Lake Definitions and Morphology

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Questions and Answers

Which of the following statements about lakes is true?

Lakes can be described as relatively uniform water bodies. (correct)

There is an official distinction between lakes and ponds.

Lakes always have waves smaller than 10 cm in height.

Lakes never receive inflow from rivers.

A reservoir is always a natural lake.

False

What is the largest salt-water body in the world?

Caspian Sea

The formula for calculating the volume of a lake is Volume = Surface Area x ________.

Mean Depth Signup and view all the answers

Match the following lakes with their characteristics:

Quesnel Lake = 610m depth Skaha Lake = Bathymetric Map Creation Okanagan Lake = Less than 150m depth Kootenay Lake = Surface Area = 421 km2 Signup and view all the answers

What does a hypsographic curve represent?

How much of each depth zone is present in a lake. Signup and view all the answers

Lotic refers to standing water bodies like lakes.

False Signup and view all the answers

How deep is Kootenay Lake at its deepest point?

150 m Signup and view all the answers

The average discharge of Kootenay River at Kootenay Lake is ________ m3/s.

782 Signup and view all the answers

Which lake is known as the largest freshwater lake in the world?

Lake Superior Signup and view all the answers

What does the Shoreline Regularity Index (SRI) measure?

How the shape of a lake deviates from that of a circle. Signup and view all the answers

The photic zone is the area where photosynthesis occurs more than respiration.

True Signup and view all the answers

What is the Hydraulic Residence Time (HRT)?

Approximate time any molecule of water spends in a lake. Signup and view all the answers

The minimum value of the Shoreline Regularity Index (SRI) is _____ .

1.0 Signup and view all the answers

Match the lake characteristic with its correct description:

Photic Zone = Area where photosynthesis occurs more than respiration Aphotic Zone = Area where respiration exceeds photosynthesis HRT = Time water spends in the lake SRI = Measure of lake's shape regularity Signup and view all the answers

What is Kootenay Lake's SRI value?

5.56 Signup and view all the answers

Reservoirs have smooth shorelines because they consist of flooded river valleys.

False Signup and view all the answers

The ____ consists of unceded Indigenous lands or public land in BC.

foreshore Signup and view all the answers

What is the average Secchi Disk depth measurement for Crater Lake?

43 m Signup and view all the answers

The equation for Hydraulic Residence Time (HRT) includes which factors?

Volume and outflow rate Signup and view all the answers

Study Notes

Lake Definitions

There is no official distinction between a lake and a pond.
To determine if a body of water is a lake or a pond, consider if light reaches the bottom at the deepest point, if the water body is relatively uniform, and if the waves are smaller than 30 cm in height.
Lakes and rivers are distinct, but there is overlap. Lakes are lentic and rivers are lotic ecosystems.
Reservoirs can be a combination of lakes, rivers, and reservoirs.
Reservoirs are artificial lakes filled by river inflow.

Lake Morphology

Surface Area:
- Measured using maps or remote sensing techniques.
- Caspian Sea is the largest saltwater body.
- Aral Sea is a shrinking saltwater body.
- Lake Superior is the largest freshwater body.
Depth:
- Measured using soundings (weighted line) or sonar.
- Bathymetry is a map of the lake bottom.
- Mean depth (z) is the average depth of the lake.
- Volume is calculated by multiplying surface area by mean depth or by summing the product of area and depth of horizontal segments.
Hypsographic Curve:
- Represents the depth-area distribution of the lake.
- Shows the amount of each depth zone, useful for assessing biological reproduction potential.
Bathymetric Map:
- A map of the lake bottom topography.
- Shows the depth contours of the lake.

Kootenay Lake

Located in the Kootenay River Basin, which is 50,298 km2.
The Kootenay River has a stream order of 7.
Kootenay Lake Basin is 31,264 km2, with 174 inlets and one outlet (Kootenay River).
Average discharge of the Kootenay River at Kootenay Lake is 782 m3/s.
Dimensions:
- Length: 104 km.
- Width: 3-5 km.
- Surface Area: 421 km2 or 421,730,000 m2.
- Perimeter: 405 km or 405,082 m.
- Deepest Point: 150 m.
- Average Depth: 94 m for the main lake, 10 m for West Arm.
Volume:
- Calculated as Area x Mean Depth.
- Volume = 421,730,000 m2 x 94 m = 39,642,620,000 m3.

Foreshore

Land between the high and low watermarks, including beaches.
In BC, foreshore is either unceded Indigenous lands or public land, not private land.

Shoreline Characteristics

Reservoirs have jagged shorelines due to the flooding of river valleys.

Shoreline Regularity Index (SRI)

Measures the deviation of a lake's shape from a circle.
Minimum is 1.0 for circular lakes.
Higher values (4+) indicate irregular shapes like reservoirs or shoestring shapes.
High SRI and shallow depths create extensive littoral zones.
Calculation:
- SRI = Shoreline Length / Circumference of Area.
- For Kootenay Lake: SRI = 405,082 m / (2√421,730,000π) = 5.56.

Hydraulic Residence Time (HRT)

The average amount of time water spends in a lake.
Important for pollution studies and nutrient regimes.
Calculations:
- HRT (years) = Volume (m3) / Q (m3/s) x 1 year / 31,536,000 s/year.
- For Kootenay Lake: HRT = 39,642,620,000 m3 / 782 m3/s x 1 year / 31,536,000 s/year = 1.6 years.
- Alternatively, HRT (years) = Volume (Lake) (m3) / (Basin Area (m2) x Avg. Precip (m/year) x 0.85).
- For Kootenay Lake: HRT = 39,642,620,000 m3 / (31,264,000,000 m2 x 0.9 m x 0.85) = 1.66 years.

Light Penetration

Photic Zone:
- Surface down to where 1% of light penetrates.
- Zone of net oxygen production (photosynthesis > respiration).
- Depth depends on water clarity.
Aphotic Zone:
- Bottom of the photic zone to the bottom of the lake.
- More carbon dioxide is produced than oxygen (respiration > photosynthesis).

Water Transparency

Measured using Secchi Disk Depth.
Secchi Disk Depth is the depth at which the disk disappears and then reappears.
Photic Zone is roughly 2.5 times the Secchi Disk Depth.

Crater Lake

Average Secchi Disk Depth of 1-10 meters.
Crater Lake has a Secchi Disk Depth of 43 meters.

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Description

Explore the essential definitions and morphological characteristics of lakes in this quiz. Learn about the distinctions between lakes and ponds, measurement techniques, and notable lakes around the world. Test your knowledge on the features that define these important aquatic ecosystems.