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The Water Cycle (changes in the magnitude of the water cycle stores (how…
The Water Cycle
changes in the magnitude of the water cycle stores
how long does water remain in each of the stores?
groundwater - 10,000 years
glaciers - 20-100 years
rivers - 2 - 6 months
snow cover - 2- 6 months
soil - 1 - 2 months
processes of change
precipitation, evaporation, condensation, sublimation, interception, overland flow, infiltration, throughflow, percolation, groundwater flow
climate change
18,000 years ago 1/3 of land was covered up by glaciers and ice sheets
total melting of ice sheets would cause a 60m rise in sea level. rising sea levels destabilise ice shelves, triggering calving and further melting
affected at a local hillslope scale
affects the water balance
the drainage basin system
open system
precipitation - input to the system - rainfall may be intercepted and stored, or may runoff, or may infiltrate into soil directly
groundwater flow - feeds rivers through bank and bed, moves out of the system as runoff.
infiltration - varies on soil type and antecedent conditions. soil water recharge, usage, deficit, surplus
overland flow - surface runoff
throughflow - flows through the soil
water cycle component
precipitation
summer - total rainfall may be less but storms are more frequent
winter - greater quantities of rainfall and possibly
vegetation
summer - grows rapidly
winter - dies back
evaporation
rapid evaporation
reduced evaporation
river channel flow
summer - low flow conditions are more likely
winter - high flow conditions are more likely
soil water
summer - dry soils encourage infiltration
winter - soils may become saturated, leading to runoff
the global water cycle
closed system
stored in the lithosphere, the hydrosphere, the cryosphere and the atmosphere
97% of earths water is saline - 3% is freshwater
the global distribution of water stores
groundwater aquifers
30% of freshwater is stored in rocks deep below the ground surface forming aquifers, after travelling through permeable and porous rocks
Factors affecting changes in the water cycle
Natural factors affecting change
drought - causes reduction in water storage in lakes and rivers. affects processes such as transpiration, interception and infiltration. makes groundwater flow more important
california drought 2016 they relied on groundwater storage
human activities affecting change
land use change - urbanisation and deforestation
farming practises - arable farming, ploughing, desertification, deforestation
water abstraction - aquifers can become depleted, can become contaminated
the water balance
the water balance P = O + E +/- S