Urban suppliers should ensure their water sources meet demand during dry years without increasing reliance on Delta water supplies.

The Measure

Water contractors or urban water suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, demonstrate reliability during single and multiple dry years through their Urban Water Management Plans (UWMPs).

  • Expectations

    Suppliers relying on the Delta watershed should account for decreased availability in their projections during dry years and should demonstrate supply reliability through their UWMPs.

  • Performance Metrics

    • Percentage of Delta-reliant contractors or suppliers projecting reliability during a single dry year
    • Percentage of Delta-reliant contractors or suppliers projecting reliability through three dry years

Water Supply Reliability by Hydrologic Region

The graph displays two bars for every year.  The first one shows the percentage of all urban water suppliers projecting reliability during a single dry year (i.e., lowest water supply available to the agency for a single year). The other bar shows the percentage of all urban water suppliers that rely on water from the Delta watershed, projecting reliability for multiple dry years (i.e., lowest water supply available to the agency for three consecutive years).   

Click a hydrologic region to see if they're meeting their targets.

A reliable water supply is necessary to meet California’s current and future needs for water. California experiences routine droughts. During drought years there will be increased demand for scarce Delta water if suppliers are not prepared to meet local demand during dry years. Reliability can be achieved through increased use of alternative supplies, demand management, or both. 

Urban water suppliers demonstrate that they are able to provide reliable service during single and multiple dry years. Dry year reliability is based on water supply available during a supplier's historically driest years.  The UWMPs must include an estimate of service changes during the historic driest three years and if necessary must identify a mechanism for limiting water demand during those three years (Water Code § 10632). Tracking projected reliability in  UWMPs provides information on urban water suppliers’ performance related to dry year water supply reliability.

Reliance on the Delta for water during dry years would mean greater pressure on the Delta ecosystem. Dry year water reliability benefits both the ecosystem and water suppliers, while providing resilience to the impacts of climate change and catastrophic events. Improving dry year reliability supports the State policy of reducing reliance on the Delta for water by ensuring there is enough water supply to meet demand during droughts. Reducing reliance on the Delta is essential for achieving the coequal goals of improving the Delta’s ecosystem and providing a more reliable water supply for the state of California.

Urban Water Management Plans (UWMP) are prepared by urban water suppliers every five years to support long-term water resource management. Any urban water supplier in California that provides water to more than 3,000 water connections or provides more than 3,000 acre-feet of water must prepare a UWMP. The goal of the plan is to ensure that California water supply is not vulnerable due to a lack of long-term resource planning. UWMP are significant efforts that include planning for supply, demand, and water system improvements. For example, UWMP require suppliers to quantify existing water supply and demand, and project future demand and supply.

Urban Water Management plans are supported by the Department of Water Resources (DWR) who assists water suppliers through workshops and trainings, and the UWMP guidebook. DWR reviews individual UWMPs for completeness to ensure water suppliers have addressed legislative requirements. DWR compiles UWMP data and provides it to the public.

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. The recommendations describe more specific and implementable actions to support the achievement of Delta Plan strategies. Strategies and recommendations may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below are the strategies and recommendations associated with this performance measure.

Delta Plan Strategy
  • Increase water conservation and expand local and regional supplies

Delta Plan Recommendations
  • Implement Water Efficiency and Water Management Planning Laws
  • Require State Water Project Contractors to Implement Water Efficiency and Water Management Laws
  • Ensure Compliance with Reasonable and Beneficial Use
  • Expand Water Supply Reliability
  • Develop Water Supply Reliability Guidelines
  • Revise State Grant and Loan Priorities
  • Demonstrate State Leadership
Metric:
  • Percentage of urban water suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, projecting reliability during a single dry year (i.e., lowest water supply available to the agency for a single year). This will be evaluated at least every five years as UWMPs are updated.
  • Percentage of urban water suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, projecting reliability for multiple dry years (i.e., lowest water supply available to the agency for three consecutive years). This will be evaluated at least every five years as UWMPs are updated.
Baseline:
  • Percentage of urban water suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, projecting reliability during a single dry year in their 2015 UWMPs.
  • Percentage of urban water suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, projecting reliability for multiple dry years in their 2015 UWMPs.
Target:
  • One-hundred percent of urban suppliers that are within the Delta watershed, or those relying on water from the Delta watershed, project shortages no greater than 20 percent during single and multiple dry years by 2020—taking into account the reduced availability of water from the Delta watershed during dry years.
Methods

UWMP project single and multiple dry year supply and demand.  Dry year tolerance for each supplier was calculated by comparing the projected 2020 supply and demand using each supplier's one dry year, two dry year, and three dry year values.  If a supplier's one dry year supply could meet projected demand it was considered a single dry year reliability.  The same comparison was made for three year dry year supply.  If three dry year supply could meet projected demand it was considered as a multiple dry years reliability. The supplier data was then aggregated to the regional level and calculated as a percentage.

Data Source
2015 UWMPs

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