Amazon Rainforest - Water

• What are some characteristics of the Amazon Rainforest(water)?

  • Annual temperatures are between 25-30 degrees
  • High annual rainfall of >2000mm with no dry season
  • 55% of precipitation is recycled by evapotranspiration
• What are some flows and stores in the water cycle in the Amazon?

  • Precipitation
  • Evapotranspiration
  • Run-off
  • Vegetation
  • Soil/ground water
  • Atmosphere
• How does precipitation contribute to the Amazon's water cycle?

  • >2000mm average annual rainfall
  • Precipitation is evenly distributed throughout the year
  • High intensity convectional rainfall
  • 10% of precipitation is intercepted by trees
  • Intercepted rainfall accounts for 20-25% of evaporation
• How does vegetation contribute the the Amazon's water cycle?

  • Trees absorb, store and release water
• How does soil/groundwater contribute to the Amazon's water cycle?

  • Abundant rainfall and deep tropical soils causes significant storage of water in soils and aquifers
• How does the atmosphere contribute to the Amazon's water cycle?

  • Stores high amounts of moisture (absolute humidity) due to high temperatures.
  • High relative humidity
• How does run-off contribute to the Amazon's water cycle?

  • Rapid run-off due to high rainfall, intense storms and well drained soils
• How does evapotranspiration contribute to the Amazon's water cycle?

  • high rates of evaporation/transpiration due to high temperatures, abundant moisture and dense vegetation
  • 50% of all rainfall is returned to the atmosphere by evapotranspiration
  • Most evaporation is from intercepted rainfall from leaves
  • Moisture lost via transpiration
• How does an individual tree influence the water cycle in the Amazon?

  • Trees intercept 10% of precipitation
  • Each leaf affects the water cycle by releasing water through the stomata
  • Influence of transpiration, interception and photosynthesis
  • Roots absorb water from the soil affecting organic content
• What are the physical factors that affect the water cycle in the Amazon?

  • Geology
  • Temperature
  • Relief
• How does geology impact the Amazon's water cycle?

  • Impermeable crystalline rock in the Amazon's basin has minimal water storage capacity
  • Results in rapid runoff
  • Limestone and sandstone are permeable/porous, so store rainwater and have slow run-off
• How does temperature affect the Amazon's water cycle?

  • High temperatures mean high rates of evapotranspiration
  • Strong convections lead to atmospheric humidity
  • This creates thunderstorm clouds and intense annual precipitation
  • Water continually cycled between land, trees and atmosphere
• How does relief affect the Amazon's water cycle?

  • Most of the Amazon's water basin is made up of lowlands - water moves across the surface (overland flow) or horizontally through the soil (throughflow)
  • High run-off due to steep catchments in the West
  • The Pantanal floodplain is flooded annually, storing water and slowing movement into rivers
• What is the Amazon's basin water balance?

  • Between 50-60% of the 13.8Gt of precipitation is evaporated and transpired back to the atmosphere
  • Around 5.5Gt runs-off in rivers and is lost from the Amazon, and 3.5Gt is lost by winds blowing water vapor away from the Amazon
  • Winds blow 8-10 Gt of water vapor from the Atlantic Ocean
• How does deforestation affect the water cycle?

  • Deforestation increases the risk of flooding as stores and flows are modified
  • Reduces water storage in trees/soils/permeable rocks/atmosphere
  • Fewer trees means less evapotranspiration and less precipitation
  • Total run-off and run-off speeds have increased
  • Local climate change - run-off turns forest into grassland, less interception/transpiration so less rainfall, destabilises albedo and ground temperatures
  • Global climate changed - regional rainfall predicted to decline by 20%