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<br />0024_3 <br /> <br />Decreasing lake volumes characteristic of drought cycles exacerbated the concentration of salts in <br /> <br />the lake. Dissolved oxygen levels, on the other hand, could be elevated during drought iflake levels <br /> <br />dropped sufficiently to allow the winter oxygen plume a shorter approach to the dam. <br /> <br />Rapid releases that are not accompanied by matching inflow volume will result in a drop in lake <br /> <br />elevation. At this time, water stored in the more eutrophic side bays enter the mainstem (Thorton et <br /> <br />of. 1990). This process will contribute to meromixis during drought periods. <br /> <br />While the data during the 807s flood was compromised, the temporal resolution dwindled to I or <br /> <br />2 trips per year for 4 years from 1988 to 1991. Inflow volumes indicate these were drought years, <br /> <br />but little information can be garnered from this period except a 5 year trend. While trends <br /> <br />manifested in the forebay data could be compared to similar periods to suggest the processes behind <br /> <br />the long and short term trends, there remain questions for this period. The monthly lake-wide trips <br /> <br />from 1971 to 1982 proved invaluable in discerning the patterns to the processes. This period of <br /> <br />decreasing resolution identifies the value of the quarterly lake wide sampling for determining lake- <br /> <br />wide processes that are manifested in the fore bay data. <br /> <br />c. Flooding Cycles <br /> <br />While the salinization of the lake from a drought cycle can be manifested abruptly within the <br /> <br />hypolimnion, the freshening qualities of a flood may take several years to mix throughout the lake <br /> <br />(Fig. 3a). This relates to the density and mixing properties of the SWARM flows versus the <br /> <br />FRESCO flows. One sinks easily to the hypolimnion and mixes with previous cells and evades the <br /> <br />penstocks, the other tends to slide over the first and is evacuated at the penstocks. When a very <br /> <br />fresh flood follows a drought, the steeper salinity gradient poses a greater challenge to the mixing <br /> <br />and sinking forces. <br /> <br />The flood years of the 19807s were a dramatic example ofthe wettest series of years since 1921. <br /> <br />06/02/98 <br /> <br />DRAFT <br /> <br />P30_ :.6 of62 <br />