I'm a fifth generation CA native and know my very large Golden State -- the only states bigger are Alaska and Texas -- pretty well. It's amazing what some people consider "desert." I heard radio clowns John & Ken (KFI) once describe Cholame, where James Dean was killed in an auto wreck, as "out in the desert." Right -- rolling hills with creeks, oak trees, grazing land, and dry-farmed fields of livestock feed. If that's a desert, I'd hate to know what they thought Lancaster and out Edward AFB way is. Super desert???
I'd say maybe 25 percent of CA is actually desert -- you could irrigate those areas it 'til the cows come home and still not grow much of anything but scrub. The great, flat, and (when not irrigated) bone-dry San Joaquin Valley isn't a desert, it's a dried-up ancient inland seabed, which is why its soil is so fertile that it feeds (or did until environmentalists put a stupid tiny fish higher on the food chain than humans and stopped irrigation for farmers) most of the U.S.
It's such a myth that "Southern California is really one big desert!" Wrongo. Even before water was brought in, most of Los Angeles proper and the San Fernando Valley, and the areas from LA down to San Pedro and on down through Orange County all the way down to San Diego, are so UN desert that people settled to live here, farm, ranch, and prosper LONG before water was shipped in.
I've read enough California history and seen enough old photos, and talked to enough old-timers who remember life here in the 1800s, to know better than to believe the ol' "California is mostly desert!" poppycock.