Unit 3 - Global sytems Flashcards
What does it mean that the water cycle is a closed system?
- Inputs and outputs move to and from stores within the system. None crosses the systems boundaries.
- the amount of water in the water cycle is fixed, which means the mass balance does not change
- water is held in stores in, on and above earth
- flows are transfers of water between stores
What are the 6 major water stores?
- oceanic
- cyrosphere
- groundwater and soil moisture
- terrestrial surface water
- atmosphere
- biosphere flora and fauna
What is the cryosphere?
Any place on earth where water is frozen.
What is permafrost?
Ground permanently frozen for over 2 years
What is eustatic change?
The global change in the volume of water in the oceans
What is meant by ‘accumulation’?
The build up of snow and ice in the cyrosphere
What is meant by ‘ablation’?
Change of ice into liquid or water vapour.
How can sea level change change the size of water stores?
- eustatic change has resulted in sea levels changing significently over geological time
- during glacial periods more water is frozen, decreasing water in the oceans
- climate warming increases ice sheet melting, raising sea levels
How has changes in cryosphere processes changed the size of water stores?
- short term changes in ice accumulation and ablation occur annually due to seasonal changes in temperature
- climatic changes, resulting in glacial and interglacial periods, cause significant changes in the cryosphere
- human induced global warming may be permanently reducing the cryosphere by increasing ablation
What are the processes that control transfers in the water cycle across a range of timescales?
- short term storm events increase transfers locally
- seasonal variations in climate impact on transfer rates
-climatic variability due to events lasting years such as El Nino Southern Oscillation impacts on precipitation levels - global warming impacts on precipitation levels and evaporation rates, influencing flows between the land and the atmosphere
- climate change impacts on ablation rates, affecting transfers between the cryosphere and other parts of the system
What is a drainage basin?
An area of land drained by a river and its tributaries. The boundary of the basin is called the watershed.
What is the input component of a drainage basin?
Precipitation
What is precipitation?
Rain, snow, sleet, hail, frost: the type, amount, duration and intensity influence transfers and stores in the system
What are the 8 flow components of a drainage basin?
Throughfall
Stemflow
Infiltration
Overland flow
Throughflow
Percolation
Groundwater flow
Channel flow
What is throughfall?
Water dripping from plants to the ground; rate is influenced by leaf cover
What is stemflow?
Water flowing down stems and trunks
What is infiltration?
Water soaking into the soil; infiltration rate/capacity is the rate at which water can pass into the soil; affected by soil characters
What is overland flow and what are the 2 types?
Water flowing over the surface -
- saturation excess overland flow, the soil is saturated, so rainfall cannot infiltrate
- infiltration excess overland flow, rainfall intensity is so great that is exceeds infiltration capacity
What is throughflow?
Slow, lateral (sideways) movement downslope through the soil
What is percolation?
Downward movement from soil to underlying rock
What is groundwater flow?
Slow, downward and lateral movement through bedrock
What is channel flow?
Flow of water in streams and rivers
What are the 5 store components of a drainage basin?
Interception store
Vegetation store
Surface store
Channel store
Groundwater store
What is interception store?
Water held on leaf and plant surfaces
What is vegetation store?
Water contained in plants
What is surface store?
Water collected in depressions in the ground surface; also includes snow cover
\what is channel store?
Volume of water in a river channel
What is groundwater store?
Water stored in underground rocks, the water table marks the upper level of saturated rock
What are the 3 output components of a drainage basin?
Evaporation
Transpiration
Channel discharge to oceans
What is evaporation?
Water changing state from liquid to water vapour, it occurs from any surface store or flow
What is transpiration?
The release and evaporation of water from vegetation
What is meant by ‘channel discharge to oceans’?
The volume of water leaving a drainage basin and flowing into the sea
What is a river regime?
Annual variations in a rivers discharge, a line graph showing the changes is called a hydrograph
What is baseflow of a river?
Water entering from groundwater creates a normal minimum flow
What is stormflow of a river?
Water entering by overland flow and throughflow after precipitation creates storm flow
What is a simple river regime?
One high and one low discharge corresponding to seasonal temperature and precipitation changes
What is a complex river regime?
Several extremes of discharge in a year
What are the physical factors influencing river regimes?
- climate (annual precipitation pattern, seasonal variations in temperature, evaporation rates)
- vegetation
- soil
- geology
What are the human factors influencing river regimes?
- land use
- irrigation and use of water
- dam construction, creating reservoirs to store water and even out the flow through the year
What is a storm hydrograph?
Shows a rivers response to a precipitation event
What are the 5 features of a storm hydrograph?
peak discharge
peak rainfall
lag time
rising limb
recessional (falling) limb
What is the peak discharge of a hydrograph?
Maximum rate of flow
What is the peak rainfall of a hydrograph?
The time of the maximum rainfall
What is the lag time of a hydrograph?
The period between peak rainfall and peak discharge
What is the rising limb of a hydrograph?
Part of the graph showing increase in discharge
What is the recessional (falling) limb of a hydrograph?
Shows the decreasing discharge
What is a flashy hydrograph?
Has a short lag time, high peak discharge, and steep rising and falling limbs
What are the 3 climatic factors affecting hydrographs?
Rainfall intensity and duration
Antecedent weather conditions
Temperature
How does rainfall intensity and duration affect hydrographs?
Heavy or prolonged rainfall increases overland flow, resulting in a flashy hydrograph
How does antecedent weather conditions affect hydrographs?
Previous rainfall may saturate the ground, so overland flow occurs quickly
How does temperature affect hydrographs?
Influences evapotranspiration, affecting the amount of water available to reach the channel; frozen grounds prevents infiltration shortening lag times
What are the 6 river catchment characteristics affecting hydrographs?
Basin size and shape
Drainage density
Geology and soils
Slope angle
Type and amount of vegetation
Land use