Do you own the water coming out of your tap? In Nevada, the Southern Nevada Water Authority opposes gray water reuse and requires users to return used water through the normal treatment pathways. In other words, the Southern Nevada homeowner pays to borrow the water –not to own it.

Whether you own your tap water or not depends on the supplier you receive it from (i.e. public vs. private suppliers). A more interesting question is: Who owns the rain?

Rainwater harvesting allows people to capture and store the rain that falls on their property. By keeping a stock of rainwater around, landowners reduce demand on the public tap and spare potable water from use in non-essential applications.

You may think you own the rain that falls on your property, but in many cases the water actually belongs to someone else with a “senior water right” in your state. “Prior appropriation,” also known as the Colorado Doctrine, appropriates quantities of limited water resources to whoever laid claim to them first.

Most states west of the Mississippi have adopted the prior appropriation system to deal with water allocation (eight states operate exclusively on prior appropriation, the rest use a blend with riparian water rights). Landowners who possess senior water rights granted by the State are given priority access to water before everyone else. Junior water rights holders are allowed access to the same water resources so long as their use does not prevent senior rights holders from getting their share.

Since rainwater may eventually become part of streams, lakes, and groundwater, some states have forbidden rainwater harvesting because the act intercepts water before it can reach those with senior water rights. Until recently, you could face criminal charges for collecting rainwater in Colorado or Utah.

Policies are changing. Until June 2009 it was illegal to collect rainwater in Colorado without a water right. Today, Colorado residents can install rain collectors after obtaining a permit from the Colorado Division of Water Resources. In October, the Washington Department of Ecology clarified that homeowners do not need to obtain water rights to harvest rain, but it also stated that it would review rainwater harvesting’s impact on existing water rights to make a more absolute judgment.  Utah followed suit in may this year, making it legal to collect up to 2500 gallons in rain barrels but requiring users to register rain barrels with the Utah Division of Water Resources.

While it is now legal to collect rainwater in Colorado and Utah, the fact that you need a permit to do so suggests that the rain hitting your roof still does not belong to you.

Is it legitimate to promise senior rights holders water that hasn’t yet reached their claimed rivers and streams? Or is this extension of prior appropriation on to private property a breach on others’ property rights?  Who has the right to own water? Or should we view water as a shared resource that lies outside the realm of private ownership?

People often advocate graywater reuse or rainwater harvesting without considering the deeper political debate behind water resources. Depending on how you view water and property rights, for instance, rainwater harvesting can be interpreted as theft or it can be interpreted as use of your own naturally supplied water.

We welcome your opinions about water rights. Feel free to comment on this post and let us know what you think!

Sometimes the water rights conflict becomes a state affair. Here are a few historic state battles over prior appropriation:

Wyoming v. Colorado: Wyoming, having claimed rights to the Laramie River before the State of Colorado, sued to prevent Colorado from diverting flow away from Wyoming. The court ruled in favor of Wyoming but granted Colorado a small share of the water in the system.

Arizona v. California: Water from the Colorado River is allocated to states by prior appropriation. Arizona and California have a long history of water conflict around the Colorado. In 1934, Arizona governor Benjamin Moeur sent troops from the state’s National Guard to stop construction of the Parker Dam on the border of Arizona and California. The dam would route part of the Colorado River flow away from Arizona and into Los Angeles.

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