05 Apr BlueGold Part 1: A Rainwater Primer
Demystifying Austin Urban Residential Rainwater Harvesting
This is part one of a three part series by Sara Earl of Blue Gold Engineering, a water and wastewater firm with a division offering design/permit/build for residential rainwater harvesting, stormwater irrigation and greywater reuse systems.
As owner of a water and wastewater firm, Blue Gold Engineering, I find myself fielding a lot of the same questions about rainwater harvesting systems. This first article answers some basic questions about rainwater harvesting you may have. Part Two of this series will run April 12th and will cover system components and design considerations and Part Three will run April 19th and will address Austin’s rebate rules and applicable development codes.
I already have a rain barrel(s), why would I want to spend money on a larger system? In Austin, the average annual rain fall is 32” so, if you have an average sized roof, say 1200 sq. ft., you could collect/save over 20,000 gallons per year. For those of you who have a rain barrel, you can now quantify all the water you are notcatching. Those with rain barrels also likely struggle with limited water pressure making hand watering time consuming and inefficient.
How big of a tank makes sense for me? We only design 2,500+ gallon tank systems because that’s where you can begin to irrigate small areas (500 sq. ft.) independent of city water. While anything smaller definitely helps, you will undoubtably need to supplement with potable water. Look for more information in the next part of this series with information about how to determine the right tank size for you.
Doesn’t all that water go “bad”? You do not have to use up rainwater within a given amount of time. Techniques such as automated irrigation, recirculation and aerators eliminate insect issues and keep water from stagnating so that collected rainwater can be stored indefinitely.
But we’re in a drought and there’s no rain to collect…? Rain is inconsistent and rainwater harvesting systems help regulate the distribution of rain over an annual cycle. We suffer from an urban heat island effect that makes rain in the city more scarce in the summer. Thus, when your yard needs water most is when it’s least available. Austin is still at stage two watering restrictions—even with all the recent rain and it’s not even summer yet. If we move to stage three, you will only be allowed to hand water your yard or garden. Needless to say, if you have been collecting rain all year and have adequate storage capacity, you will not be affected by the restrictions. Plus you can use the rainwater to protect your property from wildfires that keep company with drought.
The drought won’t last forever. Actually, most of us know that it’s worse than that. Water rationing is an annual fact and will likely increase as the population continues to grow. This has motivated the state to pass legislation stating that municipalities can not limit the use of rainwater. While indoor use of rainwater in Austin is currently limited to toilets, with the right kind of roof and localized treatment, you will someday be able to bathe in it, cook with it and drink it. If you are building now, you can plumb for that future reality.
How much will the city pay me back (and why)? The City of Austin encourages citizens to use rainwater via a generous rebate: up to 50% of costs, up to $5,000. It is estimated that irrigation accounts for an indulgent 50% of all potable water usage. The city pays you back for helping reduce water use and energy demands for the treatment and transportation of potable water. In addition, Texas exempts sales and property taxes on rainwater harvesting equipment.
So, what are the benefits for me? Here’s a list of benefits for the average homeowner:
- Depending on your irrigating needs, you can potentially halve your potable water costs.
- Many customers say that harvesting rainwater is the most tangible and satisfying sustainable practice that has broad community impact.
- If you are an avid gardener or grower, you know that plants are healthier and more productive when watered with rainwater because it is filled with natural plant nutrients and free of city additives.
- As previously mentioned, irrigating independently from the city’s potable water gives you immunity from city water rationing, with a fire-protection perk.
- Rainwater harvesting can also address stormwater and drainage issues. Rainwater can be collected off of other impermeable surfaces, not just roofs. If you find yourself wanting to get rid of the runoff, you may as well collect it and put it to good use.
Why would you hire an engineer? At Blue Gold Engineering, our “resource balanced design” process delivers the most sustainable and cost-effective solution for your lifestyle, structure and site. Depending on your goals, we may also suggest stormwater or greywater solutions. Blue Gold Engineering also provides consulting services relating to greenhouses, automated irrigation systems, cool roofs, solar energy, green roofs, living walls, fountains, ponds and manmade creeks. For more information about Blue Gold Engineering, please see our web site atwww.bluegoldengineering.biz or call us at 512.944.0677.
SARA EARL, C.E.O.
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