A solution that holds water

Harvesting rain offers a common-sense alternative for new developments in dry West

By Harold Smethills

Saturday, November 17, 2007

George Kochaniec Jr. © The Rocky/2003

Far View Reservoir in Mesa Verde National Park is one of four prehistoric reservoirs built and used by the Anasazi to capture and store storm runoff and spring snowmelt.

It's often a wise move to examine the past and see how our ancestors met some of the challenges we face today.

One common problem we Westerners continually face is how to best meet the continually rising demand for water. We in the Front Range love our high desert climate of dry sunny days and crisp nights, but these delightful advantages are coupled with a limited supply of water. In fact, some alarmists have been saying that the entire West is drying up.

When I thought about how Coloradans of the past handled water needs, I was struck by the good sense of our oldest Colorado predecessors - the Anasazi Indians living in the arid conditions of what is now Mesa Verde National Park in the Four Corners area of southwestern Colorado. Simply put, the Anasazi collected and stored rainwater, an effective solution. Rainwater harvesting is practiced in various forms in states surrounding Colorado, including Arizona, New Mexico and Texas. The verdant island of Bermuda in the Atlantic has for hundreds of years harvested rainwater. I submit that rainwater harvesting is a significant part of a water- conservation ethic and can help Colorado progress toward sustainable development. There was a time in America when every country home had a rain barrel.

What's preventing Colorado from using rainwater harvesting? The stumbling block is that Colorado water law makes rainfall part of river water. If rainwater is harvested, Colorado law requires that it must be put back in the river for downstream users.

A recent Douglas County study challenged that concept, and could be the first step in changing our water law. The study focused on a large undeveloped area of northern Douglas County, but its findings are certainly applicable throughout the Front Range.

Conserving rainwater is a common-sense solution for renewable water needs in new developments and areas relying on nonrenewable groundwater supplies. Today, it is simply illegal to put a cistern on your property, capture precipitation and use it to water your lawn. Why? Because the law assumes that the rain or snow you are capturing would otherwise return to the stream system or to groundwater, and when it returns it is owned by someone who has a legal right to it. That could be the case for existing developments. However, for new development the study shows these assumptions may be wrong.

A consortium consisting of the Colorado Water Conservation Board, the Dominion Water & Sanitation District, Castle Pines North Metropolitan District, Douglas County, Thunderbird Water and Sanitation District and Plum Valley Heights Homeowner Association commissioned the study. The firms of Leonard Rice Engineers Inc. and Meurer and Associates provided the technical expertise.

The study used science to tackle two significant questions:

* What can we determine scientifically about how much precipitation that falls in a given location really makes it back to the stream system as either surface water or groundwater and is therefore legally spoken for?

* Can we capture water that has not historically returned to the stream system for new landscaping uses?

The study found that only a very small percentage of the total precipitation that fell on the undeveloped study site returned to the stream system - and possibly none returned.

For example, the study indicated that in a dry year, none of the precipitation that fell on the undeveloped site made it back to the stream system. In a wet year, only about 15 percent of the precipitation would return to the stream system.

The study is clear. When the study site is developed - and the development is combined with waterwise landscaping - harvesting rainwater would have the potential to ease pressure on existing water resources. The study showed that with just moderate conservation - sensitive landscaping outdoor water demand can be cut by approximately one-third. If there is aggressive waterwise landscaping - known as xeriscaping - outdoor water demand would be cut by more than 60 percent.

The study indicated a number of other potential benefits from practicing rainwater harvesting:

* Reducing consumption helps conserve the drain on existing groundwater, eases the pressure for more water storage projects and reduces the energy costs to treat and distribute water. It further reduces the pressure to dry up farms for the purpose of growing grass and shrubs in the metropolitan areas.

* Reducing peak summer water demands and peak summer energy demands associated with pumping water through distribution systems.

* Helping planted landscapes thrive with rainwater irrigation because untreated water is better for plants than typical deep groundwater supplies.

Rainwater harvesting is an old idea that's new and vital again. It's time for our legislators to rewrite our water law and enable us to make real water conservation progress.