Evaporation from (Blue-)Green Roofs: Assessing the benefits of a storage and capillary irrigation system based on measurements and modeling

Dirk Gijsbert Cirkel*, Bernard R. Voortman, Thijs van Veen, Ruud P. Bartholomeus

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

8 Citations (Scopus)

Abstract

Worldwide cities are facing increasing temperatures due to climate change and increasing urban density. Green roofs are promoted as a climate adaptation measure to lower air temperatures and improve comfort in urban areas, especially during intensive dry and warm spells. However, there is much debate on the effectiveness of this measure, because of a lack of fundamental knowledge about evaporation from different green roof systems. In this study, we investigate the water and energy balance of different roof types on a rooftop in Amsterdam, the Netherlands. Based on lysimeter measurements and modeling, we compared the water and energy balance of a conventional green roof with blue-green roofs equipped with a novel storage and capillary irrigation system. The roofs were covered either with Sedum or by grasses and herbs. Our measurements and modeling showed that conventional green roof systems (i.e., a Sedum cover and a few centimeters of substrate) have a low evaporation rate and due to a rapid decline in available moisture, a minor cooling effect. Roofs equipped with a storage and capillary irrigation system showed a remarkably large evaporation rate for Sedum species behaving as C3 plants during hot, dry periods. Covered with grasses and herbs, the evaporation rate was even larger. Precipitation storage and capillary irrigation strongly reduced the number of days with dry-out events. Implementing these systems therefore could lead to better cooling efficiencies in cities.

Original languageEnglish
Article number1253
JournalWater (Switzerland)
Volume10
Issue number9
DOIs
Publication statusPublished - 14 Sep 2018

Keywords

  • Blue-green roofs
  • Capillary irrigation
  • Latent heat flux
  • Lysimeter
  • Potential and actual evaporation
  • Sedums
  • Sensible heat flux
  • Urban areas
  • Water availability

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