Quiz 1

Question 1

Henry David Thoreau Quote from Walden

Answer 1

“A lake is a landscapes most beautiful and expressive feature.
It is earth’s eye; looking into which the beholder measures the depth of his own nature.”

Question 2

How much water is there on the planet?

Answer 2

1.37 billion km2 but 97.6 is in the oceans as salt water

Question 3

Where is water stored? (5)

Answer 3

Most is in oceans
Then glaciers
Then ground water

Glaciers hold the majority of freshwater (for now) though they’re melting at an alarming rate

About 0.009% is stored in lakes

Question 4

What are some characteristics of water (10)

Answer 4

Found even on Mars 
Colourless 
Odourless
Tasteless 
Easier to melt ice at higher pressure 
Easier to boil water at lower pressure 
Ice is lighter than water 
High specific heat capacity 
Can dissolve substances better than any other liquid 
It is the only substance that is found in all three states at the temperatures normally found on earth

Question 5

What is the importance of water? (3)

Answer 5

Water influences the:
physical
chemical
and metabolic

properties and dynamics of freshwater ecosystems

Question 6

What is the benefit of water’s thermal density properties in terms of life? (2)

Answer 6

Because water can absorb and release heat energy from the environment causing it to change state, it provides a tempered environment in which temperature extremes are moderated relative to in terrestrial ecosystems

These properties, coupled with viscosity, have resulted in the development of a large number of adaptations for aquatic life

Question 7

What is water?

Answer 7

Made up of H2O molecules (O molecules having 8 protons and 8 elections, and (H molecules having 1 proton and 1 electron)

Question 8

How does water get it’s characteristics? (7)

Answer 8

Lone pair electrons are electrons that are not suited with another atom in a covalent bond

Only the oxygen atom in water has lone pairs

The oxygen atom has 3 lone pairs, 1 of which is in covalent bonds with the hydrogen atoms, and 2 of which are spread around the oxygen atom in a tetrahedral form

Because oxygen has 8 protons and hydrogen only has one, these negatively charged pairs are attracted to the upper side of the molecule

Because the highly charged lone pairs repellent each other, they push the hydrogen atoms closer together

This gives the molecule a bent structure (104.5 degree angle between hydrogen atoms) and is the reason for waters unique characteristics

Question 9

Is it correct to think of water as just H2O? (2)

Answer 9

No - it ya made up of different oxides, isotopes of oxygen; and different ionic forms

There are at least 33 different combinations that make up water

Question 10

Covalent bonds

Answer 10

Sharing of electrons between atoms to create a molecule

Question 11

Hydrogen bonds (4)

Answer 11

Interaction involving a hydrogen atom between molecules when positive hydrogen side of molecule attracts to negative side of oxygen molecule

Water does not exist as a single H2O molecule, but rather many molecules linked together by hydrogen bonding

Are weaker than covalent bonds but become strong in water because there are so many of them

Hydrogen bonding give water its gel-like properties, as bonds can break and reform extremely rapidly

Question 12

Unusual properties of water caused by hydrogen bonding (4)

Answer 12

As molecular weight decreases in alcohol and hydrides, so does its boiling point

But in water, it’s molecular weight is lowest but has the highest boiling point - so it doesn’t fit this pattern

To put into perspective, CH4 has a molecular weight similar to water (16 to 18), but it’s boiling point is -161, while water’s is 100

In essence, water melts and boils at much higher temperatures than other covalently bound but non-polar compounds with similar molecular weight (due to hydrogen bonding)

Question 13

Why is water a good solvent?

Answer 13

Because of its negatively and positively charged “clouds” (oxygen negative, hydrogen positive), it dissolves polar solutes easily (eg. Sodium chloride crystal is broken into positive sodium ion which bonds to negative oxygen side, and negative chloride ion which bonds to positive hydrogen side)

Question 14

Bonding and state of water (3)

Answer 14

In liquid, each molecule is bonded to approximately 3.4 other water molecules

In gas, there is no bonding

In solid, each molecule is bonded to 4 other water molecules giving ice a tetrahedron shape
(Eg. Cube)

Question 15

Why is ice less dense than water? (4)

Answer 15

As water freezes, tetrahedrons come closer together and crystallize into a six-ring or hexagonal structure

Unlike most substances, when water is near freezing, instead of continuing to contract, it expands slightly from about 4 degrees to 0 degrees) (Eg. Bottle of water will explode in freezer)

This is due to hydrogen bonds, as they extend the molecules to their fullest distance from each other

This makes ice less dense than water, allowing it to float (bond angle 106.6 rather than 104.45)

Question 16

How is the latent heat of fusion for ice to water and water to vapour different? (4)

Answer 16

The latent heat of fusion for ice to water is low (80 calories per gram)

As ice heats up, the latent heat is focused on the phase change and so the temperature does not change (beneficial for us as the ice caps melt, because the water does not increase temp which would speed up the process) - this is due to the higher bond angles found in ice making the hydrogen bonds easier to break (giving ice a lower latent heat needed to melt)

The latent heat of fusion of water to vapour is high (540 captives per gram)

So when water is changing to vapour, the energy is moved away in the steam and this is why steam burns hurt so badly (so much latent heat being transferred)

Question 17

Lake facts (5)

Answer 17

Lakes cover less than 2% of earth’s surface

Only 20 lakes in the world are deeper than 400m

20% of all the worlds fresh water is in Lake Baikal, Siberia

Caspian Sea is biggest in area (but debatable whether it’s considered a lake because it’s salty)

Second is Lakes Michigan and Heron

Question 18

What is the largest contiguous mass of freshwater lakes on earth? (2)

Answer 18

The Great Lakes

Collectively have just over the volume of water of Baikal

Question 19

Which lake has the greatest surface area of any lake on earth?

Answer 19

Lake Superior

Question 20

Which lake has the greatest volume of fresh water on earth?

Answer 20

Lake Baikal

Question 21

What are the types of lake formation? (11)

Answer 21

Tectonic basin formation 
Volcanic basin formation 
Lakes formed by landslides 
Lakes formed by wind 
Lakes formed by rivers 
Lakes formed by glacial activity 
Solution lakes 
Lakes associated with shorelines 
Lakes formed by meteor impact 
Biogenic lakes 
Anthropogenic lakes

Question 22

Tectonic basin formation lakes (4)

Answer 22

Tectonic basins are depressions formed by movements of the earth’s crust

Can be due to:

1. Tectonic uplift: causing marine sea bed to be isolated into very large lake basins

Ex: Caspian Sea, Great Salt Lakes in Utah

2. Tectonic down faulting: tectonic basins formed as a result of faulting causing depressions called Grabens

Ex: Baikal, Lake Tahoe

Question 23

Grabens and horsts

Answer 23

During tectonic faulting, horsts are the upfaulted ridges and grabens are the downfaulted troughs that fill with water and become lakes

Question 24

Why do tectonic downfaulting lakes have a large number of endemic species? (2)

Answer 24

Because they are very old

Over 80% of the plant and animal species in Baikal are endemic

Question 25

Volcanic basin formation (3)

Answer 25

Volcanic activity generates several types of lake basins: 1. Cinder cones - small, wide lakes formed in volcanic cone 2. Maars lakes - deep, narrow (<2km in diameter), and has steep sides. Magma chamber still intact 3. Calderas - deeper than maars because roof of magma chamber collapsed in on itself. Also have a minimum diameter of 5km Ex. Crater Lake in Oregon

Question 26

Lakes formed by landslides (3)

Answer 26

Only last a couple of years (ephemeral) and generally result in a blowout once water builds up Are often very large lakes Are usually found in glaciated mountains and formed by icefalls

Question 27

Lakes formed by wind (3)

Answer 27

1. Pan lakes - animal trampling removes organic matter and dirt is blown away to create depression 2. Playas - wind erodes ground in arid basins. Playas are often large and shallow 3. Sand dune lakes - sand dunes in large deserts are blown around, creating wide depressions that fill with water

Question 28

Lakes formed by rivers (2)

Answer 28

1. Plunge pool lakes - formed by vertical I water movement. Usually deep and narrow. Eg. Beneath waterfall 2. Oxbow lakes - formed by lateral water movement. The. bends in a river than are cut off and become isolated. Oddly shaped and shallow.

Question 29

Lakes formed by glacial activity (6)

Answer 29

Most important agent in the formation of lakes in B.C./Canada Are the gradual erosion and deposition effects of glacial ice movement 1. Glacial lakes - temporary lakes that occur on the surface, within, or under thousands of meters of ice. Eg. Lake Vostok, Antarctica (under ice, still has 3500 different species found using metagenomics - “a lost word” 2. Proglacial lakes - form in front of glaciers. Are created when water from meltwater streams gets dammed by the terminal moraine. When glacier melts, all that is left are delta kames from deposited till 3. Kettle lakes - formed by blocks of stranded ice in the glacial outwash, melting and forming a lake. Generally shallow and small. Many found throughout the Southern Interior Plateau 4. Glacier scour lakes - termed cirques and tarns. Formed when a cirque is excavated by a glacier near the snow line and a terminal moraine forms a natural dam. When the cirque is filled with water, it is called a tarn. Eg. The Great Lakes. In B.C., scour lakes are in u-shapes valleys. Eg. Lake Okanagan 5. Cryogenic lakes - formed inside an ice-wedge polygon which grows in the permafrost from water seepage through cracks in the ground 6. Thermokarst lakes - formed when several cryogenic lakes merge and the permafrost melts due to the removal of soil and plant cover

Question 30

Solution Lakes (3)

Answer 30

Formed by deposits of soluble rock such as limestone being slowly dissolved by percolating water (caused by positive and negative charged clouds in water dissolving limestone) Usually circular, found in the Alps, Florida, and the Balkan Peninsula etc. Long-lived lakes

Question 31

Lakes associated with shorelines (3)

Answer 31

Found on the shores of oceans and large lakes 1. Deltaic lakes - sedimentation as river currents slow when they enter a large lake or the ocean - may isolate lakes on deltas 2. Coastal lake - movement of sand in bars may enclose basins

Question 32

Lakes formed by meteor impact (4)

Answer 32

``` Can be perfectly round Can be quite large Distinct circular ring shape Middle part resurfaced because of fast meteor causing molten surface - often sites of mining activities because meteor did all the work Eg. Manicouagan Lake ```

Question 33

Biogenic Lakes (3)

Answer 33

Caused by animals 1. Bison wallows - caused by bison rubbing their back on the ground 2. Beaver ponds - caused by beavers damming a river

Question 34

Anthpogenic Lakes (4)

Answer 34

1. Dams produced by humans (not really a lake, called a reservoir) Generally 10% the volume of natural lakes 2. Borrow pit mine lake - small lakes caused by surface mining. Eg. Lafarge Lake, Coquitlam 3. Surface mine lakes - large lake created from surface mining. Eg. Colomac Zone 2 Pit Lake, NWT 4. Bomb crater lake - caused by bomb dropping during wars. Eg. WWII largest bomb on the planet created crater lakes in Tromso, Norway and B-52 raids in Vietnam caused Vietnam to be riddled with crater lakes

Question 35

What is lake morphometry?

Answer 35

The quantitative description of the shape and size of lakes Eg. Shoreline length, surface area, depth, volume etc.

Question 36

Why is lake morphometry important? (3)

Answer 36

The measurements define a lake’s physical dimensions and involve the quantification and measurement of lake basin shape These dimensions influence the lakes water quality, productivity levels, and habitat suitability This is because the shape of a lake controls the nature of its drainage, inputs to the lake, and the volume of influx in relation to flushing renewal time

Question 37

What determines a lake’s productivity? (4)

Answer 37

Edaphic - what sort of soil is the lake sitting in? Geographic location - where is it? Morphometrics - shape, deep shallow etc.? Anthropogenic influence - near an agricultural area etc.

Question 38

What are the 3 basic zones of a lake?

Answer 38

Limnetic or pelagic (offshore) Littoral (near shore zone) Profundal (dark bottom zone)

Question 39

Littoral zone (3)

Answer 39

Defined as a depth of 6m or less or the max depth of rooted aquatic vegetation 10X more productive than the limnetic zone Littoral zone is where the majority of aquatic plants are found and is the primary area used by young fish

Question 40

Profundal zone (2)

Answer 40

Dark zone of a lake above the benthic (lake bottom) zone Zone is aphotic (insufficient light for photosynthesis, usually defined as <1% of surface light)

Question 41

Limnetic zone

Answer 41

Has sufficient light for photosynthesis (photic)

Question 42

Morphometric indices (2)

Answer 42

Key morphometric indices are used to characterize, and gain a quick understanding of lake productivity and likely responses to restoration Eg. ``` % littoral area shoreline development index mean depth max depth max length and orientation volume mean discharge mean lake outflow mean water residence time water renewal rate watershed to lake area ratio ```

Question 43

% littoral area

Answer 43

Portion of the lake area where sufficient light can penetrate to the lake bottom

Question 44

Shoreline Development Index (SDI) (6)

Answer 44

Index of the regularity of the shoreline Is a measure of habitat complexity SDI = 1 for a perfectly circular lake SDI > 1 for a more convoluted lake SDI = L/2(sqrt(A(Pi))) L = shoreline length (m), A = lake area (m2) The higher the SDI, the higher the littoral area, and the higher the productivity

Question 45

Mean depth (4)

Answer 45

Used in many different calculations Rough index of lake productivity Zmean = mean depth (m) = volume (m3)/surface area (m2) If Zmean is low, the lake is more productive

Question 46

Max depth (3)

Answer 46

Deepest spot in the lake (measured as Zmax in meters) Often used for location of sampling station Often a consideration when doing lake restoration (eg. location of treatment or in-lake installations)

Question 47

Max length and orientation of main axis (3)

Answer 47

Max length is the longest straight line that may be drawn without intersecting (m) Orientation is expressed as opposing points on a 16 point compass (eg. SSE -NNW) Orientation is important for wind mixing and degree of spring and fall circulation For example, in B.C. wine blows N to S because of valley development. Therefore, oxygenation and mixing in lakes can depend on its orientation (ephemeral or not etc.)

Question 48

Volume (4)

Answer 48

If a lake can be considered a cone, then the volume can be calculated as 1.047 r2*h (~80% accuracy) But for accurate measurement, we must use a morphometric map and sum the volumes of a series of conical segments V = sum of frustum volumes (m3), a = area at each depth interval (m2), h = depth of frustum (m) Each frustum volume = (h/3)*(a1 + a2 + sqrt(a1*a2))

Question 49

Hypsographic curve (4)

Answer 49

Also called depth-area curve or volume-depth curve Graphic representation of the relationship between the surface area or volume of a lake and it’s depth For area: may be expressed in % of an area or actual area (m2 or hectares) For volume: may be expressed in % of volume or actual volume (m3 or km3)

Question 50

Mean discharge (2)

Answer 50

Qi = mean discharge from watershed INTO a lake (m3/yr) Qi = watershed area*runoff coefficient (m2*m = m3/yr)

Question 51

Mean lake outflow (5)

Answer 51

Qo = mean lake outflow (m3/yr) Equal to mean discharge into lake + ([P-E]*A) Where P-E = annual precipitation - annual evaporation (mm) A = area of lake (m2) Therefore: Qo = area of watershed*runoff coefficient + ([P-E]*A)

Question 52

Mean water residence time (4)

Answer 52

How long would it take the land to refill if it were drained Shows a lake’s ability to take abuse. The lower the residence time, the less susceptible a lake is to major damage tw = V/Qo per year = #years V = volume (m2), Qo = mean lake outflow (m3/yr)

Question 53

Water renewal rate (4)

Answer 53

Also called flushing rate - rate at which water is fully renewed in a lake Rate = Qi/V = yr-1 (# per year) Qi = mean water discharge INTO lake (m3/yr) V = volume of lake (m3)

Question 54

Difference between water residence time and flushing rate (2)

Answer 54

Residence time and flushing rate are not the inverse of each other because residence time is based on outflow Qo and flushing rate is based on inflow Qi However, if in a rush, can use inverse for general calculations (eg. 0.28 yr-1 flushing rate is 3.4 years residence time, but can just assume 3.7 year residence time)

Question 55

Watershed to lake area ratio (4)

Answer 55

Describes the relationship between the size of the watershed and surface area of the lake (Awatershed/Alake) Used to estimate potential nutrient loading by various land use types Can be used to calculate flushing rate, based on annual precipitation (mm/m2) and runoff coefficient The larger the watershed, the more potential for nutrient loading, but if there is a lot of rain, flushing rate may be higher

Question 56

What does the watershed to lake area ration tell us?

Answer 56

Potential runoff contamination from surrounding areas If high precipitation, flushing rate might be higher and so shows us which areas might be more susceptible to contamination than others, and for a longer time