What's a fair way to divide up something that's scarce and valuable? That "something," in this case, is water.
The California drought actually has 2 parts of the conflict to it. 1 part is the addressing the actually drought itself. However, the 2nd part is always emphasized more than the essential conflict, the drought, which is how to deal with the current situation, dividing up the water so it could please everyone, rather than how to fix the current essential conflict.