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Austin's Zilker Park Showcases Rainwater Harvesting
by Karen Stewart, City of Austin
 Zilker Park, in the heart of downtown Austin, is set to become the prime rainwater harvesting demonstration site for the City of Austin.
The completed system is ready for public viewing and is meant to educate visitors in the forgotten benefits of rainwater.
For centuries people relied on rainwater harvesting to supply water for household, landscape, livestock, and agricultural uses. However, with the development of large, reliable water treatment and distribution systems and more affordable well drilling equipment, rainwater harvesting systems have been all but forgotten, even though they offer a source of pure, soft, low sodium water.
A renewed interest in this time-honored approach has emerged in Texas and elsewhere due to:
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the escalating environmental and economic costs of providing water by centralized water systems or by well drilling;
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the human and plant health benefits of rainwater; and
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the potential cost savings associated with rainwater collection systems.
The City of Austin has been promoting water conservation for several years by selling rain barrels, giving rebates for larger systems, and conducting tours of commercial and residential rainwater harvesting systems. The rainwater harvesting system at Zilker Botanical Garden, built by volunteer Master Gardeners and funded by the City's Water Conservation Program, provides a very visible, permanent demonstration.
Zilker Park Schematic: Click on Image for Enlargement
The tanks at the Zilker site have been selected to show a variety of styles, types, and prices available:
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The 2000-gallon gray tank is made of fiberglass, a material sturdy enough to be used for larger tanks. The cost is twice that of the poly tanks, with a lifespan greater than 20 years.
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The black and green polyethylene (or "poly") tanks hold 2500 gallons each, with an expected lifespan of over 20 years. Poly tanks must be colored or painted to prevent algae growing inside the tank. These tanks come in a large variety of sizes to fit into any home or landscape site. Polyethylene tanks have significantly reduced the price of small to medium size systems.
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Metal farm tanks, like the 3100-gallon tank at Zilker, are often selected for their old-fashioned charm. Typical galvanized tanks rust out, and have a limited life span. This tank has a geotextile pre-liner to protect the seams and metal from condensation and moisture. The tank is then lined with a 25 mil rubber "bladder" or flexible membrane lining. The lifespan of this tank is more than 20 years, and the cost is roughly four times that of the poly tanks.
The fiberglass and poly tanks can be painted, resurfaced with stone, stucco or wood trim to fit into any home or landscape.
Greenbuilder: Dick Peterson gives a tour of the system. HarvestH2o photo
When considering a home rainwater storage system, size matters. Rainwater tank and storage size needs to relate to the size of the roof and the amount of landscape to be watered. It typically takes about 30,000 gallons of water to irrigate a typical home lawn/landscape with one inch of water. In other words, one or two waterings would empty most small tanks. So if building a system, make sure to build it big enough to handle your watering needs.
Rainwater harvesting is not always an economical choice when compared to potable water provided by most cities. However, most people choose to collect rainwater for reasons other than cost savings.
Rainwater harvesting:
- is environmentally friendly
- is better for plants
- prevents soil erosion by reducing rainfall runoff
- can be self-sufficient
- conserves energy from potable water processes, and
- fosters a greater appreciation of nature.
The rainwater harvesting system at Zilker Botanical Gardens will benefit not only garden plants, but will help homeowners understand whether or not a rainwater harvesting system is right for them, and which features and types of materials they prefer.
HarvestH2o photo
 Zilker Park's older tanks being updated.
They are used to feed the greenhouses in the back of the park.
Zilker Park has been using rainwater harvesting for years to assist with watering their lush gardens. The tanks and equipment have not been visible or accessible to the public but have been vital to the nurturing of new plants. With these new tanks the public can visit and learn more about rainwater harvesting.
Zilker Park is located at 2220 Barton Springs Rd, in the heart of downtown Austin and is open 7 days a week.
Related Links:
History of Rainwater Harvesting at Zilker Park
Reprinted with permission from the WaterWise Newsletter, a publication of the Austin Water Utility’s Conservation Program
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