Benefits of Rain Harvesting

by Jonathan McGaha | June 30, 2015 12:00 am

We live in a time of chronically poor ground and surface water quality and uncertainty of sustainable supplies nationwide. Cities face numerous water supply challenges, including:

• Shortages of freshwater due to rising demand and shrinking cost-effective resources; and
• Climatic oscillations that confound supply planning, such as more intense precipitation and wasteful runoff, and less snowpack compounded by earlier melting, making storage more difficult for long-term management.

Landscape and general architects, engineers of all types, suppliers of water harvesting, piping and treatment equipment, should implement a sustainable water demand and supply-side management portfolio. Such a portfolio must focus increasingly on local non-potable water resources, such as recycled water, gray water, rain and storm water for indoor flushing, cooling and landscape irrigation. Additionally, the attributes of precipitation harvested as rainwater or stormwater for direct-active, or indirect-passive applications should be considered.

Rain Harvesting Benefits

The primary benefits of harvesting precipitation are non-potable and potable water supply augmentation and receiving water quality improvement:

• On-site rain harvesting retains the maximum rainfall possible on an annual and sustainable basis.
• On-site rain harvesting effectively delivers a water supply to an end use at an acceptable water quality and minimal energy cost; and
• On-site rain harvesting is the least polluted water resource and cheapest to treat compared to stormwater flowing in the public right-of-way and available to harvest.

The secondary benefits of harvesting precipitation are important:

• Reduces peak flows, flooding and erosion.
• Reduces combined sanitary sewer overflows.
• Reduces the heat island effect by converting impermeable, heat-reflecting surfaces (driveways, parking lots) to permeable, heat-retaining surfaces.
• Promotes a water self-sufficiency goal.
• Increases property value due to sustainable water earthworks and storage systems.
• Reduces potable water demand.
• Keeps more freshwater in watersheds for wildlife and human enjoyment, and reduces environmental consequences when overexploited.

Five Design Steps

As the rain harvesting industry continues to grow, it is important to understand that an effective rain harvesting system with minimal annual maintenance is essential. No matter the size of the system, five design steps will ensure an effective and sustainable harvesting system. A typical direct-use harvesting system has the following components:

• Collection system, e.g., impermeable surfaces (metal, tile, shingle roofs), upon which rain lands, and a conveyance conduit to move the rainwater to a storage tank;
• Pre-treatment (screening-separation) device;
• Storage tank (cistern);
• Polishing treatment system to meet water quality standards for end-uses; and
• Distribution plumbing system to final end uses, whether outdoor or indoor applications and overflow.

Using these steps as guidelines will ensure your rainwater system is of the highest quality and requires minimal maintenance, regardless of its size. Because rain harvesting design and installation involve several disciplines, it is recommended to consult a qualified professional of rain harvesting systems, which is a time-honored and recently rediscovered practice.

Case Study

The Luci and Ian Family Garden at the Lady Bird Johnson Wildflower Center[1] (LBJWFC) in Austin, Texas, was developed by the creative imagination of W. Gary Smith, a talented landscape architect and artist. With help from the staff and educators, Smith designed an area dedicated to educating children about nature, water and energy conservation and creating hands-on interaction with the outdoors.

One goal was to meet the requirements of the Sustainable Sites Initiative (SITES). The original plan was to repurpose a used steel oilfield storage tank. After evaluating both the cost and potential environmental destruction involved in cleaning and painting a used steel tank, it was determined that a new steel tank, manufactured with a high percentage of recycled steel scrap, was both more cost-efficient and better for the environment.

Water Storage Tanks Inc.[2], Austin, worked with TBG Partners Architects[3], Austin, to design and build an 8,000-gallon CorGal inverted roof rainwater storage cistern in the imaginative Family Garden. Water Storage Tanks donated this tank in support of the LBJWFC and its mission to educate children about nature. The tank sits beautifully between a solar-powered, wood pavilion and a stone restroom building where water is collected from both buildings’ roofs to replenish a creek, which houses fish, tadpoles, frogs and native water plants. The water tank also feeds the gorgeous waterfall display in the center of the garden. The Family Garden connects the younger generation with nature and influences environmental attitudes and conservation activism. Both buildings have metal roofs and both have metal gutters and metal leaders that convey the rainwater to the cistern.

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Neal Shapiro, CPSWQ, CSM, Watershed Management Section, Office of Sustainability and the Environment, City of Santa Monica, Calif., and the secretary of the American Rainwater Catchment System Association (ARCSA). For more information, visit www.arcsa.org[4]. The opinions stated in this article are of the author only and do not necessarily reflect those of the City of Santa Monica or ARCSA.

Source URL: https://www.metalarchitecture.com/articles/benefits-of-rain-harvesting/

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