some areas may provide Permits For You To Use Rainwater (for a fee). Check with your local rainwater racketeers for details.
Colorado: http://www.denverwater.org/cons_xerisca ... rLaws.html
Colorado Water Law requires that precipitation fall to the ground, run off and into the river of the watershed where it fell. Because rights to water are legally allocated in this state, an individual may not capture and use water to which he/she does not have a right.
Utah: http://www.naturalnews.com/024402.html (couldn't find official docs)
Many people are under the false impression (apparently) that they own the water that falls on their own land. Technically, it's even a violation of Utah state law for homeowners to collect rainwater in a barrel and use it to water plants. Although state officials admit that it is unlikely that they will target individuals, the law states that a valid water right is needed in order to divert rainwater.
Washington: http://www.mrsc.org/Subjects/Environmen ... #Rainwater
Much rainwater collection is already illegal or at least highly regulated in WA state. And in most areas with agriculture I would bet there are similar laws or some sort of legal protection for farmers to buy access to water for irrigation. But our state gov’t has said they will not prosecute home owners who are simply installing rain barrels for personal use, they are more interested in regulating commercial use.
it should be noted that these areas have rarely enforced (or have the resources to enforce) these asinine laws en masse -- but every once in awhile I've seen reports (usually TV or other mass media) of local crackdowns which may serve as cheap deterrents for widespread use of rainwater collection systems in these areas.
for a brief overview of the legal hoops jumped through to make this possible, see:
http://robinson-solutions.blogspot.com/ ... water.html
questions to ask your local legislators:
If I collect rainwater in a barrel that means I’d be stealing from the state. But what about my lawn and flower beds? They absorb some of the water before it runs off into the rain gutter, so is my lawn breaking the law? Do I need to put a big tarp over my house and direct all the rainwater into the gutter for fear of prosecution?
If the rain belongs to the State, it’s effectively the property of the State. In that case is the State liable for damages caused by their property such as water damage and flooding? If they’re not liable for damages caused by their property, is it right that they hold you liable for damages caused by your property?
You can't be serious. Are you fucking serious?
Thankfully, many sane state and local governments in the US encourage, or even require, rainwater harvesting. Tuscon, AZ, Santa Fe County, Bernalillo County and the city of Albuquerque in New Mexico are examples.
Good News for 2009 -- with the new year, some states are reconsidering their stances: http://www.rainwatercollecting.com/blog/?p=122