[jonhohle]

I don’t understand the justification for not allowing the collection of rain water on private property. If airspace is owned by the owner, what claim does the state have to any water that falls? Why limit to water and not sun or wind?

Water rights from streams and rivers make sense, since there are obvious, literal downstream effects.

In Arizona, where aquifers are continually at risk, there are no state laws against water collection.

[jcrawfordor]

The streams and rivers are charged by rainfall. If stream and river water is property of the state, the rainwater must be as well, otherwise owners of well-placed property can greatly diminish the downstream flow of rivers through strategic earthworks. This isn't a theoretical problem, it has happened fairly regularly in high-rainfall areas. The legislation in Oregon is a result of past practices by ranchers who would dam the lower watersheds of their property and eliminate streams.

The concern here is much less in southwestern states like Arizona because rainfall is only an extremely small portion of aquifer charging. Most water entering this region is the result of snow and snowmelt in further north states, so you can't really change much through control of precipitation... consider, for example‚ that Arizona has had a very unusually wet monsoon season this summer, but this has had basically no effect on Lake Meade. The total rainfall in Arizona is a tiny portion of river and reservoir volume.

Broadly speaking, water in Arizona and New Mexico is the result of precipitation in Colorado and Wyoming. Water in Oregon is mostly the result of precipitation in Oregon (excepting the major Columbia river system which involves BC).

[PaulDavisThe1st]

The airspace is not owned by the land owner, certainly not above a relatively low height. Since the rain originates outside the owner-controlled slice of airspace, there's an argument that they do not have the right to control it.

[dredmorbius]

There's an interesting (and in my view very poorly grounded in factual basis) common law (caselaw) doctrine called Rule of Capture which applies in at least some jurisdictions concerning various "wild and migratory" resources, including both wild animals and mineral resources, with notable case history involving both groundwater (see Pecos County Water District #1 vs Clayton Williams et al (1954), concerning Stockton, TX) and petroleum and natural gas.

<https://en.wikipedia.org/wiki/Rule_of_capture>

I'd written up the Stockton, TX, case at Reddit: <https://old.reddit.com/r/dredmorbius/comments/5w1zw3/rule_of...>

I'd submitted an article some years back that's one of the few I've found even discussing the principle:

<https://www.texasobserver.org/playing-by-the-rule/>

<https://news.ycombinator.com/item?id=18005310>

What's fascinating to me are a few elements of this rule:

- It's effectively an argument from ignorance, with a key element being that the behaviours of these resources is not and cannot be known. Increasingly, both premises are now false, but significant case law still stands. One specific being a Texas Supreme Court ruling, Houston & Texas Central Railroad Co. v. East (1904). I've been unable to acquire a copy of this and would very much like to do so.

- The principle has exceedingly interesting implications over just what "property" is, and where property rights emerge. Given the centrality of this principle to virtually our entire present economic system and technological civilisation, this seems ... important.

- There's been some movement against Rule of Capture, and in particular, the concepts of unitised production (concerning oil and gas in Texas) and "certificates of clearance" (instituted by the US Department of Interior under Harold Ikes), both in or around 1931. National producers (notably Saudi Arabia) have instituted their own novel solution through a family-owned / nationalised oil industry But so far as I'm aware, the principle still stands as valid caselaw.

And, incidentally, you're correct on the airspace issue, see US v. Causby (1946) <https://en.wikipedia.org/wiki/United_States_v._Causby>. I was interested in the other elements discussed above.

[WJW]

Eventually all streams and rivers get fed from the rainwater in their catchment area, so catching/collecting rainwater does have downstream effects.

[jonsen]

You can't hold it indefinitely. Eventually you will have to pass it on. When the process settles you will just induce a delay.

[tmnvix]

You can capture it and export it in produce though. It's not just a delay.

[idiotsecant]

You might be surprised to learn that all fresh water was in fact rain on someones property. Rainfall is the water in streams and rivers. I'm not sure what logic allows illegal use of rainwater but doesn't allow illegal use of lake water.