Quantifying Evapotranspiration Rates for New Zealand Green Roofs
Publication: Journal of Hydrologic Engineering
Volume 15, Issue 6
Abstract
Green roofs are an emerging storm-water management tool that has predominantly been analyzed for runoff volume reduction and peak flow mitigation. Little research has been completed on evapotranspiration (ET) in green roofs. Sedum mexicanum (Mexican stonecrop) and Disphyma australe (New Zealand iceplant) in a New Zealand designed, pumice- and zeolite-based substrate were analyzed to determine daily and hourly ET rates under both water-abundant and drought-stressed conditions. Water loss, and thus storage recovery of the substrate, was greatest in the first 9 days. Transpiration by S. mexicanum contributed up to 48% of total ET (2.19 mm/day) and D. australe contributed up to 47% of total ET (2.21 mm/day). After the initial rate of rapid water loss, plants conserved water and ET was not significantly different from evaporation from unplanted substrate. S. mexicanum had a greater ability to conserve water and thus a greater longevity of life than D. australe under harsh drought conditions.
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Acknowledgments
The research team thanks the Auckland Regional Council for project funding and Earl Shaver for overall support. Additional thanks go to the University of Auckland postgraduate researcher Chunsen Tang and Landcare Research technicians Chris Winks and John Dando for their continued assistance.
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© 2010 ASCE.
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Received: Dec 1, 2008
Accepted: Apr 2, 2009
Published online: May 14, 2010
Published in print: Jun 2010
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