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Physical geography > Water and carbon cycle 4 - Variations in runoff and the water cycle > Flashcards

Water and carbon cycle 4 - Variations in runoff and the water cycle Flashcards

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1
Q

What is river discharge

A

The volume of water that flows in a river per second

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2
Q

What is river discharge measured in

A

cubic metres per second

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3
Q

What is runoff

A

Water flowing on the surface of the land

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4
Q

What happens when there is high levels of run off

A

Increases the discharge of a river because more water makes it into the rivet, increasing its volume

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5
Q

What are hydrographs

A

Graphs of river. discharge over time

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6
Q

What do they show

A

How the volume of water flowing at a certain point in a river changes over time

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7
Q

what do flood / storm hydrographs show

A

River discharge around the type of a storm event

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8
Q

What time frequency do flood / storm hydrographs show

A

a relatively short time period (normally days or hours)

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9
Q

What are the 4 parts of a hydrograph?

A

1) Peak discharge
2) Lag time
3) Rising limb
4) Falling limb

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10
Q

What’s peak discharge

A

The highest point on the graph, when the river discharge is at its greatest

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11
Q

What is lag time

A

The delay between peak rainfall and peak discharge

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12
Q

Why does this delay happen

A

It takes time for rainwater to flow into the river.

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13
Q

What does a shorter lag time mean

A

Increases peak discharge because more water reaches the river during a shorter period of time

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14
Q

What is rising limb?

A

The part of the graph up to peak discharge. river discharge increases as rainwater flows into the river

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15
Q

What is falling limb

A

Part of the graph after peak discharge

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16
Q

Why is discharge decreasing

A

Less water is flowing into the river

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17
Q

What does a shallow falling limb show

A

Water is flowing in from stores long after it’s stopped raining

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18
Q

What kind of hydrograph does a basin with rapid run off and not much storage give

A

A hydrograph with a short lag time and high peak discharge

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19
Q

What is this known as

A

Flashy hydrograph

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20
Q

What does a flashy hydrograph look like

A

Its steep, roughly symmetrical rising and falling limbs

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21
Q

What 4 factors does the amount of runoff and shape of hydrograph depend on

A
  • Size of drainage basin
  • Shape of drainage basin
  • Ground steepness
  • Rock and soil type
22
Q

What happens when it is a larger drainage basin

A

They catch more precipitation so have a higher peak discharge

23
Q

What happens when its a smaller drainage basin

A

Have shorter lag times because precipitation has less distance to travel, so reaches the channel more quickly

24
Q

What are circular basins hydrograph like

A

More likely to have a flashy hydrographs compared to long, narrow basins

25
Q

Why is this

A

All points on the watershed are roughly the same distance from the point of discharge measurement

26
Q

What happens the ground is downhill

A

Water flows more quickly in steep-sided basins shortening lag time

27
Q

What does this mean

A

Lots of water will reach the measuring point at the same time

28
Q

How does this affect the run off

A

Water has less time to infiltrate the soil so run off is higher

29
Q

What is the hydrograph like in impermeable rocks and soils

A

As they don’t store water or let water infiltrate it increases surface runoff. Peak discharge also increases as more water reaches the river in a shorter period

30
Q

What are these 2 natural processes

A
  • Storms and precipitation
  • Seasonal changes and vegetation
31
Q

What are hydrographs, runoff and the water cycle affected by

A

Natural processes

32
Q

What influence do intense storms have

A

They generate more precipitation and greater peak discharge than light rain showers

33
Q

What happens if the input of water is larger

A

It causes flows, like runoff and stores

34
Q

What can increase run off

A

Some flows may not be able to occur rapidly enough for the size of the input

35
Q

What varies with seasons

A

The size of inputs, flows and stores

36
Q

What happens during the winter

A

temp drops below 0 causing water to freeze. This reduces the size of flows through drainage basins, while the store of frozen water grows

37
Q

What happens as the temperature increases again

A

Flows through drainage basins and outputs are much larger as ice melts

38
Q

How do plants show seasonal variation?

A

Vegetation intercepts precipitation and slows its movement to the river channel

39
Q

When’s interception highest

A

When there’s lots of vegetation and deciduous trees have their leaves

40
Q

What happens when there is more vegetation in the drainage basin

A

The more water is lost through transpiration and evaporation before it reaches the river channel, reducing runoff and peak discharge

41
Q

What affects the size of stores and size and speed of flows

A

human activities

42
Q

What are these 3 human activities

A

1) Farming practices
2) Land use change
3) Water abstraction

43
Q

What is a key part of the water cycle

A

Infiltration

44
Q

What happens when rain can’t infiltrate

A

It runs off

45
Q

What 4 ways does farming practices affect infiltration.

A

1) Ploughing breaks up the surface so more water can infiltrate, reducing the amount of run off

2) Crops increase infiltration and interception. compared to bare ground, reducing run off. Evapotranspiration also increases, increasing rainfall

3) Livestock, like cattle, trample and compact the soil, decreasing infiltration and increasing run off

4) Irrigation can increase runoff if some of the water can’t infiltrate. Groundwater or river levels can fall if water is extracted for irrigation

46
Q

What is irrigation

A

Artificially watering land

47
Q

How does deforestation affect this?

A

reduces the amount of water that’s intercepted by vegetation, increasing the amount that reaches the surface. In forested areas dead plant material on the forest floor helps to hold the water, allowing it to infiltrate the soil rather than run off. When forest cover is removed the amount of infiltration that can take place decreases

48
Q

What does the construction of new buildings and roads create

A

An impermeable layer over land, preventing infiltration. This increases runoff, resulting in water passing through the system much more rapidly and making flooding more likely

49
Q

When is more water abstracted

A

To meet demand in areas with high population density

50
Q

What does water abstraction do

A

Reduces the amount of water in stores such as lakes, rivers, reservoirs and groundwater

51
Q

What happens during dry Seasons

A

Even more water is abstracted from stores for consumption and irrigation so stores are depleted further

Physical geography (16 decks)

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