May 10, 2007

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COLLEGE STATION - With the news that La Nina may bring another dry spring to the state, Texans may be looking at installing rainwater harvesting systems to help water landscapes and ease utility bills, according to a Texas Cooperative Extension agricultural engineer.

Water resources will become more limited in the state of Texas due to increasing demand,. said Dr. Bruce Lesikar.

However, if we can capture part of our rainwater and use it in the landscape, that will offset the landscape irrigation demand on our drinking water supplies. Then we can efficiently utilize the water that is available to us..

Rainwater harvesting can be accomplished in several different ways, Lesikar said. The first is a system that catches rainwater runoff and diverts it to tanks for storage until used to irrigate the landscape plants.

"Rainwater harvesting tanks come in many shapes, sizes, colors and materials, so depending on your vision for your landscape, you need to choose the most appropriate material," he said.

Homeowners may want to choose a galvanized tank similar to the ones that were used for many years in rural areas. Others are made of wood or come with wooden frames to mask the tank. Still others are made of fiberglass or plastic and come in different colors or can be painted to match the landscape.

Rain gardens are a second rainwater harvesting option that can take several different forms. This rainwater harvesting technique takes advantages of natural or man-made depressed areas in the landscape that store water for short periods of time - usually 24 hours - before allowing it to infiltrate into the soil, he said. The water enters the soil and is used by the plants growing in the rain garden. A portion of the water may reach the groundwater or move to streams through the ground.

A third type of rainwater harvesting is soil storage and infiltration systems, which are sub-soil gravel systems that can store rainwater below the surface and allow it to infiltrate into the soil, he said,

The main advantage of rainwater is that it is a source of high quality water, he said.

"A lot of times our drinking water will have minerals and salt that can then build up in the landscape over time," Lesikar said.

Rainwater has few minerals and salts in it, and it works very well to irrigate plants. It usually has a lower pH as well, he said.

Rainwater can also help by leaching out the salts that build up in the soil and thus maintaining soil health, he said.

Another benefit is that it cuts down the peak runoff rate that leads to problems in our streams and drainage ways.

"Before we build on a piece of property, the soil and vegetation that are on that property hold water from the initial rainfall event," he said. "But after we put buildings on it, driveways, sidewalks, those surfaces will not hold any water. So when a rainfall event occurs, you get a rapid first flush of water that moves off of those properties."

Rainwater harvesting systems slow down the first flush, which mimics the natural process.

That limits the impact on our streams that we have in our urban areas,. he said. .Therefore you have a high-quality water that you can use in your landscape, which is a benefit for you. It can reduce your water bills because you are not using potable water that you have to buy in order to irrigate your area/ And you.re benefiting your community and your area by limiting that water that leaves your property from that first flush and brings it back to more natural rain..

Wildlife also benefit from rainwater harvesting.

"Many people view rainwater harvesting for the production of landscape plants or flower beds," Lesikar said. "However, rainwater harvesting can also be used for watering wildlife in the area."

On smaller acreages, water will be available for rabbits, birds, squirrels or butterflies, he said. But even on acreages, water can still be provided for deer or other larger animals.

Before installing any system, homeowners need to know any restrictions that the community or city might have.

"You do need to consider how it.s going to look in your landscape," Lesikar said.

The tank material or color needs to stop sunlight from passing into the stored water. Generally the few nutrients that are naturally present and collected from the guttering system allow algae growth, and sunlight can cause this plant to grow out of control, he said.

Screens may be used to filter out trash in gutters before it enters tanks.

Also, stored rainwater may attract pests such as mosquitoes, so homeowners will need to screen all inlets and outlets to tanks to control those, he said.

Extension has two publications to help with planning rainwater harvesting systems available through http://tcebookstore.org .The first is .Rainwater Harvesting. (No. 6153), and the second is .Harvesting Water for Wildlife. (No. 6182).