Conclusions 
Since the late 1950s, diversions of water from the San 
Francisco Bay watershed have increased from 20-30 percent to as 
much as 63 percent annual runoff and from 30-35 percent to 60-85 
percent for spring runoff (April-June). During the same period, 
the predominant ranges of negative deviations from the "normal" 
runoff (1921-1978) for the 5-year running means of annual dis¬ 
charges (regulated) to the Delta and Bay is 35-60 percent, the 
range is 40-85 percent for the spring discharges. Without regu¬ 
lation, outflow deviations of natural water supply for both 
annual and spring 5-year running means of normal runoff varied 
only 15-25 percent from the same mean value. Overall, between 
1955 and 1978, (a period when the major water storage and 
diversion facilities were fully operational about 286 km 3 (240 
MAF), or as much as 40 times the volume of San Francisco Bay, 
was diverted from the system. 
These reductions of freshwater flow to the estuary have: 
greatly increased salt intrusion into Delta waters, threatening 
agricultural and municipal water intakes; produced massive 
reduction of nutrients and sediment load; and greatly reduced 
flushing and circulation activity formerly accomplished by heavy 
spring inflows. 
Concurrent with these flow-related changes, there have been 
massive reductions of fish populations. Salmon are down to 30 
percent of 1960s levels, while striped bass are down to 2 0 
percent of their levels of 20 years ago. Statistical analyses 
reflect an underlying relationship between catch of salmon, 
striped bass, and shad and freshwater flow to the estuary for 
the preceeding 2-4 years. 
High correlations obtained between commercial fish catches 
(prior to construction of California water projects) and running 
mean Delta outflow indicate that annual water supply had to be 
at least 23.0 km 3 (19.0 MAF) and spring runoff (April-June) in 
the range of 3.1-3.7 km 3 (2.5-3.0 MAF), 69 percent and 68-84 
percent of the historic unimpaired flow, respectively, for the 
2-4 preceding years to ensure optimal commercial catch. Similar 
analyses for successful sportfishing catches (post project 
construction) show that annual mean flows of 21.0 km 3 (17.0 
MAF) and spring Delta outflows of 2.5-3.1 km 3 (2.0-2.5 MAF) 
are needed for the 2-3 preceding years to ensure significant 
catches. However, during 1967-1982 (CVP and SWP operating at 
full capacity), the 3-5 year running mean spring and annual 
water supply into and out of the Delta was several times less 
than this. 
The result has been a major impact on recruitment and 
recreational catches of striped bass and salmon since the late 
1960s. Salmon and striped bass natural reproduction has been 
reduced 65 percent and 80 percent, respectively, over the past 
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