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One billion gallons: ASU and the future of the Colorado River

Amid shortages in the Colorado River and a historic megadrought, cities, the agriculture industry and ASU may need to look to other water sources. Sustainability experts say ASU isn’t worried yet

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One billion gallons: ASU and the future of the Colorado River

Amid shortages in the Colorado River and a historic megadrought, cities, the agriculture industry and ASU may need to look to other water sources. Sustainability experts say ASU isn’t worried yet

The Colorado River supplies water to Mexico and seven U.S. states, serving millions of households, businesses and a multi-billion dollar agriculture industry. The water running through it, however, is dwindling.

In 2021, the U.S. Bureau of Reclamation declared a shortage in the Colorado River, requiring drastic cuts to how much water communities can draw from the vital source.

The Colorado River is aridifying — becoming drier — and its supply has been over-allocated in the past, said Sarah Porter, director of ASU’s Kyl Center for Water Policy. Cities and states relying on the river will have to adjust the way they consume water in order to support the populations and industries that depend on it.

ASU has improved its water efficiency in recent years. In 2007, ASU started reporting its water use to an external sustainability ranking system.

Since then, it has used 16.77% less potable water per campus user, 28.38% less per gross square feet in building spaces and 45.59% less per acre in areas with vegetation according to data recorded from July 1, 2018 to June 30, 2019. These improvements come from various sustainability initiatives, such as updating water fixtures and watering the landscape at night.

The future of water in Arizona is uncertain and precarious, but sustainability experts say the University is well-prepared for impending cuts to the Colorado River supply.

Water in the desert

The Colorado River provides over a third of Arizona’s water supply. The rest is from in-state rivers, groundwater and reclaimed water.

Arizona doesn’t have enough groundwater to support its growing population in the long term, so it draws some of its water from the Colorado River system. The state is usually entitled to 2.8 million acre-feet of water — the amount of water needed to fill an acre of land one foot high — from the Colorado River system, its second-largest source after groundwater.

“The problem with groundwater in a place like Arizona, where it doesn’t rain much, is that we are good at pumping water out of the ground a lot faster than it’s replenished,” Porter said.

Over-reliance on groundwater can have serious consequences. In San Joaquin Valley, California, the ground is projected to physically sink for decades unless the groundwater is replenished. Building new groundwater wells or deepening existing ones can also be expensive, disproportionately affecting those living in low-income rural areas who often don’t have the resources to diversify their water supply or dig new wells.

A study this year by the Bureau of Reclamation projected a Tier 2a shortage in 2023 on Lake Mead, a reservoir along the Colorado River that supplies water to Arizona, California, Nevada and Mexico. Once water levels fall below a certain level, a shortage is declared and restrictions on how much water can be drawn are put in place, depending on the shortage tier.

Consequently, Arizona has to reduce 21% of its Colorado River usage beginning in 2023.

Although that is three percentage points more than the existing cuts required by the Tier 1 shortage, which was declared in August 2021, the additional restrictions will undoubtedly impact the state’s water use.

Agriculture will be the most affected by these cuts to the water supply. Nearly three-fourths of Arizona’s water goes to agriculture, which was already impacted by the existing Tier 1 shortage. However, a Tier 2a shortage will begin to impact the water that is supplied to municipalities. Each city in metro Phoenix has a unique water portfolio, meaning their water supply comes from a variety of sources and is apportioned differently.

Although cities won’t immediately face cuts in their Colorado River supply, Porter said it’s likely they will face obligatory reductions in the future. If that happens, cities will have to either draw more from groundwater wells or find alternative water sources.

ASU’s water supply

ASU mainly draws water from the cities its campuses reside in, said Alex Davis, assistant director of University Sustainability Practices, in an email. Unsurprisingly, the Tempe campus uses the most — it accounted for over half of the University’s total water consumption in 2019.

During the fiscal year 2021, over 1 billion gallons of water were used across all ASU campuses. To put that number to scale, 1 billion gallons comes out to only about 6% of the city of Tempe’s potable water distribution to Tempe and Guadalupe customers that year. Davis said the University is prepared for cuts to its water supply, but does not anticipate any in the foreseeable future.

ASU’s water use has grown alongside the University’s population. The amount of water the University consumed increased by about 34% in 2021 compared to 2007, while University enrollment over that same period grew by about 21%.

Wastewater, on the other hand, declined steadily between 2014-2020.

Wastewater from the Tempe, Downtown Phoenix and West campuses is treated at the 91st Avenue Wastewater Treatment Plant and then reused. About half of the recycled water goes to the Palo Verde Generating Station while the rest filters through a man-made wetland and flows back into the Salt River, said Nazario Prieto, Assistant Water Services Director for the city of Phoenix.

Alongside the increase in water consumption since 2007, ASU has simultaneously become more water efficient.

ASU’s biggest improvement is in its outdoor water use — the University has nearly halved the amount of water that it uses per acre of vegetated grounds since 2007.

Unlike most of Arizona, where 70% of water in municipal areas is used outdoors, the Tempe, Downtown Phoenix and West campuses use the largest proportion of their water indoors, according to Davis.

Katie Spreitzer, a sophomore studying sustainability, said the University is good about using its water supply wisely. She applauded the University’s plan on updating and installing more water-efficient fixtures.

“In 2020 the university completed a multi-year project to retrofit 2,000 high-water-use plumbing fixtures [mainly toilets] on the ASU Tempe campus,” Davis said. “More recently, we have been transitioning shower heads in residence halls to lower flow models.”

Madisyn Langford, a sophomore studying sustainability and financial officer for Campus Student Sustainability Initiatives, agreed the University has quality sustainability initiatives in place, but said she would like to see improved efficiency.

“I think one of the biggest areas that ASU could improve is [in] a lot of the residential dorms,” Langford said. “So many people are reporting having leaks and flooding issues.” In August, Best Hall reported having plumbing issues, while Hayden West had a sewer backup.

Just a short walk from these dorms, the Barrett, The Honors College Academic Complex has a state-of-the-art greywater capture-and-reuse system. Barrett’s greywater system captures and treats up to 10,000 gallons a day from water fountains, showers and sinks in the complex before treating it to a standard that’s reusable for irrigation.

“The system ... supports the University’s commitment to sustainability and serves as an example for campus housing,” read a statement by Biohabitats, an ecological conservation and restoration company which designed the greywater system.

Steps toward water conservation are needed as the chance of water falling low enough in 2024 to trigger a Tier 3 shortage in Lake Mead is nearly 60%. If a Tier 3 shortage occurs, Arizona would have to give up 720,000 acre-feet of its apportionment, which would restrict water usage in municipalities.

The Southwest’s water system is designed for drought, said Margaret Garcia, an assistant professor in ASU’s School of Sustainable Engineering and the Built Environment. Arizona has built-in storage for extra water from wetter years to supply the area during drier ones, she said. However, the state’s water system is struggling to adapt to the current “megadrought,” which began in 2000. It’s considered the most intense drought in the past 1,200 years.

“That system was not designed for the type of drought we’re experiencing now,” Garcia said. “And that’s both in terms of the physical design, but even more importantly the way water has been allocated, and the rules around allocation.”

Water law

Water allocation laws in Arizona are old and highly complex. The law dividing up the Colorado River — the Colorado River Compact — was signed 100 years ago. The compact had a major flaw: it assumed the Colorado River had more water than it actually did.

The compact divided 16 million acre-feet among the seven Colorado River system states, assuming the river flowed with more than 17.5 million acre-feet yearly.

The reality was very different. The average flow between 2000 and 2020 is actually 12.5 million acre-feet — much lower than it was believed to be when the compact was signed.

“The compact is bad,” said Rhett Larson, professor at the Kyl Center for Water Policy. “We would all probably be better off to just take the whole system apart and rebuild something new.”

Water-conscious policy in Arizona is nothing new. In 1980, the state signed into law the Groundwater Management Act. This law identified areas with high use of groundwater and required any new development in these areas to have enough water to support its population for 100 years.

In 2015, Arizona’s water use had declined by 3% from 1957; its population ballooned nearly 500% during that time frame. Despite an overall decrease in water use, the state faces the largest cuts from the Colorado River system due to its junior water rights. Arizona’s junior water rights means the state is impacted the most by water cuts to the river since it held the water rights for less time than other states.

Indigenous tribes were not included when the compact was originally signed, as they were not considered U.S. citizens until 1924. Many Indigenous water rights are senior to the Colorado River Compact. The 1908 Supreme Court case Winters v. U.S. established the “Winters Doctrine,” which protects senior water rights on federal reservations.

Some tribes have asked for their full allotment of water from the Colorado River. The Gila River Indian Community said in August it will stop leaving its unused allotment in the river and instead store it underground for future use.

In spite of its inaccuracies and lack of inclusivity, the Colorado River Compact has been extremely difficult to renegotiate, “mainly because there are so many legal rights that are founded on the compact,” Larson said.

“It is a weight-bearing pillar,” Larson said. “If you pull it out a lot of things would fall apart and a lot of people would bring a lot of lawsuits.”

But eventually, legislators may have no choice but to renegotiate or set a new precedent entirely.

“The more dire our situation gets, the more radical solutions start seeming realistic,” Larson said.

ASU is in a safe spot for now. While the University is prepared for potential cuts to its water supply, it’s not anticipating them, Davis said.

“Several University departments have been collaborating for multiple years to identify and implement water conservation projects and plan for hypothetical water restrictions, should conditions warrant them in the future,” Larson said.

ASU has invested in reducing its water consumption and becoming more water efficient. Since it established the first comprehensive degree-granting sustainability school in the country in 2006, ASU’s commitment toward a sustainable campus continues. 

As the Southwest faces water shortages in the Colorado River system unlike anything that it’s experienced before in modern history, innovations on the local, state and national levels are needed to conserve this valuable resource.

“Nothing else matters if you don’t have water,” Larson said. “We need to reinvest into taking care of water infrastructure. That probably means that our largest water consumers need the largest incentives to conserve.”

Edited by Alexis Moulton, Camila Pedrosa, Sam Ellefson, Greta Forslund and Luke Chatham

This story is part of The Sanctuary Issue, which was released on Oct. 5, 2022. See the entire publication here.

Reach the reporter at and follow @BippusKeetra on Twitter.

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Keetra BippusMagazine Reporter

Keetra Bippus is a reporter for State Press Magazine and a journalism student at Walter Cronkite School of Journalism and Mass Communication. She's previously reported for AZ Big Media and the Downtown Devil. 

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