Thats not the point. The point is that the Colorado River water for California is drawn out of just above the Parker Dam.
Close the water off at the Hoover Dam and you close it off for AZ also.
But, I can go for shutting down the generators at the Hoover and cutting the Power for Kalifornia.
I thought at Hoover there are two release points Arizona and Cal and you can shut one and not the other or adjust one and not the other.