Studies on a Kentucky Knobs Lake. IV

Physical and chemical conditions in Tom Wallace Lake, Kentucky, were studied through three intermittent ice covers for a period of 49 days during January and February 1958. A Birgean heat budget, based on temperatures observed from a station over the deepest part of the basin, involved a loss of 80 g‐cal/cm 2 for the entire period. However, temperature profiles made from several stations revealed that there was considerable vertical and horizontal turbulence within the water mass beneath the ice, and that isotherms were not horizontal. Although temperatures of the sediment and deep waters fluctuated, the direction of heat flow from the thin layer of profundal sediment was always upward into the overlying one or two meters of water. Most temperature changes at mid depths, especially at 5 m, were probably caused by lateral transport of heat, since vertical thermal gradients were nonexistent or very slight at those levels. The direction of thermal gradients in the uppermost one or two meters beneath the ice was more varied. At times heat seemed to be moving downward from the ice; at other times an inverse gradient was observed even though the upper water was gaining heat. On several days the vertical temperature profile could not be reconciled with the density of water as a function of the prevailing temperatures, and in a few instances these anomalous stratifications could not be correlated with available chemical data. Some relative‐density determinations of water from different depths showed on one occasion that there was no instability in spite of an anomalous temperature profile. Freezing‐out effects during times of ice formation, and diluting caused by rain and melting were reflected beneath the ice in changing values of total alkalinity, total iron, and total solids. Stratification and variation in values of dissolved oxygen, total alkalinity, iron, and total solids are discussed.