Water Cycle Flashcards
What is the difference between an open and closed system?
Open systems - both energy and matter CAN enter and leave the system (e.g. drainage basin)
Closed system - MATTER CAN’T enter and leave, but ENERGY CAN (e.g. carbon cycle)
What is dynamic equilibrium?
A system is in a dynamic equilibrium when the inputs and outputs of a system are balanced
How is positive and negative feedback triggered?
Large long term changes to the balance of inputs and outputs cause a system to change and establish a new dynamic equilibrium. Changes can trigger positive/ negative feedback.
What is positive feedback?
Amplifies the change in inputs and outputs
The system responds by increasing the effects of change, moving the system even further away from its previous state
What is negative feedback?
Counteracts the change in inputs and outputs
System responds by decreasing the effects of change, keeping the system closer to its previous state
Give an example of a positive feedback system
Temps rise
Ice melts due to ^temps
Less ice cover = less of suns energy reflected
Less energy reflected = more absorbed by earth
Temps rise
Give an example of a negative feedback system
Lots of CO2 emitted CO2 in atmosphere increases ^CO2 causes plants to grow more Plants remove CO2 from atmosphere CO2 in atmosphere reduces
What are the subsystems of the earth system?
Cryosphere Lithosphere (crust and upper mantle) Hydrosphere Atmosphere Biosphere
What type of system is the Earth system?
A cascading system
Changes in one system can effect what happens in others
How much water does the hydrosphere contain? How much of this is fresh water?
1.4 sextrillion litres of water
Less than 3% water
What is the make up of the earths fresh water?
69% cryosphere
30% groundwater
0.3% liquid fresh water
0.04% water vapour in the atmosphere
How come only a small amount of the water in the hydrosphere can be used?
What’re must be physically and economically accessible to humans for them to be able to use it.
What type of system is the global hydrological cycle?
Closed system
Water is continuously cycled between different stores
What is evaporation?
When liquid water changes state to gas, becoming water vapour.
^amount if water in atmosphere
Magnitude of evaporation varies by location and season
What is condensation.
When water vapour changes state to become a liquid
Air containing what’re filled to dew point
Magnitude of condensation depends on…
Amount of water vapour in atmosphere
Temperature
How do clouds form?
Clouds form when warm water cools down, causing the water vapour in it to condense into water droplets, which gather as clouds
Cloud formation and precipitation varies seasonally and by location
How does frontal precipitation form?
When warm air meets cool air, the warm air is forced up above the cool air. It cools down as it rises = frontal precipitation
How does orographic precipitation form? (Relief rainfall)
When warm air meets the mountains it is forced to rise, causing it to cool
How does convective precipitation form?
When the sun heats up the ground, moisture on ground evaporated and rises up in a column of warm air. As it gets bigger it cools = convective precipitation
Water droplets caused by condensation are too small to form clouds by themselves, so therefore…
There needs to be tiny particles other other substances to act as CLOUD CONDENSATION NUCLEI.
These give the water molecules something to condense on.
How do cryospheric processes change the amount of water stored in the cryosphere?
Accumulation and ablation.
The balance of the two varies with temperature
What happens to crysopheric processes in a period of global cold?
Inputs are greater than outputs. Vice versa when hot.
Earth emerging from glacial period that reached its max 2100 years ago
How do variations in cryospheric processes happen over different time scales?
Global temperature change occurs over 1000s of years
Also annual temperature fluctuations
What is the drainage basin?
The area surrounding the river where rain falling on the land flows into the river
Boundary of drainage basin = watershed
Is the drainage basin open or closed system?
Open
Enters as precipitation
Leaves via evaporation , transpiration , river discharge
What are the stores of the drainage basin?
Interception Vegetation storage Surface storage Soil storage Ground water storage Channel storage
What are the flows of the drainage basin?
Infiltration Overland flow Through fall Percolation Groundwater flow Baseflow Inter flow Channel flow
How does the UK water balance vary?
WET SEASON - precipitation exceeds evapotranspiration - WATER SURPLUS in ground stores
DRY SEASON - precipitation lower than evapotranspiration - WATER DEFECIT
ground stores recharged the next season
What is a hydrograph?
Graphs of river discharge over time
What is river discharge measured in?
Measured in m3 per second - CUMECS
What increases river discharge?
High levels of runoff
What are the features if a flood hydrograph?
Peak discharge
Lag time
Rising limb
Falling limb
What is a flashy hydrograph?
A basin w rapid runoff and not much storage capacity
Short lag time and high peak discharge
How does drainage basin size affect hydrograph shape
Larger basin - higher peak discharge
Smaller basin - shorter lag time
How does drainage basin shape affect hydrograph shape
Circular basins - more likely to have flashy hydrograph than a long narrow basin
Lots of water will reach the main channel at the same time
How does ground steepness affect hydrograph shape?
Steeper - shorter lag time
How does rock and soil type affect hydrograph shape?
Impermeable rocks higher surface runoff
This means a higher peak discharge
How do storms and precipitation affect variations in the water cycle
Intense storms - ^precip & ^peak discharge
Larger the input the bigger the flow
Some flows may not be able to occur rapidly enough
^runoff
How do seasonal changes and vegetation affect variations in the water cycle
Size of inputs / flows / stores varies by season
Winter - water freezes - reduces size of flows through drainage basin - store of frozen water increases
Plants show seasonal variation - highest level of interception when trees have their leaves
The more veg = more water lost through evapotranspiration = reduces runoff and peak discharge
How do farming practices affect variations in the water cycle
Affects infiltration :
PLOUGHING - breaks up surface , ⬆️ infiltration, ⬇️ runoff
CROPS - ⬆️ infiltration & interception , ⬇️ runoff , ⬆️evapotranspiration, ⬆️ rainfall
LIVESTOCK - trample and compact soil, ⬇️ infiltration &⬆️ runoff
IRRIGATION - ⬆️ runoff. Groundwater/ river levels fall if water extracted for it.
How does deforestation affect variations in the water cycle
⬇️ amount of water intercepted by vegetation, ⬆️s amount that reaches the surface
Dead plant material helps to hold water, allowing it to infiltrate rather than runoff - forest cover removed = ⬇️ infiltration
How does construction affect variations in the water cycle
Buildings and roads create an impermeable layer over the land
Prevents infiltration - ⬆️ runoff= water passes through system faster = flooding more likely
How does water abstraction affect variations in the water cycle
More water abstracted where pop density high
⬇️ in water stores e.g. reservoirs
Dry seasons = ⬆️ abstraction for consumption and irrigation = stores depleted further
