Cadillac Desert [0] remains as relevant as always.

The state of water security is California - and the US West more broadly - is a fascinating history problem in my mind. I focus on California due to the enormity of its investments to attempt to sustain its massive population. And within California, I think a lot responsibility for the current state of affairs falls on the head of Los Angeles.

The City of Los Angeles Dept of Water and Power serves a population of over 4 million. Only 13% of that water is from local/recycles water supplies. That approximates to a natural water supply that can sustain around 500,000 people. To sustain the current and forecast populations, ~40% of water is pulled from the SF Bay Area Delta and another ~40% is pulled from the Eastern Sierra. The remainder is pulled from the Colorado River. From my last study of the subject over a decade ago, effective desalination strategies were still forthcoming.

The survival of Los Angeles - and the broader Southern California region - is heavily dependent on these outside sources. And each sources has it's own threats and challenges.

Receiving water from the Bay Area Delta is the result of the State Water Project (SWP) - which happens to be the single largest energy consumer in the state of California (it takes a lot of juice to pump all that water up and over the mountain ranges that separate Southern California from the Central Valley). One threat that water/government agencies have been concerned about is the affect of a major Bay Area earthquake on the SWP and on the water supply of Southern California. If the levees scattered throughout the Bay Area Delta were to fail in significant quantity, salt water would be pulled in from the Pacific and would contaminate 40% of Los Angeles's fresh water supply (affecting over 1.6 million people). To avert this potential crisis - there have been talks for 20-some years to build a tunnel and divert the SWP-bound water from the Delta. The State of CA has put forth plans to proceed with the tunnel bypass [1] - at an estimated cost of 16 billion.

Then we have the Eastern Sierra - which, again, contributes nearly 40% of water to Los Angeles. The historic extraction of water from that region has resulted in a least one massive (mostly) dried lakebed (Owen's Lake) [2]. It should be pointed out that this dried lakebed became one of the single largest sources of particulate pollution (PM-10 - sand/dust) in the United States. While Owen's Lake is no longer the largest single source, Mono Lake (also in the Eastern Sierra) now is. While that lake has not been drained, is has had it's natural water sources diverted to supply Los Angeles (I can dig for those data points if need be). The extraction of water in that region has been directly attributed to the desertification of the landscape and the changing of the ecosystem.

Beyond the situation with the Colorado River, California has much to grapple with. Balancing decades of unruly development and population growth is an issue that will need to be handled for generations to come.

For a 'fun' read on the development of Los Angeles, check out the aptly named book, "Reluctant Metropolis" [3].

[0]: https://archive.org/details/cadillacdesertam00reis/

[1]: https://www.deltaconveyanceproject.com/

[2]: https://en.wikipedia.org/wiki/Owens_Lake

[3]: https://archive.org/details/reluctantmetropo0000fult