English Chick, laws in states with high rainfall are much like the UK. It's when you get out west that things get interesting. There are plenty of "ponds" and "streams" that are bone dry for 6 months out of the year.
""If you try to collect rainwater, well, that water really belongs to someone else," said Doug Kemper, executive director of the Colorado Water Congress. "We get into a very detailed accounting on every little drop."
Frank Jaeger of the Parker Water and Sanitation District, on the arid foothills south of Denver, sees water harvesting as an insidious attempt to take water from entities that have paid dearly for the resource.
"Every drop of water that comes down keeps the ground wet and helps the flow of the river," Jaeger said. He scoffs at arguments that harvesters like Holstrom only take a few drops from rivers. "Everything always starts with one little bite at a time."
Increasingly, however, states are trying to make the practice more welcome. Bills in Colorado and Utah, two states that have limited harvesting over the years, would adjust their laws to allow it in certain scenarios, over the protest of people like Jaeger.
Organic farmers and urban dreamers aren't the only people pushing to legalize water harvesting. Developer Harold Smethills wants to build more than 10,000 homes southwest of Denver that would be supplied by giant cisterns that capture the rain that falls on the 3,200-acre subdivision. He supports the change in Colorado law."
http://articles.latimes.com/2009/mar/18/nation/na-contested-rainwater18