at times, federal entities.
In Colorado, the Department of Natural Resources’ Division of Water Resources handles responsibilities related to water well permits, dams and streamflow. It administers water rights, which means in dry years, the state engineer has to cut off water to users with lower-priority rights.
Colorado Water Conservation Board addresses policy issues, like how to protect streams and lakes, mitigate floods, protect watersheds, plan for drought and fund water projects. The state legislature, governor’s office, attorney general’s office and other state agencies also take part in addressing water issues and policy.
These entities work together to represent Colorado in interstate water negotiations, like those related to management of the Colorado River’s water supply in light of prolonged drought and overuse.
The U.S. Bureau of Reclamation coordinates with state and local entities on topics like tribal water, federal funding, and water supply and management projects, like the Colorado-Big Thompson Project, which delivers Colorado River water from the Western Slope to the Front Range. Also related to the Colorado River, Reclamation manages Crystal, Blue Mesa and Morrow Point dams on the Gunnison River, known as the Aspinall Unit.
At the regional level, nine basin roundtables serve as forums to gather input across many sectors. Four water conservation districts – Rio Grande, Republican River, Southwestern and Colorado River – work on regional policy, local engineering issues and fund allocation.
At the local level, water conservancy districts; county, city and town governments; nongovernmental organizations; ditch companies and more also have a hand in water issues.
How does climate change impact Colorado’s water?
Colorado’s top climate experts say the state is likely to get warmer, but they’re not as sure what the future holds for precipitation in the state. Regardless, it’s a good bet that Colorado’s water supply will decrease over time if temperatures keep rising.
Climate experts can’t see the future, but they do use modeling techniques and historical data to identify trends (with varying degrees of certainty).
Looking ahead, they’re confident it’s going to get warmer. Already, the state’s average annual temperatures have risen 1.5 degrees Fahrenheit compared to the average temperature from 1971 to 2000. Seven of the nine warmest years have been since 2012. Temperatures could jump an additional 1 to 4.5 degrees Fahrenheit above that 30-year average by 2050, depending on greenhouse gas emissions and how the world responds to climate change.
These warmer conditions are highly likely to impact water systems. Farmers depend on irrigation water that lasts through the summer, but that snow will probably melt earlier in the year. The flow of water in streams will likely peak closer to April and May, rather than the average peak in June and July during the 20th century. Earlier runoff could unsettle species’ life and reproductive cycles that are tied to peak flows.
Another near-certainty: Snowmelt passes through soils on its way to streams, but that soil will probably be drier – and thirstier. As temperatures warm, the atmosphere will also suck up more moisture from the landscape.
Streams, necessary for environmental health and water delivery, could see lower flows, and the vital winter snowpack could also decrease, experts say. (They’re moderately sure.) Shallower streams and warmer conditions can also increase water temperatures, which can be disruptive for aquatic species.
More highly certain downers: Wildfire risk will increase. Heat waves – the deadliest kind of extreme weather – will be more frequent and intense in a warmer climate, and so will droughts. Just two decades of prolonged drought and overuse brought the Colorado River system to the brink of a water-supply crisis.
Precipitation, the primary source of water for the state, is the big unknown. It varies widely each year, which causes wet and dry periods and makes long-term trends hard to pin down. The question is, how will that change going forward – could the state return to the wet conditions of the 1980s and ’90s, or will it stay dry?
Regardless of precipitation, more warming means more stress on Colorado’s water supply. If annual precipitation increases, it could counteract some of the negative impacts of warming. If it declines, the impacts would be even worse.
Does Colorado have enough water?
For now, yes. However, Colorado’s demand is projected to outpace its supply by 2050, which means agriculture, municipalities and industries could face critical water shortages. The size of the gap depends on how the climate changes and how the state responds.
If temperatures keep climbing, the most likely outcome is that the state’s water supply will shrink. The state might also see even more variable water supply conditions from year to year: The drought years could be worse than in the past, but extreme wet years could also become more common.
Cities, towns and industries currently have enough water, but by 2050, they could be short 230,000 acre-feet to – in the worst case scenario – 740,000 acre-feet in dry years, according to the 2023 Colorado Water Plan. (Not calculating in efforts to address the supply issue.)
That’s a potential shortage that could equal, or surpass, all current municipal and industrial water use, which hovers around 496,000 acre-feet on average.
Already Colorado’s farmers and ranchers face shortages in dry years when their irrigation water gets cut off earlier in the season. By 2050, the industry could be short by around 2.6 million acre-feet to about 3.5 million acre-feet statewide. For reference, its current annual use hovers around 4.84 million acre-feet each year.
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