“On a nonprofit Woodinville farm devoted to sustainable practices, rain hits a green shed roof covered in a carpet of herbs and moss.

Drops run down a chain into four weathered barrels, draining to a small pond ringed by cherry trees, huckleberry bushes and native plants.

Its a system the 21 Acres farm wants to create on a much grander scale when it breaks ground next year on an agricultural center with farm stalls, classrooms and test kitchens. The new addition could store 150,000 gallons of rain to irrigate dozens of adjacent garden plots, currently sucking up expensive city water.

Theres just one problem.

It almost certainly would violate state water law. And if one wanted to be persnickety, so might the rain barrels cities encourage conservation-minded homeowners to buy.

Were all promoting it, its the right thing to do, it makes sense, but its illegal, said Vince Carlson, a meadmaker and architect for 21 Acres. Nobody says anything, and were all kind of hush-hush about it.

Technically, rain that falls on your roof isnt yours for the taking. Its a resource of the state, which regulates the use of public waters through an allocation process that can take years to navigate.

The state has long allowed people to collect a small amount of rain without asking.

Although no one wants to police homeowners harvesting a few hundred gallons for a backyard garden, the state hasnt defined where that regulatory threshold lies. Someone collecting rain in larger quantities to irrigate a farm or wash laundry in a new condo building without a state water right could be breaking the rarely enforced law…

A well small enough to be exempt from state regulation runs on a solar pump, filling a new 5,000-gallon tank designed to irrigate the agricultural fields. The proposed rain storage system would soak smaller garden plots, currently watered with an octopus-like tangle of hoses drawing Woodinville water.

With little hope the farm could get a new water right, theyre not planning to apply for one. Instead, Carlson and others hope the state makes it easier to legally collect rainwater…

He worked for six years to legalize small-scale rainwater harvesting. But thresholds kept rising as interest groups cities, gravel mines, builders weighed in.

Some large water users would like to see rainwater collection projects exempt from state permits, unless a downstream water user argues they would be harmed,” quoting the Tacoma News Tribune.