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1. Limnology(lentic = lakes and ponds; lotic = streams and rivers) Properties of Lakes
Origins
Water Balance
Light
Heat and Stratification
Oxygen
Nutrients: Nitrogen and Phosphorous
2. Origins of lakes
Tectonic
Volcanic
Landslides
Glacial action
Solution of rock
River activity
Shoreline activity
Biological (beavers)
Human
3. The distribution of reservoirs
4. Limnology: water balance Water inputs:
Precipitation, surface runoff from basin, groundwater, diversion
Water losses:
Drainage, seepage, evaporation and evapo-transpiration (plants), diversion
5. Global water supply
6. Limnology: light
7. Heating and cooling Sources of heat:
Direct solar radiation (most important)
Groundwater and springs
Ground (minor)
Losses of heat:
Thermal radiation (primary)
Conduction
Evaporation
Outflow
8. Heat and the density of water
9. Distribution of heat Horizontal distribution is primarily driven by wind
Vertical stratification is seasonal, driven by the relationship between density and temperature
10. Limnology: heat
11. Limnology: heat
12. Limnology: heat The distribution of heat within a lake depends on water movement
Surface waves
Langmuir circulation waves
River Influents
13. Dissolved Oxygen
14. Dissolved Oxygen Air contains 300 mg O2/L; the rest is mostly nitrogen
Water contains 14.6 mg O2/L
Gasses diffuse slowly in water, so distribution is governed by circulation, not diffusion
Eutrophic Lakes: hypolimnion depleted by decomposition (biotic processes)
Oligotrophic Lakes:
Distribution governed by physical processes
15. Dissolved Oxygen Winter Kill:
Occurs when a shallow lake is ice-covered and hence dark for a long period. The DO demand of plants can drive levels below the 2 mg/l required by most fish.
Summer Kill:
Occurs when dense concentrations of macrophytes die at the end of their growing season. Decomposition can drive DO levels down. If the lake is shallow and macrophytes are found over the whole surface, a “squeeze” between warm surface temperatures and low DO levels on the bottom in late summer can kill fish.
22. Limnology: Nitrogen and Phosphorous
23. Primary and secondary production may be limited by Nitrogen or Phosphorus
24. Natural and human sources for Nitrogen and Phosphorous
25. Objectives
Determine empirical relationships of fish yield with abiotic factors
Provide fisheries managers with an easily applied technique for first approximation of annual fish yield.
Provide a fundamental conceptual base for the global synthesis for production process in aquatic systems.
26. Morphoedaphic Index
27. Morphoedaphic Index
29. The Morphoedaphic Index needs to be adjusted for regional climate conditions
30. Morphoedaphic Index
32. Limnology: light
33. Limnology: light
34. Limnology: Nitrogen and Phosphorous