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Controlling Water in the Lower Basin

On Easter Sunday, April 4, 2010, an earthquake of 7.2 magnitude shook Baja California for a minute-and-a-half, so damaging irrigation systems that Mexicali growers could not use their full 1.5 million acre-foot share of the Colorado River. Following the earthquake, Mexico agreed to sell 95,000 acre-feet to water districts in Las Vegas, Arizona, and Southern California.[i] The water providers paid $10 million and the U.S. Department of the Interior matched it with another $10 million, money that Mexico used to repair the earthquake damage. The water districts and environmental organizations also purchased 158,000 acre-feet of Mexico’s unused share for environmental uses. Two years later, Mexico and the Lower Basin states signed Minute 319, permitting Mexico to store up to 250,000 acre-feet in Lake Mead each year for later delivery, known as the Intentionally Created Mexican Allocation (ICMA).

Mexico has not built any dams on the Colorado River, and this was the first time Mexico had been able to store Colorado River water for later delivery. (“Minute 319” signifies that this is the 319th agreement reached by the nations to interpret the 1944 U.S.-Mexico water treaty. As of April 2024, they were up to Minute 330!). Minute 319 also established triggers that reduce Mexico’s share of the river during droughts. Mexico’s stored water isn’t guaranteed—it varies with the reservoir level. In flush times, Mexico gets more water. But if reservoir levels drop, Mexico loses some of the ICMA water it has stored in Lake Mead. Time will tell whether Mexico gets extra water or less water than the amount it stores in Lake Mead. The triggers are portrayed in the table below.

Figure 16.1 Lake Mead elevation and storage levels[ii]

Active storage means that releases from Hoover Dam are still generating power. Once Mexico stores at least 80,000 acre-feet in Lake Mead, it can receive the extra water, as shown in blue in the figure above. Given recent events, it is more likely that Mexico will lose water under Minute 319, since Lake Mead’s level has not been 1,145 feet above sea level since 2005. Arizona and Nevada also take reduced deliveries when water levels dip below 1,075 feet. Only California, true to form, keeps its full deliveries as Lake Mead shrinks. Together, the Lower Basin states and Mexico receive 9 million acre-feet each year; in October 2024, Lake Mead held less than a single year’s supply.

Minute 319 had its own fifteen minutes of fame in 2014 when it delivered a pulse flow of 105,392 acre-feet from Lake Mead down to the Gulf of California, the first time water was released solely to reach the ocean since the dams forming Lake Mead and Lake Powell were built. The pulse flow reached the sea on May 5, 2014, launching a multi-week beach party in San Luis Rio Colorado along the way and capturing the world’s attention before the Morelos Dam gates were shut tight sixteen days later. [iii] Today, the end of the river is dry again. The Colorado River has not consistently reached the sea for over sixty years. Minute 319 is noteworthy because it “appears to be the first international agreement to allocate a specific amount of water to provide an environmental benefit,” according to Jonathan King and Peter Culp, who co-authored an article in the 2014 University of Denver Water Law Review. The environmental release was made possible because Mexico stored extra water in Lake Mead when its irrigation systems were damaged. The water that serviced the environmental flow was Mexico’s untapped share, and Mexico was paid for it. Minute 319 provided only this single environmental release, but it contains hopeful language that “water generated in potential future binational projects be reserved for environmental purposes.”[iv]

The Colorado River once supported nearly 2 million acres of wetlands in the delta, an area 55 miles square and nearly as large as Weld County. Naturalist Aldo Leopold described it as "awesome jungles" and "lovely groves" when he explored the area in 1922.[v] In high flow periods, scientists believe the river pushed a freshwater plume 40 miles out into the Gulf of California. The end of those flows was sealed in 1963 when the flood gates closed at Glen Canyon Dam. Scientific American ran a story about the “vaquita” in August 2017, which means “little cow” in Spanish, the name the locals give to a porpoise native to the Gulf of California.[vi] Only about thirty survived in 2017, and scientists are trying to capture the last ones in hopes they’ll breed in captivity, something that’s never been done with marine mammals. “The Sea of Cortez is among the most impressive ecosystems on earth,” writer Erik Vance said. “Almost 1,000 species of fish live here, 10 percent of which are found nowhere else. Half of Mexico’s commercial fishing haul comes from this sea.” As with all environmental disasters, there are many causes for the vaquita decline, and drying up the Colorado River delta is only one. Chinese herbalists pay $10,000 per kilogram for the vaquita’s fish bladders, and organized crime has moved in to capture that lucrative trade. But I learned as a boy that the best places to fish in a lake include the inlet streams, since fish hang out there to feed on the critters flowing into the lake. Drying up the Colorado River delta is inextricably linked to the health of the Gulf of California. “Regardless of who is responsible, the vaquita is more than just a lonely animal watching its own sad demise in the turbid Gulf waters,” Vance laments. “Rather it is a harbinger of extinction in the 21st century.”

Today, the river dries up for the last 45 miles of its journey to the sea because Morelos Dam diverts the last flows of the Colorado River to irrigators in Mexico. Below Morelos Dam, saline return flows from an irrigation canal support about 150,000 acres of wetlands in an area called Cienega de Santa Clara. That equals about 7 percent of the area that used to flood as wetlands. In 1999, the Environmental Defense Fund concluded that annual flows of 32,000 acre-feet combined with a pulse flushing flow of 260,000 acre-feet every fifth year would be sufficient to restore constant perennial flows all the way to the Gulf of California.[vii] That amounts to less than 1 percent of the Colorado River’s annual average flow—incredibly, this is all it would take to start restoring the river! As the pulse flow advanced in the spring of 2014, the water had to first saturate the dry ground before the river could actually flow. National Geographic photographer Pete McBride has done as much as anyone to publicize the plight of the Colorado River. He walked this stretch in 2010 and paddle-boarded it during the 2014 pulse release, counting both trips among the most arduous he’s ever taken. (That was before he walked through the Grand Canyon, but that’s another story you can read about in A Walk in the Park.)[viii]

The Gulf of California is a rift valley, meaning that it is widening from plate tectonics, with Baja California pulling west relative to the rest of Mexico about 2 inches per year.[ix] As it widens, the land between Baja California and the Mexico mainland is sinking.” Sea water in the Gulf of California used to extend all the way to present day Palm Springs at the north end of the Coachella Valley, long before such places had names. But when the Colorado Plateau started uplifting around 5 million years ago, the Colorado River carried sediments through the Grand Canyon and filled in the upper reach of the Gulf of California with 20,000 feet of sediment, today known as the Salton Trough.[x] The river would also sometimes flow into the Salton Sea, but when silt deposits raised the riverbed or earthquakes altered the topography, the Colorado River would change course and flow again to the Gulf of California.

Today, man has changed the river’s course, directing what’s left of it into the Salton Sea, instead of the Gulf of California. The Salton Sea is bordered by the San Andreas Fault on the east and the San Jacinto fault zone to the west. Geologists have correlated earthquakes with sedimentary deposits and found a connection between flooding and earthquakes in the Salton Trough. Earthquakes used to occur every 180 years or so, but it has now been 300 years since the last major quake. Geologists are concerned that damming the Colorado River has not only stopped it from flooding the delta and depositing silt but is also preventing moderate stress-relieving earthquakes in the Salton Trough. Pressure is building and the area could be as many as 100 years overdue for a mega-quake measuring 7.5 or larger. A quake that size would pack nearly three times the destructive force of the “Easter Earthquake” that damaged Mexicali irrigation systems in 2010.[xi] Scripps seismologist Debi Kilb compares the stress now building up in the fault zone “to a woman who is 15 months pregnant.”[xii]

The Salton Trough is still subsiding as the rift widens, which is why the Salton Sea’s water surface was 226 feet below sea level in 2013. The Salton Sea dropped to 234 feet below sea level in 2015 and 240 below sea level in 2024, and is continuing to drop because San Diego is taking 200,000 acre-feet every year following an agreement with the Imperial Valley Irrigation District.[xiii] It is in a death spiral leaving it more salty and polluted every year.[xiv]

As one travels south, the Salton Trough contains Palm Springs and its 130 golf courses, the agricultural Coachella Valley, the Salton Sea, the Imperial Valley, the California-Mexico border, the Mexicali Valley, and the Colorado River delta.[xv] Sediments from the Colorado River are responsible for the broad floodplain surrounding the Salton Sea and nearby irrigated agriculture. An ancient lake called Lake Cahuilla covered all of Coachella and Imperial Valleys until as recently as 1600, a huge freshwater body covering over 2,000 square miles to a depth of more than 300 feet. The lake was almost 100 miles long by 35 miles across at its widest point, extending from the delta in Mexico north to the vicinity of Indio, six times the size of the present Salton Sea. It was filled with Colorado River water until enough sediment dropped out and raised the flood plain that the river shifted course again and resumed flowing to the Gulf of California. We know this not only from ripple marks and shell deposits at the lake’s margins, but also from conversations with Indians living in the area before whites arrived. During an 1854 exploration, Indians told Professor William Phipps Blake, one of Yale’s first geology graduates, of a time when a great body of water was populated with many fish.[xvi] The water disappeared 'poco a poco,' little by little, until the lake disappeared. The Indians now living in the desert put this event as far back as the lives of four or five very old men, approximately to 1600 AD.[xvii]

Sediments from the Colorado River didn’t just fill in the basin stretching 130 miles north to Indio—most flowed into the Gulf of California as far south as Tiburon Island, about a third of the way down the Gulf of California.[xviii] In all, sediments from the Colorado River blanketed a region 400 miles long and over 100 miles wide at its widest point, about a quarter the size of Colorado. Glen Canyon and Hoover Dams have stopped this process, a stark reminder of why humans are the dominant factor on earth in landscape evolution today.[xix]

Land Plus Water

The Imperial Valley owes its founding, indeed its very name, to George Chaffey, a farmer turned water engineer from Ontario, Canada. Chaffey had earlier established Ontario and Etiwanda in San Bernardino County in 1881, agricultural communities whose innovations included lined irrigation canals, pressurized water pipes, and hydroelectric plants that harnessed power from irrigation canals. Chaffey obtained water for these communities by tunneling into an aquifer at the head of a canyon in the San Bernardino Mountains, another first in water engineering. By purchasing lots in these communities, the new owners automatically received shares in the water company.[xx] Chaffey tried to duplicate his success in Australia, but the Australian government decided that water systems should be publicly owned, not held for private investment. Chaffey returned to California and joined forces with Charles Rockwood who had been promoting an irrigation canal to the Salton Sink since 1892. Chaffey joined Rockwood’s California Development Company on one condition, that he control it. Rockwood agreed, knowing that Chaffey would give the company sufficient stature to entice investors. With a $150,000 loan from a Los Angeles bank, they started building a diversion from the Colorado River in 1900. The irrigation canal ran parallel to the river until reaching a dry overflow arroyo that Chaffey called the “Alamo.” It then meandered for 50 miles through Mexico before the engineers dug another canal to turn it back north toward California.[xxi]

To obtain permission to route the canal through Mexico, the California Development Company agreed that 50 percent of the water would be delivered to farmers south of the border in the Mexicali Valley. In fact, the top landowner there was Harry Chandler who purchased 832,337 acres in 1898 for $0.60 an acre. To put that in perspective, there were 880,613 irrigated acres in all of Arizona in 2012.[xxii] With the promise of irrigation water, Chandler watched his Mexican land holdings soar to $280 per acre.[xxiii] Chandler, who owned the Los Angeles Times, has been described as the eleventh richest person in the world at the time.[xxiv] His empire included vast tracts in the arid San Fernando Valley and other Los Angeles suburbs that became valuable when the Owens River aqueduct was completed in 1913. Most observers credit Chandler with being the prime force behind the successful campaign in the early 1900s to bring water to Los Angeles from the Owens Valley, which drains the eastern flank of the High Sierra.[xxv]

The first settlers arrived at the Imperial Valley in 1901. By 1905, 12,000 settlers were irrigating 67,000 acres. Real estate promoters marched buyers to the U.S. Land Office in Los Angeles where they could purchase from 40 to 320 acres for $1.25 an acre, with a down payment of only 25 cents an acre. Imagine purchasing 40 acres for $10 down! Homesteaders that purchased land under the Homestead Act had to actually live on the land, but if they bought land under the Desert Land Act, they didn’t even have to live on the property. Many “homesteaders” were actually investors who made a quick visit to the desert, bought water stock, and never returned, instead selling their land and water stock to syndicates from Los Angeles, San Francisco and Portland, according to Power and Control in the Imperial Valley, by Benny Andres.[xxvi] The California Development Company sold shares in the water company, one share per acre, typically on credit with the land providing the collateral to secure the debt owed for water shares. When farmers defaulted, the California Development Company foreclosed on their land, in time owning 200,000 acres and becoming the largest landowner in the Imperial Valley with nearly one-third of its farmable acres.

The turnout from the Colorado River quickly silted in and ended up being five feet above the level of the Colorado River. To solve this, Chaffey floated a mass of brush into the river just below the diversion to create an artificial sandbar. It raised the river enough that water again flowed into the canal for a time.[xxvii] Meanwhile, Rockwood, irritated over Chaffey’s control of the California Development Company, maneuvered to oust him.[xxviii] The river turnout continued to have problems, so Rockwood, back in control, built a succession of turnouts downstream—as one silted in, he dug another to reach the Alamo Canal running parallel to the river. The last turnout was actually built on Mexican soil. None of these had control gates that could close and keep the river in its original channel, an oversight that Rockwood later explained away by saying the river never flooded. A large flood roaring down the Gila River in 1905 directed the entire flow of the now swollen Colorado River into the ancient Alamo arroyo and eventually to the Salton Sea. The river surged unchecked into the Alamo canal from 1905 to 1907, creating a channel a half-mile wide with forty-foot waterfalls. Those were big water years, with flows at the Kremmling gage near the Colorado River’s source nearly reaching or surpassing 12,000 cubic feet per second each year, a very high flow historically at that location.[xxix]

The U.S. Congress refused to take responsibility for the disaster, contending that since the turnout was in Mexico, it was Mexico’s problem. President Roosevelt strong-armed the Southern Pacific Railroad into repairing the breach. The California Development Company went bust, and the farmers that remained formed the Imperial Irrigation District that eventually took over the bankrupt company.

Figure 16.2 How lower basin states and Mexico use 9 MAF

The dark blue slice in the above is water from the Central Arizona Project that is being stored underground in Maricopa, Pinal, and Pima counties where Phoenix and Tucson are located.

Arizona receives over half of its share of Colorado River water, 1.5 million acre-feet, by pumping it 2,900 feet up through 14 lift stations from Lake Havasu at Parker, Arizona, and then piping it 336 miles south to Phoenix and Tucson. It’s a massive project, requiring 2,500 megawatts of electricity. That equals 1,100 times more watts to transport water from the Colorado River to Tucson compared to the 2.2 Mw, it takes to lift water to Orchard Mesa in Grand Junction. In 2024, about 65 percent of CAP water was used by cities and 35 percent by Indian Tribes. Farmers were no longer getting their share after low reservoir levels caused the Drought Contingency Plan to kick in. And much of the remaining water was stored underground as an emergency supply in case Lake Mead levels get so low that Arizona’s share of the Colorado River declines.[xxx]

The Imperial Irrigation District is the largest water right holder on the Colorado River, controlling 3.1 million acre-feet, almost 25 percent of the river’s average annual flow. Some of that water, about 500,000 acre-feet, goes to cities. San Diego, a city of 1.4 million that imports 80 percent of its water, is the biggest beneficiary since it signed a 75-year lease in 2003.[xxxi] Early on, farmers in the Imperial Valley were agitating for Reclamation to buy out the California Development Company, hoping that it could provide cheaper water. But Reclamation demurred because the price was too high and from fear of getting involved in a trans-border water project involving Mexico.[xxxii] A lot of money was at stake−if a private company could build the irrigation system, it would control the water and the revenue it would create.

At the bottom of the Colorado River, Reclamation built Laguna Dam in Yuma in 1909, but that only irrigated land on Arizona’s side of the river. And Reclamation did not play a major role in the Imperial Valley until it built Imperial Dam in 1939. The Imperial Dam blocks the Colorado River about 18 miles upstream of where the Gila River meets the Colorado River at Yuma, Arizona. Imperial Dam diverts the river into three spigots: 2,700,000 acre-feet go west each year in the All American Canal to water the Imperial and Coachella valleys; 600,000 acre-feet goes down the Gila Canal on the east side of the river to irrigate farms in Arizona, and the remaining 1,360,000 acre-feet continue down river.[xxxiii] What water remains in the river is diverted 27 miles further downstream at Morelos Dam to irrigate the Mexicali Valley, an extension of the Imperial Valley on the south side of the U.S.-Mexico border. Morelos Dam typically takes the entire flow, leaving the Colorado River dry. The Colorado River forms the boundary between Mexico and the United States for 22 miles in an area known as the “limitrophe,” a word describing states along a border or frontier. Below Morelos Dam, the river reappears sporadically in brief stretches of the upper 15 miles of the limitrophe where the water table is high enough to support cottonwoods and willows. The Colorado River used to recharge this aquifer, but groundwater levels fell more than 30 feet from 1983 to 2009. Groundwater pumping in the 5-mile zone on either side of the border doubled from about 89,000 feet a year between 1975-2000 to nearly 200,000 feet per year from 2005-2009.

Initially, the water irrigating the Imperial Valley flowed through the Alamo Canal into Mexico before turning back north into the United States. In 1942 Reclamation completed the All American Canal, so named because it flows solely within the United States just north of the Mexican border. The All American Canal is the largest irrigation ditch in the world, 200 feet wide and capable of carrying 15,000 cfs, a level that would be an exciting flow for rafters through the Grand Canyon, where the normal minimum flow is 8,000 cfs. This is the canal’s maximum capacity. On average, the All American Canal flows at one-quarter its capacity, about 3,800 cfs. The canal has been called the most dangerous river in the world, responsible for over 600 deaths. Water in the canal can flow faster than 5 miles per hour, and Mexican citizens trying to swim across have a difficult time escaping the steep and slippery cement walls, particularly when the water is cold during the winter. In 2011 the Imperial Irrigation District began installing lifesaving buoys in 105 straight lines across the canal, despite debates that this safety measure would encourage illegal immigration.[xxxiv]

Resembling Nevada and Arizona, Imperial County is not only the hottest and driest county in California, it was also one of its fastest growing. Imperial County doubled its population from 92,000 in 1980 to 183,000 in 2015, faster than any southern California county except for its neighbors to the north, Riverside and San Bernardino counties.[xxxv] It receives less than three inches of rain a year, and its average daily high temperature all year long is 88oF (31oC)! The hot season lasts for 3.6 months, from June 3 to September 21, with an average daily high temperature above 99°F.[xxxvi]

Here is what Google AI said about Imperial County in 2024: “In 2020, Imperial County's population declined for the first time since the 1960s due to a sharp negative net migration. Imperial County's agriculture industry is not expected to create many new jobs in the future. The county is also one of California's most economically distressed areas. The Salton Sea, the largest and most toxic lake in California, is an environmental disaster in the region. Imperial County's politics have been dominated by a conservative white elite, despite its Latino majority. The county also has some of the lowest voter turnout in California.”[xxxvii]

The Imperial Valley is still primarily agricultural, with farm workers accounting for about 25 percent of all jobs; government and retail are the two other biggest employers.[xxxviii] Even with its accelerated growth rate, Imperial County still has less than 1 percent of southern California’s population. This has people grumbling, since that 1 percent controls 60 percent of California’s share of the Colorado River.[xxxix] In fact, only a fraction of Imperial County’s population owns land in the Imperial Irrigation District, and of the landowners that do, over half live elsewhere, many along the California coast.[xl] The primary crops grown in the Imperial Valley are alfalfa (70 percent), wheat (7 percent), and vegetables (22 percent). I calculate that alfalfa and hay consume 55 percent of all water used by California, Arizona, and Mexico in the Lower Colorado basin. Before 2000, most of the Imperial Valley canal system was unlined. As much as 400,000 acre-feet a year was leaking from canals into the ground, with much of it resurfacing into the New River and Alamo River that drain into the Salton Sea.[xli] When the United States floated the idea of lining the canals, Mexican farmers objected because the porous canals were replenishing the groundwater they were pumping on the south side of the border. Today, much of the canal has been lined. It has sparked controversy since the canal-lining has limited groundwater recharge, just as Mexico predicted.

U.S. and Mexico

Nearly half of the world’s land mass lies in international river basins. Water is often a major source of conflict, as it sometimes is between the United States and Mexico. The United States did not formally agree to share water in the Rio Grande or Colorado River with Mexico until 1944, and that treaty failed to address water quality, groundwater pumping, and what constitutes an “extraordinary drought.” The United States was delivering water that had between 850 and 1,500 salt parts per million after it had been used by American farmers. While that has much less salt than ocean water, crops suffer once saline reaches 800 parts per million, a salt concentration of only .08 percent. Ocean water is 3.5 percent salt, 35,000 parts per million. But the Salton Sea now has 44,000 parts per million, and it is getting about 1 percent more salty every year. What is keeping the salt concentration down are the agricultural return flows pouring into the sea. If they ceased, salt concentrations would grow far more rapidly.[xlii]

Many border aquifers have experienced significant declines in both water quantity and quality, but the United States and Mexico have no broad agreements on groundwater management other than Minute 242, which states the US will deliver 140,000 acre-feet to the limitrophe boundary region “with a salinity substantially the same as that of the waters customarily delivered there.” The U.S. Congressional Research Service said in 2017, “Knowledge about the extent, depletion rates, and quality of transboundary aquifers is extremely limited.”[xliii] This situation had changed little four years later: “While the general perception is that groundwater is being extracted at rates greater than . . . recharge, there are no datasets to assess or confirm this. [T]here is no integration of withdrawal rates and other data into a single continuous database. . .”[xliv] Jay Famiglietti, a professor of global futures at Arizona State University, has been using satellites to track change in freshwater availability and groundwater supplies for the past 25 years. In an interview with May Chari of the American Public Media APM Research Lab on September 12, 2024, Famiglietti said, “I’ve been screaming into the wind about this for 15, 20 years now. We don’t know how much groundwater we have, which seems ridiculous. And the reason we don’t know is because it costs money [to find out].”[xlv]  

Groundwater pumping is limited in the Imperial Valley because the water quality is low from too much salt—agricultural return flows percolating through the soil into the Salton Sea have 4,400 parts per million (ppm) of salt, a level at least four times too high for viable agricultural production.[xlvi] But in the Mexicali valley further south, farmers get over a third of their water from groundwater pumping. I have been unable to find out whether and how fast groundwater levels are depleting. A 2008 groundwater study points out that Colorado River no longer floods to recharge the Colorado River delta south of the border, and that “pumping is a key factor” in capturing the groundwater, but this is merely stating the obvious.[xlvii] Elsewhere in Arizona and California, indeed throughout the West, declining water tables are well documented, but that has not limited groundwater pumping there.

Initially salt was not such a big a problem because Arizona and the Upper Basin states were not using their full Colorado River allotment. Mexican irrigators supplemented saline water with groundwater pumping to keep saline levels manageable. Irrigators in the United States retaliated by increasing their own pumping, creating a groundwater trough below ground that reduced the amount of water left to Mexico and increasing hard feelings. In 1973, the U.S. and Mexico agreed in Minute 242 to limit groundwater pumping within five miles (8 km) of the border to 160,000 acre-feet each.[xlviii]

Today the higher saline return flows in the Wellton Mohawk canal, about 120,000 acre-feet each year, are routed to the Cienega de Santa Clara swamp in the former Colorado River delta 10 miles north of the Gulf of California. Despite the higher salt content, the swamp has thrived, giving scientists hope that the rest of the Colorado River delta can recover. Today the Colorado River delta is becoming more and more saline since the Colorado River has stopped reaching it.[xlix] The tides at the upper end of the Gulf can exceed 10 meters during new or full moons, a rise of almost 35 feet! It rises so high because the tide-driven sea water at the closed north end of the 750-mile long Gulf of California has nowhere to go but up the ancient Colorado River channel. The fresh water that used to flow into the Colorado River delta no longer prevents ocean water from creeping up the delta. The delta is becoming more and more salty as the salt water evaporates and leaves salt behind. The delta is also degrading, since it is no longer replenished by silt now trapped by upstream dams. The river once delivered approximately 160 million metric tons of sediment to the delta every year, equivalent to the volume of six ocean liners the size of the Queen Mary every day.[l] The sediment load today is almost zero.

To drain away excess water, Imperial Valley farmers lay perforated plastic pipe about 8 feet deep spaced at 250 to 300-foot intervals beneath their fields. These pipes carry away the salty return flows. Water entering the All American Canal from the Colorado River at the Imperial Dam contains about 700 ppm of salt, but we’ve seen that return flows that enter the Salton Sea contain more than six times this much salt. In 1981, the Salton Sea was slightly saltier than the ocean (35,000 ppm). Today it has 44,000 ppm, about 30 percent more salty than the ocean. It had 3,500 ppm when it first formed from 1905 to 1907.[li]

Another way to manage salt is to use sprinklers, watering just long enough that water percolates to the bottom of the root zone and no further. This requires using moisture sensors that dictate when fields should be watered and when watering should cease. If salts build up, farmers can give the soil a good rinsing by flooding the field to flush the salt away. Flood irrigation is still common in California, but its use is slowly decreasing, dropping from 70 percent of all irrigation in 1991 to 43 percent in 2010. Drip irrigation replaced nearly all of the fields converting from flooding, since sprinkler use barely budged upward from 15 percent to 17 percent. Drip irrigation lines can even water alfalfa.

Ed Hale Jr., who grows alfalfa in the blazing-hot Imperial Valley, converted his 2,600-acre alfalfa field to drip irrigation. He told reporter Matt Weiser of the Sacramento Bee in 2014 that flood irrigation caused lots of water waste because the field sloped too much, causing water to run off too fast. He estimates that drip lines use about 65 percent less water while doubling the crop yield. [lii] But Hale is the exception.

When you build an irrigation system as massive and complex as Lake Mead and the All American Canal, inefficiencies are inevitable. Lake Mead is 375 miles upstream and it is difficult to time irrigation deliveries so that the right amount is delivered to Imperial Valley farmers at the right times. In 1983, John Elmore sued the Imperial Irrigation District, claiming its wasteful irrigation practices were making the Salton Sea rise and flood his property. Elmore claimed the Imperial Irrigation District could conserve 438,000 acre-feet a year and stop flooding his property if it just adopted efficient irrigation practices.[liii] The irrigation district’s bank-full irrigation canals frequently spilled, and excess tail-water at the end of the irrigation ditches rushed out and into the Salton Sea. Also, Imperial Irrigation only delivered water to its customers in 24-hour batches, with no ability to shut off irrigation when the fields were saturated.

The Metropolitan Water District of Southern California watched Elmore’s lawsuit with interest. In 1986 Metropolitan Water was using 1,162,000 acre-feet from the Colorado River to serve 14 million people in southern California from Ventura to San Diego. The district feared that it would be unable to supply the 5 million new residents that the California Department of Water Resources projected would move into the region by 2010.[liv] In 2014, Metropolitan Water was serving 19 million people, attesting to the accuracy of water planners in forecasting population growth.[lv] In the 1980s, Metropolitan Water was diverting 662,000 more acre-feet per year under a secondary priority because Arizona was not using its full 2.8 million acre-foot share of the Colorado River. When the Central Arizona Project came on line, Metropolitan Water predicted that it would be facing a system-wide shortfall of 560,000 acre-feet by 2000, and 980,000 acre-feet by 2010.

In fact, Metropolitan Water now serves less water to 19 million people than it served to 15 million people 25 years ago.[lvi] Water utilities find a way to conserve when forced to. And nineteen million people is a lot of people.

California is by far the nation’s largest dairy producer, accounting for 18.4 percent of all dairy sales nationwide in 2022, and that is one reason that so much alfalfa is grown in the Imperial Valley.[lvii] But alfalfa production nearly doubled n from 258,918 acres in 2017 to 436,728 acres in 2022 according to the USDA Agricultural Censuses for 2017 and 2022.[lviii] Imperial Valley farmers produce a lot of vegetables, particularly in the winter, accounting for 22 percent of all acres planted. But since the alfalfa crop consumes 7.5 acre-feet of water and vegetables consume only 2.3 acre-feet of water, alfalfa consumed 89 percent of irrigation water in the Imperial Valley in the 2022 USDA Agricultural Census.[lix]

On the other side of the Colorado River, Arizona farmers also grow a lot of vegetables and fruit. Farmers in Yuma County, Arizona, are the nation’s second largest producer of cantaloupe and honeydew melons, spinach, broccoli, cauliflower, lemons, and different varieties of lettuce. Not one of these crops is native to the lower Colorado basin.[lx] Just as in the Imperial Valley, alfalfa consumes more water than any other crop (48 percent of all irrigation water) in Yuma County, Arizona.[lxi]

As Powell and Mead reservoirs kept dropping, the Lower Basin states have been forced to use less water. The Interim Guidelines adopted in 2007 required Arizona to reduce use by 320,000 acre-feet if Lake Mead dropped below 1,075’ elevation. That occurred in April 2021, and Lake Mead has stayed below that level ever since except for two brief months in February and March 2024. If reservoir levels dropped below 1,050’ Arizona would have had to decrease consumption by another 80,000 acre-feet (400,000 total).

Lake Mead in fact dropped below 1,050’ elevation for 12 months from May 2022 through April 2023, but Arizona was spared having to suffer the additional 80,000 acre-foot reduction because of the vagaries of reservoir accounting. It is not the actual reservoir volume each month that determines whether the cutback occurs—it is instead Reclamation’s prediction of the January 1 reservoir level made the previous August that determines whether the cutback occurs (known as the “August 24 Month Study”). This is because water managers need advance notice of what the next 12 month water deliveries will be, and this would be infeasible if releases were changed monthly as the year unfolded. Thus, Lake Mead reservoir releases are determined by predicting what Mead’s level will be on the upcoming January 1, not based on what they actually are on January 1. Because of this accounting rule, Arizona never suffered the second cutback to 400,000 acre-feet required by the Interim Guidelines. 

Nevada also had to reduce consumption by 13,000 acre-feet.[lxii] Nevada’s reduction is so little because Nevada only receives 300,000 acre-feet from Lake Mead each year, compared to California’s 4.4 million acre feet and Arizona’s 2.8 million acre feet shares.

California did not have to reduce its share of Lake Mead releases at all under the 2007 Interim Guidelines because Arizona agreed to California’s seniority as a quid pro quo for California agreeing to support the Central Arizona Project when Congress approved it in 1968. Arizona had to alone suffer the water delivery cutbacks or else California would not have supported the Central Arizona Project and Arizona would not have received any CAP water at all.

As the 2000 drought gripping the Colorado River Basin approached its third decade, Reclamation required the Basin States to further reduce their consumption of the Colorado River. The Upper and Lower Basins each adopted a second set of shortage criteria in 2019 known as Drought Contingency Plans. The Upper Basin States agreed to increase flows to Lake Powell by paying irrigators in the Upper Basin to use less, known as “Demand Management,” and by emptying the the Colorado River Storage Project reservoirs including Flaming Gorge Reservoir in Utah and Blue Mesa Reservoir in Gunnison, Colorado. That in fact occurred in the 2020 and 2021 Water Years. Flaming Gorge and Blue Mesa Reservoirs released 806,000 more acre-feet than they took in, thereby boosting Lake Powell’s elevation.[lxiii]

Under the 2019 Drought Contingency Plan the Lower Basin States agreed to further reduce releases from Lake Mead beyond the cutbacks required in the 2007 Interim Guidelines. Arizona again took the brunt of the reductions, reducing use by another 192,000 acre-feet if Lake Mead dropped below 1,090’ and by 240,000 acre-feet if it fell below 1,045’ on the ensuing January 1 (again as predicted by the preceding “August 24 month study”). Arizona therefore suffered a second cutback of 192,000 acre-feet in 2022, reducing its total 2022 delivery by 512,000 acre feet, and by 592,000 in 2023.

The table below summarizes the situation. Colorado River consumption dropped by about 12 percent each year in 2022 and 2023. Arizona is receiving only two-thirds of its Colorado River allocation, confirming that California’s water negotiators were on the ball in 1968. When there is less in the Colorado River, the Lower Basin states take less out.

[lxiv]

Even California is not immune from water cutbacks, agreeing to reduce use in the Lower Basin Drought Contingency Plan by 200,000 acre-feet if Lake Mead dropped below 1,045’ elevation, 300,000 acre-feet if the reservoir dropped below 1,035’ elevation, and 350,000 acre-feet if the reservoir dropped below 1,030’ elevation. If you wonder how California is managing these cutbacks, it’s pretty simple—it’s growing less hay. The Imperial Irrigation District is paying $300 per acre-foot for conservation through its 2024 Deficit Irrigation Program (DIP), conserving 106,111 acre-feet in 2023. The District’s solicitation for the 2024 DIP has garnered 170 applications covering over 2,300 fields and approximately 160,000 acres of alfalfa, Bermuda grass, and Klein grass (crops that people eat like vegetables don’t qualify). The participation represents more than 85 percent of the eligible acreage, with an estimated at-farm conserved water yield of approximately 215,000 AF.

One thing the Lower Basin states are steering clear of s irrigation efficiency. A drip-irrigation study in 2021-2022 I found on the web reported a ‘huge’ reduction in water and fertilizer use for sweet corn in the Imperial Valley, showing annual water savings of 2.2 acre-feet per acre. But in the comment section to the blog, a contributor going by Dr. Aqua Sprinky said, “The problem is that when water is cheap, expensive solutions don’t pencil out. So in this case saving 2AF per acre could cost $10,000 or more, I.e. $5K per AF. THIS WATER IS WORTH ABOUT $20 in Imperial County. Even with increased yield there is no economic incentive to drip irrigate any crop in this area.”[lxv]

When I Googled “How many acres in Imperial Valley use drip line irrigation” in 2024, nothing useful came back. I got the same result when I Googled this in 2015, reminding me of hundreds of searches I’ve made over the years where I open link after link until I finally discover a tiny morsel of knowledge, if any. The people and organizations who know the answers to these queries don’t want them known. Dr. Aqua Sprinky likely knows how many acres are irrigated with drip lines in the Imperial Valley Irrigation District, it’s probably not very many, and he could lose his job if he tells us how many.

Alex Hager, a reporter who specializes in the Colorado River Basin for KUNC , a public radio station in Greeley, interviewed Imperial Valley farmer John Hawk on July 17, 2023. Hawk’s family has been growing crops in the Imperial Valley since the early 1900s. They probably have some pretty good family stories about the 1905 Gila flood that diverted the Colorado River into the Salton Sea. Hawk, who also serves as a county supervisor, said, “We need to conserve, but we need to be paid for the conservation. We could use drip or sprinklers,” Hawk said. “But you got to remember that the cost goes way up in a crop. And so how are we compensated for doing that?” He thinks cutbacks should follow the longstanding legal system of prior appropriation: "Don't crowd to the front of the line," he said. "It doesn't work, and you'll get a fight out of me."

I can’t think of a single commodity on earth that is more poorly used than water in the Colorado River. That’s the bad news. The good news is there’s lots of room for improvement.

Figures

Figure 16.1 Lake Mead elevation and storage levels

Figure 16.2 How lower basin states and Mexico use 9 MAF

Figure 16.3 Graph showing water consumption to grow the least valuable crops

Figure 16.4 Graph showing cotton production as it relates to subsides and rainfall

Notes

[i] The water providers are the Central Arizona Water conservancy District which operates the Central Arizona Project, the Southern Nevada Water Authority, and the Metropolitan Water District of Southern California.

[ii] Minute No. 319, Sections 2, 3.a., pg. 16, International Boundary and Water Commission, Nov. 20, 2012, http://www.ibwc.gov/Files/Minutes/Minute_319.pdf.

[iii] King, J., Culp, P., de la Parra, C., “Getting to the Right Side of the River: Lessons for Binational Cooperation on the Road to Minute 319,” Fall 2014, 18 Univ. of Denver Water Law Review 1, 104.

[iv] Minute No. 319, Section 7, pg. 18.

[v] Leopold, A., A Sand County Almanac, 1949. Aldo Leopold’s son Luna published A Sand Country Almanac, a collection of Aldo’s papers a year before Aldo’s death; more than 2 million copies have been printed. Luna worked for the USGS and testified before Congress in 1958 that Lake Powell was unnecessary to manage release flows to Lower Basin States and Mexico, as reported in Dead Pool, by Powell, J., 2008, pg. 141, Univ. of Calif. Press.

[vi] Vance, E., “Requiem for the Vaquita,” Aug. 2017, Scientific American, pg. 36. https://www.scientificamerican.com/article/goodbye-vaquita-how-corruption-and-poverty-doom-endangered-species/

[vii] Luecke, D., Pitt, J., Congdon, C., et al, “A Delta Once More: Restoring Riparian and Wetland Habitat in the Colorado River Delta,” June 1999, Environmental Defense Fund, pg. iv, http://www.edf.org/sites/default/files/425_delta.pdf.

[viii] Fedarko K., A Walk in the Park, The True Story of a Spectacular Misadventure in the Grand Canyon, 2024 (New York: Scribner).

[ix] Alles, D., “Geology of the Salton Trough,” Oct. 28, 2011, pg. 2, http://fire.biol.wwu.edu/trent/alles/GeologySaltonTrough.pdf.

[x] For a depiction of these events, see figure 2.4, Processes leading to the formation of Lake Cahuilla and the Salton Sea, from Tompson, A., et al, “Ground Water Availability within the Salton Sea Basin: A Final Report,” Jan. 29, 2008, Lawrence Livermore National Laboratory, pg. 20, http://www.usbr.gov/lc/region/saltnsea/SaltonSeaBasinGroundwater.pdf.

[xi] The Richter Scale is logarithmic, and each 0.1 increase on the scale equates to about 1.4 times more energy. A 7.5 magnitude earthquake is 2.8 times larger than a 7.2 magnitude quake. USGS, "How much bigger is a magnitude 8.7 earthquake than a magnitude 5.8 earthquake?," downloaded Jan. 25, 2016, https://earthquake.usgs.gov/education/calculator.php

[xii] Chillymanjaro, “Faults beneath the Salton Sea ruptured during Colorado River floods,” June 30, 2011, The Watchers, http://thewatchers.adorraeli.com/2011/06/30/faults-beneath-the-salton-sea-ruptured-during-colorado-river-floods/. “San Andreas Fault,” last modified Jan. 24, 2016, and “2010 Baja California earthquake,” last modified Jan. 22, 2016, Wikipedia.

[xiii] Cohen, M., “New Hope for the Salton Sea,” Sep. 3, 2015, National Geographic.

[xiv] Ranoa, R., “Drought, drawdowns and death of the Salton Sea ,” Oct. 21, 2014, LA Times, http://www.latimes.com/local/california/la-me-g-drought-drawdowns-and-death-of-the-salton-sea-20141021-htmlstory.html.

[xv] “Palm Springs Golf Courses & Resort Vacations,” downloaded July 8, 2024,  https://desertluxuryestates.com/palm-springs-area-info/golf/

[xvi] William Phipps Blake was one of the first seven graduates awarded the Bachelor of Philosophy degree at Yale in 1852. He represented the US in the nascent field of geology at world fairs between 1867 and 1878, and ended his career as head of the school of mines at the University of Arizona, 1895-1905. “William Phipps Blake,” Wikipedia, last modified 18 Nov. 2017.

[xvii] Singer, E., “Ancient Lake Cahuilla,” downloaded Feb. 7, 2018.

[xviii] Researchers sampled 114 collection points to determine changes in sedimentation in northern Mexico.  Carriquiry, J., Sanchez, A., Camacho-Ibar, V., “Sedimentation in the northern Gulf of California after cessation of the Colorado River discharge,” Sedimentary Geology, Vol. 144, Issues 1-2, Oct. 2001, https://www.sciencedirect.com/science/article/pii/S0037073801001348.

[xix] “It is estimated that the worldwide deliberate annual shift of sediment by human activity is 57 000 Mt (million tonnes) and exceeds that of transport by rivers to the oceans (22 000 Mt) almost by a factor of three. Price, S., et al, “Humans as major geological and geomorphological agents in the Anthropocene: the significance of artificial ground in Great Britain,” Jan. 31, 2011, Philosophical Transactions of the Royal Society, The Royal Society Publishing, http://rsta.royalsocietypublishing.org/content/369/1938/1056.

[xx] “City History,” City of Ontario, downloaded Jan. 24, 2016, http://www.ontarioca.gov/about-ontario/city-history.

[xxi] “History of Irrigation in the Imperial Valley,” downloaded Jan. 4, 2016, DesertUSA, http://www.desertusa.com/cities/ca/imperial-valley-irrigation.html.

[xxii] USDA Ag Census, 2012, Table 1, Arizona.

[xxiii] Hiltzik, M., 2010, Colossus, pg. 59 (New York: Free Press)

[xxiv] Hiltzik, pg. 104.

[xxv] Ulin, D., “There it is. Take It.,” Fall 2013, Boom, Vol. 3, No. 3, http://www.boomcalifornia.com/2013/09/there-it-is-take-it/. See also, “Harry Chandler,” downloaded Jan. 24, 2016, Wikipedia; Grenier, J.A.,"Harry Chandler,” 1973, Dictionary of American Biography, Supplement 3: 1941-1945, American Council of Learned Societies, available online at “Harry Chandler,” http://sunnycv.com/steve/ar/mm3/chandler.html.

[xxvi] Andres, B., 2014, Power and Control in the Imperial Valley: Nature, Agribusiness, and Workers on the California Borderland, 1900-1940, pg. 16, (College Station: Texas A&M Univ. Press).

[xxvii] “History of Irrigation in the Imperial Valley,” see footnote 23.

[xxviii] Andres, B., 2015, Power and Control in the Imperial Valley, pg. 17.

[xxix] Beeby, J., et al, 2014, Colorado River in Eagle County Inventory and Assessment, Table 3.5, pg. 67, Colorado State University.

[xxx] CAP, “Monthly Deliveries,” 2015, http://www.cap-az.com/documents/departments/water-operations/2015_Monthly_Delivery_Report.pdf.

[xxxi] Lippert, J., “A Few California Farmers Have Lots of Water. Can They Keep It?,” Nov. 4, 2015, Bloomberg Business, http://www.bloomberg.com/features/2015-imperial-valley-water-barons/. “FAQ and Key Facts,” downloaded Feb. 15, 2016, San Diego County Water Authority,

https://www.sdcwa.org/. Fleck, J., “In defense of Imperial Valley farming,” May 7, 2015, Inkstain, http://www.inkstain.net/fleck/2015/05/in-defense-of-imperial-valley-farming/.

[xxxii] Even before Congress created the Bureau of Reclamation in 1902, the USGS had scouted and penciled in several dam sites on the lower Colorado River. See, Dowd, M.J., “IID: The First 40 Years,” 1956, Imperial Irrigation District.

[xxxiii] Arizona’s 600,000 acre-foot share from the Colorado River at the Imperial Dam is split into two irrigation districts, the Yuma Mesa which extends south along the east side of the Colorado River and the Wellton-Mohawk extending east along both banks of the Gila River. Each irrigation district receives 300,000  acre-feet, enough to irrigate about 98,000 acres using 6  acre-feet per acre.

[xxxiv] “All-American Canal,” Wikipedia; “Officials doing little as more migrants drown in Imperial County canal,” Solis, G., Investigative Border Reporter, KBPS Radio,https://www.kpbs.org/news/local/2022/02/08/officials-doing-little-as-more-migrants-drown-in-imperial-county-canal.

[xxxv] Imperial County’s average high temperature all year is 88oF (31oC), and its annual average low temperature is 59oF (15oC). “Average Annual Temperatures for Cities in California,” Current Results, downloaded Jan. 17, 2016. Its population growth rate from 1980 to 2015 was 2.2 percent, 50 percent higher than the statewide growth rate of 1.5 percent. “1850-2010 Historical U.S. Census Populations of Counties and Incorporated Cities/Towns in California,” CA. Dep’t of Finance, March 25, 2013. From 1900 to 2010, Arizona grew 3.7 percent per year and Nevada grew 3.9 percent per year, the two fastest growing states.

[xxxvi] Climate and Average Weather Year Round in Imperial, Weather Spark, https://weatherspark.com/y/2204/Average-Weather-in-Imperial-California-United-States-Year-Round.

[xxxvii] “Why is Imperial County losing population?, Google AI search 11-27-24.

[xxxviii] “Imperial Valley,” last modified Dec. 26, 2015, Wikipedia.

[xxxix] Perry, T., “Despite drought, water flowing freely in Imperial Valley,” Apr. 13, 2015, LA Times, http://www.latimes.com/local/california/la-me-drought-imperial-valley-20150412-story.html.

[xl] Lippert, note 32.

[xli] Loeltz, O.J., et al., “Geohydrologic Reconnaissance of the Imperial Valley, California,” USGS Professional Paper 486-k, 1975, pg. K1, http://pubs.er.usgs.gov/publication/pp486K.

[xlii] Montazar, Ali, “Salton Sea and Salinity,” University of California Agriculture and Natural Resources, Imperial Valley, downloaded November 29, 2024, https://ceimperial.ucanr.edu/Custom_Program275/Salton_Sea_and_Salinity/#:~:text=Salton%20Sea%20salinity%20is%20about,million%20tons%20of%20salts%20annually.

[xliii] This is a slight improvement from a 2015 version of this research paper, where Nicole Carter, the lead author, wrote, “Knowledge about the extent, depletion rates, and quality of transboundary aquifers is limited and in some areas completely absent.” Carter, N., et al, “U.S.-Mexico Water Sharing: Background and Recent Developments,” Mar. 2, 2017, Congressional Research Service, pg. 4, https://www.fas.org/sgp/crs/row/R43312.pdf.

[xliv] Rosario Sanchez, José Agustin Breña-Naranjo, Alfonso Rivera, RandallT. Hanson, Antonio Hernández-Espriú, Rick J. Hogeboom, Anita Milman, Jude A. Benavides,Adrian Pedrozo-Acuña, Julio Cesar Soriano-Monzalvo, Sharon B. Megdal, Gabriel Eckstein& Laura Rodriguez (2021) Binational reflections on pathways to groundwater securityin the Mexico–United States borderlands, Water International, 46:7-8, 1017-1036, DOI: 10.1080/02508060.2021.1999594, https://doi.org/10.1080/02508060.2021.1999594

[xlv] Chari, Maya, “Managing groundwater on the US-Mexico border is challenging—but vital,” APM Research Lab, September 12, 2024, https://www.apmresearchlab.org/10x/border-groundwater#:~:text=by%20Maya%20Chari%20%7C%20September%2012,spans%20the%20U.S.%2DMexico%20border.

[xlvi] Id note 45.

[xlvii] Feirstein, E., et al, “Simulation of G” roundwater Conditions in the Colorado River Delta, Mexico,” May 2008, Univ. of Arizona, pg. 109, http://www.geo.arizona.edu/rcncrd/documents/Delta percent20Study_Eden, percent20Francisco_Maddock_2008.pdf.

[xlviii] Minute 242, Permanent and Definitive Solution to the International Problem of the Salinity of the Colorado River, Aug. 30, 1973, Int’l Boundary & Water Com., Par. 5.

[xlix] Alles, D., “Geology of the Salton Trough,” Oct. 28, 2011, pg. 30. This paper has an excellent photo gallery indicating the geology of the Salton Trough and tidal flows in the Gulf of California.

[l] Id, pg. 23.

[li] Ponce, V., “The Salton Sea: An Assessment,” June 2005.

[lii] Weiser, M., “Flood irrigation still common, but drip method is gaining ground,” Feb. 16, 2014, The Sacramento Bee.

[liii] “Imperial Irrigation District Alleged Waste and Unreasonable Use of Water,” June 1984, Water Rights Decision 1600, State Water Resources Control Board, pg. 3-5.

[liv] Reisner, M., Bates, S., 1990, Overtapped Oasis Reform or Revolution for Western Water, at footnote 18 on page 162, Washington, D.C.: Island Press.

[lv] “Metropolitan Water District of Southern California,” About Your Water, Storage and Delivery, downloaded September 16, 2014.

[lvi] Fishman, C., “How California is Winning the Drought,” Aug. 14, 2015, The New York Times. http://www.nytimes.com/2015/08/16/opinion/sunday/how-california-is-winning-the-drought.html?_r=0.

[lvii] California produced $9.7 billion dairy products in 2022. Wisconsin came in second at $7.4 billion, and no other state had over $3.9 billion, 40% of California’s 2022 production. “Dairy Cattle and Milk Production,” 2022 Census of Agriculture, USDA.

[lviii] USDA Census of Agriculture – County Data, California, Imperial Valley, Table 1, 24, Imperial County, https://www.nass.usda.gov/Publications/AgCensus/2022/Full_Report/Volume_1,_Chapter_2_County_Level/California/st06_2_024_024.pdf

[lix] Imperial County acres under production are from USDA Ag Census 2022, Table 1, California County Summary Highlights,  https://www.nass.usda.gov/Publications/AgCensus/2022/Full_Report/Volume_1,_Chapter_2_County_Level/California/st06_2_001_001.pdf. Water use is from Inouye David, “Crop Water Requirements, Imperial Valley,” State of California, The Resources Agency, Department of Water Resources, Southern District

Planning Branch, Table 5, Estimated Total Crop Water Use Requirement for Major Crops in The Imperial Valley, pt. 13, 1981.

[lx] Pima cotton is native to Arizona, but it was grown on only 3,127 acres out of the 197,455 acres devoted to growing cotton in Arizona in 2012. Upland cotton was grown on the rest, nearly 99 percent of cotton. Upland cotton is native to Mexico and possibly Florida, but not Arizona. “Gossypium hirsutum,” last modified Sep. 2, 2015, Wikipedia.

[lxi] Alfalfa and other forage crops accounted for 52,539 acres, 23% of the total, but 48% of total estimated irrigation consumption. Vegetables accounted for 109,195 acres, 49% of total, but only 30% of water consumption. Yuma County, Arizona, irrigated acreage in 2022 was from USDA Ag Census 2022, Table 1,  Arizona County Summary Highlights, https://www.nass.usda.gov/Publications/AgCensus/2022/Full_Report/Volume_1,_Chapter_2_County_Level/Arizona/st06_2_001_001.pdf. Water consumption was from “Crop Water Requirements, Imperial Valley,” id, note 61.

[lxii] Bureau of Reclamation, ROD - Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead, 1 December 2007 Final Environmental Impact Statement (November 2007). Shortage criteria and cutbacks to Arizona and Nevada are at Section 2(D)(1), page 37.

[lxiii] Flaming Gorge and Blue Mesa Reservoirs released 806,000 more acre-feet than they took in in water years 2020 and 2021. Flaming Gorge released 144,000 extra acre-feet in water year 2020 ending 9-30-2020, and 178,000 extra af  in water year 2021 ending 9-30-2021 (322,000 af total), and Blue Mesa released 289,000 extra af in water year 2020 ending 9-30-2020, and 195,000 extra af in water year 2021 ending 9-30-2021 (484,000 af total). Source: Operation Plan for Colorado River System Reservoirs (24-Month Study) for December 2020, and December 2021, https://www.usbr.gov/lc/region/g4000/24mo/index.html

[lxiv] Bureau of Reclamation, Colorado River Accounting and Water Use Report: Arizona, California, and Nevada Interior Region 8: Lower Colorado Basin, Calendar Year 2022 (and 2023), Table 11, State Apportionments, Adjustments, and Total Consumptive use, Calendar year 2022, pg. 37 (2023 pg. 36), https://www.usbr.gov/lc/region/g4000/wtracct.html. For a table combining Lower Basin cutbacks under the 2007 Interim Agreement and the 2019 Lower Basin Drought Contingency Plan, see Exhibit 1 to the Lower Basin Drought Contingency Plan Agreement, LOWER BASIN DROUGHT CONTINGENCY OPERATIONS, 2019, Table 1, pg. 5.

[lxv] Hsu, M., “Drip-irrigation study sees ‘huge’ reduction in water, fertilizer use for sweet corn,” Univ. Calif. Div of Ag. & Nat. Res., June 16, 2022, https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=53466