Stratification of Lake Waihau (Tiniroto, North Island) and calculations on small lake heat budgets / by Clive Howard-Williams and Robert Spigel.

By: Howard-Williams, C.
Contributor(s): Spigel, R. (DSIR, Division of Marine and Freshwater Science, Taupo Research Laboratory. Taupo).
Material type: materialTypeLabelBookSeries: Taupo Research Laboratory report: no. 60Publisher: Taupo, N.Z. : Taupo Research Laboratory, 1983Description: 20 pages (various pagings) : illustrations (figures, tables) ; 30 cm.Subject(s): LAKE WAIHAU | NZMS260X18 | STRATIFICATION | HYPOLIMNION | WATER TEMPERATURE | EUTROPHIC LAKES | HEAT EXCHANGERS | PHOTOSYNTHESIS | RADIATION | HEAT BALANCE | TEMPERATURE DISTRIBUTION | TURBIDITY | HEATING | COOLING | MIXING | DISSOLVED OXYGEN | HEAT FLUX | WINDS | CONVECTION | THERMOCLINES | DIFFUSION | EPILIMNION | MATHEMATICAL MODELS | SOLAR RADIATION | HEAT LOSS | HEAT FLOW | WATER MIXING | BOUNDARY LAYER FLOW | WATER DENSITY
Incomplete contents:
The calculations show that the diurnal patterns of heating, cooling and mixing, and longer term diffusive processes can explain the cold temperatures of the hypolimnetic waters of Lake Waihau. Mixing and diffusion are limited by the intense stratification caused by the high algal turbidity (ultimately an expression of nutrient status), small size (which precludes efficient mixing) and sheltered conditions. The heating of hypolimnetic waters to temperatures greater than 9 deg. C in late summer can only occur through increased wind mixing. However, the highest mean daily wind speed during the summer months of 1982 at Tikitere was 7.9 metres per second (corresponding to a stirring energy per unit area of approximately 1.0 kilograms per second per second for 3 hours). If we apply this wind energy to the water column and maximum and minimum stratification (6 p.m. and 6 a.m. on Fig. 2), mixing only occurs to 1.25 m at 6 p.m and 2.0 m at 6 a.m. Occasional gusts of high wind may mix further on odd occasions, but the lower water temperatures in Lake Waihau hypolimnion are clearly residual winter temperatures which have not received surface heat input
In: Taupo Research Laboratory report In: Taupo Research Laboratory report
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JOURNAL JOURNAL WELLINGTON
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STACK NO. 60 1983 1 Available J016624
JOURNAL JOURNAL WELLINGTON
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STACK NO. 60 1983 2 Available J016625

10 refs; 3 figs; 3 tables; unpublished file report 27/T/60

The calculations show that the diurnal patterns of heating, cooling and mixing, and longer term diffusive processes can explain the cold temperatures of the hypolimnetic waters of Lake Waihau. Mixing and diffusion are limited by the intense stratification caused by the high algal turbidity (ultimately an expression of nutrient status), small size (which precludes efficient mixing) and sheltered conditions. The heating of hypolimnetic waters to temperatures greater than 9 deg. C in late summer can only occur through increased wind mixing. However, the highest mean daily wind speed during the summer months of 1982 at Tikitere was 7.9 metres per second (corresponding to a stirring energy per unit area of approximately 1.0 kilograms per second per second for 3 hours). If we apply this wind energy to the water column and maximum and minimum stratification (6 p.m. and 6 a.m. on Fig. 2), mixing only occurs to 1.25 m at 6 p.m and 2.0 m at 6 a.m. Occasional gusts of high wind may mix further on odd occasions, but the lower water temperatures in Lake Waihau hypolimnion are clearly residual winter temperatures which have not received surface heat input

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