Not really, since other than the small amount of water that gets shipped out in the plant, the rest is just released right back out. Besides, as long as you're only collecting the water that falls directly on you as rain, you're not taking any more than your lot; someone 'downstream' can also collect water that falls directly on them.

That's great if the entire river system is continually receiving decent amounts of rain. In most real world scenarios there's a rain-rich area in the top of the watershed, then a less rain-rich but flood-prone area, then a bit more rain closer to the seashore, then the river delta.

In Australia for example there's a practise of "flood water harvesting" where you build large earth walls along your property boundary, and collect all the water that falls on your land. Combined with irrigation downstream this means the river dries up in the space of a hundred kilometres.

There's very little water released back into the river, since that's basically wasting water as far as the agriculture industry is concerned.

If you’re talking rain barrels, sure. But some states in America make it illegal for you to collect rainwater on your own property because it legally belongs to someone else.