CONVECTIVE AND ADVECTIVE CIRCULATION OF LAKE POWELL, UTAH-ARIZONA, DURING 1972-1975

The water circulation in Lake Powell has been documented and analysed for the period 1972–1975 on a monthly, synoptic basis. From its inception Lake Powell has convectively mixed only during the winter cooling period. At no time, however, during 1972–1975 did this vertical mixing extend to the lake bottom. During the winter dissolved salt becomes important in stabilizing the lake. The yearly heat budget of the lake averages 40 kcal/cm2. A dominant feature of the summer circulation of the lake is an overflow density current from the upstream Colorado River. The overflow current mechanically sets the depth and extent of the thermocline. During maximum stratification (July–September) a pervasive and intense oxygen‐depletion layer develops immediately below the epilimnion‐thermocline interface. Cold, dense upstream waters intrude the lake during the winter as an underflow density current, which annually replenishes the oxygen supply of the bottom waters. An integral component of the lake's circulation throughout the year is a withdrawal current at mid‐depth within the lake. The configuration and extent of the withdrawal current is a function of dam operation and seasonal density stratification. Copyright 1979 by the American Geophysical Union.