Four things to know about the lower Colorado River basin
Western Slope water officials tour sites integral to lower basin consumption
COLORADO — Staff and board members from the Glenwood Springs-based Colorado River Water Conservation District, along with other water managers from across western Colorado, this month visited the lower basin states — Nevada, Arizona and California — on what they called a fact-finding trip.
The tour took participants by bus from Las Vegas though the green alfalfa fields of the Fort Mohave Indian Reservation, past the big diversions serving the Central Arizona Project and Metropolitan Water District of Southern California, and to the hot, below-sea-level agricultural expanse of the biggest water user on the river: the Imperial Irrigation District. Among the about 50 participants on the three-day tour were Kathy Chandler-Henry and Steve Beckley, River District board representatives from Eagle and Garfield counties. Pitkin County representative John Ely did not attend.
The River District’s mission is to protect, conserve, use and develop the waters within its 15-county area of western Colorado and to safeguard the water to which the state is entitled.
With the nation’s two largest reservoirs — Lake Powell and Lake Mead, which store Colorado River water — at record-low levels that threaten hydropower production, and calls for conservation coming from the federal government, it’s more important than ever for western Colorado residents to understand how water is used in the lower basin, said River District general manager Andy Mueller.
“We have to be able to understand (lower basin) interests and their needs so that we can find ways to meet their interests while protecting our own,” he said. “There’s a system at risk of collapse, and we are an integral part of that.”
One in 17 people
An often-repeated fact about the Colorado River is that it provides water to 40 million people in the Southwest. But perhaps an even more salient statistic is that 1 in 17 people in the U.S. — about 19 million — get their water from the Metropolitan Water District of Southern California. About half of that comes from the Colorado River.
Since 1941, MWD’s Whitsett Pumping Plant has taken water from Lake Havasu and pumped it into the Colorado River Aqueduct, where it then travels 242 miles to urban Southern California. The water district spans 26 municipalities and six counties.
The future of providing enough water to all these urban customers may be something called direct potable reuse — MWD calls it raw-water augmentation — which would allow them to recycle wastewater into drinking water instead of discharging it into the ocean. MWD is testing this concept with its Pure Water Southern California demonstration facility, located in Carson, Calif., which was the last stop on the tour.
Direct potable reuse takes sewage, treats it using sophisticated — and expensive — filtering and disinfection techniques and returns it to taps as drinking water without first diluting it in a larger body of water. Last month, Colorado’s Water Quality Control Commission gave preliminary approval to regulate direct potable reuse.
MWD is working toward using the recycled water for industrial purposes and groundwater recharge, and it eventually hopes to deliver it to residents’ taps. The water provider could have a preliminary portion of the project online by 2028. This new supply of recycled water could meet about 10% of MWD’s demands, according to Rupam Soni, MWD’s community-relations team manager.
“It provides us with so much operational flexibility and water reliability because this supply is available to us rain or shine, it’s climate resilient, and that’s really important to us right now, with climate change and the challenges it’s imposed on our imported supplies,” Soni said.
Forage crops are No. 1
Although it’s true that much of the country’s winter produce, especially lettuce, comes from lower basin farmers, the No. 1 thing grown with Colorado River water is forage crops: alfalfa and different types of grasses to feed livestock.
The Imperial Irrigation District uses 3.1 million acre-feet a year of Colorado River water. By comparison, the entire upper basin (Colorado, Utah, New Mexico and Wyoming) uses between 3.5 and 4.5 million acre-feet per year from the Colorado River. An acre-foot is the amount of water needed to cover an acre to a depth of one foot and is enough to supply one or two families for a year.
IID’s No. 1 crop is alfalfa and represents almost 31% of the acres grown. Bermuda grass and Sudan grass are second and third, respectively. These top three crops account for about 56% of the acres grown in IID.
Forage crops comprise the majority of what is grown in the upper basin, too. But growers in Colorado’s high-elevation valleys can expect about two cuttings a year, while much of the lower basin grows hay year-round, getting seven to nine cuttings. That means switching to less-thirsty forage crops in the lower basin could have a greater impact on the amount of water used.
In Colorado, some irrigators are experimenting with growing forage crops that use less water in an effort to adapt to a hotter, drier future.
Kremmling rancher Paul Bruchez, a representative on the Colorado Water Conservation Board, is trying out test plots on his family’s ranch. He’s growing sainfoin, a legume with a nutritional value similar to that of alfalfa. Bruchez, a participant on the tour, said some lower basin water managers and growers have expressed interest in meeting with him to learn more about growing less-thirsty crops.
Bruchez stressed that switching forage crops in the upper basin is not about propping up Powell and Mead with water saved from agriculture, especially since there isn’t currently a demand-management program in place to account for that water savings. It’s about survival.
“People just don’t have enough water to irrigate the way they used to irrigate,” he said. “They are just trying to make a living and stretch their water to go further.”
Upper basin bears brunt of climate-change impacts on streamflows
Over the past two decades, the Colorado River has lost nearly 20% of its flows. Part of that is because of the ongoing drought, the worst in 1,200 years, which means less precipitation. But according to researchers, about one-third of that loss can be attributed to hotter temperatures driven by climate change. Decreased river flows mean that less water ends up in Lake Powell and Lake Mead.
These reduced streamflows in the upper basin mean water users may have to adapt their operations because less water is available to them. If there’s less water in the stream, junior users may get cut off and senior users may not be able to take their full amount. Streamflows can be particularly inadequate during the late-summer and early-fall irrigation season and some water users are at the mercy of dry local conditions.
Upper basin water managers like to point out that this isn’t the case in the lower basin. Although western Colorado has thousands of small-scale water users diverting from dwindling rivers, the lower basin has just a handful of large-scale water users who have the benefit of two huge upstream storage buckets that release the water exactly when it’s needed.
“Our farmers in particular live within that hydrology in flux and we have learned how to adapt to climate change,” Mueller said. “In the lower basin, their agriculture and outdoor landscaping are absorbing more water because of the hotter temperatures, so they just call for more from the reservoirs.”
Evaporation loss not accounted for in lower basin
The thing about building giant reservoirs in the desert is that a portion of the water evaporates into the hot, dry air. In the upper basin, these evaporative losses from the reservoirs of the Colorado River Storage Project are accounted for and charged as part of the consumptive use to each state depending on their allocation of water.
For example, as laid out in the 1948 Upper Colorado River Compact, Colorado’s allocation of upper basin water is 51.75%. Therefore, the state takes 51.75% of the evaporative losses for Blue Mesa, Flaming Gorge and Lake Powell. Such is not the case in the lower basin, where evaporative losses in reservoirs remain unaccounted for.
Upper basin water managers have long said this accounting is unfair and enables overuse in the lower basin.
“We are asking for (the lower basin) to be treated the same way we are so the system and the playing field is even,” Mueller said. “Once we are on an even playing table, then we can address the way we work in the future, but it’s really hard to do that when the rules they play by down here enable so much more water use than what we have in the upper basin.”
The upper basin may finally be making progress on this point, for at least one lower basin water provider has taken up the rallying cry. In an August letter to federal officials, Southern Nevada Water Authority’s John Entsminger recommended that each lower basin contractor be charged for evaporation losses so that “the lower basin can reduce its reliance upon excess water from the upper basin to balance reservoirs.”
A subsequent study by SNWA found about 1.5 million acre-feet in evaporation and transit losses each year downstream of Lee Ferry, the dividing line between the upper and lower basins that is just downstream of Lake Powell’s Glen Canyon Dam.
“We divorced the water use in the lower basin from the hydrology,” Mueller said. “When you have 50 years of reliable water supply, you don’t think about the fragility of the natural system that’s providing that water.”
This story is from AspenJournalism.com.
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