Water Cycle 2 Flashcards

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1
Q

Give 4 possible ways human can affect the water cycle within a drainage basin (local scale)

A

Throughout the world there have been major changes to the water cycle from climate change and land use change

Deforestation means there is less interception so overland flow increases. Also decreases evapotranspiration so maybe less precipitation from conventional rainfall

Land use change may increase flood risk (urbanisation, deforestation)

Humans modifying the flows of rivers by abstraction of water (dams). When water is released back it may be of different tempatue/quality

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2
Q

Give 3 types of system

A

Open

Closed

Isolated

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3
Q

What is an open system

A

Moist environment systems are open and there are inputs and outputs of both energy + matter

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4
Q

What is a closed system

A

Inputs and output of energy but not matter (planet earth)

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5
Q

What is an isolated system

A

No input or output of energy or matter (universe)

Some claim this idea is not applicable to geography

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6
Q

What is dynamic equilibrium

A

When opposing inputs and outputs in the system are balanced

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7
Q

Give an example of a cause on the water cycle for disrupting the dynamic equilibrium of a system

A

Prolonged heavy rainfall causes an increase in the discharge and velocity of a river, increasing rate of erosion

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8
Q

How do Chroley and Hagget describe systems

A

A simplified structuring fo reality which presents significant features/relationships in a. generalised form, allowing the fundamental aspects of reality to appear

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9
Q

An open system tends to…….itself by modifying the interrelationships between different elements fo the system so….and output flows………each other out

A

Adjust
Inputs
Balance

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10
Q

What is feedback

A

Occurs when one element of a system changes because of an outside influence, upsetting the dynamic equilibrium

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11
Q

What is negative feedback

A

When a system acts by lessening the effects of the original change and ultimately reverses it

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12
Q

What is positive feedback

A

When a change causes a further/snowball effe t, continuing or accelerating the original change

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13
Q

What is the dew point temperature

A

The temperature bellow which droplets begin to condense and dew forms (air saturated)

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14
Q

How does precipitation vary worldwide

A

Influenced by general circulation of the atmosphere, proximity to large bodies of water and topography

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15
Q

Give the 4 global stores of water, their percentage of total water and residence time

A

Hydrosphere (97%) 3,600 years

Lithosphere (1.7%) 10,000 years

Cryosphere (1.7%) 15,000 years

Atmosphere (0.001%) 10 days

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16
Q

Why are residence times longer in larger stores

A

Big stores - vast majority fo water molecules are very far from he boundary and thus takes a long time to escape

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17
Q

Are the cryosphere and hydrosphere in a state of equilibrium

A

No

Crysophere - more out than in

Hydrosphere - More in than out (Global warming) (opposite in ice age - temperature dependent)

Lithosphere and atmosphere tend not to change a great deal

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18
Q

What does the atmosphere have such short residence times

A

Water only stays in atmosphere if not very dense (air can only hold so mcc water for a limited amount of time)

19
Q

Do the water stores experience a significant change in volume

A

Whilst the overall volume of water contained in stores does not change significantly on the global scale, transfers and flows will affect the amount of water over time that remains in a store

An example = how levels of evaporation increase in summer which leads to higher atmospheric storage and a slight drop in ocean storage.

However, these are not significant changes in volume and the ocean will always remain the primary store in water cycle

20
Q

Give 4 transfers that slightly change the size of the stores

A

Evaporation

Condensation

Cloud formation

Precipitation

21
Q

How does evaporation affect the amount of water held in stores

A

The level of evaporation on global scale ocean and sea levels is minima but within a drainage basin, evaporation can have a large regional impact

Lakes/rivers in areas of high summer temperatures will experience high levels of evaporation and hydrological storage will reduce significantly in that area

22
Q

How do clouds form

A

When water molecules aggregate - temperatures drop at altitude to allow condensation

23
Q

How does precipitation occur

A

When the water molecules within a cloud combine and become to big (coalescence)

If the droplets fall velocity is greater than the clouds updraft velocity, precipitation will occur

24
Q

Give 4 reasons for differing rainfall patterns globally

A

Desert areas have limited rainfall as they receive sinking dry air from pressure systems

Large continental interiors tend to be dry because of distance from moisture sources and many clouds loose moisture before they reach the centre of large continents

Polar areas are dry because cold air cannot hold as much moisture as warm air, less precipitation

Areas near equator receive high rainfall amounts because constant solar heating produces intense heating, large-scale evaporation and moist rising air that cools with altitude and forms convectional rainfall

25
Q

Why do mountain ranges near water sources reviewed high levels of precipitation

A

Precipitation occurs when clouds rise to go over mountains and the air cools which encourages the water molecules to join and then precipitation occurs (relief rainfall)

26
Q

Why are hydrographs important

A

Can be used in predicting the flood risk and in making the necessary changes

27
Q

Put factors influencing hydrographs into 3 groups

A

Climate

Natural catchment

Land use

28
Q

How do 3 different types of precipitation influence the shape of a hydrograph

A

Prolonged rainfall - flashy hydrographs most frequently occurs following a long period of heavy rainfall when the ground has become saturated

Intense storms - when heavy rain occurs, the rainfall intensity may be greater than the infiltration capacity of the soil, causing surface run-off and flash floods

Snowfall - heavy snowfall means water is held in storage and river levels drop initially. When temperatures warm, meltwater soon reaches river though ground may be frozen so infiltration impeded

29
Q

How does temperature influence infiltration

A

Extremes can restrict infiltration and increase surface runoff

Very cold (frozen) in winter 
Hot, dry in summer
30
Q

Gve some interrelationships between factors influencing the shape of the hydrograph

A

When considering natural catchment characteristics, geology is an important control

Fcsators that impact on the hydrograph like rock permeability, groundwater storage capacity and soil type all stem from the underlying geology

Combination of a multitude of factors that will determine the shape of the hydrograph

31
Q

How big is the Mississippi drainage basin

A

4th largest in the world (1.2 million square miles)

32
Q

Give 3 physical factors that influence the run-off and consequently, flow of the Mississippi-river

A

Precipitation/snowmelt

Corresponding variability between precipitation and evapotranspiration

Weather events - storms/droughts

33
Q

How does precipitation/snowmelt affect the flow of the Mississippi River

A

Maintained by precipitation/snowmelt (paramount factor), however, not all runs off into river channels

Some infiltrates into spil and is eventually transpired or evaporated directly

Over the basin, evapotranspiration losses account for over 75% the annual precipitation

However, these losses vary regionally. Arid western part, very little water is left to run off and most of the river’s run off is indebted to wetter eastern part of basin

34
Q

How does variability in precipitation and evapotranspiration affect the flow of the Mississippi River

A

Flow varies over time

Seasonally, there is an increase in precipitation in winter months compared to drier summer months. However, this simple seasonal pattern is far too simplistic and there is a variability in precipitation levels within the seasons

North west region receives lower rainfall than the S.E corner, particularly Nov-Feb. The uneven nature of rainfall distribution as well as the amount of it significantly alters runoff levels throughout the year

35
Q

How do weather events (storms) affect the flow of the Mississippi River

A

Impact upon the amount of runoff within the basin and the flow shape of the hydrograph

High levels of precipitation can lead to saturated soil as soil water storage limits are reached

This can lead to increased surface runoff which increases discharge within river channel

E.g 2014 summer - record rainfall fell in Minnesota, Iowa and Illinois leading to a flood in the upper Mississippi basin

36
Q

How do weather events (droughts) affect the flow of the Mississippi River

A

Limited precipitation reduce river discharge initially

However, over a longer time period, drought conditions can harden the soil, making it impermeable and increasing runoff during a period of subsequent rainfall

37
Q

What is the main human activity that significantly influences runoff in the Mississippi River

A

Agriculture

Constitutes a key economic activity in arid western part which provides 92% USA’s total agricultural exports

38
Q

How does agriculture influence the Mississippi River

A

Large volumes of runoff are collected in man-made reservoirs, which is then extracted and irrigates crops

Changes the water cycle as water is diverted from surface runoff/infiltration and through flow - greatly impacting the amount water reaching the river Chanel

Storage and mass use off irrigation results in higher levels of evapotranspiration from crops, so water returned to atmosphere instead of hydrosphere

39
Q

Give 3 human impacts on the Mississippi River

A

Agriculture

Reservoirs

Climate change

40
Q

How do reservoirs influence the Mississippi River

A

43 dams along course of Mississippi which hold back water

6% of total runoff is transferred to atmosphere by the higher levels of evaporation during summer from surface reservoirs

Increasing population and demands for domestic and uindustrial use has meant it will only continue

41
Q

How does climate change influence the Mississippi River

A

Predictions estimate a reduction of 5 inches of rainfall a year in the lower basin due to changing precipitation patterns

Less rainfall = decreasing runoff and channel flow

42
Q

What is meant by potential evapotranspiration

A

The highest amount of evapotranspiration possible (theoretical) with unlimited water

43
Q

Define the water balance

A

Balance between the inputs and outputs of a drainage basin