Changes to water budget and cycle
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30 Terms
1
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What biome is responsible for generating high river discharge
tropical rainforest
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What percentage of the worlds river discharge is due to the amazon
25%
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what percentage of the amazon has permanently dissapeared in the last 50 years
10%
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Why is the amazon being deforested
\-cattle feed
\-cash crops eg sugar cane soy
\-cash crops eg sugar cane soy
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How does the new vegetation that grows after deforestation affect the water cycle in the **short term**
* shallow roots and few leaves
* plant uses less water
* less evaporation through evotranspiration
* more surface run off
* more river discharge
* plant uses less water
* less evaporation through evotranspiration
* more surface run off
* more river discharge
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How does the new vegetation that grows after deforestation affect the water cycle in the **long term**
* initial rise in river discharge drops to low
* less evotransipiration
* less atmospheric water
* water leaves system
* less evotransipiration
* less atmospheric water
* water leaves system
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why is less atmospheric water caused by deforestation negative
\-less rainfall
\-lower river levels
\-less atmospheric water regionally due to circulation
\-lower river levels
\-less atmospheric water regionally due to circulation
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drainage pipes
remove excess water below surface
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What is the network of perforated clay drainage pipes called
Tiles
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Water table
* boundary between the unsaturated zone and the saturated zone underground.
* Below the water table, groundwater fills any spaces between sediments and within rock.
* Below the water table, groundwater fills any spaces between sediments and within rock.
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what happens if water table is higher than tiles
* water flows into tubing
* lowers water over several days
* lowers water over several days
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Why do tiles not drain June-October
water table low
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Controlled discharge
water table remains high in off season
\-increasing denitrification
\-reduces eutrophication
\-increasing denitrification
\-reduces eutrophication
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eutrophication
water draining into water courses contains nutrients like nitrogen
\-causes rapid algae growth
\-fish struggle to survive due to lack of oxygen
\-causes rapid algae growth
\-fish struggle to survive due to lack of oxygen
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dentrification
nitrate becomes nitrogen gas in soil when it warms
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positives of draining farmland through tiles
* soil structure improves
* improved aeration and therefore decomposition of organic matter
* increases soil warming and vegitation
* less likely compaction of soil
* less overland flow
* improved aeration and therefore decomposition of organic matter
* increases soil warming and vegitation
* less likely compaction of soil
* less overland flow
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negatives of draining farmlands
* increase throughflow speed and risk of flooding
* dry topsoil subject to wind erosion
* eutrophitication of water courses
* dry topsoil subject to wind erosion
* eutrophitication of water courses
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Water abstraction
taking or extracting water from natural sources
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negatives of water abstraction
* when demand exceeds supply
* sinking water tables
* empty wells
* saline intrusion
* sinking water tables
* empty wells
* saline intrusion
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common areas where demand exceeds supply
arid areas
\-intensive agriculture and industry
\-intensive agriculture and industry
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overabstraction
groundwater sources pumped faster than they can recharge
\-causes depletion
\-causes depletion
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saline intrusion
slatwater enters and ruins quality of freshwater ground sources
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where and why is saline intrusion occuring
Mediterranean coastline
\-demands of tourism
\-unusable for consumption and agriculture (Malta)
\-invested in expensive desalination plants
\-demands of tourism
\-unusable for consumption and agriculture (Malta)
\-invested in expensive desalination plants
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sinking water tables
rivers less reliable
feeder springs dry up
surface resviors like lakes and wetlands not sustained
feeder springs dry up
surface resviors like lakes and wetlands not sustained
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main cause of groundwater over-exploitation
irrigation
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how is water replenished within chalk aquifer
rainfall on exposed chalk
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when do chalk aquifers replenish
during winter
\-low evotranspiration
\-surface run off
\-low evotranspiration
\-surface run off
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when do groundwater levels fall
summer
\-springs dry up
\-evotranspiration
\-soil moisture defecit
\-little percolation
\-springs dry up
\-evotranspiration
\-soil moisture defecit
\-little percolation
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Bournes
groundwater streams that feed chalk environments
\-provide high quality groundwater
\-provide high quality groundwater
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economic impact of over abstraction
\-tourism, agriculture and fishing all affected