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<br />00 1.. :)t) \ <br /> <br />OO"l.~O I <br /> <br />lCC200 <br /> <br />SWARM flow to quickly dominate the hypolimnion if it is of sufficient salinity, while the <br /> <br /> <br />diluting processes of the hypolimnetic overflow or underflow is less efficient. Winter inflow <br /> <br /> <br />salinity values today range from 800 to 1200 IlS/cm:This cycle of events is a product of the low <br /> <br /> <br />level of the lake, and the placement of the penstocks,andriver~outletworks,which were both <br /> <br /> <br />functioning in this period. <br /> <br /> <br />In addition, the left river diversion tunnel, at the bottom of the dam, had not yet been sealed, <br /> <br />and was used for discharges when the lake level had not yet reached the jet tubes or penstocks or <br /> <br /> <br />when higher discharge could not be achieved through the penstocks and jet tubes alone (U.S. <br /> <br /> <br />Bureau of Reclamation, 1970, Martin 1989). At these low lake levels, both upper release ports <br /> <br /> <br />drew from the epilimnion, stripping out the spring floodwaters before they were integrated into <br /> <br /> <br />the lake's depths, while the diversion tunnel drew off the deepest hypolimnetic waters. The result <br /> <br /> <br />was rapid turn-over of the lake's volume in 1965 with pronounced refreshment of the <br /> <br /> <br />hypolimnion. The diversion tunnel was permanently sealed in September 1965. The bi-level <br /> <br /> <br />epilimnetic withdrawals that followed in 1966 and strong SWARM currents that followed in the <br /> <br /> <br />late 1960's resulted in an exceptionally persistent and very saline hypolimnion-meromixis-- that <br /> <br /> <br />dominated the lake through 1971. <br /> <br /> <br />Oxygen levels for this period remained fairly high. Although the early dissolved oxygen data <br /> <br /> <br />was sometimes noisy, the pattern of winter oxygenation predictable under the circumstances. <br /> <br /> <br />Although quite saline, the winter bottom flows were cold and well oxygenated. Furthermore, <br /> <br /> <br />these flows were entering a smaller lake and the cold, oxygenated FRESCO plume had less <br /> <br /> <br />distance to travel to the dam than in later years when the lake was deeper and longer. <br /> <br />b. Drought Cycles <br /> <br /> <br />For the purposes of this assessment, basin-wide drought is measured by the total inflow to the <br /> <br /> <br />lake and not local weather patterns. At least 5 major drought cycles can be observed in the long <br /> <br />03/06/98 <br /> <br />DRAFT <br /> <br />Page 25 of 62 <br />