Cho Kwong Charlie Lam Ailie Gallant Nigel Tapper Nocturnal irrigation alleviates urban heat island Potential 12C cooling modified after City of Melbourne 2012 Threshold Temperature ID: 935084
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Slide1
The irrigation cooling effect at the Royal Botanic Garden Melbourne and Cranbourne
Cho
Kwong Charlie Lam, Ailie Gallant, Nigel Tapper
Slide2Nocturnal irrigation alleviates urban heat island
Potential 1-2°C cooling
modified after City of Melbourne 2012
Slide3Threshold Temperature
Nicholls et al. 2008
Reducing 1-2 °C at night saves lives during heatwaves
This morning’s minimum
Slide4Identify neighbourhoods that require intervention
Norton et al. 2015
A = Moderate priority
B = Medium priorityC = Highest priority
Slide5O Gate (ref.)
Oak Lawn
Fern Gully
Hourly-
avg
Ta data
18/12/13 – 26/3/14
Slide6Desert Discovery Camp
(ref.)
Ian Potter Lawn
Bloodwood Garden
Hourly-
avg
Ta data
18/12/13 – 26/3/14
Cranbourne Garden
Slide7Well-irrigated areas were 2-4
°C cooler than non-irrigated areas during heatwave
Ta average of 12-4pm, 14 – 17 January 2014(Tmax > 41 °C)
Melbourne GardenWarm
Hot
Slide8Nocturnal irrigation cooling and residual daytime cooling
Ta difference: O Gate – Oak Lawn Average of 10 irrigation events
Positive values indicate cooling.
Slide9Irrigation intensified nocturnal cooling during heatwave
Ta difference:
O Gate – Oak Lawn
Heatwave days: Ta ≥ 35
°
C (n = 3)
Slide10Limited nocturnal cooling effect when daytime misting systems were used
Ta difference:
O Gate – Fern Gully
Average of 10 irrigation events
Slide11Lawn surface produced 1-2 °C nocturnal cooling
Ta difference:
Desert Discovery Camp – Ian Potter Lawn
Average of 15 irrigation
events
Slide12Gravel surface had negligible irrigation cooling effect
Ta difference:
Desert Discovery Camp – Bloodwood Garden
Average of 16 irrigation
events
Slide13Slide14Prioritising the landscape zones that require additional mitigation
Landscape place
Obs Café
Volcano precinct
Central
lawn
Fern Gully
Duration of
exposure to
radiation1128Capacity to find respite21210Length of exposure1383Access to water5111
Patronage
1353
Percentage of hard surface1
2
38
Exposure to hot winds
Total
11
11
21
33
0
10
Very poor
Very positive
Well-being nodal space
Slide15Incorporating water-sensitive urban design in cooling sculptures for heat respite
Breeze shelter in Singapore
Misting system
Slide16Summary
Greater irrigation cooling effect during heatwaves
Consider shifting irrigation timing
Irrigation cooling effect differed between two gardens with distinct characteristics
Slide17Landscape
coefficient determines irrigation priority
Connellan 2013
Slide18Royal Botanic Garden Cranbourne 2016