EARTH221 Lecture Notes - Lecture 17: African Lakes, Epilimnion, Thermocline
26 Aug 2016
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Lecture 17: 9% difference in density b/w water and ice, max density at 4 degrees, mixing water- need to overcome density gradient. Difference in density results in more energy required to mix. African lakes steep gradient so waters do not mix easily. First layer epilimnion, top most warm water in contact with surface. Zone in between is the thermocline (temperature changes rapidly) Fish in hypolimnia have limited oxygen supply, if the oxygen in that layer escapes it is not replaced: autum. Storms mix water(fall turnover) and temperatures become constant at all layers: winter. Tops freeze first and ice floats on top: spring. Lake mixes: dimictic two turnovers (mixings) every cycle. Water as a solvent: 3 steps: 1. Water quality and watersheds: watersheds are defined topographically, catchment, subcatchment, watersheds (terms used interchangeably, water quality. Precip water will have tds of around 10-20.
