Some Random Facts About Water Harvesting

May 18, 2016

In May 2016, the governor of Colorado signed a bill legalizing rain barrels. Before then, the capture and use of rainwater, even on so small a scale, was illegal in Colorado. It wasn’t the first time such a bill had been proposed—a similar effort failed last year—and the decision, hailed by conservationists, is still controversial because of the complex system of water rights within the state; opponents of the bill say it will reduce the amount of water available to senior water rights holders. You can read more about the bill and its history here.

We’ve run articles in Stormwater dealing with the use of harvested rainwater—this one, for instance. A recent blog post from the Arizona Municipal Water Users Association (AMWUA) delves a bit deeper into the related question of just how to put recycled water to use—specifically, things homeowners should think about before using water from the laundry to irrigate their landscaping. Using graywater—that is, water from clothes washing machines, bathroom sinks, tubs, and showers, as opposed to “black water” from kitchen sinks, dishwashers, and toilets—is becoming a more popular option in Arizona and elsewhere as people try to reduce their potable water use.

The AMWUA encourages the practice, but cautions that it needs to be done right. The post raises some excellent points that many of us wouldn’t have thought of. For example, certain detergents are better than others. (The blog contains a link to a list of popular commercial detergents and the characteristics of each, such as conductivity, alkalinity, and sodium, boron, and phosphate content, along with an explanation of what each of these means for the health of the soil and different types of plants.) You’ll probably have to give up using water softener, which adds too much sodium to the water. You don’t want to irrigate close to your house with graywater, because it can stain walls and damage the foundation. And you won’t want to use it to irrigate most kinds of food plants—those where the edible vegetable or fruit will come into contact with the irrigation water. (Although it’s fine for citrus and nut trees.) 

The blog also urges homeowners who are considering the process to get a professional to handle the plumbing; one city even offers a rebate to help pay for installation of a graywater system. Still, AMWUA points out, even if homeowners don’t use the graywater themselves, many Arizona cities are putting it to use for them—recycling wastewater for irrigating parks and golf courses, cooling the Palo Verde Nuclear Generating Station, restoring groundwater supplies, or simply storing the water for future use. (If you’re storing graywater yourself, the blog cautions, make sure you’re not creating an ideal habitat for mosquitoes.)

One additional note on terminology: As one of Stormwater’s long-time readers—who is also a member of the American Rainwater Catchment Systems Association—has pointed out, the words “use” and “reuse” are commonly misapplied; we can’t reuse something that hasn’t been used before. “Whether we harvest rain or storm water, or wet-weather runoff from a roof, parking lot, or storm drain system, it is a first use. When captured and treated, this water resource is ready for non-potable and potable applications or uses. It is not a reuse, though most in our profession speak of reuse when talking about rain- or storm water capture and applications,” he wrote in an editorial for Stormwater. (You can read the whole article here.)

Are rain barrels or other lot-level means of rainwater harvesting commonly used in your area? What about large-scale recycling of water from treatment plants?

About the Author

Janice Kaspersen

Janice Kaspersen is the former editor of Erosion Control and Stormwater magazines.