Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: https://read.dmtmag.com/i/282929
www.landscapeirrigation.com * Reduces peak flows, flooding and erosion; * Reduces combined sanitary sewer overflows; * Reduces the heat island effect by converting impermeable, heat-storing surfaces (driveways, parking lots) to permeable, heat- phobic 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 overex- ploited. For many areas, potable water is removed from local water- sheds and pumped to distant water users. Landscape applications Direct/Active Systems: Low-volume irrigation is most practical when using rainwater for landscape irrigation. It can often be applied by gravity alone or used in combination with pumping (e.g. under additional pressure) systems. Spray irrigation is also an option; how- ever, spray uses more water and could quickly exhaust one's rain supply. Spray for a small area would be effective, especially in climates with year-round rain. Indirect/Passive Systems: Various types of earthworks (land- scapes) are used to harvest and retain runoff from roofs, roadways and parking surfaces for passive infiltration. Such examples include biofilters, swales and green strips. One can build mounds around fruit trees to retain runoff onsite to build a sub-surface water reser- voir used during the dry season. Where soils have good infiltration rates, and groundwater is relatively shallow, retention features for large runoff volumes can recharge groundwater for future extrac- tion. These types of solutions are called Low Impact Development (LID) or Green Infrastructure (GI). The rest of this article will focus on harvesting rain for direct applications, not passive, earthen- infiltration solutions. Rain harvesting system components — direct use Five steps for a rain harvesting system As the rain harvesting industry continues to grow, it is impor- tant to understand that an effective rain harvesting system with minimal annual maintenance is essential as this industry continues to make positive strides. No matter the size of the system, five es- sential design steps will ensure an effective and sustainable harvest- ing system. A typical direct-use harvesting system has the following components: * Collection system: impermeable surfaces in which rain lands, and conveyance conduit to move the rainwater to a storage tank; * Pre-treatment (screening-separation) device; * Storage tank (cistern); * Polishing treatment system for end-uses; and * Distribution plumbing system to final end-uses, whether out- door or indoor applications, and overflow. Step one: Collection surface A collection system harvests rain that falls on impermeable sur- faces and transports it to a storage tank. For a roof surface, gener- ally, gutters and downspouts direct rain to a tank. For a surface parking area, generally, rain would sheet flow to a centralized lo- cation, such as a catch basin, trench drain or hardscaped swale, and then continue to a storage tank. For a large project involving har- vesting from a stormwater surface channel or drain pipe, collection would involve diverting stormwater flow out of a channel or pipe to a storage tank. Landscape and Irrigation 23 The American Rainwater Catchment Systems Association (ARCSA) is a 501(c)3 tax-exempt, non-profit, whose mission is to promote sustainable rainwater harvesting practices to help solve potable, non-potable, stormwater, water-quality and en- ergy challenges throughout the world. Presently some of its members and friends are preparing an updated and expanded teaching manual, along with associated PowerPoint teaching presentations and online classes. The new 23-chapter harvesting manual will contain expanded information on harvesting in container systems, and will address passive harvesting systems, capturing stormwater using Low Impact Development and Green Infrastructure strategies, and a num- ber of other water-harvesting topics. ARCSA's website (www.arcsa.org) has a variety of useful and helpful information on all aspects of rainwater harvesting, from the regulatory field (a list of laws, policies, guideline man- uals, and standards around the country) to the "nuts and bolts" of how to install rainwater harvesting projects. It offers work- shops that elaborate on the subjects discussed in this article. Its members and friends continue to be in the forefront in seeking, creating and implementing solutions. More informa- tion is available at www.arcsa.org, including designers, engineers, equipment suppliers and regulators. ARCSA, with its partners, American Society of Plumbing Engineers (www.aspe.org) and American National Standards Institute (www.ansi.org), produced a Rainwater Harvesting Design Stan- dard 63 in 2013. This document provides plumbing guidelines and standards in designing a system. It is available through all three groups. The International Code Council is currently devel- oping a similar standard. ARCSA and ASPE are presently working on a parallel docu- ment for stormwater (78) for publication in 2014; it will follow the same format as 63. — Neal Shapiro, CPSWQ, CSM The American Rainwater Catchment Systems Association at your service