Water cycle in the Amazon Flashcards
Describe the Amazon rainforest
- 6 million km2
- mainly covers Brazil
- high amounts of precipitation, high humidity and high temperatures ranging from 22-34 degrees
- high cloud coverage
What are the flows and stores in the water cycle
FLOWS: - precipitation - evapotranspiration - run-off STORES: - atmosphere - soil - vegetation
Describe the characteristics of precipitation in the Amazon
- High average rainfall = more than 2000mm
- High intensity convectional rainfall allows for high interception (about 10% of precipitation) - about 20-25% of evaporation
Describe the characteristics of evapotranspiration in the Amazon
- High rates due to high temperatures, lots of moisture and vegetation
- Strong evapotranspiration-precipitation feedback loops
- 50% of incoming rainfall is returned by evapotranspiration
- Majority of evaporation occurs on leaves
Describe the characteristics of run-off in the Amazon
- Rapid run-off is caused by intensive rainfall events and well-drained soils
- River discharge can peak in one or two months of the year
Describe the characteristics of the atmosphere in the Amazon
- High temperatures allow atmosphere to store huge amounts of moisture
- Absolute humidity is high
- Relative humidity is high
What is absolute humidity?
The mass of water vapour in a given volume of air
What is relative humidity?
The mass of water in a given volume of air as a ratio of the mass needed to saturate it
Describe the characteristics of the soil/groundwater in the Amazon
- Lots of rainfall and deep tropical soils leads to significant water storage in soils and aquifers
Describe the characteristics of the vegetation in the Amazon
Rainforest trees absorb and store water and then release it through transpiration
How are water losses replenished in the amazon?
By an inward flux of moisture from the Atlantic Ocean
What physical factors affect flows and stores of water in Amazon
geology
relief
temperature
Geology: How do impermeable catchments alter water cycle and give example
They have minimal water storage capacity which leads to rapid run-off
EG. Ancient Shield area of Amazon is made up of impermeable crystalline rocks
Geology: Give an example of a permeable/porous rock in the Amazon
Limestone is a good storage of water and slows run-off
Relief: What is the majority of the Amazon comprised of?
Extensive lowlands
Relief: In areas with gentle relief how does water move?
Via overland flow (across the surface) Via throughflow (horizontally through the soil)
Relief: What is the relief like in the West?
The Andes create steep catchments with rapid run-off
Relief: What occurs annually across extensive floodplains? +eg
Widespread inundation
EG. The Pantanal
Temperature: What do high temperatures cause in terms of weather?
High convection = high atmospheric humidity = thunderstorms = high precipitation
Where is water cycled continuously, and by what flows?
Between the land surface, vegetation and atmosphere
By evaporation, transpiration and precipitation
How much primary forest has been destroyed or degraded since 1970?
One third
What is the average rate of deforestation in Amazonia between 1970 and 2013?
17,500km2 per year
How has human activity modified stores and flows in water cycle + where?
In Upper Madeira drainage basin deforestation has:
- reduced water storage
- reduced precipitation rates as less evapotranspiration as fewer trees
- increased run off total and speed
What happened in April 2014?
Floods on Madeira River (largest tributary of amazon) Record levels of 19.68m above normal 60 people died 68,000 families evacuated Outbreaks of cholera
What was the main cause of Madeira River floods?
- Deforestation in Bolivia and Peru for subsistence farming and cattle ranching was the main cause
- Mainly occurred on steep lower slopes of Andes so massive reduction in water storage and accelerated run-off
Converting rainforest to grassland increases run-off by how much?
How much rainfall goes straight into rivers from grassland?
A factor of 27
50%
Why are rainforest trees crucial?
Rainforest trees are crucial in extracting moisture from soil, intercepting rainfall and releasing it into atmosphere by transpiration as well as stabilising forest albedo and ground temperatures - cycle sustains high atmospheric humidity which is responsible for cloud formation and heavy conventional rainfall so with deforestation the cycle can break and leads to permanent climate change
How much is it predicted regional rainfall will decline by in the future?
20%
Whats the main way of improving agriculture?
Diversification
How can diversification be achieved?
- Rotational cropping
- Combining livestock with arable (would also allow a fivefold increase in production)
