Click to download a copy.

Department of Water Resources releases the 2013 State Water Project Delivery Reliability Report

Click to download a copy.
Click to download a copy.

The Department of Water Resources has released the 2013 State Water Project Delivery Reliability Report, intended to inform the state water contractors, planning departments, and the public about key factors important to the operation of the State Water Project (SWP) and the reliability of its water deliveries.

Water provided by the SWP is a major component of water supplies for SWP contractors, and the availability of SWP water is an important component to their water supply planning.  DWR is required to prepare and distribute the report every 2 years as part of the Monterey Amendments settlement agreement.

The report describes the expected SWP deliveries under expected existing and future conditions. The term ‘water delivery reliability’ as used in the report is defined as “the annual amount of SWP water than can be expected to be delivered with a certain frequency”, or in other words, the probability that a certain amount of water will be delivered by the SWP in a given year.   The analyses in the report factor in all of the regulations governing SWP operations both in the Delta and upstream, and assumptions about water uses in the upstream watershed.  The analyses consider climate change and the effects of sea level rise, but do not incorporate the probability of catastrophic levee failure.

Table 4-1Many of the same challenges to SWP operations that were identified in the 2011 State Water Project Delivery Reliability Report remain, the report says, most notably the regulatory restrictions imposed by the 2008 and 2009 biological opinions.   Estimated average annual Delta exports have decreased since 2005, with the sharpest declines occurring by 2009 as the biological opinions went into effect.

The findings of the report as taken from the summary are:

  • The estimated average annual SWP exports has decreased from 2.612 MAF to 2.466 MAF, a decrease of 5.6%, between existing-conditions and future-conditions scenarios.
  • Under existing conditions, the average annual delivery of Table A water is 1% more than the estimate for the 2011 Report.
  • Under future conditions, the average annual delivery of Table A water is about 1% less than the future conditions scenario presented in the 2011 report.
  • The likelihood that supplemental water deliveries (termed Article 21 deliveries) under existing conditions being greater than 20,000 AF has decreased relative to the 2011 report, as has the same deliveries under future conditions.  Both reports show the likelihood to range between 21 and 26% under both existing and future conditions.

The report summarizes issues affecting SWP water supply reliability;  describes the SWP’s background, facilities, water contracts and contractors; explains how water supply reliability is calculated and describes the factors that make forecasting that challenging; discusses how restrictions on operations have reduced exports; and estimates the SWP’s water supply reliability for existing and future conditions.  There are plenty of interesting and informative charts and tables throughout, as well as historical tables and a technical addendum which accompany the 81-page report.

Download a copy of the report here:  State Water Project Delivery Reliability Report 2013

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