Water Cycle and Water Insecurity Flashcards
Describe the hydrology in polar regions
- 85% radiation reflected
- permafrost - impermeable
- rapid runoff in spring
describe hydrology in tropical rainforests
- dense vegetation consumes most precipitation
- limited infiltration
2 processes that drive the hydrological cycle
- solar energy
the more heat = more evaporation = more precipitation - gravitational potential energy
keeps water moving inputs, outputs, stores, and flows
what are stores, fluxes, and processes
store - water is held
flux - the rate of flow of water
processes - physical factors that drive fluxes
residence time
average time water molecules remain in a store
what is a drainage basin
subsystem - open system with many inputs and outputs
physical factors affecting drainage basin
- climate - evaporation and precipitation
- soils - determine infiltration
- geology - permeable rocks infiltrate
- relief - slopes increase runoff
- vegetation - transpiration and interception
human factors affecting drainage basin
deforestation
over-abstraction
pollution
global warming
why does groundwater extraction negatively affect a drainage basin?
- water extracted at a faster rate than it is recharged
also reduces storage
dam construction and drainage basins
increases surface water and evaporation
reduce downstream flow and discharge
what is a water budget?
the annual balance between inputs and outputs
shows when water naturally leaves and enter the system
what does a water budget show?
- more than enough water (positive water balance)
- not enough water (negative water balance)
what is a river regime
annual variation in discharge or flow of a river
main factors affecting regime
- drainage basin size / capacity
- geology and relief
- land use
- precipitation and climate
simple regimes
seasonally high discharge followed by a low discharge
complex regimes
larger rivers that cross several different relief and climatic zones e.g. Mississippi or the Ganges
2 examples of complex regimes and where they cross
river Nile - North Africa - Uganda, Ethiopia
Amazon - South America - Brazil, Ecuador
what do storm hydrographs show
how river discharge varies after precipitation especially during storms.
drought
an extended period of below-average precipitation
meteorological drought
long-term precipitation lower than normal
affected by atmospheric conditions
agricultural drought
not enough soil moisture - caused by precipitation shortages
hydrological drought
surface water is deficient - occurs after meteorological and agricultural
socio-economic
water demand outstrips water availability
causes of Brazil drought 2014-2015
- over-abstraction of water supplies
- series of high-pressure systems diverted rain-bearing winds away from brazil - dry air
impacts of Brazil drought
- water rationing for 4 million people
- the halting of HEP - power cuts
- depletion of reservoirs
- reduced crops led to increased prices
drought in the Sahel
- provided opportunity for re-greening the desert
restoration technique - planting vegetation
low costs reforesting
water harvesting techniques
naturally regenerating water shrubs and trees
California and climate change
- severe mega-droughts wildfires due to droughts
- 90% chance of decade long drought
- increased evaporation and fall in precipitation
impacts on California
- surface runoff and moisture levels decreased
- forested areas reverted back to scrub and grassland
- reservoir levels have fallen significantly
ecosystem stress
constraints on the development or survival of ecosystems
why is the amazon rainforest so important?
- earth’s lungs absorb masses of Co2
- flying river in the sky
- carries 17 million tonnes of water back to the Atlantic each day
drought effects on rainforests
- younger trees die, reducing canopy cover which reduces humidity and therefore rainfall
- larger risk of wildfires - sunlight on dying vegetation
wetlands
areas where the soil is waterlogged with freshwater or salt-water
importance of wetland
- rich biodiversity and cultural value
- responsible for nutrient recycling
- tourist attraction
impacts of droughts on wetlands
- increased tree mortality - reduced habitats
- wildfires - cattle farmers burning old grass
meteorological causes of droughts
UK - depressions causing low-pressure areas
physical causes of flooding
- intense precipitation
- sudden snowmelt
- monsoon rainfall
- vegetation
- rock type
- relief
monsoon season in southeast Asia
- seasonal change in direction of prevailing winds
- April and September
- 70% rainfall in 100 days
how do humans exacerbate flood risk
- changing land use
- mismanagement of rivers
- poor maintenance of rivers
physical causes of storm desmond
- Atlantic low-pressure system (depression)
- heavy rainfall as a result
- jet streams - fast-moving air determining speed and direction of depressions
human causes of storm desmond
- mismanagement of land - removal of trees for farming
- hard engineering was not sufficient
- mismanagement of rivers
mitigating flood risk
- afforestation
- restoring river channels
- refusal of planning permission near rivers
physical water scarcity
- not enough water to meet demands
