Transcript Slide 1

Delivering Green Space Benefits:
Irrigation planning implications
Geoff Connellan
G&M Connellan Consultants
[email protected]
Website: www.geoffconnellan.com.au
What is special about green
space?
I.
The nature and range of services to
be provided
II. Quality and/or standard of services
III. Reliability of service delivery/supply
Green Space
Potential Landscape Outcomes or Services
Provided
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

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Exercise – Organised sport & walking
Microclimate modification (UHI)
Contact with nature
Habitat protection
Biodiversity preservation
Aesthetics
MESSAGE
Quality Green Space = Liveable Cities
Water/Irrigation has a critical
role.
Some Challenges for Green Space

Lack of security of water supply

Low water quality

Footprint of WSUD systems
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Maintenance of WSUD systems
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High cost of potable water

Cost of recycled water – capital and
operating
What is role of irrigation?
Provides critical green space in urban
environments where vegetation growing
under natural (rainfall only) conditions
cannot deliver the required services.
Main Applications - Health
 Exercise – Active and passive
 Microclimate modification, extreme
temperature reduction including Urban Heat
Island (UHI)
Exercise/Recreation - Green Space
Obesity a major health issue
Active Recreation
Passive Recreation
Without irrigation many sites do not deliver
positive services during low
rainfall/drought
To deliver Health Benefits from Green
Space
(1) Spaces for Exercise
1. Attractive – Healthy, high quality plants
2. Usable and safe – Surface functional
3. Access – 300 to 400 m
4. Area – e.g. 3.0 ha per 1000 residents
5. Reliable – Independent of climate variations
such as drought
Urban areas and cities can be hot!
The Urban Heat Island (UHI) Effect
Deaths from excess urban heat
Feb. temps
2009
Extra Deaths in
2009 heat wave
Av. Deaths
2004-2009
Reference: Rod Dedman, Vic. Depart of Health.
Alternative water supplies for health and wellbeing.
To deliver Health Benefits from Green
Space
(2) Spaces for Heat Moderation
1. Full coverage of vegetation
– high Leaf Area Index (LAI)
2. Healthy vegetation with high ET rate.
3. Trees are powerful microclimate modifiers
Role of Trees – Environmental modification
Crop Coefficient:
E.g. Strong healthy growth (Kc 0.8), not Survival (Kc
0.4)
To achieve cooling
Lower air temperature
ETo – Evapotranspiration
Energy partition – Latent Heat
ETo
Message: Irrigation is often required to
achieve microclimate cooling.
Microclimate Cooling
High Crop Coefficients (Kc) required
Security of Water Supply
Strategies
• Work with constraints (e.g. limited volumes
or times, reduced pressure) of supply from
reticulation mains
• Water source independent of climate
conditions (e.g. recycled or desalination)
• Storage size to meet risks
• Integrated approach
Stormwater Harvesting
– Meeting irrigation demand
Storage
Storage Sizing and Reliability of
Supply
Increasing
reliability
of supply %
Diminishing returns
Increasing
storage
capacity &
$s
Storage Sizing and Reliability of
Supply
Use potable
Increasing
%
reliability
100
of supply
80
water to provide
security of
supply during
drought
60
Increasing
storage
capacity &
$s
Storage Sizing for Reliability of Supply
Is 75% or 80% reliability adequate?
Balancing increasing cost of storage and
value of the benefits and/or potable water
savings delivered by the system.
*Important to note that the value of the
services will be greatest at the time that
the supply is likely to fail.
Water Quality
What are the risks?
1. Chemical
2. Physical
3. Biological
Key Water Quality Parameters
Chemical
 pH (Acid/Basic)
 Dissolved elements E.g. Sodium
 Heavy metals E.g. Mercury, Zinc
Physical
Suspended solids – irrigation blockages
Microbiological – Human health & Plant health
Viruses, Bacteria - Pathogens
• Human: e.g E. coli
• Plant: Phytophthora spp.
Irrigation Water Quality Parameters
Parameter
Unit
Acidity/Basic
pH
Salinity Electro Conductivity (EC)
Total Dissolved Solids (TDS)
dS/m
mg/L; ppm
Sodium Adsorption Ratio (SAR)
SAR units
Total Suspended Solids (TSS)
mg/L
EG. Sodium, Chloride, Phosphorous,
Nitrogen .
e.g. Sodium mg/L
Biological/Biochemical Oxygen
Demand (BOD) (5day)
Dissolved oxygen mg/L
Message: Define Water Quality Criteria
Risk of Blockage of Drip Emitter
Water
Parameter
Unit
Low Risk
High Risk
Acid/alkaline
pH
< 7.0
> 8.0
Suspended
solids
(TSS)
mg/L
< 50
 100
Salinity
TDS/EC
mg/L
< 500
 2000
Iron,
Bicarbonates
Source: Harris (2006) DPI, Qld.
Stormwater Storages
What are the risks?
1. Human health
2. System effectiveness and functioning
Strategies to minimise the risks
a) System design (e.g. treatment systems)
b) Water quality standards
c) Regular monitoring
Water Quality Considerations
• Characteristics of catchment – Urban or
industrial. Hydrocarbons, Oil spills, Chemical
spills, Plant health chemicals
• Frequency of testing of stormwater E.g. 2
weeks
• Time for some tests e.g. pathogen to be
done may be 2 weeks. Well after the event.
Efficient Use of Water
1. Water Use Efficiency (WUE)
and
2. Irrigation Efficiency (IE)
Efficiency
- Essential component of Green Space
Irrigation
How do you encourage or foster efficiency?
• Irrigation design standards.
E.g. IAL Urban Best Management Practice
In-house Irrigation standards
* Specify regular performance evaluation.
Message: Strongly endorsed irrigation
standards
Irrigation Efficiency
APPLICATION
EFFICIENCY
OVERALL
IRRIGATION
EFFICIENCY
SCHEDULING
/WATER
MGT.
EFFICIENCY
Message: Both need to be high to achieve
High Overall Efficiency
Green Space Messages
1. Define site outcomes and services
E.g. Exercise? Cooling?
2. Secure water source to deliver benefits during
low rainfall/drought.
3. Set water quality standards for sustainable use.
Monitor both (a) water and (b) soil.
Green Space Messages
4. WSUD systems need monitoring and
maintenance. Resource provision.
5. Apply design, installation and management
standards that promote efficiency.
6. Irrigation zoning to allow separate watering of
areas with different demand.
E.g. Trees separate to grass/lawn.
Keep trees healthy.
Green Space (Irrigation)
Health
Community
Wellbeing