Water Harvesting Making a Comeback

In the American Southwest, water is a valuable resource that is almost always in short supply. Yet, despite the frequent discrepancy between supply and demand, homeowners and municipal managers alike  have been obligated – by law – to let the rain that runs off of their roof or falls in their jurisdiction to go its own way.

Under state water laws in Colorado, Utah, Arizona, and New Mexico, it has been illegal to collect rainwater in the past. Such restrictions relate to long-standing water rights laws that were established during the late 1800’s. These laws separated land ownership from water rights, meaning that land-owners did not necessarily have any claim to the water that ran through or fell on their land.

For example, Colorado water law has been governed by the doctrine of prior appropriation – otherwise known as “first in time, first in right”. In such a system, users are permitted to withdraw a specified amount of water for a beneficial use – such as irrigation or grazing livestock – on a first come, first serve basis. Those with the oldest water rights are guaranteed their water before more recent permit holders are allowed to take theirs. In years of shortage, this means that some water rights owners are left high and dry – literally.

Additionally, because water was allocated as a set, discrete amount, rain water collected by land-owners on their property was considered to belong to someone else downstream. Therefore, collection was technically illegal, as it was thought that diverting water that could potentially feed into nearby rivers and streams.

Yet, an important study that was published in 2007 by Douglas County, Colorado, found that 97% of rainfall never made it to the waterways where water rights owners typically divert their fair share of water. The conclusion was that most of this water either evaporated rapidly, due to the arid climate, or was consumed by vegetation before it could make its way to nearby rivers and streams.

In light of such findings, old laws are being reconsidered, and rain water collection may be making a comeback in southwestern states. As was reported by the New York Times last week, the state of Colorado passed 2 new laws, which will now make it legal for some residents to collect rainwater in the state. In order to legally collect water, however, a permit will be necessary. The law will also allow for the creation of up to 10 test sites to measure the impact of rain water collection. Additionally, in some parts of Arizona and New Mexico, catchment is catching on.

For example, some cities, such as Tucson, are exploring the potential of advocating residential water collection within their jurisdiction. Such developments are likely to be a welcome change for residents, for whom rain water collection has the potential to provide enough water to irrigate a standard lawn for months.

Despite this, the debate about the benefits and drawbacks of rain water collection are likely to continue for some time to come. For example, in Washington State, there is still little clarity in state law that regulates rain water collection. The Washington State Department of Ecology has issued statements, highlighting the benefits of rain water collection, but also stressing that only de minimus amounts of water collection do not require permit.

Even with such murky definition of laws regulating collection, the state has issued island-wide rain water collection permits in the San Juans, where low infiltration rates  make natural water storage difficult and where rain water collection is the only solution to the rapid loss of water resources directly to the ocean. The Washington State Department of Ecology is awaiting further clarification of state law regarding rain water collection other portions of the state, especially for the eastern portion of the state, where allocation is more constrained.

Despite the ongoing debate, there are several benefits of rain water collection that have been well-documented. For example, use of rain water for non-human consumption, such as watering lawns, means that treated drinking water can be used for just that – drinking. Additionally, it has been shown that rain water collection can help to minimize runoff during storm events, thus reducing erosion, pollution, and stress on aging drainage infrastructure.

But, the impacts of climate change and existing water disputes may prove to be barriers to rain water collection in the future. (For more information on this, see a recent publication highlighting these issues further.) Such challenges must be taken into account as new water laws are formulated in the region.