Newsom didn't let southern California get northern California water!

Sigh. If you don't know California water policy, please stop.

First, most LA water comes from the Colorado River (via the infamous Metropolitan Water District), the Owens Valley (Eastern Sierra), and local ground water, not from northern California. But LA does get some NorCal water via the State Water Project. This wager has to be pumped up a 2,000 foot elevation gain to transfer it from the Central Valley over the Tehachapi Mountains (and San Andreas Fault) to LA. That's energy intensive, so expensive, and the pipes have a limit to their capacity, so even though the pumps don't run 24/7/365, there's a limit on how much more NorCal water LA can get without expanding this (wonder of the world, IMO) infrastructure.

Second Newsom never vetoed a bill to transfer more water from NorCal to SoCal because no such bill ever existed.

Third, Newsom did apparently oppose a Trump proposal to direct more water from the Sacramento-San Joaquin Delta to Central Valley farmers. But however one feels about smelt v. agriculture a) that's not a state bill Newsom could refuse to sign, b) because a President does not have authority over the State Water Project, this proposal must have been for the federally managed Central Valley Project, and c) the Central Valley is in no way part of SoCal, so d) although wager can be transferred between the State Water Project and Central Valley Project, sending more water to Central Valley farmers does not necessarily make one drop of water more available to LA.

Fourth, the reports are that LA area reservoirs were at peak capacity, meaning no more water could have been hens there in preparation anyway. The already-famous "hydrants running dry" story appears to have occurred because the reservoirs were being emptied much faster than usual (washing dishes and taking showers uses less than fighting massive fires), and because power had to be cut off, or was cut off by fire, in some areas, making pumps unavailable to immediately refill those reservoirs from upstream reservoirs. But they have been refilled now, because there is no current water shortage, and I would eager that water is flowing down from the Owens Valley, being pumped in from the Colorado River, and being pumped over the mountains at whatever rate is necessary to replenish the LA area reservoirs.

So, what's the big water to-do all about? Knee-jerk ideological/partisan attacks stoked by the outrage machine. Nothing more than that.