Physical Geography - The Water Cycle and Water Insecurity

Question 1

L1 5.1a,b,c Define hydrological

Answer 1

Study of water on Earth

Question 2

L1 5.1a,b,c Summarise solar energy’s role in the water cycle

Answer 2

• Water on the surface is heated by the Sun’s energy and evapourates
• It is also drawn from the soil and evapourated from leaves in the process of evapotranspiration
• When humid air rises, condensation forms clouds which leads to precipitation

Question 3

L1 5.1a,b,c Summarise Gravitational Potential Energy’s role in the water cycle

Answer 3

• On Earth’s surface GPE is converted to KE & water moves through the system by plant interception or over land or surface run off
• Water flows through soil as infiltration, percolation, & throughflow
• Water is stored as soil moisture or if the rock is permeable then it will percolate & be stored as groundwater
• Over time some of this water returns to the ocean via rivers & can be stored in lakes/glaciers en route

Question 4

L1 5.1a,b,c Describe the location of the Earth’s total water

Answer 4

97% is in the ocean, 2.5% is freshwater

Of the total freshwater, 69% is in ice caps/glaciers (cryosphere) & 30% is groundwater

Question 5

L1 5.1a,b,c Define Global Water Budget

Answer 5

Balance of water fluxes (flows) and the size of stores

Question 6

L2 5.2a Define infiltration

Answer 6

When water penetrates through a permeable surface and enters the water table

Question 7

L2 5.2a Define throughflow

Answer 7

When water travels downhill within the soil

Question 8

L2 5.2a Define surface runoff

Answer 8

When water travels down an impermeable surface

Question 9

L2 5.2a Define transpiration, define evapotranspiration

Answer 9

Flow & release of water in a plant

Evapotranspiration is when water is transferred into the atmosphere through evapouration and transpiration

Question 10

L2 5.2a Define residence time

Answer 10

The average duration that a water molecule spends within a particular water store, e.g. atmosphere, oceans, glaciers, or groundwater

Question 11

L2 5.2a Summarise residence time of water on Earth

Answer 11

• Annually, 460,000km^3 of water passes through the atmosphere (35x more than it can hold) - short residence time of 10 days
• Water stays in oceans for a long time (3600 years)
• Constant circulation of water - considered renewable

Question 12

L2 5.2a What is an exception to residence time?

Answer 12

• Fossil water - water stored in an aquifer in a different climatic time. Therefore, not being removed

Question 13

L2 5.2a What water store is climate change affecting?

Answer 13

• Water stored in the cryosphere (ice)
• Water is released from it faster than it is being replaced

Question 14

L2 5.2a Define drainage basin

Answer 14

Land that is drained by a river and its tributaries. Separated from neighbouring drainage basins by a ridge of highland called a watershed.

Question 15

L3 5.2a Define percolation

Answer 15

Water moves downwards through the soil due to gravity

Question 16

L3 5.2a Define groundwater flow

Answer 16

Movement of water deep underground (slowly)

Question 17

L4 5.2b+c What are the physical factors that affect drainage basins?

Answer 17

Climate, soils, geology, relief, and vegetation

Question 18

L4 5.2b+c How does the physical factor, climate, affect drainage basins?

Answer 18

-Influences type & amount of precipitation & the amount of evapouration
- Impact on the vegetation type
- Impacts the amount of evapotranspiration

Question 19

L4 5.2b+c How does the physical factor, soils, affect drainage basins?

Answer 19

• Determines the amount of infiltration & throughflow
• Indirectly determines the type of vegetation
• Infiltration rates will increase as porosity & permeability increase

Question 20

L4 5.2b+c How does the physical factor, geology, affect drainage basins?

Answer 20

• Can impact on subsurface processes such as percolation & groundwater flow (& therefore on aquifers)
• Indirectly geology alters soil formation
• Infiltration rates will increase as porosity & permeability increase

Question 21

L4 5.2b+c How does the physical factor, relief, affect drainage basins?

Answer 21

• Altitude can impact percolation totals
• Slopes affect the amount of runoff
• As gradient increases, more water will flow over the surface, reducing infiltration

Question 22

L4 5.2b+c How does the physical factor, vegetation, affect drainage basins?

Answer 22

• Presence or absence of vegetation affects amount of infiltration, interception, & occurrence of overland flow, as well as transpiration rates
• Roots help to break up the soil, increasing infiltration rates

Question 23

L4 5.2b+c What human factors affect drainage basins?

Answer 23

Overabstraction, deforestation, urbanisation, reservoirs

Question 24

L4 5.2b+c How does the human factor, overabstraction, affect drainage basins?

Answer 24

• Abstracting too much water leads to rivers drying up in times of low rainfall
• e.g. Thames Basin home to 13m people (one of the driest UK areas w/ 690mm a year) under pressure from growing water demands

Question 25

L4 5.2b+c How does the human factor, deforestation, affect drainage basins?

Answer 25

- Removal of dense, tropical forest canopy protecting vital topsoils can accelerate natural processes - Soil is eroded quicker, rainwater moves over the surface causing flooding

Question 26

L4 5.2b+c How does the human factor, urbanisation, affect drainage basins?

Answer 26

- Impermeable surfaces of built-up areas can alter natural water flow - On natural ground: 50% of water infiltrates & 10% is runoff - In built-up areas: 15% infiltrates & 55% is runoff

Question 27

L4 5.2b+c How does the human factor, reservoirs, affect drainage basins?

Answer 27

- Interrupt natural water flows - delays flows through drainage basins & adds to amount lost through evapouration - In Tropics, floating plants on surface make evapotranspiration rate 6x higher than open water - Dams reduce river flow behind them, e.g. Kenya's Tana River floodplain forest dying b/c upstream dams prevent flooding

Question 28

L5 5.3a Define water budget

Answer 28

The annual balance between inputs (precipitation) and outputs (evapotranspiration & channel flow)

Question 29

L5 5.3a What is the equation for water budget?

Answer 29

P = Q + E ± S where P is precipitation, Q is channel discharge (amount of water flowing past a given point), E is evapotranspiration, and S is the change in storage

Question 30

L5 5.3a Describe the graph of the annual water budget for South Hampshire

Answer 30

Jan-Mar: Rainfall high, evapotranspiration low so there is a soil moisture surplus -> runoff Apr-Jun: Rainfall low, evapotranspiration increasing to high so soil moisture is utilised and used up Jun/Jul: Max. annual temps., rivers fall & crops irrigated Jul-Sep: Rainfall low, evapotranspiration decreasing to low so soil moisture deficient, plants survive only if adapted or are irrigated Sep-Dec: Rainfall high, evapotranspiration low so soil moisture increases again until field capacity (runoff begins)

Question 31

L6 5.3b Define River Regimes

Answer 31

The annual variation of discharge of a river at a particular point, usually measured in cumecs (m^3s^-1)

Question 32

L6 5.3b What are the two types of River Regimes?

Answer 32

Simple Regimes and Complex Regimes

Question 33

L6 5.3b Define Simple River Regimes

Answer 33

Rivers experience periods of high discharge, followed by low discharge. They are typical of rivers where inputs include glacial meltwater, snowmelt, or seasonal storms.

Question 34

L6 5.3b Define Complex River Regimes

Answer 34

Larger rivers cross several relief/climatic zones & therefore experience different seasonal climatic events. Human factors, like dams/irrigation, also contribute. e.g. Mississippi, Ganges

Question 35

L6 5.3b Describe how the Murray-Darling's River Regime is affected throughout the year

Answer 35

- Higher in wetter season - Lower in drier season - Human influences - Australia's major cities, irrigation for farms

Question 36

L7 5.3c What is a Storm Hydrograph?

Answer 36

Shows variation in a river's discharge at a specific point over a short period of time

Question 37

L7 5.3c What are the key features of a Storm Hydrograph?

Answer 37

- Lag time: time between peak rainfall & peak discharge - Bankful discharge: the level at which the discharge is too great for the channel, causing flooding - Rising/falling limb: Increasing/decreasing discharge either side of peak discharge, (falling limb less steep b/c throughflow is released relatively slowly into the channel) - Base flow: Discharge contribution from long-term storage sources, e.g. bogs, marshes (what the discharge would be without rainfall)

Question 38

L7 5.3c What are some physical factors that affect Storm Hydrographs?

Answer 38

- Vegetation & soil types - soil permeability changes throughout the year, soil can be permeable/impermeable, dense vegetation has high interception, infiltration, & fast percolation - Size/shape of drainage basin - Large catchments have high flows but take longer to peak, more tributaries=higher peaks - Steepness of slopes - steep catchments transfer water quickly via overland flow

Question 39

L7 5.3c What are some human factors that affect Storm Hydrographs?

Answer 39

- Water management - abstraction, dams, reduce lag time - Land Use - deforestation for agriculture - Urbanisation - built up areas have more impermeable surfaces, water diverted through drains & reach rivers quickly