2.a. it is possible to identify the physical and human factors that affect the water cycles in a tropical rainforest Flashcards
the rates of flows and distinct stores in the Amazons water cycle
Dense forest cover -> lots of interception -> biosphere store
Lots of vedgeation -> Lots of evapotranspiration -> atmospheric store
High temps -> warm air can hold more water -> atmospheric store
Areas of shield rock -> impermeable -> more run off -> storage in river channel
Areas of limestone -> large lithospheric storage
Deep soils allow water to infiltrate -> lots of through flow + infiltration
High levels of precipitation (2,500mm/year)
+
high temperatures (av. 20-25C)
= lots of CONVECTIONAL RAINFALL
high humidity -> more cloud cover -> keeps forest warmer -> further accelerating evapotranspiration rates
how an individual tree through to the rainforest as a whole can influence these cycles
the physical factors effecting the flows and stores
temperature
rock permeability and porosity
relief
how temperature effects the flows and stores
high temps all year round (20-25C)
-> Lots of evapotranspiration -> higher humidity -> more cloud formation -> more rainfall -> large atmospheric + biosphere stores
-> warm air can hold more water -> higher humidity
-> optimal growth conditions for vegetation -> large biosphere
how rock permeability and porosity effects the flows and stores
Areas of ancient shield rock (impermeable) + areas of limestone (permeable)
Ancient shield rock -> less groundwater flow + percolation -> more run off
Limestone -> more groundwater flow + percolation -> more infiltration + throughflow -> less run off
how relief effects the flows and stores
Majority of the amazon has a low relief
However -> the relief is high at the Andes mountains
Flat relief -> more infiltration + percolation -> less run off -> less river storage
Steep relief -> more surface run off due to gravity -> less time for infiltration + percolation -> less groundwater storage
Steep relief will also experience relief rainfall
the natural and human factors changing the flows and stores
deforestation
farming
urbanisation
how is deforestation causing changes to the flows and stores
- past 50 years -> 1/5 destroyed
less interception -> less biospheric storage (in trees + soils) -> more run off -> more storage in rivers -> could lead to floodings e.g. Maderia river in 2014 -> evacuation + cholera outbreak -> 60 killed
less transpiration -> precipitation is 20% lower
how is farming causing changes to the flows and stores
- deforestation to create cropland
Deforestation of forests -> turning into grasslands
-> increasing run off by 27% -> more storage in rivers + floodings
-> less transpiration -> lower humidity -> less cloud cover -> less atmospheric storage
-> forests have low albedo (absorbing more radiation -> increasing temperatures) whereas grasslands have a higher albedo (more radiation reflected -> cooler temperatures -> less evapotranspiration)
albedo = the reflective ability of a surface
Combining livestock + crop farming -> to maintain soil fertility + maximise productivity -> less deforestation -> however -> plots are often abandoned -> and once turned into grassland -> the soil becomes infertile
Machinery compacts the soils -> reducing infiltration + increasing run-off -> more storage in rivers
how is urbanisation causing changes to the flows and stores
Concrete surfaces -> impermeable -> reduces infiltration + percolation -> less storage in ground rock -> more run off -> more storage in rivers
strategies to manage the Amazon that have positive effects on the water cycle
Afforestation
planting trees to replace those deforested
e.g. the parica project in the western Amazon
- aims to plant 20 million fast growing trees
aims to
- protect primary rainforest on tribal land from further illegal logging
- and reforest degraded areas
the trees planted can provide native indigenous people with
- timber for construction
- and a sustainable source of income- through logging
more interception -> less run off -> less risk of flooding
more transpiration -> higher humidity -> more precipitation
how water extraction, including surface extraction and sub-surface groundwater extraction (including aquifers and artesian basins) impact the flows and stores
Increased in recent years due to ->
Increased agriculture + manufacturing -> to accommodate for the growing demand
Removal of groundwater stores + flows
Meaning less storage in rivers -> as less water is discharged via groundwater flows
Over extraction at a faster rate than the aquifer can recharge -> groundwater stores depleted
E.g. in the River Kennet
Taken way too much -> aquifers cannot recharge -> less water fed into rivers
Artesian basins-
Where sedimentary rocks form a sink rock -> and aquifers are confined between impermeable rock layers -> which are under artesian pressure -> meaning water travels at a higher pressure
