Here’s an article discussing a massive tunnel project in Northern California to move water to the southern cities.  More and more people are actively digging tunnels and pipelines for water in California.

https://calmatters.org/environment/water/2025/03/california-delta-tunnel-residents-fear

‘This will make our town uninhabitable’: The long-awaited Delta tunnel strikes fear in locals

In an early iteration in 1965, the Delta tunnel was to be an aqueduct. Billed “the peripheral canal,” it was killed by voters in 1982. It reemerged in the 2000s as a pair of tunnels. In 2019, Gov. Gavin Newsom downsized the plan to a single tunnel and has promoted it since.

California’s Natural Resources Secretary Wade Crowfoot said the “whiplash between very dry conditions and very wet conditions” gives the project great urgency. In December, Newsom called the tunnel “the most important climate adaptation project in the United States of America.”

According to state officials, the tunnel will increase annual Delta exports of water by half a million acre-feet, enough to serve almost 5 million people. Buckman said this will offset expected water losses this century due to climate change.