The Water Cycle - A Level Geography OCR

Created by

Emma Vtk

Cards (43)

Hydrosphere - all water on planet Earth 
97% Ocean
3% locked up in fresh water
What makes up the hydrosphere
Oceanic water
Cryospheric water
Terrestrial water
Atmospheric water
Oceanic Water 
Largest store of water of earth (97% of Earth's water in total)
- Cover 72% of the Earth's total surface
- Typically salty
- falling pH (becoming more acidic over time)
What is Cryospheric Water?
Water that is stored on Earth in solid form (ice)
- sea ice
- permafrost (water is frozen into the soil)
- ice caps
- ice sheets
-glaciers
Cryospheric processes
Ablation
Terrestrial Water 
Water that is fresh water and free flowing
- surface water (rivers and lakes)
- groundwater
- soil water
- biological water (biomass - plants and animals)
Atmospheric Water 
Held in all three states - solid, liquid, gas (water vapour), clouds.

Water held in the atmosphere acts as a greenhouse gas and is used to control the Earth's temperature.
Factors driving the change in magnitude of water stores
Solid to liquid (melting and freezing)
Liquid to gas (evaporation)
Gas to liquid (condensation)
Liquid - gas (factors affecting)
Controlled by a variety of factors:
The process requires energy in the form of solar radiation (heat up water)
Availability of water - no water, no gas forming
Humidity - air is saturated with water vapour, makes it harder for liquid to turn into a gas.
Temperature - too cold, the process won't take place, hot it increases the rate of evaporation.
Gas - Liquid (factors affecting)
The main form of precipitation (rain - condensation)
- Air temp is reduced: hot air can hold more water vapour so when it cools it can no longer hold it and will return into the form of water.
- volume of air increases without a temperature rise will cause water vapour to turn into a liquid.
What is the drainage basin?
Area of land drained by a river and it's tributaries.
What is the water shed?
Border around the drainage basin, marking the boundary of the drainage basin.
Drainage basin 
- open system (energy and matter can transfer in and out of the system. water can come outside of the drainage basin e.g. through clouds)
- cascading system (inputs and outputs of one open system within the drainage basin system flow into the inputs of another system)
Drainage Basin System Diagram
Inputs into the drainage basin system
- precipitation (rain/snow)
Stores in the drainage basin system
- interception (trees and plants collect water, trapped in the vegetatation, stopping the water hitting the ground directly)
- soil
- rivers
- lake
Processes/flows in the drainage basin system
= ways that water is moving within the drainage basin system, between the stores
- stemflow (water moving down the stems of plants)
- surface runoff (water flowing across the surface of the ground)
- infiltration (water is moving downwards through the soil)
- throughflow (faster movement of water through the soil)
- percolation (water moving down through rocks)
- groundwater flow/base flow
- channel flow (water flowing within rivers)
Outputs within the drainage basin system
- evaporation
- transpiration (evaporating straight from plants/transpiring)
Transport within the Global Water Cycle
- ocean-land-ocean
- recirculation of water over land
- ocean-ocean
What is the water balance
= inputs-outputs in the water system
(e.g. drainage basin)
Equation for Water Balance
Precipitation (p) =Evapotranspiration + Streamflow +- storage
Processes of the water cycle
- precipitation
- transpiration
- condensation
Transpiration 
= diffusion of water vapour to the atmosphere from stomata of plants.
Factors influencing transpiration
- temperature
- wind speed
-water availability to plants (e.g. deciduous trees shed their leaves in climates with dry or cold seasons to reduce moisture loss through transpiration)
Condensation 
= the phase change of vapour to liquid water.
- occurs when air is cooled to its dew point. At this temperature air becomes saturated with vapour resulting in condensation.
Precipitation 
= water and ice that falls from clouds towards the ground (form of snow, hail, rain, sleet and drizzle)
How does precipitation form?
= vapour in the atmosphere cools to its dew point and condenses into tiny water droplets/ice particles to form clouds. These tiny droplets aggregate, reach a critical size and leave as precipitation.
Environmental Lapse rate (ELR) 
= vertical temperature profile of the lower atmosphere at any given time. On average the temperature falls by 6.5c for every klm of height gained.
Dry adiabatic lapse rate (DALR) 
= rate at which a parcel of dry air (less than 100% humidity so that condensation is not taking place) cools. Cooling, caused by adiabatic expansion is approximately 10c/km
Saturated adiabatic lapse rate (SALR) 
= rate at which a saturated parcel of air (one at which condensation is occuring) cools as it rises through the atmosphere. Because condensation releases latent heat, the SALR at around 7c/km is lower than the DALR
Clouds 
= visible aggregate of water or ices or both that float in the free air. Form when water vapour is cooled to its dew point.
Absolute instability
Absolute stability
Conditional instability
Soil Moisture graph
What is a soil moisture graph?
recording the amount of water held in the soils throughout the year - measuring precipitation and evapotranspiration.
What is soil moisture recharge?
= precipitation is greater than evapotranspiration, so there is more water entering the soil than leaving so there is a surplus.
What is river discharge
= volume of water passing a measuring point in a given time
Factors affecting interception loss
- interception storage capacity
- wind speed
- vegetation type
-tree species
Interception storage capacity
Vegetation surfaces are dry before rainfall and ability to retain water is at a maximum. Initially most rainfall is intercepted. As vegetation becomes saturated, output of water through stemflow and throughfall increases. Interception depends on the duration and intensity of rainfall.