A Level Geography - Water

Input

Material or energy moving into a system from the outside

Output

Material or energy moving from the system to the outside

Energy

Power or driving force

Stores/components

The individual elements or parts of a system

Flows/transfers

The links or relationships between the components

Positive feedback

A loop of events that increases change and environmental instability; an initial change creates a secondary change that amplified the effect of the initia.

Negative feedback

A loop of events that reduces change and promotes stability and dynamic equilibrium; an initial change creates a secondary change that decreases the effect of the initial

Dynamic equilibrium

A state of balance in a constantly changing system

System

A framework applied to the natural world to represent inputs, outputs, flows, transfers and stores of energy or matter

Closed system

Energy is able to be transferred in and out of the system but all matter is enclosed within the system

Open system

Both matter and energy are exchanged between a system and the surrounding environment

Hydrosphere

A discontinuous layer of water on or near the Earth's surface, including all frozen and liquid surface waters, groundwater and atmospheric water.

Atmospheric water

Water found in the atmosphere; mainly water vapour with some liquid water (cloud and rain droplets) and ice crystals

Cyrospheric water

The water locked up on the Earth's surface as ice

Lithosphere (terrestrial)

Water stored on the land consisting of ground water soil moisture, lakes, wetlands and rivers

Oceanic water

The water contained in the Earth's oceans and seas, not including mainland seas such as the Caspian Sea

Ocean Residence Time

3000 years

Permafrost residence time

50-60 years

Glaciers residence time

20-100 years

Seasonal snow residence time

2-6 months

Rivers residence time

2 weeks - 6 months

lakes residence time

10-100 years

Soil moisture residence time

2 weeks - 1 year

Biosphere residence time

1 week

Shallow groundwater residence time

100-200 years

Deep groundwater residence time

10000 years

Atmospheric water vapour residence time

9 days

Antarctica residence time

20000 years

Precipitation

water that falls to the earth in any form: rain, sleet, hail or snow.

Channel fall

precipitation directly entering the river channel

evaporation

moisture lost into the atmosphere by suns heat and wind

soil water

water stored in the soil above the water table

interception

raindrops fall on vegetation, preventing it from reaching the soil and river

surface water

water stored on the surface e.g. lakes and rivers

transpiration

biological process where water is lost as vapour through small pores on plant's leaves

throughflow

Water flows laterally through the soil to the channel, mainly along "pipes" caused by animal activity or growth of plant roots

infiltration

the passage of water vertically into the soil. Infiltration cannot occur if soil is too saturated

percolation

a vertical movement of water from above to below the water table. If the bedrock is impermeable than percolation cannot occur

groundwater flow

water in this zone moves laterally at a very slow rate. It transfers water to the river through their bed and banks long after a rainfall event (even during dry periods)

Groundwater

water stored below the water table in saturated soil or rock

overland flow

also called surface runoff. occurs during heavy rainfall when the ground is saturated or if surfaces are impermeable. very rare except in urban areas.

stemflow

water reaches the ground by flowing down trunks or stems or by dropping off of leaves.

Ablation

water loss from snow or ice

water table

the level below which the ground is saturated with water

sublimination

water changing from a solid to a gas

Flood hydrograph

graph that shows how discharge of a river changes over time

Rivers regime

Variation of rivers discharge over a year

Flashy hydrograph

Short lag time and high peak discharge

Subdued hydrograph

Long lag time and low peak discharge

Lag time

Time between peak rainfall and peak discharge

Rising limb

The period of rising river discharge following a period of rainfall

Falling limb

The period of time when the river's discharge is falling after it has reached Peak Discharge

Baseflow

The part of the river's discharge that is provided by groundwater seeping into the bed of the river

Bankfull discharge

maximum discharge that a river can hold before it bursts its banks

Physical factors that effect lag time

Relief, rock type, soil type, vegetation cover, drainage basin size and shape

Human factors that effect lag time

farming, afforestation, deforestation, river management schemes, increased urbanisation

Purpose of hydrographs

Useful information for flood management and prevention.

Discharge

volume of water passing through a particular point at a given time

How much of world's water is in oceans?

97%

How much surface freshwater?

0.3%

How much freshwater?

3%, mostly in icecaps and glaciers

Deforestation's effect on rivers

Less leaves and shallower roots - less interception and infiltration - increased surface runoff - short term flash floods - less evotranspiration - water leaves system and is not replaced - less condensation - river level lowers long term

Soil drainage tiles

plastic tubing with small perforations to allow water entry - when water table is higher than tile, water flows into tubes and slowly drains away

Advantages of draining farmland

improves soil structure (deeper roots) improves aeration (microorganisms) compaction of soil because of animals and farm equipment is less likely (less overland flow) warmer soil, seeds sown earlier

Disadvantages of draining farmland

increases speed of throughflow, can lead to floods dry topsoil can have wind erosion, loss of soil Nitrate loss, eutrophication leads to algae growth in water sources, can kill fish and pollute water sources

Eutrophication

excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.

Water abstraction

The extraction of water from rivers or groundwater aquifers

Issues with water abstraction

pumped at rates that rainfall cannot replenish - sinking water tables- less reliable rivers, feeder springs dry up, saline intrusion (eg Malta and Italy)

Examples of saline intrusion

Greece - 400m boreholes contaminated with seawater

water abstraction -chalk environments in southern England

replenished by rainfall on the hills, safe for public consumption, over abstraction means streams dry up, effects fishing, tourism and agriculture industries economically

bournes

groundwater streams which feed into rivers in chalk environments - position of these relates to position of water table

relief rainfall

When warm moist air arrive at a mountainous area, it is forced to rise and condense which makes precipitaion fall on the windward side.

frontal rainfall

The mass of warm air meets the colder air and rises over it, creating rain

convectional rainfall

warm surfaces heat air above, expands becoming less dense and rising, condenses to make clouds - shows variations in water cycle as it is not certain

dew point temperature

the temperature to which air has to be cooled in order to reach saturation

condensation nuclei

Microscopic particles on which water vapor condenses to form cloud droplets.

cloud formation

water reaches dew point temperature and excess water is condensed on condensation nuclei or surfaces colder than dew point