The Water Cycle

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Where is the WATER? -

ll water on earth is stored in the hydrosphere

It can be divided into

- oceanic

- cryospheric

- terrestial

- atmospheric

oceanic water accounts for 97% of all of the earth's water and 72% of the earth's surface water. Over time it is becoming more acidic.

cryospheric water is water that is stored on earth is solid form (sea ice, permafrost, ice caps, ice sheets and glaciers)

terrestrial water is fresh water that is on the earth (surface water, groundwater, soil water and biological water)

atmospheric water can be held as a solid, liquid or gas. Water held in the atmosphere is a greenhouse gas and helps to regulate the temperature of the earth.

What is causing CHANGES in the MAGNITUDE of the earth's water stores?

Evaporation

- liquid -> gas

- requires energy to heat up the water

- the availability of water

- humidity

- temperature

Condensation

- gas -> liquid

- precipitaion

- reduces air temperature so it can no longer hold the water

- volume of air increasing causes water vapour to change back into a liquid

What is a DRAINAGE BASIN? -

A drainage basin is the area of land drained by a river and its tributaries

- open system (cascading)

Inputs

- rain

- snow

Stores

- interception

- soil

- river discharge

- lake

Processes

- (ways water is moving)

- stemflow

- surface runoff

- infiltration

- throughflow

- percolation

- groundwater flow

- channel flow

Outputs

- evaporation

- transpiration

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How is water cycled on a GLOBAL SCALE? -

Recirculation of water

- ocean-land-ocean

- ocean to ocean

- recirculation of water over land (greater in tropical areas)

What is the WATER BALANCE? -

Inputs minus the outputs of a system

Soil Moisture graphs

- graph recording the amount of moisture in the soil of a particular area over the course of a year

Runoff variation

Discharge is the volume of water passing a measuring point in a given time

- can have human and physical influences

- important in flood protection

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The Storm Hydrograph

measure the discharge of a river during a flood event

Can be influenced by both human and physical features

Physical

- size and shape of the drainage basin (large basin catches more rain so more reaches the river and steeper hills means the water will flow faster)

- amount of precipitation

- drainage density (number of rivers and streams)

- saturation of the soil

- permeability of the rock type

- vegetation cover

Human

- deforestation

- agriculture

- flood engineering

- urbanisation

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Does LAND USE change the water cycle?

Deforestation

- less interception

- increased discharge

- higher chance of flooding

- new vegetation is shallow and has fewer leaves leading to reduced transpiration and interception

Soil drainage

- removes excess water from the soil profile

- subsurface drainage (pipes that remove excess water from the soil)

- flashier floods

- risk of flooding increased - artificial system moving on the water from the soil much faster than natural

- improves aeration

- easier to grow crops

Water Abstraction

"water is removed from the ground for use by humans"

- empties wells

- sinks the water table

- occurs in areas where demand is higher than the availability

- where water tables are being sunk in coastal areas, saline intrusion can occur (where sea water gets into underground water stores. It therefore cannot be used by humans ad is expensive to de-salinify the water to make it safe.)

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