Master Naturalisits: There are many variations of rainwater harvesting
July 7, 2010 at 2:07 a.m.
By Paul and Mary Meredith
While Hurricane Alex threatened the Gulf Coast, we joined several other Texans in learning about rainwater harvesting - its benefits for Texas and how we can harvest rainwater.
Texas doesn't have enough water to keep on doing what we want to do. Citizens in some parts of the state are working to use rainwater harvesting to increase the amount of water their residents and/or businesses have to use.
Rainwater harvesting offers ways to increase our water resources and to use those resources more effectively, so that we can have larger water supplies. It includes ways to capture more rainwater to use. It also includes more effective and efficient ways to use our water resources to achieve our objectives. We can utilize existing systems, or we can design custom systems to collect and utilize our water resources. We may use techniques that others have found effective, or we may devise other techniques to reach our goals.
Ways to accomplish those goals are what we learned.
Understanding how our water system works
To start, we need to understand more about how rainwater works. A demonstration display has been designed to show how rainwater retention works, so we can apply better retention techniques to increase the amount of water available to us.
The display shows how rainwater falling on different kinds of surfaces acts once it hits the ground. Water hitting the ground can soak into the ground to become groundwater, or it can run off. For example, running off is common when rain falls on typical paved surfaces. The runoff flows into storm drains and water drainage ditches, unless it is harvested for other uses.
Some other alternatives the demonstrator can show about what happens to falling water usually deal with situations where water falls on areas where turfgrass or "bunchgrasses" grow.
Bunchgrasses are grasses that grow in clumps or bunches. Some are "well-mannered" and can be planted in flower beds, perhaps instead of small bushes. They remain clumps, rather than spreading like many grasses tend to do. Examples of these bunchgrasses include sideoats grama, little bluestem, Indiangrass and upland switchgrass. However, other bunchgrasses take over larger areas. They can be used for erosion control or for large areas of landscape. Examples of those bunchgrases include Indian seaoats and lowland switchgrass. Bunchgrasses, compared to other grasses, have very long roots - generally as long as the grass is tall. The long roots convert falling water to groundwater, so it may be available for future use. Turfgrass, however, has much shorter roots and, especially when it's affected by, for example, like being walked on, cannot convert much water hitting the ground into groundwater. The demonstrator part for turfgrass areas shows that most water falling on it becomes runoff.
Most people seeing the demonstrator probably find the most startling part is the part providing an example of what happens when water falls on hard surfaces. For the demonstrator, we're setting up a bird feeder shaped like a schoolhouse, sitting on a piece of hard plastic.
The scenario depicts a building sitting on an impermeable surface, like typical pavement in a parking lot. Rainwater falling on the schoolhouse roof runs off the roof onto the pavement, becoming runoff. But we've modified the schoolhouse to have functional gutters.
When rainwater falls on the schoolhouse roof, some runs off through those gutters onto the paved surface. But when collection tanks are placed under the low end of the gutters, water running off the schoolhouse roof through the gutters can be collected in those tanks and used for other purposes. The tanks can include such things as barrels, trash cans and other "tank-shaped" containers.
Another benefit of rainwater harvesting is wildlife watering. It can be done by constructing a lean-to of sorts. The lean-to's roof is sloped, corrugated metal. And the lean-to sits atop a wooden base that has all four sides open. A collection tank sits under the roof. A gutter is attached to the roof's lower edge, and a PVC-pipe drain is attached to the gutter to collect water and condensate into the tank. A drip outlet attached to the tank's lower edge allows water to flow from the tank at a rate of one drip a second (about a gallon a day) into a shallow pan, shaped like a bird bath. The pan holds the water collected for animals to drink when they visit the tank. Depending on the tank, more than one drip outlet and pan can be used.
A motion-sensing camera attached to the waterer takes photos of animals visiting at night. One photo we saw showed a mountain lion drinking from a wildlife waterer located northwest of San Antonio. A larger waterer or smaller wildlife waterer can be set up by using a larger or smaller tank to collect the moisture. A smaller waterer usually has the tank lying on its side under a shorter stand.
We first saw a wildlife waterer near Fort Davis in 2005, in an extremely dry area. The waterer consisted of a corrugated tank whose top was attached upside down (pointed side pointing down into the tank), so that water and condensation hitting the upside-down roof ran into the tank. Multiple drip outlets were attached near the tank's base to accommodate multiple animals getting water at the same time.
Learning how rainwater harvesting is done overseas
One member of our group was originally from an extremely dry area of Australia. That area has had a drought for 15 years now. And a normal year's rainfall is only about 10 inches. Area residents are required to use rainwater harvesting. Each household receives their water allocation in liters of water per person per day. In the U.S., we use about the same number, but in gallons of water per day. In that part of Australia, if someone uses more than their share of water, or if they're reported to be using the water to irrigate their lawn or other plants, their home's water supply is turned off. After that, they must take a bucket to the community tap, fill it and carry it back to their house to get water.
Graywater and its uses
Australians use graywater for such things as watering plants. In general, graywater is any water used for washing in the home, except water from toilets. Graywater comprises 50 to 80 percent of residential waste water and may be reused for other purposes, especially landscape irrigation.
Supplies for implementing rainwater harvesting
Box stores in South Australia have large sections for rainwater-harvesting system materials. Water line available is color-coded to indicate the quality of water the line carries.
Sharing ideas, techniques, and designs with others
One of the biggest, most rewarding advantages of such sessions as the one we participated in, is learning from other participants. We shared experiences with rainwater harvesting. Systems yield better results when they're tailored to the particular circumstances where they're used. The advantages and constraints for each place they will be used must be taken into account, including any legal constraints involved.
Paul and Mary Meredith are master naturalists. Contact them at email@example.com.