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Water: Green Infrastructure

Build Resilience to Drought


Cracked soil from an extended drought
Why Green InfrastructureHow to Resources
Why Green Infrastructure
In some areas of the country, decreased precipitation associated with climate change will stress already fragile local water supplies. By allowing rainwater to soak into the ground, infiltration-based practices such as raingardens and green streets (PDF) (19 pp, 2MB, About PDF) can help replenish local groundwater reserves.[1]

During storm events, rain falling on hard surfaces such as roofs, parking lots and streets often runs directly into water bodies or city storm drains, directing water away and out of sight. By channeling rainwater directly into streams, rivers and oceans, communities lose out on a valuable opportunity to keep water around for when they need it most. Locating infiltration-based green infrastructure practices in parking lots, along streets and near buildings can provide an opportunity for rainwater to slowly soak into the ground.[2] While some of this water will evaporate or be soaked up by plants, studies show that over time, green infrastructure can infiltrate enough rain to replenish groundwater reserves.[3][4]

Reduce the need for imported water. On individual properties, rainwater harvesting techniques such as rain barrels and cisterns can reduce demand for potable water. By using stored rainwater to irrigate landscaping in public parks, schools or municipal buildings, or for non-potable uses such as toilet flushing and cooling system make-up cities can eliminate the need to purchase water from out of town. A recent study estimates that by instituting a combination of stormwater capture, water efficiency and water harvesting programs, California could save 4.5 trillion gallons of water a year – more than is needed to irrigate all of it’s orchards, nuts, berries, vineyards and tomatoes.[5][6]

Recharge groundwater, recharge your wallet. EPA recently conducted an analysis estimating the value of groundwater recharge that could be achieved through small storm retention alternatives for new development and redevelopment. This study found that stormwater retention requirements applied nationwide in areas that do not already have state or local requirements could lead to replenishment of groundwater reserves and stream flow.

The analysis also estimates the value of encouraging groundwater recharge in these areas at more than $50 million. For more information on how green infrastructure can increase rates of groundwater recharge, click here.

Cistern collecting stormwater from the roof of a building
How To
Becoming a drought resilient community means making the most of rainwater when it is available through capture and use, as well as storing it for later within deep groundwater reserves. Start by prioritizing areas in your community where it makes sense to locate infiltration-based green infrastructure practices such raingardens,planter boxes and bioswales. Opportunities to locate these features will depend on local soils, slope and current land use. Proper siting of green infrastructure should be considered to protect ground water supplies. For example, avoid infiltrating large quantities of water in contamination hot spots or on steep slopes.

Communities may want to consider incentives or local requirements to encourage on-site rainwater harvesting. In Tucson, Ariz., city officials passed a commercial rainwater harvesting ordinance Exit EPA Disclaimer requiring facilities to meet 50 percent of landscape irrigation demands using harvested rainwater. The ordinance also requires covered facilities to prepare a water harvesting plan and water budget, meter outdoor water use, and use irrigation controls that respond to current soil moisture conditions.

Areas dependent on groundwater supplies for drinking water and irrigation should consider including green infrastructure as part of long-range water planning efforts. Milwaukee, Wis., used a University of Wisconsin-Madison model to help inform a Regional Green Infrastructure Plan. Their analysis showed that approximately four billion gallons of stormwater could be infiltrated in the area per year using a combination of porous pavement and bioretention practices.[7]

Parking lot designed to infiltrate runoff in Tucson, AZ. Photo credit: Watershed Management Group
Resources
Commercial Rainwater Harvesting Ordinance Exit EPA Disclaimer – In October 2008, the City of Tucson adopted the first commercial rainwater harvesting ordinance in the country, requiring facilities to meet 50% of their landscaping demand using harvested rainwater.

Pima County Flood Control District – “How to Harvest Rainwater” Exit EPA Disclaimer – Regional guide to rainwater capture and reuse.

University of Arizona – Center for Climate Adaptation Science and Solutions Exit EPA Disclaimer – Practitioner network and clearinghouse for Southwest regional adaptation resources, research and tools.

The Untapped Potential of California’s Water Supply: Efficiency, Reuse, and Stormwater Exit EPA Disclaimer – NRDC and Pacific Institute. Statewide analysis examining the significant potential contributions achievable from a combination of improved efficiency in agricultural and urban water use, water reuse and recycling, and increased capturing of local rainwater.

References

1. W.D. Shuster, R. Gehring, and J. Gerken. (2007). Prospects for enhanced groundwater recharge via infiltration of urban storm water runoff: A case study Journal of Soil and Water Conservation. Vol.62(3):129-137.

2. Dussailant, A. R., Wu, C. H., & Potter, K. W. (2004). Richards Equation Model of a Rain Garden. Journal of Hydrologic Engineering, 9(3), 219–225.

3. Potter, K. W. (2000). Final Report: Field Evaluation of Rain Gardens as a Method for Enhancing Groundwater Recharge. University of Madison, WI. Retrieved July 1, 2014, from

4. Swann, L. (2008). The Use of Living Shorelines to Mitigate the Effects of Storm Events on Dauphin Island, Alabama, USA. . Retrieved July 1, 2014, from http://wri.wisc.edu/Downloads/Projects/Final_WR01R002.pdf (15 pp, 90K, About PDF) Exit EPA Disclaimer.

5. Pacific Institute and Natural Resources Defense Council. (2014). The Untapped Potential of California’s Water Supply. Retrieved July, 1, 2014, from http://pacinst.org/publication/ca-water-supply-solutions/ Exit EPA Disclaimer.

6. Joseph S. Devinny, Sheldon Kamieniecki, and Michael Stenstrom.(2005). Alternative Approaches to Stormwater Quality Control, Center for Sustainable Cities, University of Southern California, Los Angeles, CA.

7. Milwaukee Metropolitan Sewerage District. (n.d.).Green infrastructure Benefits and Costs: Draft Final MMSD Regional Green Infrastructure Plan. Retrieved July 1, 2014, from http://h2ocapture.com/PDF/05_Benefits_Costs_Draft_Final.pdf (14 pp, 3MB, About PDF) Exit EPA Disclaimer.

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