DENVER -- Every raincloud that passes over her eastern Colorado ranch tempts state Rep. Marsha Looper to break the law.

A long, hard drought has settled across the land, and on those rare occasions when the sky opens, Ms. Looper longs to set out some rain barrels to collect the bounty for future use. She'd like to use the rain to grow hothouse tomatoes. But she refrains.

"I don't want to get thrown in jail," she explains.

It is, in fact, illegal in Colorado to collect rainwater. State law is vague about the penalties, except to say that violators can be taken to court and ordered to pay damages. The state lacks the resources for vigorous enforcement and fines are extremely rare, officials say. Still, the law is the law -- and so Ms. Looper has set out to change it. This might just be her year.

Colorado, like most Western states, lives by a rigid and byzantine knot of water laws. Vast quantities of river water are made available, free of charge, to a variety of public and private interests, including oil companies, ski resorts, fire districts and breweries. The international food conglomerate Nestlé has applied for a permit to draw water from a Colorado aquifer and sell it in plastic bottles under its Arrowhead brand.