The Water Cycle

Model

Model

A representation of some phenomenon of the real world made in order to facilitate an understanding of its workings.

Lithosphere

The lithosphere is the outermost layer of the Earth’s surface.

Hydrosphere

the watery part of the earth's surface, including oceans, lakes, water vapour in the atmosphere, etc

Cryosphere

the part of the earth’s surface where, the water is frozen solid. (below 0°C)

Atmosphere

the gaseous envelope surrounding the earth

Biosphere

the part of the earth's surface and atmosphere inhabited by living things

System

They are a series of stores or components that have flows or connections between them.

Isolated system

An isolated system allows neither mass or energy to pass across the system boundary.

Closed system

a system that transfers energy, but not matter, across its boundary to the surrounding environment

Open system

Open systems allow energy and mass to pass across the system boundary

Subsystem

A smaller system within another

Input

where power or information enters a system

Output

where power or information leaves a system

Stores

a quantity or supply of something kept for use as needed.

Flows/Transfers

A form of linkage between one store / component and another that involves movement of energy or mass

Positive feedback

These are knock-on effects in natural systems which act to accelerate and amplify any changes that have already started to occur.

Negative feedback

negative feedback decreases the amount of change by reducing some of the inputs, returning the system to stability.

Dynamic equilibrium

Where inputs are equal to outputs within a system

Oceanic water

a continuous body of salt water that is contained in an enormous basin on Earth's surface

Crysopheric water

All of the frozen water stored on earth including ice sheets, snow and glaciers

Terrestrial water

Terrestrial water storage can be defined as the summation of all water on the land surface and in the subsurface. It includes surface soil moisture, root zone soil moisture, groundwater, snow, ice, water stored in the vegetation, river and lake water

Atmospheric water

All water vapour contained within the air/atmosphere

Evaporation

Change of state from liquid to gas due to heating

Transpiration

the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers

Evapotranspiration

Loss of water from the soil both by evaporation from the soil surface and by transpiration from the leaves of the plants growing on it.

Condensation

Change of state from gas to small liquid particles due to cooling

Orographic water

Water from relief rainfall; occurs when air masses are forced to flow over high topography. As air rises over mountains, it cools and water vapor condenses. As a result, it is common for rain to be concentrated on the windward side of mountains, and for rainfall to increase with elevation in the direction of storm tracks

Frontal rainfall

The heavier cold air sinks to the ground and the warm air rises above it. When the warm air rises, it cools. The cooler air condenses and form clouds. The clouds bring heavy rai

Convectional rainfall

Here the clouds carrying the water vapour are not carried away by the wind and hence, it rains in the same plac

Accumulation

the acquisition or gradual gathering of something

Ablation

the removal of snow and ice by melting or evaporation, typically from a glacier or iceberg.

Sublimation

conversion of a substance from the solid to the gaseous state without its becoming liquid

Drainage basin

an area of land where water from rain or snow melt drains downhill into a body of water such as a river, lake, wetland or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surface from which water drains into those channels

Watershed

the area of high land forming the edge/boundary of a river basin

Precipitation

The transfer of water from the atmosphere back into the drainage basin

Run-off

The water that flows off the surface

Interception storage

Vegetation and other objects store water on their surface, intercepting it and delaying its return to the river.

Surface storage

water accumulated on the soil surface or underground, and intercepted water

Soil water storage

The amount of water that is held in the soil layer. Can depend on precipitation, saturation and soil type

Groundwater storage

When infiltrated water is stored in the soil

Channel store

Water that is collected in channels and rivers

Vegetation store

Water that has been uptake by plants

Stemflow

Water transfered by flowing down the stem or trunk

Infiltration

Water travels down into the soil due to gravity

Overland flow

Water that runs over the surface after a period of rainfall

Channel flow

Water that is being transferred by the channel of the river

Throughfall

Weather being transferred from interception stores to the surface

Throughflow

Weather travelling through the soil layer to the channel

Percolation

Water is transferred down to the rock layer, only happens with permeable porous rock.

Groundwater flow

Transfer of perlocated water via rock

Water balance

the amount of precipitation compares with the water leaving the system as runoff or as evapotranspiration

Positive water balance

indicates that inputs are greater than outputs and water will be stored in the system

Negative water balance

indicates that outputs are greater than inputs and stores will deplete

Utilisation

When the water stores are being used and therefore depleted

Deficit

When there is less supply than demand

Surplus

When there is more supply than demand

Recharge

When water stores are replenished

River discharge

the amount of water flowing through a crossection of the river per second

River regime

the changes in a river's discharge over the course of a year in response to a number of factors

Hydrograph

a dual graph that shows the relationship between rainfall and discharge of a particular river basin

Flashy flood hydrograph

Flashy hydrographs have a steep rising limb and a small lag time. This indicates that river discharge increases rapidly over a short period, indicating rainwater reaches the river very quickly. This means the river is more likely to flood

Subdued flood hydrograph

hydrographs with gently inclined limbs, a low peak discharge and a long lag time.

Peak rainfall

Highest amount of rainfall per time period

Baseflow

the level of the channel before precipitation

Rising limb

the period in which the discharge is increasing

Receding limb

the period in which the discharge is decreasing

Lag time

the time between peak RF and peak discharge

Bankfull discharge

the maximum discharge that a particular river channel is capable of carrying without flooding

CUMECs

Units of discharge

Physical factors (affecting a flood hydrograph)

Soil type, rain intensity, size/shape of the basin ext

Human factors (affecting a flood hydrograph)

Land use, afforestation or deforestation, global warming changing weather patterns

Permafrost

Land that is frozen the majority of the year