Water cycle

What type of system is the Earth

Closed

(It’s also a cascading system)

Dynamic equilibrium in relation to the water cycle

\-Tendency towards a natural state of balance within

\-It’s a closed system (water is recycled around)

\-Drainage basin element is an open system (inputs and outputs can change)

\-Easily upset by extreme events (storms and droughts)

\-Human activity disrupts it and can cause flooding

Positive feedback in the water cycle

\-Deforestation = reduced size of biosphere store = more carbon dioxide in the atmosphere = temperatures rise = more evaporation = more water vapor in atmosphere = enhanced greenhouse effect = temperatures rise further

\-More carbon dioxide in atmosphere = temperatures rise = the warm air holds more water vapor = earth holds onto more heat energy = temperatures rise further

Negative feedback in the water cycle

\-Increased farming production = more carbon dioxide in atmosphere = increased temperature = more evaporation = increased water vapor in atmosphere = more cloud formation = more energy from sun is reflected back into space = temperature falls

Cascading systems

\-Hydrosphere, lithosphere, biosphere, atmosphere and cryosphere are all interlinked by cycles and processes

\-Matter and energy move between these subsystems

\-The Earth is a cascading system

5 major subsystems of Earth

\-Hydrosphere

\-Lithosphere

\-Biosphere

\-Atmosphere

\-Cryosphere

Hydrosphere

Water

Lithosphere

Geology (soil and rocks)

Biosphere

Living things

Atmosphere

Gases

Cryosphere

Ice

What % of Earth’s water is oceanic

97%

What % of Earth’s water is fresh

3% (99% of this is not accessible, in ice sheets)

Rank of fresh accessible surface water stores

Lakes, soil moisture, atmospheric water vapor, rivers, water within organisms

Earth’s water is distributed between (biggest to smallest)

\-Oceanic

\-Cryospheric

\-Terrestrial

\-Atmospheric

Amount of oceanic water

Over 1 billion km3

Oceans cover what % of the Earth’s surface

72%

Cryospheric water classes

\-Sea ice

\-Ice caps

\-Ice sheets (biggest store)

\-Alpine glaciers

\-Permafrost

\-Iceshelves

Biggest cryospheric store of water

Ice sheets

Sea ice

\-Ocean water is cooled down to below freezing

\-Such as Arctic and Antartica

Ice shelves

\-Platforms of ice from glaciers moving into the oceans

\-Found in Arctic, Antarctica and Greenland

Ice sheets

\-Mass of glacial land ice

\-Such as Greenland and Antarctica

\-Form where snow that falls in winter, does not melt entirely over summer. The layers over years grow thick and dense

Ice caps

\-Smaller ice sheets (thick land ice)

\-Tend to be dome shaped

Alpine glaciers

\-Thick masses of ice found in deep valleys

Permafrost

\-Ground remaining at/below freezing

\-Most existing today formed during glacial periods and have persisted through interglacial period

Name of the current interglacial

Holocene

What does permafrost release as it melts

CO2 and methane

Terrestrial water classes

\-Surface water

\-Ground water (biggest store)

\-Soil water

\-Biological water

Biggest terrestrial store of water

Ground water

Surface water

\-Free flowing water of rivers, lakes and ponds

Rivers

\-Streams of water within defined channel

\-Act as both store and transfer of water

\-Transfer water from the ground, soils and atmosphere to a store

Amazon river discharge

1/5 of worlds total river flow

Lakes

\-Mostly freshwater

\-Most lie in Northern hemisphere at higher latitudes

Ground water

\-Water that collects underground in pore spaces of rocks

\-Amount is reducing rapidly due to extensive extraction for irrigation

Water table

Depth at which soil pore spaces in rock become completely saturated with water

Soil water

\-Water held in unsaturated upper layers of the Earth

\-Fundamental importance to hydrological, biological and biogeochemical processes

\-Effects weather, climate, run off potential, flood control, soil erosion and water quality

What does soil moisture play an important role in

The development of weather patterns and precipitation production (it controls the exchange of water and heat energy between land and atmosphere, through evaporation and transpiration)

Biological water

\-Stored in biomass

\-Varies, depending on vegetation cover and type

Atmospheric water

\-Exists in all 3 states (gas is most common, water vapor)

Why is atmospheric water vapor important

It absorbs, reflects and scatters incoming solar radiation

The amount of water vapor air can hold depends on what

Its temperature (cold air cannot hold as much water vapor as warm air, resulting in dry poles and humid tropics)

Clouds

Visible mass of water droplets or ice crystals suspended in the atmosphere

What type of system is the water cycle

Closed

What type of system is the drainage basin

Open

All water on Earth is found in which subsystem

Hydrosphere

What processes that drive change in water stores

\-Condensation

\-Sublimation

\-Evaporation

\-Melting

\-Freezing

\-Deposition

Change from oceanic and terrestrial water to atmospheric water

Evaporation

Change from atmospheric water to cryospheric, oceanic and terrestrial water

Condensation and precipitation

Change from atmospheric, terrestrial and oceanic water to cryospheric water

Freezing

Change from cryospheric water to oceanic and terrestrial water

Melting

There are no inputs/outputs to the global water cycle, but processes can drive change in where the water is stored

Condensation, sublimation, evaporation, melting, freezing and deposition can change water stores to oceanic, cryospheric, terrestrial and atmospheric

Evaporation

When solar radiation energy hits waters surface, causing the liquid to change to gas (water vapor)

Rate of evaporation depends on

\-Amount of solar radiation (greater heat energy and radiation = greater evaporation)

\-Availability of water (more water = more evaporation)

\-Humidity of air (the closer air is to saturation point, the slower the rate of evaporation as there’s less space for more water vapor)

\-Temperature of air (warmer air holds more water vapor = higher evaporation)

Humidity

Amount of water vapor in the air

Saturation point

Maximum humidity of air

Evaporation will be high when

There’s lots of solar radiation, large supply of water and warm dry air

Evaporation will be low when

There’s little solar radiation, small supply of water and cool saturated air

Condensation

Water vapor (gas) changes state to liquid water, losing energy to the surroundings

Dew point

\-The temperature at which air is completely saturated and condensation can occur

\-Excess water in the air is converted to liquid via condensation

Condensation nuclei

\-Something water molecules condense on below dew point temperature

\-Can be tiny particles like smoke, salt and dust

\-Can be surfaces like leaves and windows

Dew

Water vapor condenses onto vegetation

Frost

Water vapor sublimates (gas to solid)

Condensation will be high when

There’s lots of water vapor in the air, many nuclei and large rapid drop in temp

Cloud formation and precipitation varies seasonally

Usually more rainfall in winter than in summer, in the UK

Cloud formation and precipitation varies by location

Precipitation is usually higher in the tropics than the poles, due to pressure difference

Precipitation is the main flow of

Water from the atmosphere to the ground

Condensation is the direct cause of

All forms of precipitation

Cloud formation

\-Warm air cools down as it rises

\-It reaches its dew point

\-Water vapor condenses into water droplets, which gather as clouds

\-Once the cloud is saturated enough, precipitation will fall

Types of precipitation

Rain, snow, hail, sleet

Types of rainfall

\-Convectional

\-Relief

\-Frontal

Convectional rainfall

\-Sun heats the ground

\-Moisture on the ground evaporates and rises up in a column of warm air

\-As it rises, it cools

Relief rainfall

\-Warm air meet mountains

\-Air is forced to rise upwards, causing it to cool

Frontal rainfall

\-Less dense warm air meets denser cool air

\-Warm air is forced to rise above cool air

\-It cools down as it rises

Cryospheric processes

\-Processes that affect the total mass of ice (amount of water stored in the cryosphere)

\-Includes accumulation and ablation

Accumulation

Build up of ice

Ablation

Melting of ice

Glacial budget

\-Balance between accumulation and ablation over the year

\-Shows whether the mass of ice has increased or decreased, determining whether the front of the glacier advances or retreats

\-If there’s more accumulation than ablation in a year, the glacier has a positive mass balance (it will grow)

\-It varies with temperature

Upper part of glacier has

More accumulation than ablation (zone of accumulation)

Lower part of glacier has

More ablation than accumulation (zone of ablation)

Glacial periods in the cryosphere

\-Inputs are greater than outputs

\-Water is transferred as snow

\-Less melting

\-Interrupts global hydrological cycle as there’s less water available to be transferred (effecting sea level and ocean stores)

Interglacial periods in the cryosphere

\-Outputs are greater than inputs

\-More melting

\-More water available for the water cycle

Role of cryospheric change

\-Regulatory role in sea level

\-Major store of water

\-In glacial period, it will grow

\-In interglacial period, it will shrink (more melting returning water to sea)

Temporal variation in cryospheric processes

\-Change of global temperature over 1000s of years

\-Annual temperature fluctuations (more snow fall in winter than summer)

Spatial and temporal variation of evaporation

\-Climate (seasons and glacial periods)

\-Humidity

\-Latitude

\-Water availability

\-Air temperature

Spatial and temporal variation of condensation

\-Seasons

\-Humidity

\-Latitude

\-Air temperature

\-Nuclei available

\-Dew point

Spatial and temporal variation of cloud formation and precipitation

\-Temperature (convectional)

\-Altitude (relief)

\-Air masses (frontal)

\-Water quantity

\-Location

Spatial and temporal variation of cryospheric processes

\-Climate

\-Temperature

\-Altitude

Drainage basin

\-Area of land drained by a river and its tributaries

\-They are separated by watersheds (high land)

What system is a drainage basin

Open system

Drainage basin inputs

Precipitation

Drainage basin outputs

\-Transpiration

\-Evaporation

\-Run off

Run off / channel flow

River discharge (all water that enters the river channel and flows out the basin)

Drainage basin stores

\-Soil storage

\-Surface storage

\-Vegetation storage

\-Interception storage

\-Channel storage

\-Groundwater storage

Drainage basin flows

\-Channel

\-Surface

\-Overland

\-Throughfall

\-Stem

\-Through

\-Infiltration

\-Percolation

\-Groundwater

Aquifer

Permeable rocks which can store a lot of groundwater

Groundwater flow

\-Movement of water through permeable rock under force of gravity

\-Slowest flow of water on a hillslope

Infiltration

Downward movement of water from surface into soil

Factors affecting infiltration rate

\-Level of soil saturation

\-Soil porosity (fine, sandy soils have greater porosity, allowing greater flow of water. clay soils have lower flows)

\-Burrowing animals and plant roots present (can create channels which increase infiltration)

Interception storage

Precipitation that fall on vegetation surfaces (leaves, branches)

Vegetation storage

Plants remove water from soil and store it in their structure