UCLA Dept. of Civil & Environmental Engineering
C & EE 200 Seminar
THURSDAY, November 16, 2017
4275 BOELTER HALL 11:00 to 12:00 PM
Ryan Thacher, Ph.D, P.E.
Managing Engineer, Exponent

Availability of Water in Clifton Court Forebay, Sacramento-San Joaquin Delta, to Byron-Bethany Irrigation District during Drought Conditions

The Sacramento-San Joaquin River Delta (Delta) is the transition zone between the San Francisco Bay and its watershed, a 62,900-square-mile basin that occupies roughly 40% of California’s land area. Roughly seven million acre-feet of water per year is exported or diverted from the Delta; the majority goes to agricultural use, and the balance meets nearly two-thirds of California’s domestic demand. The Delta was historically a natural freshwater marsh but has been altered by nearly two centuries of channelization and development. The Delta now serves as the hub of California’s water distribution system.

California’s recent drought put severe pressure on the ability of State Water Project (SWP) and Central Valley Project (CVP) operators to meet water demands with the supply available in the Delta and in upstream reservoirs. On June 12, 2015, the State Water Resources Control Board (SWRCB) issued orders requiring water users with pre-1914 appropriative water rights with a priority date of 1903 or later to curtail diversions. The SWRCB Order was based on a finding that the available supply of water through the Delta watersheds was insufficient to meet their demands.

Byron-Bethany Irrigation District (BBID), an agricultural water district that also provides water for a residential community, was unable to immediately comply with the curtailment order and diverted approximately 2,067 acre-feet of water between June 13 and June 25, 2015. On July 20, 2015, BBID was issued an Administrative Civil Liability (ACL) complaint by the SWRCB Division of Water Rights, which asserted that BBID continued to divert water “despite lack of availability of water to serve its right during extreme ongoing drought conditions.”

Exponent was asked by BBID to investigate the basis of the complaint and the SWRCB’s claim that water was unavailable. As detailed in this presentation, Exponent used a source-water fingerprinting approach to conclude that the water diverted by BBID between June 13 and 25, 2015 had entered the Delta several months prior to the curtailment order and consisted primarily of natural flows, not stored water released by the SWP and CVP. Thus, Exponent concluded that water was available to BBID during this period, independent of the operations of the SWP and CVP. Exponent formed these conclusions in consideration of the configuration, hydrodynamics, residence time, and quality of water within the Delta, and an analysis of the salinity and the source, both in terms of location and time, of water available for diversion by BBID. On March 25, 2016, the SWRCB suspended hearings in the matter, and on June 7, 2016, the SWRCB dismissed the ACL.

Date(s) - Nov 16, 2017
11:00 am - 12:00 pm


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