Page 19 - Efficient Irrigation and Landscape Design Standards

Language from the Sammamish, WA Municipal Code offers a terrific example of how water efficiency can be required. Sammamish provides calculations and standard budgeting values within their code to simplify review.
Water use – Irrigation water budget calculated.
1.The water budget (WB) allocation shall be calculated using the following formula:
» WB = (ETO) x (AF) x (LA) x (CF)
» ETO: Referenced evapotranspiration rate (net seasonal
irrigation requirement in inches; see table below)
» AF: Adjustment factor value of 0.8 (i.e., 0.5 x (ETO)/0.625 irrigation efficiency coefficient)
» LA: Landscape area (square feet)
» CF: Conversion factor value of 0.62 (ETO inches to
gallons per square foot)
3. The water budget will be calculated upon the total area of the site in landscape areas and in landscape water features (such as decorative ponds, pools or fountains) that are fed by irrigation water. For the purpose of calculating the water budget, “landscape area” shall mean the entire parcel, less:
» Sensitive areas and their buffers;
» The building footprint;
» Driveways;
» Paved portions of parking lots; and
» Hardscapes (e.g., decks, patios, sidewalks, and other nonporous areas).
4. Areas such as playgrounds, sport fields, golf courses, school yards, or other recreational spaces where
the turf provides a playing surface or serves other recreational purposes may be allowed additional water beyond the calculated water budget. In order to receive additional water for such turf areas, the applicant shall submit a statement designating such turf areas for recreational purposes and specifying additional water needs above the water budget. This additional water need will be based upon the ETO information for the turf grass species or species mix used in such turf areas.
5.Landscape water features shall not use potable water unless the water feature recirculates water used in its operation.
6.The irrigation water use may be monitored by the water purveyor after the date of release of the performance bond.
7.Alternative water sources such as [reclaimed] water or rainwater are encouraged as permitted by the Department of Ecology. Such water sources shall not be subject to the limits of the water budget.
Monthly Net Irrigation Requirement (inches)
January
.00
February
.00
March
.00
April
.00
May
1.59
June
3.13
July
4.46
August
3.51
September
1.77
October
.03
November
.00
December
.00
Season Total
14.49
*These figures are based on a 30-year average of National Weather Service Data and represent the amount of additional irrigation required for turf grass. The figures are adjusted for turf typically used in commercial landscaping.
2. The City shall periodically undertake an evaluation of the WB calculation (formula shown above). The evaluation shall include a recommendation to retain or modify the adjustment factor or components thereof, and shall be made in consultation with groups including landscape professionals and water purveyors.
EFFICIENT IRRIGATION & LANDSCAPE DESIGN STANDARDS 19
5.3 MAINTENANCE
Irrigation systems should be regularly inspected and maintained. Consider the language below from the City of Sammamish, Washington.

Irrigation systems shall be maintained and inspected annually to assure proper functioning and compliance with the calculated water budget for the system. Replacement of components shall be of originally specified parts or materials, or their equivalents.