ESS 328 Limnology
Fall 2020
Chapter 7 Lakes and Reservoirs
Stratification / Turnover / Mixing
Heat, light, density difference with depth
Annual cycle for a temperate lake
Thermal (Summer) Stratification
Epilimnion
Metalimnion (Thermocline)
Hypolimnion --- COLD Handout
©2010 Elsevier, Inc.
FIGURE 7.11
Temperature as a function of depth for Triangle Lake, Oregon, on October 1, 1983, and positions of epilimnion,
metalimnion, and hypolimnion. (Data from R. W. Castenholz).
Thermal resistance to mixing
©2010 Elsevier, Inc.
FIGURE 7.12
Stability of the thermocline in Linsley Pond, Connecticut, before and after a hurricane on September 21, 1938, with
wind speeds up to 100 km h21. (From G. E. Hutchinson, A Treatise on Limnology, Vol. 1, Geography, Physics and
Chemistry. John Wiley & Sons, Inc., 1957. Reprinted by permission of John Wiley & Sons, Inc.).
FIGURE 7.10
Holomixis
Lake mixing
– Amictic
– Monomictic
Warm
Cold
– Dimictic
– Meromictic
– Polymictic
Depth-Time Isopleths
Implications
Stratification
Turnover (mixing)
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