Nice little trick the left plays with that 80% statistic: they only look at human consumption. The conveniently leave off the amount of water that is diverted for environmental uses like increased river flows for the Delta Smelt. I don't have the number nor the time to find it right now, but I believe the amount that is used for environmental "use" dwarfs what the humans - including the farmers that grow the food we eat - are using.
This is a government made crisis to manipulate
First off, blame the feds for Endangered Species legislation that requires efforts to save the smelt. Second, it looks like the smelt will be extinct within a couple of years anyway. The latest count found exactly one. Third, pumping more water out of the river has the effect of allowing sea water to push inland. The brackish water is already further inland than ever before, and there’s salt buildup in the eastern delta because there’s almost nothing to flush it out to sea.