Green Roofs - Living Architecture Monitor - Winter 2009 - (Page 29) reclaimed water is delivered in the right amount and at an appropriate pressure for each specific application. In the case of irrigation systems, it is important to integrate soil moisture sensors and weather predictions to control the amount of water required by each irrigation zone. DRIP/SUBSURFACE IRRIGATION FOR ROOFS WALLS AND LAND SCAPED AREAS According to the American Water Works Association Research Foundation, outdoor water uses in hot-dry places such as Las Vegas or Phoenix constitute 59 to 67 percent of the total residential water use. In the United States southwest, traditional landscape irrigation practices oftentimes waste large amounts of water due to evaporation, piping leaks and poorly targeted spray nozzles. Practices like xeriscaping have helped reduce the need for irrigation. However, buildings featuring green roofs/walls, sports facilities, recreational parks or other outdoor amenities requiring vegetated areas still necessitate irrigation to keep the plant material alive during established periods and times of drought. For this reason, the Living Oasis concept advocates an efficient use of non-potable water through drip/subsurface irrigation. Drip irrigation reduces evaporation losses, over-watering and inadequate delivery of water. Subsurface irrigation goes one step further delivering water directly to the root zone, significantly reducing evaporation losses. Drip/subsurface irrigation work best when coupled with a digitally controlled distribution system that adjusts water delivery according to soil moisture and weather predictions. MINIMIZE DEPENDENCE ON MUNICIPAL WATER SUPPLY REUSE AND LIMIT WASTE The Living Oasis concept reduces the use of municipal water supply by harvesting and continuously reusing economically available onsite water supply sources. But more importantly, centralized water supply infrastructure makes cities and buildings extremely vulnerable in the event of catastrophic failure of such infrastructure. An earthquake, a terrorist attack, a power outage or any other unforeseen situation affecting water supply infrastructure during the summer in the southwestern United States could kill thousands of people in a matter of hours. The Living Oasis concept addresses this very important issue by allowing the possibility of treating, in the event of an emergency, onsite harvested water supply sources to satisfy the most essential needs. While performance data and a comprehensive economic analysis are not available at this time, the Natural Energies Advanced Technologies (NEAT) Laboratory at the University of Nevada, Las Vegas (UNLV) continues to work in a partnership with Green Roofs for Healthy Cities (GRHC) to provide this information through the development of joint-research initiatives. D Alfredo Fernández-González is director, Natural Energies Advanced Technologies (NEAT) Laboratory at the University of Nevada, Las Vegas and member, GRHC Integrated Building Water Management Committee. LEARN MORE Barnett, T. P., and D. W. Pierce. 2008. When will Lake Mead go dry?, Scripps Institution of Oceanography. La Jolla: University of California San Diego. US General Accounting Office. 2003. Freshwater Supply: States Views of How Federal Agencies Could Help Them Meet the Challenges of Expected Shortages. Report GAO-03-514. Washington, DC: US General Accounting Office. Energy Information Administration. 2007. Annual Energy Review 2007. Report No. DOE/EIA-0384. Washington, DC: US Energy Information Administration. http://www.tucor.com http://www.tucor.com
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