The Colorado River — not enough water; too many straws

The U.S. Reclamation Act of 1902 is a federal law that works to fund and manage water projects in the arid regions of the American west. Much of the work is focused on the Colorado River. By the end of the 20th century, the engineers of the Bureau of Reclamation had built the system of dams, reservoirs, and aqueducts that control the river and distribute its waters to the surrounding seven states. About 4 million acres of agricultural land and 40 million people consume the river’s entire flow. By the time the river reaches its estuary at the north end of the Gulf of California in Mexico, its flow is reduced to a trickle. The following map shows the extent and main water features of the Colorado River Basin.

Map of the Colorado River Basin
The Colorado River Basin. Image: Bureau of Reclamation

Today, the viability of the Colorado River project is threatened by two powerful forces: drought and global warming. The regional drought, now in its nineteenth year, has reduced river flow volumes to the point where the basin states, for the first time ever, are talking about cuts to water consumption.

The Hoover Dam is located about 35 road miles SE of Las Vegas. The effect of drought plus global warming is measured by the level of water in Lake Mead, the reservoir for the Hoover Dam. When full, the elevation of the lake surface above sea level is 1,221 ft. — the  lip of the dam. The lowest possible elevation of the lake surface is 895 ft. — the bottom water outlet in the dam. The lake at its lowest water level is known as ‘dead pool’. That’s when the Colorado River downstream from the Hoover dam would run dry. Before that happens, a drop to 1,025 ft. will trigger an emergency and the Bureau of Reclamation will take control and enforce water consumption cuts on all the basin states.

The current water level in Lake Mead (April 8) is 1,090 ft., which is 131 ft below full pool. The level fluctuates by 10 to 12 ft every year due to the spring release of the annual allotment of water to farmers, mainly in California  (see chart below). Since 1983 — the last time the lake was full — the water level has dropped around 4 feet per year on average. If the drought continues unabated and no drastic cuts are made to water consumption, a rough calculation suggests that panic time will arrive in about 12 years.

Chart showing water level in Lake Mead, AZ
Water level in Lake Mead during 2017, 2018, & 2019 (to 8 April). Image from LakeLevels.info

The Parker Dam is located 160 miles downstream from the Hoover Dam. The water backed up by the Parker Dam Is called Havasu Lake. The lake stores water for pumping into two aqueducts, namely the Colorado River Aqueduct that feeds water to Southern California, and the Central Arizona Project (CAP) that delivers water to Phoenix and Tucson in Arizona (see map above). While the Hoover Dam is the Bureau of Reclamation’s greatest engineering achievement, the CAP project may prove to be the Bureau’s last major construction job — and the Colorado River’s last straw.

To reach the Parker Dam after visiting the Hoover Dam, take US-93 to Kingman, then west on I-40, then south on AZ-95 to the dam, a total of 160 miles of desert driving. The source of the CAP aqueduct, and the pumping station that draws its water from Lake Havasu, is located to the left of the highway a few miles short of the dam. The only way to see it is to park by the side of the highway (there are wide gravel verges) and walk to the bridge overlooking the station.

Photo of CAP pumping station on Lake Havasu
CAP pumping station on Lake Havasu

The water for the aqueduct is pumped at the rate of 3,000 cubic feet per second through a 7 mile long tunnel driven upward through the mountain behind the pumping station. The discharge end of the tunnel is 824 ft higher in elevation than its intake end. The aqueduct itself is basically a concrete-lined canal, open to the elements. The aqueduct snakes across the desert to Phoenix and Tucson for a total length of 336 miles. Over its length, there are 12 tunnels and 4 pumping stations. The total rise in elevation from Lave Havasu to Phoenix is 1,247 ft.

Aerial photo of CAP aqueduct
Central Arizona Project (CAP) aqueduct. Image: USBR.gov

To reach Phoenix from the Parker Dam, drive south on AZ-95, then east on Interstate-10. It requires another 170+ miles of desert driving. The CAP aqueduct took 20 years to construct. Completed in 1993, it cost about $3.5 billion to bring water from the Colorado River to the desert city of Phoenix. Will the CAP aqueduct contain water 20 years from today? My guess is, no, not a drop.

Photo of CAP aqueduct, Phoenix AZ
CAP aqueduct looking west from Black Canyon Hwy., Phoenix

Arizona Governor Doug Ducey, is fully aware of the water shortage problems threatening the south-west states. The Governor, however, does not like to talk about global warming or climate change. He prefers the phrase: “transitioning to a dryer future.” Accurate but not accurate enough. If the Governor wants us to face the future squarely, he needs to add the word ‘hotter’ to his phrase. The following graph shows average annual temperature for Phoenix since 1900. It shows that it is indeed getting hotter in that city.

Graph showing average annual temperature in Phoenix AZ since 1900
From U.S. National Weather Service