water cycle Flashcards
(10 cards)
systems and drainage basins
what are systems made up of?
- inputs - matter or energy is added to the system
- outputs - matter or energy leaves the system
- stores - a part of the system where something is held for a period of time
- flows - when energy or matter move from one store to another
- boundaries - the edge of the system (the line between 1 system and another)
- open system - energy and matter enter and leave the system
- closed system - energy can enter and leave but matter cannot enter or leave
- dynamic equilibrium - inputs and outputs are equal - no overall change to the system
- drainage basin - catchment area for water
- confluence - the point at which 2 rivers meet
- tributary - a small river or stream that joins a larger river
- source - the start of a river
- mouth - where the river meets the sea
inputs - precipitation
outputs - evaporation, transpiration, evapotranspiration, discharge
boundary - water shed - area of land that separates 2 drainage basins
stores (CIGS):
- channel storage - water held in a river
- interception - water stored by trees
- groundwater - water stored in the ground
- soil storage - water stored in the soil
flows:
- stemflow - water running down a tree trunk
- surface runoff
- infiltration - water moving from the ground into the soil
- throughflow - flow of water through soil (downhill)
- percolation - water moves from soil into rocks
- groundwater flow - flow of water through rocks
- channel flow - movement of water within the river channel
positive and negative feedback loop
- positive feedback - when a chain of events amplifies the impacts of the original event - move system away from dynamic equilibrium
- negative feedback - when a chain of events nullifies the impacts of the original event - move system back towards dynamic equilibrium
positive feedback example - water cycle:
- higher temperatures - ice melts - reduced albedo (less of the suns energy is reflected and more is absorbed) - temperatures increase further - further melting
- higher temperatures - evaporation increases - amount of water vapour in the atmosphere increases - greenhouse effect increases - temperatures increase
negative feedback example - water cycle:
- higher temperatures increase evaporation rates - leads to more cloud formation - increased cloud cover can block solar radiation, cooling the surface - cooler temperatures reduce evaporation
water stores/states
distribution of water on earth:
- 97% of water is found in oceans
- only 3% of water on earth is fresh water
out of the 3% fresh water:
- only 1% of fresh water is easily accessible fresh water
- 30% is groundwater
- water must be physically and economically accessible for humans to be able to use it e.g. groundwater is hard to access so it may not be cost effective to extract it
- gas to liquid/ liquid to gas - condensation/ evaporation
- solid to liquid/ liquid to solid - melting/ freezing
- solid to gas - sublimation
- gas to solid - deposition
evaporation, condensation, cloud formation, precipitation, cyrospheric processes
- global hydrological cycle - water is continuously cycled between different stores in a closed system
evaporation:
- evaporation increases the amount of water stored in the atmosphere
- long term changes in climate can affect the magnitude of evaporation
- magnitude of evaporation depends on the supply of water and temperatures e.g. low temperatures and a small supply of water will lead to low evaporation levels// high temperatures and a large supply of water will lead to high evaporation levels
condensation:
- magnitude of the condensation depends on the amount of water vapour in the atmosphere and the temperature e.g. if there is lots of water vapour in the air and there’s a large or rapid drop in temperature, condensation will be high
cloud formation and precipitation:
- clouds form when warm air cools down - water vapour condenses into water droplets, which gather as clouds - when the droplets get big enough, they fall as precipitation
- water droplets caused by condensation are too small to form clouds on their own - there have to be tiny particles of other substances (e.g. dust or soot) to act as cloud condensation nuclei
things that cause warm air to cool, leading to precipitation:
- other air masses - warm air is less dense than cool air - when they meet, the warm air is forced to rise - it cools down as it rises and condenses to form clouds - results in frontal precipitation
- topography - when warm air meets mountains, it is forced to rise - it cools down as it rises and condenses to form clouds - results in orographic precipitation e.g. the pennines
- convection - as the sun heats up the ground, the moist air rises - as it rises, it cools and condenses to form clouds - results in convective precipitation
cyrospheric processes:
- cold periods - more inputs (accumulation) than outputs (ablation) - more snow enters than melts - amount stored in the cryosphere grows
- warm periods - more outputs (ablation) than inputs (accumulation) - more snow melts than enters - amount stored in the cryosphere shrinks
past events and their impact on cryospheric processes:
- glacial periods - water moves from the hydrosphere to the cryosphere
- interglacial periods - water moves from the cryosphere to the hydrosphere
future events and their impact on cryospheric processes:
- recent global warming has reduced accumulation and increased ablation levels - water moves from the cryosphere to the hydrosphere - leads to higher global sea levels
water balance and soil budget
water balance:
- water balance - balance between inputs and outputs
- equation - precipitation = total runoff + evapotranspiration +/- changes in storage
- wet seasons - precipitation exceeds evapotranspiration - creates a water surplus - positive water balance
- dry seasons - precipitation is lower than evapotranspiration - water deficit - negative water balance
soil water budget:
- shows balance between inputs and outputs in the water cycle and their impact on soil water storage
- soil water budget depends on soil depth and permeability etc
autumn:
- precipitation > evapotranspiration
- soil water starts to recharge
winter:
- precipitation > evapotranspiration
- soil becomes saturated
- water surplus
summer:
- evapotranspiration > precipitation
- plants and animals utilise the water in the soil - soil moisture utilisation
hydrographs
- hydrographs - shows river discharge over a period of time
- flood hydrographs - shows river discharge around the time of a storm event
- discharge - volume of water that flows into a river per second (cumecs)
- river regime - shows the variations in river discharge over a year
parts of a hydrograph:
- lag time - the delay between peak rainfall and peak discharge - takes time for rainwater to flow into a river
- peak discharge - when the river discharge is at its greatest
- rising limb - where the river discharge increases as rainwater flows into the river
- falling limb - where the river discharge decreases because less water is flowing into the river
flashy:
• short lag time
• steep rising and falling limb
• higher flood risk
• higher peak discharge
subdued:
• long lag time
• gentle rising and falling limb
• lower flood risk
• lower peak discharge
factors affecting hydrograph shape (flashy and subdued):
ground steepness:
- steep - less time to infiltrate - surface run-off increases - river discharge increases// water flows more quickly downhill - short lag time
vegetation:
- more vegetation - interception increases - surface run off decreases - river discharge decreases// vegetation binds the soil together and increases its capacity to store water - infiltration increases - surface run off decreases - river discharge decreases// interception increases - trees slow the movement of water into river channels - longer lag time
soil type:
- impermeable soils - infiltration decreases - surface run off increases - river discharge increases
urban and rural areas:
- urban - covered in impermeable surfaces - infiltration decreases - surface run off increases - river discharge increases
drainage basins:
- circular basin - water reaches the river at the same time - high peak discharge
- larger basin - longer lag time - travels further
physical factors affecting the water cycle
extreme weather:
storms:
- intense storms with heavy rainfall - soil becomes saturated - infiltration decreases - surface run-off increases - river discharge increases
droughts:
- drought - vegetation dies - less evapotranspiration - less precipitation - drought (positive feedback loop)
seasonal changes:
summer:
- higher temperature cause the ground to be harder and more impermeable - infiltration decreases - surface runoff increases
- summer - less input of precipitation - runoff levels are low - surface runoff decreases - discharge decreases
- more vegetation - interception and evapotranspiration increases - surface run off decreases
winter:
- vegetation dies and leaves are lost - interception and evapotranspiration decreases - surface run off increases
- winter - more input of precipitation - runoff levels are high - soil becomes saturated - decreased infiltration - discharge increases
human factors affecting the water cycle
deforestation:
short term:
- deforestation - less interception - surface run off increases - river discharge increases - risk of flooding increases
long term:
- deforestation - less evapotranspiration - less water vapour in the atmosphere - fewer clouds form - less precipitation - changes in precipitation patterns - risk of drought increases
positive feedback loop:
- deforestation to create space for crops - less evapotranspiration - less rainfall - ground becomes drier and less fertile - new areas of land need to be cleared to grow crops
land use (urbanisation):
- construction creates impermeable surfaces - infiltration decreases - surface runoff increases - river discharge increases
agriculture:
- ploughing breaks up the surface of the soil - infiltration increases - surface run off decreases
- crops - interception increases - surface run off decreases (short term)// evapotranspiration increases - more water vapour in the atmosphere - clouds form and precipitation increases - soil becomes saturated - infiltration decreases and surface run off increases (long term)
- compaction - livestock and machinery compact the soil - infiltration decreases - surface run off increases
water abstraction:
- growth of global population - increased water demand - where precipitation levels are low, an alternative supply is ground water - soil becomes dry - infiltration decreases - surface run off increases - river discharge increases
river eden case study
facts and location:
- the river eden is 145km long and is located in north west of england in cumbria
- source - pennine hills
- mouth - solway firth
physical:
- geology - upland areas of river eden are mainly covered in igneous rock - impermeable// low land areas of the river eden are mainly covered in sandstone and limestone - permeable rocks
- gradient - elevation drops from 690m to 180m - water doesn’t have time to infiltrate - surface run off increases
- weather - rainfall is higher than the national average in the eden basin due to topography - mountainous terrain encourages orographic rainfall - around 2800mm annual rainfall in the upland areas
human:
- deforestation - make space for farming and housing etc - 10,000 new homes were built in carlisle - interception decreases - surface run off increases
- construction - surfaces tend to be impermeable - infiltration decreases - surface run off increases
- farming - soils become compacted by heavy machinery or trampling by livestock e.g. between 2000 and 2009, there was a 30% increase in the number of cattle in the eden valley - compaction increases - infiltration decreases - surface run off increases
- climate change is predicted to change rainfall patterns - rainfall is predicted to increase by 35% by 2080 - increase flooding
storm desmond:
- december 2015 - flooding in cumbria
- carlisle was particularly affected - more than 2000 properties were flooded - homeless
5 subsystems of the earth
- hydrosphere - all the water on earth - it may be in liquid, solid and gas form
- cryosphere - frozen water
- biosphere - all living things e.g. plants, animals, fungi, insects and bacteria
- lithosphere - the outermost part of the earth, including the crust and upper parts of the mantle
- atmosphere - layer of gas surrounding the planet
