Instream Flow Studies for the Protection of Public Trust Resources: A Prioritized Schedule and Estimate of Costs

Chapter 5 of the 2009-10 Seventh Extraordinary Session (SB X7 1, Simitian) directs the State Water Resources Control Board (State Water Board) to submit to the Legislature, by December 31, 2010, a prioritized schedule and estimate of costs to complete instream flow studies for two categories of rivers and streams, by two specific deadlines:

1) high priority rivers and streams in the Delta watershed that were not covered in the Board’s “Final Report on Development of Flow Criteria for the Sacramento-San Joaquin Delta Ecosystem” by 2012; and

2) all major rivers and streams outside the Sacramento River watershed by 2018.

The definition of the two stream categories is ambiguous. There are a number of tributaries that are both in the Delta watershed and outside the Sacramento River watershed, including the San Joaquin, Calaveras, Cosumnes, and Mokelumne Rivers. The State Water Board interprets the first category to mean all Delta and Sacramento River tributaries not covered under the Board’s “Final Report on Development of Flow Criteria for the Sacramento-San Joaquin Delta Ecosystem.” Two additional schedules are prioritized for “all major rivers and streams outside the Sacramento River watershed.”

This report identifies 138 rivers and streams for instream flow studies. The total estimated cost to conduct scientific instream flow studies for the high priority rivers and streams tributary to the Delta is $32.46 million.

The total estimated cost to conduct scientific instream flow studies for the high priority rivers and streams outside the Delta watershed is $107.25 million. The detailed schedules and costs are preceded with a few short discussions on the timelines given in the directive, the organization of schedules, the cost estimates for instream flow studies, and cost estimates for the next logical step: setting instream flow objectives.