WATER CYCLE /INSECURITY: What are the processes operating within the hydrological cycle from global to local scale?

Question 1

What type of system is the global hydrological cycle and why?

Answer 1

A closed system - made up of a series of linked processes

Question 2

What is a closed system?

Answer 2

Has no external inputs & outputs (only energy), matter is contained within the system boundary

Question 3

What is a system?

Answer 3

Connected components that create a working whole. They have inputs, stores, processes (flows) and outputs

Question 4

Why is the global hydrological cycle a closed system?

Answer 4

It is the circulation of water around the earth - so no water is gained or lost

• so the amount of global water is finite and constant

Has inputs, stores, processes (or flows and outputs which makes it a system

Question 5

What drives the global hydrological cycle?

Answer 5

Solar energy: in the form of heat

Gravitational potential energy: causes rivers to flow downhill & precipitation to fall to the ground

Question 6

How does solar energy drive the hydrological cycle?

Answer 6

1. Water on earth’s surface evaporates into atmosphere
2. water is also drawn from soil by plants and evaporated from leaves and stems (evapotranspiration)
3. The humid air rises and condensation occurs at the cooler temperatures to form clouds
4. This eventually leads to precipitation and water is returned back to the land and oceans on the earth’s surface

Question 7

How does gravitational potential energy drive the hydrological cycle?

Answer 7

1. gravitational potential energy converted into kinetic energy - as water moves through the system by plant interception or overland as surface runoff
2. Water also flows through soil by infiltration & throughflow
3. water is then stored as soil moisture or ground water (if the bedrock is permeable or porous)
4. Some of this water will then return to the oceans via streams and rivers

Question 8

What are fluxes?

Answer 8

The rate of flow between the stores

Question 9

Would the local hydrological system be an open or closed system?

Answer 9

An open system - as it still moves water between stores but in addition has inputs and outputs

Question 10

Example of Inputs

Answer 10

• Precipitation

Question 11

Example of outputs

Answer 11

• Evaporation
• Transpiration
• Evapotranspiration

Question 12

Example of processes (flows)

Answer 12

• Infiltration
• Through Flow
• Percolation
• Stem flow
• Base flow
• channel flow
• Surface runoff
• Groundwater runoff

Question 13

Example of Stores in the global hydrological cycle

Answer 13

• Oceans
• Cryosphere (Ice caps & glaciers)
• Groundwater
• Surface water (rivers & lakes)
• Soil moisture
• Atmospheric moisture
• Biosphere (biological water)

Question 14

What is the difference between blue and green water?

Answer 14

Blue water is the visible part of the hydrological cycle

Green water is the water stored in the soil and vegetation

Question 16

What are flows?

Answer 16

How water moves from one store to another

Question 17

What are processes?

Answer 17

They drive the flows between the stores

Question 18

What is a drainage basin?

Answer 18

An area of land drained by a river and its tributaries where any precipitation is collected or drained into it

Question 19

What percentage of solar radiation is reflected in polar regions? What are the impacts?

Answer 19

85%
- permafrost creates impermeable surfaces (nothing can saturate these surfaces)
- lakes and rivers freeze
- rapid surface runoff in spring
- biogenic gases