The LA Times has a good explainer on the matter.

The winds were so strong that air support was unable to do fire suppression, so it really put pressure on the ground fire operations in the hills.

The demand was so high from firefighters that the pumps couldn't keep up, and the tanks got temporarily exhausted.

It wasn't a matter of LA water shortages per se.

Tankers eventually rectified the matter and air support has been able to fly with the winds improving.