Freshwater - Drainage basin hydrology + geomorphology Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is the global hydrological cycle?

A

A closed system - the Earth’s water never changes in quanitity, but constantly changes location and form as it moves through the cycle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a drainage basin?

A

The area of land from which a river recieves water (area of land drained by a river and its tributaries) -> its catchment area.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the name of the higher land that separates river basins?

A

the watershed (basin boundary).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the largest drainage basin in the world?

A

The Amazon Basin - 7.5 million km^2 (The size of Europe)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is North America’s largest drainage basin?

A

The Mississippi Basin (spans almost 50% of the US).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why is any drainage basin system an open system within the closed system of the global hydrological cycle?

A
  • Water can cross the boundaries of a drainage basin
  • The amount of water in a drainage basin varies over time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are 4 important things a drainage system has?

A
  • Inputs = additions of water
  • Stores = storage of water
  • Flows (transfers/processes) = movements of water
  • Outputs = losses of water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Flow diagram of drainage system

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are factors that affect the store + transfer of water in a drainage basin?

A
  • Climate - temperature
  • Soil type
  • Geology
  • Climate- rainfall
  • Relief
  • Land use
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why and how does ‘Climate - temperature’ - affect the store + transfer of water in a drainage basin?

A
  • Climate - Temperature –> >Evapotranspiration increases with temperature
    >Ice - water locked in ice becomes a store not a flow. Maybe a flow later.
    >Frozen ground - prevents infiltration (transfer to groundwater)
    >Snow-capped peaks hold water back until thaw (delayed flow)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why and how does ‘Soil type’ affect the store + transfer of water in a drainage basin?

A
  • Permeability
  • Clay/sand
  • Impermeable soils prevent infiltration + cause surface saturation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why and how does ‘Geology’ affect the store + transfer of water in a drainage basin?

A
  • Permeability of the surface
  • Granite/sandstone
  • Impermeable rocks prevent infiltration + cause surface saturation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why and how does ‘Climate - rainfall’ - affect the store + transfer of water in a drainage basin?

A
  • Intensity + duration –> impact on ground saturation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why and how does ‘Relief’ affect the store + transfer of water in a drainage basin?

A
  • Steeper gradients reduce infiltration + increases surface runoff
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why and how does ‘Land use’ affect the store + transfer of water in a drainage basin?

A
  • Permeability –> urban vs rural land surfaces will reduce infiltration (if impermeable)
    > Man-made drainage can be used to transfer water
    > Forested slopes intercept more precipitation, increased levels of evapotranspiration + reduce surface runoff
    > Urban surfaces are impermeable and increase rapid surface runoff (cement), evaporation and interception
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does discharge mean?

A

The volume of water passing a given point on the river over a set time

17
Q

How is discharge measured?

A

m^3/secs
(cumecs)

18
Q

How is discharge calculated?

A

CSA (m^2) x Velocity (m/s)
(CSA = Cross-sectional area = width x mean depth)

19
Q

By what two opposing forces are discharge and stream flow influenced? And how?

A
  • Gravity: causes water to flow downstream to sea level
  • Friction: creates resistance between the water and the beds + banks, and opposes flow downstream
20
Q

What does the Bradshaw model show?

A

It suggests how river channel characteristics change moving downstream

21
Q

What is expected to be found in a river’s characteristics if it follows the Bradshaw model?

A

Discharge is expected to increase downstream despite the decrease in gradient

22
Q

How is the width and depth (CSA) expected to change according to the Bradshaw model?

A

They are expected to increase as more water enters the river channel (from tributaries + run-off) eroding a wider, deeper channel = a more efficient channel shape

23
Q

What does a more efficient channel shape result in?

A

It results in proportionally less water being in contact with the bed and banks = less friction = faster flow

24
Q

What does increased erosion do?

A

It reduces the size of bedload material + decreases channel roughness = less friction = faster flow

25
Q

How is the efficiency of a stream’s shape measured?

A

By its hydraulic radius

26
Q

What is the hydraulic radius?

A

The CSA (cross-sectional area) divided by wetted perimeter (the total length of beds + banks in contact with the water)

27
Q

What does a higher hydraulic radius mean?

A

A more efficient flow
The smaller the frictional loss the higher the velocity

28
Q

Therefore what is the ideal form for the hydraulic radius?

A

Semi-circular