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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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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 • 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 • Minimize water demand • Meet demand with non-potable water • 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 • Rainwater is free – helps to reduce utility bills • Can eliminate costly infrastructure • Not subject to watering restrictions • Eliminates the need for water softeners if used indoors • Rainwater is the most pure water (chemical free) to use on plants, vegetables, etc. • Reduces runoff to storm drains • Entire system costs range from $.75/gallon to $2/gallon with a payback period of less than ten years (NCSU). • Important part of an overall strategy to conserve water resources
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… Meet Demand with Non-potable Water
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