Lecture 7a - Lake Structure

Question 1

Lakes Have a Vertical Structure Due to (3):

Answer 1

1. Stratification
2. Thermal Stratification
3. Lake Mixing

Question 2

What is Stratification:

Answer 2

Structuring of water body into ‘layers’ due to physical, chemical, and biological inputs and processes

Question 3

What is Thermal Stratification:

Answer 3

Varies with latitude and climate due to different thermal inputs including wind fields

Question 4

What is Lake Mixing:

Answer 4

is caused by energy inputs in a balance between buoyancy and inertia. There are seasonal mixing patters caused by a variety of energy inputs

Question 5

Lake Structure is Based on (5):

Answer 5

1. Morphometry
2. Hydrology
3. Light
4. Heat
5. Turbulence

Question 6

Lake Structure - Morphometry:

Answer 6

Determines basin shape

Question 7

Lake Structure - Hydrology

Answer 7

Retention time and chemical properties of the lake

Question 8

Lake Structure - Light

Answer 8

Determines compensation depth
1. littoral
2. limnetic zones
3. profundal zones

Question 9

Lake Structure - Heat

Answer 9

Determines the 1. Epilimnion, 2. Metalimnion, and 3. Hypolimnion zones in the lake

Question 10

Lake Structure - Turbulence

Answer 10

Determines lake mixing, sediment stability/mobility in littoral

Question 11

What Creates Stratification:

Answer 11

1. Thermal inputs and lack of mixing
2. Different layers with different densities and conditions
3. less dense water has to rise above the other layers
4. Different densities arises because of temperature but also due to chemistry
5. Mixing occurs (no more stratification) when it overwhelms the buoyancy of different layers

Question 12

Different Stratification/Mixing Patterns (7):

Answer 12

1. Diel/episodic
2. Dimictic
3. Monomictic
4. Amictic
5. Polymictic
6. Holomictic
7. Meromictic

Question 13

What is the Dimictic Mixing Pattern:

Answer 13

Spring and fall mixing

Question 14

What is Monomictic Mixing Pattern:

Answer 14

Fall mixing

Question 15

What is the Amictic Mixing Pattern:

Answer 15

No mixing

Question 16

What is the Polymictic Mixing Pattern:

Answer 16

Pccurs in small, shallow lakes

Question 17

What is the Holomictic Mixing Pattern:

Answer 17

Entire lake mixes

Question 18

What is the Meromictic Mixing Pattern:

Answer 18

Deepl layer of non-mixing water

Question 19

What Does Thermal Energy do For Lake Mixing:

Answer 19

• Heating
• Convection
• Precipitation
• Evaporation

Question 20

What Does Wind Energy Do for Lake Mixing:

Answer 20

• Creates waves
• Stokes Drift
• Seiches
• Horizontal mixing
• Langmuir circulation

Question 21

What Do Density Interactions Do for Lake Mixing:

Answer 21

• Stratification
• Instabilities
• Pumping
• cooling
• Morphometry

Question 22

What are Seiches:

Answer 22

Typically caused by strong winds and rapid changes in atmospheric pressure push water from one end of a body of water to the other. THe water then rebounds when the wind stops

Question 23

What are Internal Waves:

Answer 23

Propogation of a disturbance at the interface of two fluids of different density

Question 24

What is Langmuir Circulation:

Answer 24

Are a powerful mechanism of vertical mixing in natural bodies of water, driven by wind and waves