Water Efficient Landscaping

According to the U.S. Environmental Protection Agency, outdoor water use makes up one-third of residential water use, or approximately 9 billion gallons of water per day. About 50% of this water is wasted because of inefficient watering methods and irrigation systems. In a commercial setting, outdoor water use can make up 5 to 30 percent of the building’s water use.

In most cases, the water used for irrigation is potable drinking water. By using this water for irrigation, people are requiring municipal water supply systems to use more energy to treat large amounts of water. While water is technically recycled through natural processes, water can take a long time to be returned to the groundwater system, so water suppliers can struggle with meeting demand.

There are two ways to address this problem: water conservation through reduced irrigation and non-potable water reuse. Projects can strategically plant drought-resistant plants or arrange them such that less water will not be wasted when they are watered. Projects can also install water efficient irrigation systems, such as drip irrigation or weather-sensing systems that use less water than traditional irrigation methods. Alternatively, a project can use recycled graywater or blackwater, captured rainwater, or treated wastewater to irrigate plants. A project can also choose to use both strategies and reduce the water needed for irrigation, and then use non-potable irrigation for the rest of the property’s needs.

LEED 2009 and Water Efficient Landscaping

LEED 2009 rewards projects that reduce their potable water use for irrigation through these methods. Water Efficient Landscaping, Water Efficiency Credit 1, awards projects two to four points, depending on how much outdoor water use reduction they achieve. The credit requirements are as follows:

Option 1: Reduce by 50% (2 points)

Reduce potable water use for irrigation by 50%. The potable water for irrigation can be reduced by using more efficient irrigation systems, captured rainwater, recycled wastewater, or non-potable water that has been treated by a public agency. It can also reduce potable water use by changing any one of the factors in this equation:

K_L = K_s x K_D x K_MC

K_L = Landscape coefficient, volume of water lost via evapotranspiration

K_s = Plant species factor

K_D = Plant density factor

K_MC = Microclimate factor

Option 2: No potable water use or irrigation (4 points)

Meet the requirements for the first option, but reduce potable water use for irrigation by 100%. There are two paths for achieving this credit:

Path 1: For irrigation, use only captured rainwater, recycled wastewater or non-potable water treated by a public agency.

Path 2: Install landscaping that does not require permanent irrigation systems. Temporary systems are allowed for the first 18 months if used to establish plant growth.