Managing Water to Protect Fish A Review of Califo

Authors: Larry R Brown Wim Kimmerer Randall Brown

Publish Date: 2008/10/02

Volume: 43, Issue: 2, Pages: 357-368

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Abstract

The SacramentoSan Joaquin Delta the landward reach of the San Francisco Estuary provides habitat for threatened delta smelt endangered winterrun Chinook salmon and other species of concern It is also the location of huge freshwater diversion facilities that entrain large numbers of fish Reducing the entrainment of listed fishes into these facilities has required curtailment of pumping reducing the reliability of water deliveries We reviewed the first 5 years 2001–2005 of the Environmental Water Account EWA a program instituted to resolve conflicts between protecting listed fishes and providing a reliable water supply The EWA provided fishery agencies with control over 02–04 km3 of water to be used for fish protection at no cost to users of exported water and fish agencies guaranteed no disruption of water supply for fish protection The EWA was successful in reducing uncertainty in water supply however its contribution to the recovery of listed fishes was unclear We estimated the effectiveness of the EWA to be modest increasing the survival of winterrun Chinook salmon by 0–6 dependent on prescreen mortality adult delta smelt by 0–1 and juvenile delta smelt by 2–4 Allocating EWA water for a single life stage of one species could provide larger gains in survival An optimally allocated EWA of equal size to the median of the first 5 years could increase abundance of juvenile delta smelt up to 7 in the springs of dry years If the EWA is to become a longterm program estimates of efficacy should be refined If the program is to be held accountable for quantitative increases in fish populations it will be necessary to integrate scientific possibly experimental approachesWe thank the many agency biologists and others that reviewed early versions of the manuscript The authors thank the CALFED Science Program for providing funding for this review This article is dedicated to the memory of our friend and coauthor Randy Brown who passed away while it was being written

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