Farmers at least should know they have to operate in a market, with all kinds of conditionality on interrupting flow, capture of water which falls over their land (but is not entirely theirs to keep, because they are in a catchment for a water supply for other people) -And the same with bore water: there's no extraction without impacting somebody else, unless you're in a very unusual position: ground water is another shared commons.
Reticulated water in domestic contexts? Sure. A lot of people don't understand the social and economic pressures. Down here in Australia, with 10+ year droughts across large metro areas recent history and investment in desalination plants, we have a very good idea of the limits to domestic water usage which can be required of us. The farmers in NSW are at war with themselves and riverine management processes around retention of water flows over land, in the streams.
For the rest of the community, it doesn't matter whether you water you fill your swimming pool or flush the toilet a few extra times. Or does it?
Not because of anything directly in the economics, but because people have really weird ideas and emotional attachments. So instead of charging a market rate proportional to usage (plus a fee to access the network etc, and giving poor people money to afford all this), there's all kinds of weirdness and grandstanding.
See https://slatestarcodex.com/2013/08/25/fake-consensualism/ for a wider exploration of sacred value and taboo trade-offs.
People seem to prefer having the government snoop on and micromanage what you use your water for, eg watering your lawn or filling your pool, instead of charging people a reasonable rate like you suggest.