amazon rainforest - water cycle Flashcards
1
Q
flows and stores in water cycle
A
evaporation precipitation run-off atmosphere soil/groundwater vegetation
2
Q
evaporation
A
- 50-60% of precipitation in Amazonia is recycled by evapotranspiration
- High rates due to high temps, abundant moisture and dense vegetation
- Precipitation feedback loops sustain high rainfall totals
- ½ incoming rainfall is returned to the atmosphere by evapotranspiration
- Most evaporation intercepted moisture from leaves surfaces
- Moisture lost in transpiration is derived from the soil via tree roots
3
Q
precipitation
A
- High average annual rainfall >2000mm with no dry season
- Fairly evenly distributed throughout the year
- High intensity, convectional rainfall
- Interception by forest trees is high (10%)
- Intercepted rainfall = 20-25% of all evaporation
4
Q
run-off
A
- Rapid run-off related to high rainfall, intensive rainfall events and well-drained soils
- River discharge may peak on 1-2 months depending on seasonal distribution of rainfall
5
Q
atmosphere
A
- High temperatures allow atmosphere to store large amounts of moisture
- Absolute and relative humidity is high
6
Q
groundwater/ soil
A
- Abundant rainfall and deep tropical soils leads to significant water storage in soils and aquifers
7
Q
vegetation
A
- Rainforest trees = crucial role absorbing and storing water from the soil and releasing it through transpiration
8
Q
physical factors affecting water cycle in amazon
A
geology
relief
temperature
9
Q
geology
A
- Impermeable catchments (crystalline rocks) have minimal water storage capacity = rapid run-off
- Permeable and porous rocks (limestone and sandstone) store rainwater and slow run-off
10
Q
relief
A
- Majority of Amazon Basin = lowlands
- Overland flow: in areas of gentle relief water moves across the surface
- Through flow: water moves horizontally through the soil to streams and rivers
- In the West – the Andes create steep catchment with rapid run-off
- Widespread inundation across extensive floodplains (Pantanal) occurs annually, storing water for months = slowing movement into rivers
11
Q
temperature
A
- High temperatures throughout the year = high rates of evapotranspiration
- Convection = strong, leading to high atmospheric humidity, the development of thunderstorm clouds and intense precipitation
- Water is cycled continually between land surface, forest trees and atmosphere by evaporation, transpiration and precipitation
12
Q
human factor effecting amazon
A
deforestation
13
Q
deforestation
A
- In Amazonia averaged around 17,500 km2/year between 1970 and 2013
- 1970: 1/5 of primary forest been destroyed or degraded
- Recent years = slowed deforestation
- April 2014: floods on the Madeira River (largest tributary of Amazon river), at Porto Velho river reached record levels = 19.68m above normal
- Floodplain wasn’t inundated; 60 people died, 68,000 families evacuated and were outbreaks of cholera and leptospirosis
- Deforestation has the potential to change climate at local and global levels
- Rainforest to grassland =increase run-off by a factor of 27 and ½ rainfall on grassland goes straight to rivers
- Rainforest tree crucial because extract moisture from soil, intercept rainfall and release it to atmosphere via transpiration, stabilising forest albedo and ground temps
- Cycle = high atmospheric humidity, responsible for cloud formation and heavy conventional rainfall – deforestation breaks this cycle = permanent climate change
14
Q
example - Upper Maderia
A
- Upper Madeira drainage basin – deforestation has reduced water storage in forest trees, soils, permeable rocks and in atmosphere (Solid eroded, rocks due to rapid run off)
- Fewer trees mean less evapotranspiration = less precipitation
- Total run-off and run-off speeds have increased easing flood risks throughout basin
15
Q
example - Bolivia and Peru
A
- Torrential rains in upper basin but main driver of floods = deforestation in Bolivia and Peru
- 2000-2012: 30,000 km2 of Bolivian rainforest leaves for subsistence farming and cattle ranching
- Deforestation occurred on steep lower slopes of Andes
- Result = massive reduction in water storage and accelerated run-off
