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<br />00Z299 <br /> <br />the previous spring's floodwaters left to convectively mix with the saline but warming riverine <br /> <br /> <br />water, This Saline and COOL flow forms around March and follows the FRESCO plume down <br /> <br /> <br />the lake's bottom. Its progress is typically stalled by April or May when warming and the <br /> <br /> <br />-- --4l.dvectiVldlow forces are diverted to the spring flood at the surface. Organic and chemical m'yg"n <br /> <br /> <br />demands, low light availability, and prolonged stagnation keep oxygen levels low in this cell. It <br /> <br /> <br />typically does not move downlake until the following winter when the SWARM's bottom hugging <br /> <br /> <br />flow will entrain it as its flows to the dam. An animated sequence of the longitudinal salinity <br /> <br /> <br />profiles for Lake Powell since 1965 can be found at website www.usbr.gov/gces.This <br /> <br /> <br />demonstrates the inflow and outflow dynamics under various filling, drought and flood cycles. <br /> <br />c. Side Channel influences <br />While the most of the side channels have not been examined throughout Lake Powell's <br /> <br />history, the San Juan and Escalante Rivers have been received some attention, primarily with the <br /> <br />instigation of the GCES program. The Escalante River contributes only -5% of the total inflow to <br /> <br />Lake Powell, yet produces a regular and pronounced effect on the main channel salinity and <br /> <br /> <br />dissolved oxygen levels (Figs. 8-10). Stagnant conditions and very low oxygen levels frequently <br /> <br /> <br />produce an oxygen sag and a salinity peak in the main channel year round, frequently at penstock <br /> <br /> <br />levels, The San Juan Arm, on the other hand, has greater discharge rates and does not suffer from <br /> <br /> <br />the anoxic conditions found in the Escalante arm. Occasionally the San Juan channel produces a <br /> <br /> <br />bottom flowing FRESCO plume in the winter that reaches the main channel of the lake, creating a <br /> <br /> <br />rise in oxygen concentrations that does not correspond to cold temperatures arising from the main <br /> <br />channel. <br /> <br />03/06/98 <br /> <br />DRAFT <br /> <br />Page 23 of 62 <br />