I understand the legality behind water rights. If enough people were to strip the rain from the ground, then it would affect people downstream. I do agree with you though, that the promise this water is all going to wind up downstream or in the water table is iffy at best.
I’ll give you an example. Here probably billions or even trillions of gallons of water can enter the L.A. river system during a rainy season. That’s kind of misleading, because what we’re actually talking about is a system of concrete troughs designed to collect the water and shunt it off in a non-destructive manor.
The L.A. river channels can flow near maximum at times, almost dry at others. When it flows hard, the vast majority of the water winds up in the Pacific Ocean. As it flows into the ocean, it actually fouls the water, a lot of vile garbage being washed out along the way to the ocean.
What do you think, 0.2% of the land in Colorado having property on it by volume? I’m sure the humans could in any measurable way stop the water from going down stream.
You’ve got some bureaucrats throwing their weight around IMO.
The other factor, which the study took into account, was evaporation. (I believe dissipation into the soil that doesn't make it to the water table was another factor.) Having seen three and four foot of heavy wet snow evaporate in less than 48 hours here in CO that was my first thought about where most of the water goes.