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Hydrology

Water is a limited resource that is essential to all life. At a time when demand for water in the United States is up 209 percent since 19501, the typical single-family suburban household uses at least 30 percent of their water outdoors for irrigation. Meanwhile, in many older cities and towns around the country, rainfall is treated as waste, to be funneled directly from roof gutters and paved surfaces to sewers, leading to increased costs in stormwater management. 

Rather than getting rid of stormwater as quickly as possible, a sustainable approach to stormwater management involves finding ways to harvest it on site, using it for irrigation, ornamental water features, and groundwater recharge. As the value of water is recognized, the value of natural systems to store, clean, and distribute available fresh water must also be recognized.  Technology exists to integrate systems that mimic nature's capacity to store, filter, and clean water.

Half of irrigation water can be wasted as a result of evaporation, wind and over-watering, but weather-based irrigation systems can reduce irrigation water use by 20 percent or 24 billion gallons per year.2

American public water supply and treatment facilities consume about 56 billion kilowatt-hours (kWh) per year—enough electricity to power more than 5 million homes for an entire year.3

Thirty-six states anticipate local, regional or state-wide water shortages by 2013.4

Examples of Sustainable Practices

Protect and restore existing hydrologic functions
Avoid development and disturbance near streams and wetlands, and in sites with high risk of flooding.  Plant native or appropriate non-native vegetation, re-grade soils where necessary, and use soft engineering techniques to restore the functions of floodplains, and riparian and wetland buffers.

Manage and clean water on-site
Design a site to capture, slow, and treat stormwater runoff by reducing impervious surfaces, harvesting rainwater, and directing remaining stormwater runoff to soil- and vegetation-based water treatment methods, such as vegetated bioretention facilities, rain gardens, wetlands, green roofs, and bioswales. Maintain and restore vegetation to ensure water can percolate into the soil or groundwater.

In Portland, Oregon, nearly 49,000 downspouts have been disconnected, removing more than 1.2 billion gallons of stormwater per year from the combined sewer system.5

A 2,500-acre wetland in Georgia saves $1 million in water pollution abatement costs each year.6

Studies of landscape preference
conducted over several decades show consistent patterns of favorable responses to views of water features across culture, landscape types, and viewer age.7

Design stormwater features to be accessible to site users
Integrate multifunctional stormwater management features into site design to improve both water quality and aesthetics. Stormwater management features can provide calming views, spaces for restoration, and even opportunities for play and interaction with water.

Design the site to minimize or eliminate use of potable water for irrigation
Use native and appropriate non-native vegetation adapted to site conditions, climate, and design intent. Group plants with similar water needs to maximize irrigation efficiency. Climate-based controllers for irrigation systems can also be used to lower water consumption.  In addition, non-potable water can be collected and used for irrigation from sources such as rainwater from rooftops, graywater, air conditioner condensate, or stormwater basins.

 

[1] U.S. Environmental Protection Agency (U.S. EPA). 2007. Why Water Efficiency. http://www.EPA.gov/WaterSense/water/why.htm
[2] U.S. Environmental Protection Agency. 2007. Outdoor water use in the United States. (EPA Pub 832-F-06-005) Department of the Interior, Editor.
[3] U.S. EPA. Why Water Efficiency. 2007.
[4] U.S. EPA. Why Water Efficiency. 2007.
[5] City of Portland. 2007. Combined Sewer Overflow Program: Progress Report. City of Portland Environmental Services.
[6] U.S. Environmental Protection Agency. 2007. Wetland Functions and Values. http://www.epa.gov/watertrain/wetlands/module05.htm (accessed July 30, 2008).
[7] Smardon, RC. 1998. Perception and Aesthetics of the Urban Environment: Review of the Role of Vegetation. Landscape and Urban Planning 15: pp. 85-106.