Town of Windsor Certification of Water Supply Reliability and Conservation Standard

Background
On May 18, 2016, the State Water Resources Control Board adopted an updated Drought Emergency Water Conservation regulation that requires urban water suppliers to self-certify a conservation standard to meet out to January 2017 based on the results of a water supply reliability assessment.   

To comply with the regulation, urban suppliers must evaluate available water supplies assuming three more dry years to come, and set a conservation target based on the percentage of expected shortfall in its water supply at the end of year three, if any. Water wholesalers, such as the Sonoma County Water Agency, were also identified in the revised regulation with requirements to provide their retail customers (Windsor & other cities) with estimates of supply availability using the same three-dry-year scenario.

After coordination with the Water Agency, it was determined that Lake Sonoma holds ample water supply to allow all of the Agency’s water contractors, including Windsor, to meet expected demands, resulting in a zero conservation standard and an end to mandatory drought cutbacks. Links to the supply reliability analysis and associated data used to determine the exemption to the conservation standard are listed below.

Water Supply
The Town’s water supply sources include Russian River surface water, separate off-river groundwater, and tertiary treated recycled water.  The majority of the Town’s potable water supply is surface water, its source being the Russian River. Roughly 90 percent of Russian River surface water is obtained from the Town’s Russian River Well Field, which diverts water under the Water Agency’s diversion rights. The Town also purchases Russian River surface water directly from the Water Agency, which is delivered into the Town’s distribution system through a connection to the Water Agency’s Santa Rosa Aqueduct.

In addition to surface water, the Town owns groundwater wells, known as off-river wells. Of the groundwater sources, some are potable, while others are considered “raw” (untreated) and non-potable.  Currently, four of the Town’s five off-river groundwater wells are inactive. One active groundwater well, the Esposti irrigation well, provides raw water for the irrigation of Esposti Park and is subsequently not included in this analysis.  Tertiary treated recycled water, although an important supply source used to offset the use of potable water, is also not included in this analysis.

Supply Reliability Analysis
The water supply reliability analysis, which details Demand, Supply, Conservation Standard, and other supporting data, was provided to the Town of Windsor by the Sonoma County Water Agency to fulfill the requirements of the May 2016 Emergency Regulation.  The regulation stipulates that water wholesalers are to provide their retail customers with information on the volume of water they can expect to deliver in each of the next three years using the assumptions in the regulation.

Because the Town's sole source of supply (Russian River) for this analysis is based on the volume of Russian River water expected to be delivered by the Water Agency (either through the Town's local supply at its Russian River Well Field or through the Water Agency's Santa Rosa Aqueduct connection), the determination of a conservation standard for the Town is tied directly to the Water Agency's analysis of expected deliveries. The Water Agency's analysis is therefore provided to demonstrate a conservation standard of zero percent for the Town of Windsor.  The pertinent information for the Town of Windsor is highlighted in yellow in the analysis.

The Water Agency has estimated the projected water storage available from Lake Sonoma for water years 2017, 2018, and 2019 by assuming hydrologic and demand conditions for water years 2013, 2014, and 2015 repeat.  A narrative description of the conservative methodology used by the Water Agency for this analysis is available online at: Sonoma County Water Agency: Supply Availability for Urban Water Suppliers.

Water Supply Reliability Analysis and Windsor's Self-Certified Conservation Standard  (Microsoft Excel version)

Water Supply Reliability Analysis and Windsor's Self-Certified Conservation Standard      (PDF version)

As a result of the zero conservation standard, the Windsor Town Council at their June 15, 2016 meeting adopted a resolution declaring an end to the drought emergency for the Town's service area, lifting drought specific restrictions on water use.  The Town's year-round Regulations and Restrictions on Water Use details prohibitions on wasteful practices that remain in effect and are continually enforced regardless of drought conditions. Although the local drought emergency has ended, conservation and the elimination of water-waste remains an everyday part of California life.

For more information about the action taken by Council, and details on year-round restrictions on water-waste, view the press release.