Methodologies for Calculating Baseline and Compliance Urban Per Capita Water Use (For the Consistent Implementation of the Water Conservation Act of 2009)

In November 2009, SBX7-7, The Water Conservation Act of 2009, was signed into law as part of a comprehensive water legislation package. The Water Conservation Act addresses both urban and agricultural water conservation. The urban provisions reflect the approach taken in the 20×2020 Water Conservation Plan. The legislation sets a goal of achieving a 20-percent statewide reduction in urban per capita water use and directs urban retail water suppliers to set 2020 urban water use targets. The Water Conservation Act of 2009 directs DWR to develop technical methodologies and criteria to ensure the consistent implementation of the Act and to provide guidance to urban retail water suppliers in developing baseline and compliance water use. To meet the legislative directives for consistent implementation, DWR has developed and published Methodologies for Calculating Baseline and Compliance Year Per Capita Water Use.

This is the third revision of the Methodologies for Calculating Baseline and Compliance Urban per Capita Water Use. The document was first released in October 2010 and then revised in February 2011 with the addition of the Provisional Method 4 for Determining Water Use Targets as Appendix C. This revision includes Methodology 8: Criteria for Adjustments for Compliance Daily per Capita Water Use and removes the former Appendix A: Alternative Methodology for Service Area Population. Methodology 8 was not included in the earlier versions of the Methodologies as it was not required for the completion of the 2010 urban water management plans and more time was needed to thoroughly develop the methodology. The former Appendix A provided instructions for using the Census Bureau’s website to calculate service area population using a person per connection approach. The Census Bureau has revised its website and the links in the former document are no longer valid. Additionally, as part of its guidance for the 2015 UWMPs, DWR has included a population mapping tool as part of the on-line urban water management plan data submittal website. The population mapping tool provides a simpler and streamlined approach to estimating service area population.