Transcript Water Conservation Strategies for Commercial Landscaping

Water Conservation Strategies for
Commercial Landscaping
Increasing demand
Metro Atlanta water use
• Single Family residential water consumption = 191 MGD
to 280 MGD (149 GPCD)
• Outdoor water consumption = 38 MGD to 56 MGD
Regional Limitations to Water Resources
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98% of Atlanta’s water needs are supplied by surface water sources
80% of surface water is supplied by the Chattahoochee
Atlanta’s location at the headwaters limits the supply
Bedrock limits groundwater sources
Increasing demand: +1,000,000 residents in 10 years
SOURCE: ARC
3 Steps for Outdoor Water Conservation
1. Minimize water demand
2. Meet demand with non-potable water
3. Deliver water efficiently
Minimize Water Demand
Use regionally native or
Drought-tolerant non-invasive species
Minimize the
use of turf
Minimize Water Demand
Keep stormwater runoff on-site to nourish the
landscape
Minimize Water Demand
Protect and restore healthy soil.
Meet Demand with Non-potable Water
Benefits of Rainwater Harvesting
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Rainwater is free – helps to reduce utility bills
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Can eliminate costly infrastructure
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Not subject to watering restrictions
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Eliminates the need for water softeners if used indoors
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Rainwater is the most pure water (chemical free) to use on plants, vegetables, etc.
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Reduces runoff to storm drains
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Entire system costs range from $.75/gallon to $2/gallon with a payback period of less than ten
years (NCSU).
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Important part of an overall strategy to conserve water resources
Meet Demand with Non-potable Water
History of Rainwater Harvesting
• Rainwater harvesting is an ancient technique dating back as far as 4,000
years ago.
• Still widespread in India, Australia, the Caribbean and other regions with
poor public infrastructure and dry climates.
• Enjoying a resurgence in the US, partly due to superior water quality and
partly due to the desire to reduce consumption – an estimated 100,000
systems are in use.
• Currently, there are no national standards governing rainwater harvesting.
• However, rainwater harvesting is currently mandated for new construction
in Bermuda, US Virgin Islands and other Caribbean islands.
• Incentives are in place to offset costs in Texas (maybe in the southeast
soon?)
• Simplest systems are land-based and may consist of earthen berms and
reservoirs.
• More complex systems take many forms…
Memorial Garden @ the SLC
(Photo courtesy of Kevin Kirsche, University Architects)
Meet Demand with Non-potable Water
Components of A Rainwater Harvesting System
Meet Demand with Non-potable Water
Water Balance and System Sizing
The supply (amount that can be collected and
stored) must equal or exceed the demand
(anticipated amount that will be used)
Meet Demand with Non-potable Water
System Sizing Example
Assumptions: demand of 3,000 gal/mo; collection efficiency of 85%; .62 gal/S.F. of catchment per inch of rain; 10,000 gallon
storage capacity; 1,000 gallon starting volume; Dallas, Texas location
Deliver Water Efficiently
Avoid waste through overspray and evaporation.
Deliver directly to the plant.
Drip Irrigation
Deliver Water Efficiently
Apply water only when and where it is needed.
Rain Sensor
Irrigation Zones
WeatherTrak Controller
Soil Moisture
Sensor
The Lady Bird Johnson Wildflower
Research Center – Austin, Texas
• 70,000 gallons of total cistern storage capacity
• 17,000 S.F. of catchment area
• Broken up into several catchments and cisterns
throughout the site
• Aesthetic / experiential system created by
conveying water through aqueducts to
exposed above-ground cisterns
• Local materials create a sense of place
• Used solely for irrigation
The Lady Bird Johnson Wildflower
Research Center – Austin, Texas
The Southface Energy Institute – Atlanta, Georgia
• 1,750 gallon rooftop cistern for toilet
flushing and mechanical demands
• Below-grade cistern stores site runoff for
non-potable uses (irrigation)
• Collector area should yield approximately
42,000 gallons per average year
• Combined with efficient interior fixtures,
this results in a total water savings
of 150,000 gallons per year when
compared to a comparable
conventional building – a 74%
reduction.
Resources:
http://www.twdb.state.tx.us/assistance/conservation/alternative_technologies/
rainwater_harvesting/rain.asp