Laserfiche WebLink
<br />0024Gl <br /> <br />volume and reduced releases, resulting in a higher exchange rate for the water within the lake: <br /> <br />between 124% to 380%. This indicates that the entire lake's water quality was more rapidly dictated <br /> <br />by inflow water quality than in subsequent periods, and such was the case in the 1960's. <br /> <br />Interpretation of this period is hampered by erratic data collection--there are holes in temperature <br /> <br />and dissolved oxygen data at critical junctures, as well as irregularities in the temporal sampling. <br /> <br />Some conclusions can still be drawn from this period. <br /> <br />One of the signatures of this filling cycle was an 8th ranked flood (the 8th highest annual inflow <br /> <br /> <br />in Lake Powell's history) in 1965. This tremendous volume of water appeared at the dam with the <br /> <br />lowest conductance values recorded since the lake's filling. This plume of fresh water shows clearly <br /> <br />in Fig. 3a and the longitudinal plots of Fig. 4, but doesn't have the diluting effect that one could <br /> <br />expect from the mass it represents, for it is flushed from the lake within 2 years. It is apparent is <br /> <br />some of it is mixed into the hypolimnion by early 1966, but by 1967, the fall SWARM plug has <br /> <br /> <br />subst~ntially salinized the lake. In spite of the high volume turnover rates for the 1960's, this <br /> <br />extremely salty hypolimnion (values up to 1300 FS/cm) developed with only one season's inflow, <br /> <br />but required 5 ?years to dilute to previous levels. One reason is the nature of the SWARM flow to <br /> <br />quickly dominate the hypolimnion if it is of sufficient salinity, while the diluting processes of the <br /> <br />hypolimnetic overflow or underflow is less efficient. Winter inflow salinity values today range from <br /> <br />800 to 1200 FS/cm. This cycle of events is a product of the low level of the lake, and the placement <br /> <br />ofthe penstocks and river outlet works, which were both functioning in this period. <br /> <br />In addition, the left river diversion tunnel, at the bottom of the dam, had not yet been sealed, and <br /> <br />was used for discharges when the lake level had not yet reached the jet tubes or penstocks or when <br /> <br />higher discharge could not be achieved through the penstocks and jet tubes alone (U.S. Bureau of <br /> <br />Reclamation, 1970, Martin 1989). At these low lake levels, both upper release ports drew from the <br /> <br />epilimnion, stripping out the spring floodwaters before they were integrated into the lake's depths, <br />06/02/98 DRAFT '\'6" 24 of 62 <br />