Rainwater collection systems have been a fundamental element of green building design. However, as larger green building projects incorporate larger cisterns and water systems, or worse, rely on rainwater for anything but supplemental use, an interesting problem arises. Collecting too much water is against the law.

Water law is a complicated animal, to be euphemistic. It varies depending on what state you live in, and is built upon very old common law principals that immigrated from England with the colonialists. There are two types of water laws: riparian, and prior appropriation. Riparian water laws are from the East Coast where water is plentiful, almost a first come, first served ethos. Appropriative rights however, which is the type of law that dominates most of the West, means that the average flow of a river has been calculated, and that amount of water has been divided among users, who own rights to it.

For instance, the Colorado River is so appropriated that by the time it gets to Mexico (which apparently has no rights) it’s dry. We use 100%+ of the Colorado every year. One hundred percent appropriation is not good water policy, but its common in the West. Now, it’s easy to understand why droughts are so completely disabling in the West; there is very little “extra” to spread around in a pinch. So when green builder XYZ builds a large-scale water cistern system for a development, he or she may be taking a volume of water that has already been assigned -- that other people already own. The rain is destined for specific uses and users before it falls.

Many people who own water rights today have had them in the family since the Native Americans were displaced. Water rights have tremendous value, especially in the arid West. As commodities, water rights have skyrocketed in monetary value based on predictions of long terms droughts resulting from climate change. Farmers, who often hold rights to large quantitites of water, are making huge profits by leasing their water rights in the Southwest and Rockies.

So far, the issue has not seen a serious legal challenge or regulatory attempt. Paul Fleming, who manages climate and sustainability projects for Seattle Public Utilities, told reporters "Since it's been an unsettled issue, I think there was a feeling that we'll [continue promoting rainwater collection] and test it." Some hope for changes to water laws, and there probably will be, but it is unlikely they will become more equitable. Water law is archaic but draws its strength from that tradition.

People who hold water rights will hardly give them up without a fight, and in some cases are willing to kill for them. The Park Rangers in Death Valley, for example, warned my backpacking group in all seriousness that they’d shoot us if we got too close to their water source. Water rights are serious, life-and-death matter in the West; it will be interesting to see where rainwater collection ends up.