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002294 water is less dense than cold water (down to 40C), and pure or "fresh" water is less dense than water with many dissolved chemicals (reflected by measurements of electrical conductivity or salinity--terms used here interchangeably). Advective Flow: A lateral or pushing~current, typically horizonW, driven by the momentum of an inflowing current. Convective circulation: As stratified water cools in the fall, the surface becomes denser than the underlying layers, eventually displacing it as the warmer water rises. This vertical density driven mixing is enhanced by wind action. The depth of convective mixing is dependent on the volume of the spring flood, as well as on the coldness of the winter. Sufficiently deep or aggressive mixing may penetrate metalimnion. Density currents: A water mass that seeks its own level based on differences in density from adjoining water masses. Its movement also involves an advective component from river inflow. This includes the bottom hugging winter flows in Lake PowelL Withdrawal currents: The current patterns established in a lake due to the operations of withdrawal ports in a dam. In general, increases in discharge result in a 3rd power increase in kinetic energy available for mixing, as KE oc Q3 (Thorton et al. 1990); this extends the vertical draw of the outlets. Hence, the increase from a discharge of 5000 cfs to 30,000 cfs increases mixing and destratification by 216-fold, while total discharge only increased by 6-fold. Wind Mixing: The vertical mixing of surface layers of a lake due to wind shear. Its effect is de'epest when combined with convective mixing on a homogeneous mass than on a strongly stratified water body. Diffusion, Dispersion and Entrainment: Diffusion is the passive mixing of water across a concentration gradient. Dispersion is the active mixing of water across a concentration gradient 03/06/98 DRAFT Page 18 of62