20 years (California Department of Fish and Game 1983). The 
direct economic impact for the last two decades has been losses 
of about 1.3 billion dollars (Meyer Resources, 1985). 
In the Sea of Azov, diversions of more than 60 percent of 
historic spring (and more than 45 percent of annual) flows have 
resulted in: 
1. Distortion of circulation dynamics and reduction in 
vertical mixing (increases in vertical stability index) 
as much as 3-5 times resulting in significant increases 
in frequency of anoxic conditions in deep water near 
the bottom, covering as much as 60 percent of the sea 
area (Volovic, 1986). 
2. Accumulation of more than 1,500 x 10 6 tonnes of salt 
and an overall increase of the mean salinity from 9-9.5 
to 14-16.0 ppt and in the pre-Delta areas from 0.5-3.0 
to 6-10.0 ppt for the last two decades. 
3. Reduction of 60-75 percent (2 x 10 6 tonnes) in sedi¬ 
ment load, and 80 percent in spawning and nursery 
areas. 
The resulting economic losses for fisheries since the late 1960s 
have been tens of millions of dollars per year (Meleshkin et. 
al. 1973, 1981; Vorovich et. al. 1981). 
These and other similar historical examples of the relation 
between human needs for freshwater and protection of estuarine 
environments (Mann, 1982; Meleshkin, 1981; Rozengurt and 
Tolmazin, 1974; Rozengurt and Herz, 1981) indicate that special 
consideration should be given to the consequences of timing and 
volume of water withdrawals on recruitment and landings of 
anadromous fish, because of their sensitivity to cumulative 
fluctuations in freshwater supply. It may be possible to 
alleviate these problems and to protect freshwater intakes in 
the Delta if limits to water diversion can be agreed upon. 
Perhaps this can be done through the establishment of salinity 
and flow standards for San Francisco Bay (neither of which 
currently exists). In addition, Rozengurt (1983a) has suggested 
a restraining channel be constructed in part of the existing 
ship channel in San Pablo Strait (2 walls 1-3 kilometers long 
and 200 meters apart, extending from the bottom to just above 
the high tide level). Hydrological model testing of this design 
will be required to determine its effectiveness in limiting salt 
intrusion into Suisun Bay and the Delta (Rozengurt, 1971, 1974). 
57 
