There is a small lake. This small lake is used as the freshwater drinking supply for a small town. The people in the small town are happy with the water.
Then someone downstream decides to grow some cows. The cows are thirsty and use a lot of water. The water comes from the lake, but there is enough rain so the people are still happy.
Then the rain stops. The lake shrinks, but the same amount of water continues to go to the cows. The water is poured onto the ground at the cows' feet. It is surely not wasted, because the water is going into the ground, but the people in the small town do not have enough water any more. They are less happy.
raldi's not calling for farmers to stop using water. He's calling for them to make the same reductions in use that everyone else has had to make. And, yeah, the water really is no longer available once it's used; Lake Oroville is not exactly the voluminous body of water it once was.
There's not really anything terribly controversial here.
Yes, there are differences in using water in one place versus another. I kind of think "growing food" is pretty important use for water though. If OP doesn't want the farmers to use the water for agriculture, then what is it being saved to use it for? Watering golf courses?