Water Flashcards
1
Q
Key points of the global hydrological cycle
A
- operates as a closed system
- inputs are - solar, gravitational potential energy (cause rivers and rain to go downwards)
- stores are - oceans, cryosphere (ice caps), lithosphere (rivers), biosphere (plants) and atmosphere
- flows include - precipitation, evaporation and evaportranspiration
2
Q
Key features of stores and fluxes
A
- saline sea water makes up 97% of world’s water
- almost 80% freshwater is in ice sheets and glaciers
- another 20% of freshwater is in the ground
- surface freshwater stores constitute of around only 1%of water
- main fluxes are - precipitation and evaporation; occur mainly over oceans
3
Q
Key points of global water budget
A
- only 2.5% of global water is freshwater
- only 1% of water is easily accessible
- residence times vary between stores - 10 days for atmosphere - 3600years in oceans and 15000years in an ice cap
- stores of fossil water and water in cryosphere said to be non renewable
- accessible freshwater is critical for all forms of life on Earth and availibility still limited
4
Q
Key features of processes of drainage basins
A
- inputs include - energy from sun and precipitation
- precipitation can be derived from - air rising over mountains, air rising along weather front and air rising due to intense heat
- outputs include - evapotranspiration, direct runoff into sea, water percolating into deep groundwater stores
- stores take place on vegetation, on ground, in soil and underlying bedrock
- transfers (flows) take place between any of these stores and ultimately into the channels of the rivers of the drainage basin
- river transfers water by its channel flow to the sea - measured by its discharge
5
Q
What are other stores and flows?
A
- groundwater store; water that collects underground in pore spaces in rock
- groundwater flow - movement of groundwater - slowest transfer of water within drainage basin and provides water for river during a drought
- infiltration - movement of water from surface downwards through soil
- interception - process where precipitation prevented from reaching soil by leaves and branches of trees as well as by plants
- saturated overland flow - movement of water over saturated or impermeable land
- percolation - downward movement of water from soil into rock below or within rock
- stemflow - water that runs down stems and trunks of plants to ground
- throughfall - water that drips off leaves during rainstorm
- throughflow - water that moves down slope through soil
6
Q
What does a water budget show?
A
- shows relationship between inputs and precipitation (P) and outputs in form of runoff (Q) and evapotranspiration (E) together with changes to amounts of water held in storage within soil and groundwater (DS)
- indicates available soil water and thus giving info on amount and timing of irrigation thats needed
P = E + Q + DS
7
Q
Whats a storm hydrograph?
A
- graph of the discharge of a river before during and following a storm event
- helps predict how river may respond to rainstorm - help in management of a river
8
Q
What are some physical factors that can affect the shape of a storm hydrograph?
A
- basin size - small basins tend to have flashy hydrographs
- rock type - permeable rocks allow percolation - slows water transfer down - impermeable reduce percolation and increase surface runoff and shorter lag times
- soil type - clay soils have low infiltration and more overland flow
- vegetation - in summer deciduous trees have more leaves so interception is higher
9
Q
Physical causes of drought; meteorological drought
A
- shortfalls in precipitation as a result of short term variability - increase duration of a dry period
- precipitation deficiency - usually associated with high temperatures, high winds sun which increases evaporation
- causes of rainfall deificiency - can be natural variations in atmospheric conditions or desiccation caused by deforestation or longer term things like ENSO cycles
- these conditions impact the hydrological cycle with decreases in infiltration, percolation and groundwater recharge
10
Q
Physical causes of drought; hydrological drought
A
- associated with reduced stream flow and groundwater levels which decrease because of reduced inputs of precipitation and high rates of evaporation
- results in reduced storage in lakes or resevoirs
- major threat to wetlands and other wildlife habitats
- linked to decreasing water supplies for urban areas which results in water use restriction to control abstraction rates of surface water resources
11
Q
Human factors in making droughts more severe
A
- increase in livestock - overgrazing - soil depleted of nutrients and land stripped of grass cover
- high birth rates and low death rates - farmers forced to use land for growing crops and food - reduced soil fertility
- immigrants - increased demand for wood for building/cooking/heating - deforestation
12
Q
Physical factors in making droughts more severe
A
- short term - less rainfall, increased drought - rivers dry up
- long term - climate change - global warming - increased evaporation - less reliability and amount of rainfall
13
Q
Ecological impacts; wetlands
A
- less precipitation - reduced interception - less infiltration and percolation to groundwater stores - water table levels fall
- evaporation will continue and may increase while transpiration rates will decrease - wetlands become less resilient
- desiccation also can accelarate destruction by wildfires
14
Q
Ecological impacts; forests
A
- with reduced precipitation - physiological damage and increased fungal diseases
- drier trees also more susceptible to fire damage
15
Q
What are physical causes of flooding?
A
- intense storms
- rapid snowmelt in tundra areas
- prolonged heavy rain
