Beorn Courtney, a water resources engineer for Headwaters Corporation, gave a presentation to the AWRA Colorado Section on October 27 on how water efficiency has been incorporated in the land use planning process for Sterling Ranch, a proposed Douglas County development. She explained how traditional land use planning has been a sequential process where water demand is calculated using standard planning numbers after land uses have been planned for a development. An existing Douglas County zoning resolution requires that a developer identify and develop a new water supply for new developments based on a standard water demand of 0.75 acre-feet per year (AFY) per single-family residential unit. The traditional sequential land use planning process in Douglas County would require the developer to develop 0.75 AFY of water supply for each residential unit regardless of water efficiency measures planned for the development.
The Sterling Ranch developer wanted to balance water efficiency planning goals with the local development regulations. To strike this balance, a more holistic land use planning process was used such that site-specific water demands were estimated for the development based on comprehensive water efficiency planning for this particular development, including the area and type of landscape for both planned open spaces and limited irrigated areas, high efficiency plumbing fixtures and appliances, and methods for redirecting stormwater runoff as a water supply to sustain open spaces. Efficient water use would be encouraged/enforced through the use of waterwise certifications for homes, public education, “ballistic” tiered water rates, and regulations to minimize water waste. Developed and impervious areas that typically affect stormwater runoff are planned to be clustered and compact to minimize the stormwater runoff associated with traditionally larger lots. Small “pocket parks” would be built to supplement smaller individual yards, to reduce demands from outdoor lawn watering. The type of landscape for these pocket parks would have low water demands, and might include community vegetable gardens or “edible landscapes” that are part of the concept of “Agriburbia™ The inclusion of water efficiency in the planning process has been encouraged by statewide thinking that considers water conservation as a supply now that other cheaper and easier supplies are not readily available, and also by recent Colorado legislation (HB08-1141) that requires developers to include water supply and conservation information in permit applications.
A modified residential water use target was developed based on the water efficiency methods planned, and review of a variety of studies done by similar sustainably designed communities throughout the Front Range and western United States. The residential water use target includes a total water water use at the home of 0.22 AFY per residential unit, or 65 gallons per capita per day (gpcd). This total demand can be further divided into 42 gpcd of indoor use, and 17.4 gallons per square foot per year for outdoor watering of up to 1,500 square feet of irrigated area. The water use target of 0.22 AFY per unit was increased to 0.286 AFY per unit (85 gpcd) to include a 10 percent system loss and 20 percent factor of safety. This is the anticipated water demand at the water treatment plant.
The Sterling Ranch developer is currently negotiating with Douglas County for an exception to the county zoning requirement of 0.75 AFY per unit, based on the holistic land use planning process completed that estimates actual water demand of 0.286 AFY per unit. This is being done through a zoning appeal process with the County. One of the goals of the appeal process is to determine an appropriate level of cushion on top of the developer’s demand estimate that the Douglas County Commissioners would be comfortable with and that provides ample protection as metered water use data is obtained for the development.
Additional resources for water efficiency planning include the Western Resource Advocate’s report “New House New Paradigm, A Model for How to Plan Build and Live Water-Smart” available online at www.westernresourceadvocates.org, and Sterling Ranch’s Water Plan also available online at www.douglas.co.us/planning/Sterling_Ranch.html. A copy of Beorn’s presentation can be accessed by clicking on the following link: EffInLndUsePlanning_20091026.pdf