Colorado just came one step closer to making rainwater harvesting a legal option for more of its residents.

Before the new law allowing rainwater collection was passed, it was illegal in Colorado to gather rainwater and snowmelt that fell from a rooftop, patio or driveway into barrels.

Rainwater harvesting occurs when storm water runoff is diverted from flowing to the ground and instead put to beneficial use by the rainwater harvester. However, in the western U.S., unlike in the East, capturing rainwater is generally illegal due to the prior appropriation doctrine that governs water.

Often called the “first in time, first in right” priority system, the first person to allocate and use water is the senior water right holder within a particular stream system. Therefore, taking water from your roof is akin to stealing from downstream water right holders.

Colorado looked to change that, especially after a pivotal study focusing on the Denver area revealed 97 percent of precipitation never makes it to streams, because it is taken up by plants or evaporated. After this research was released, the Colorado legislature voted to allow rainwater collection.

However, strict limits apply. Senate Bill 09-080, which went into effect July 1, states that rainwater collection can happen only if:

Harvesting takes place on residential property

The owner of the property has a legal entitlement to a well

No water is provided in the area by a water district or a municipality

The roof is the only location collecting rainwater

The collected rainwater is put to uses explicitly permitted in the well permit

Given these restrictions, most urban dwellers will not be permitted to install a rainwater collection system on their rooftop in Colorado any time soon.

As a representative from the Water Resources Research Center at the University of Arizona suggests, rainwater harvesting is a great way to augment precious household water supplies, while at the same time actually helping to conserve water by reducing demand on municipal supplies.

However, changing the law in many western states has proved to move at a slower pace than their eco-innovative residents. With numerous legal cases and legislative bills in the works, only time will tell if and when the floodgates to legal rainwater harvesting will open.