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Guideline S.7: Landscape Water Efficiency

 

Intent

To limit or eliminate demand for municipal potable water or harvested groundwater (well water) used for maintaining a building’s plants and lawn areas.

 

Required Performance Criteria

Required and Recommended Performance Criteria apply to all projects designated New Buildings and for all Major Renovations that include area of site disturbance that is greater than 3,000 square feet or area of imperviousness (footprint of building plus site impervious area) renovated that is greater than 2,000 square feet.

  1. Design and maintain landscape so that after a 2-year establishment period, the landscape uses 50% less municipal potable water or harvested ground water for irrigation than a base-case landscape design. (Exception: annuals are exempt.) Any amount of site-harvested rainwater, stormwater, or gray or waste water treated onsite to tertiary standards may be used. The criteria may be met by any combination of the following: selection of native or low water-use plants, use of alternatively sourced irrigation water as described, use of high efficiency irrigation systems, or other strategies. In order to verify compliance with this guideline during building operation, it is necessary to sub-meter irrigation separately from indoor water consumption.

 

Recommended Performance Criteria

  1. Design and maintain landscape so that after a 1–2 year establishment period, the landscape uses no (100% less) municipal potable water or harvested ground water than a base-case landscape design. (Exception: annuals are exempt.) Any amount of site-harvested rainwater, stormwater, or gray or waste water treated onsite to tertiary standards may be used. The criteria may be met by any combination of the following: selection of native or low water-use plants, use of alternatively sourced irrigation water as described, use of high efficiency irrigation systems, no irrigation systems, or other strategies.

 

Implementation in the Design Process:

Evaluate the site for existing natural features for water capture and vegetated areas that require low water input. Define areas of different plant communities based on water input requirements. Identify opportunities for water harvest and reuse. Perform general calculations for water consumption and identify available sources for the water.

As the design continues, update calculations and select native and water-efficient plant communities based on the community’s location, slope, soil, and hydrologic regime. Develop and finalize details and specifications for irrigation, water harvest, and water reuse systems.

Hold a preconstruction meeting to identify requirements for landscape water efficiency and maintenance requirements. Monitor submittals for compliance with plans and details as the project moves toward completion. Make bidders aware of specific requirements for landscape water efficiency and maintenance requirements.

Create an operation and maintenance manual to protect and maintain the plant material and the irrigation from potable and non-potable sources used onsite. Consider requiring a first- and second-year maintenance program to ensure establishment of plant communities, which will enable them to continue to perform, once established, with the designed level of water and chemical inputs.

Calculations and Base Case:

Calculations used for this guideline include determination of the base-case and design-case irrigation consumption.

The base and design cases water consumption may be calculated using the Interactive Water Budget Tool from EPA Water Sense: https://www.epa.gov/watersense/water-budget-tool or by a manual calculation using the landscape coefficient method The base-case water consumption should be calculated using a typical mix of turf grass, building-adjacent shrubs, and other typical vegetation.

Design:

  • S.7A: Base-case irrigation water consumption.

Final Design:

  • S.7A and S.7B: Base and design case irrigation water consumption, alternatively sourced irrigation water used, and annotated plan showing vegetated areas and plant selections.

Closeout:

  • S.7A and S.7B: Updated base and design case irrigation water consumption, alternatively sourced irrigation water used, and verification that site contractor understands the requirements and intents of this guideline.

Occupancy – Submitted annually for ten years:

  • S.7A and S.7B: Water consumption used for irrigation.

LEED v.4 Irrigation Calculator: http://www.usgbc.org/resources/outdoor-water-use-reduction-calculator

Interactive Water Budget Tool from EPA Water Sense (note that this outputs peak monthly consumption): https://www.epa.gov/watersense/water-budget-tool

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