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Major southwestern city water supplies

So, where does the water supply come from for Phoenix, Las Vegas and Los Angeles?

For Phoenix, it’s water is supplied through surface water sources. The northern end of the city gets water from the Central Arizona Project, which is supplied by the Colorado River and Lake Mead. The southern end gets its water from the Salt River Project.

as Vegas gets 90% of its water from the Colorado River and Lake Mead and 10% from groundwater sources. The groundwater supplies up to 25% during the hot summer months when demand is high. In 1971 Las Vegas with a population of 126,000 residents began getting water from Lake Mead. Today, Las Vegas has swelled to 2 million residents and increases on weekends by an additional 3 million people. Las Vegas gets a 300,000-acre feet allotment from the Colorado River each year. They only use about 240,000-acre feet and bank the rest in the groundwater table. Las Vegas has pumped enough for an eight year supply into the groundwater. The Southern Nevada Water Authority expects growth to outpace current water supplies by 2037.

Los Angeles gets its water supply from three major sources. The LA and California aqueducts supply about one-third of the water to LA from California mountain ranges. The Colorado River aqueduct provides about 50% of the supply to LA. Local groundwater provides about 10% of the supply to LA. The three major aqueducts provide about 7 million MAF/yr to greater LA. When Lake Mead runs dry in 19 years, 50% of the supply to LA (4.4 MAF/yr) will no longer be available.

All three cities will experience major water shortages when the Lake Mead water supply runs out, with Phoenix and Las Vegas experiencing the greatest impacts. Phoenix and Las Vegas populations are expected to double by 2030, thereby compounding these impacts while Los Angeles is expected to shrink by 10%.

So, what’s being done about it?

Phoenix and Arizona at large have led the pack with its groundwater management legislation-1980. This required the establishment of management areas that controls use, imposes conservation requirements and requires banking of water from the Colorado River in underground aquifers. Recent attempts at legislative action in 2020 to better factor in population growth have been shelved and are experiencing heavy lobby opposition. In the long term, Phoenix has plans to drill new groundwater wells and install piping to interconnect the CAP and Salt River systems. Arizona also published the report Long Term Water Augmentation Options for Arizona, August 2019. This looks at conservation, seawater desalination from the Sea of Cortez and brackish water desalination.

Las Vegas and the Southern Nevada Water Authority are planning a 250-mile pipeline to pump groundwater from lower population areas in Spring Valley. SNWA is also considering seawater desalination from the Pacific Ocean, which is 300 miles away.

Southern California first enacted groundwater legislation in 2014 focusing on conservation and LA instituted a “One Water LA” plan to focus on water conservation through 2040. Southern California has also built the U.S.’s largest seawater desalination facility in Carlsbad with more planned for construction.

It’s good to see recognition and action being taken to overcome the impending water shortage issues facing each of these major cities. The question is: Is it being given the priority needed recognizing it as an urgent issue? Nineteen years is not very long to implement a large civil engineering project to provide a solution. What are they waiting for?

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