Indicative Content

Commentary

Flows in the hydrological cycle include:

Any two pairs from the following:

Precipitation; [1 mark]
The process of water falling from the atmosphere to the Earth's surface in the form of rain/snow/sleet/hail; [1 mark]

OR

Advection; [1 mark]
The horizontal movement of water vapour / clouds / precipitation caused by the prevailing wind patterns; [1 mark]

OR

Flooding; [1 mark]
The overflow of water onto normally dry land, often caused by heavy rainfall / melting snow / dam failure; [1 mark]

OR

Surface run-off; [1 mark]
The movement of water over the Earth's surface, typically occurring when the ground is saturated/impermeable, leading to excess water; [1 mark]

OR

Infiltration; [1 mark]
The process of water seeping into the soil from the surface, entering the soil layers and becoming groundwater; [1 mark]

OR

Percolation; [1 mark]
The downward movement of water through the soil / underlying rock layers, eventually reaching aquifers / groundwater reservoirs; [1 mark]

OR

Stream-flow / currents; [1 mark]
The movement of water in streams / rivers / other water bodies, driven by gravity and the slope of the land, ultimately leading to oceans/lakes; [1 mark]

OR

Evaporation; [1 mark]
The process by which liquid water changes into a gaseous state / water vapour and enters the atmosphere from water bodies e.g. oceans/lakes/rivers; [1 mark]

OR

Transpiration; [1 mark]
The process by which plants absorb water from the soil through their roots and release it as water vapour through tiny openings/stomata in their leaves; [1 mark]

OR

Evapotranspiration; [1 mark]
The combined process of water vaporisation from the Earth's surface (evaporation) and the release of water vapour by plants through transpiration; [1 mark]

OR

Sublimation; [1 mark]
The direct transition of water from a solid (ice/snow) to a vapour state without melting first; [1 mark]

OR

Condensation; [1 mark]
The process in which water vapour in the atmosphere transforms into liquid water, forming clouds/dew, as a result of cooling; [1 mark]

OR

Melting; [1 mark]
The process by which solid ice/snow changes into liquid water due to an increase in temperature; [1 mark]

OR

Freezing; [1 mark]
The process by which liquid water changes into a solid state / ice / snow due to a decrease in temperature; [1 mark]

Flows are processes occurring within a system that may be either:

Transfers (a change in location) or
Transformations (a change in the chemical nature, a change in state or a change in energy)

In the list given here, the first seven are transfers and the rest are transformations

Process	Quantity of water transported in 1 000 km³ yr^-1
Evaporation	423
Transpiration	153
Precipitation	515
Percolation	72

Introduction to Water Systems (SL IB Environmental Systems & Societies (ESS))

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