Water & Carbon Case Studies Flashcards
Amazon Rainforest and River Exe (14 cards)
Key characteristics of the Amazon Rainforest
- 300 million trees covering 5.5 million km² of land
- 80-120 gigatons of carbon stored in the rainforest =1/5 of global carbon
- Absorbs 1-3 gigatons anually
- 2000+ mm of anual rainfall
- Average temperature of 27°C
Water cycle in the Amazon Rainforest
- Amazon river discharges 15% of global freshwater into the ocean daily
- Majority of rainfall does not reach the ground it is intercepted and re-evaporated (closed cycle/system)
- Direct evaporation from rivers occurs as a result of high temperatures
- High levels of transpiration
Carbon cycle in the Amazon Rainforest
- Rising productivity due to increased atmospheric co2, which leads to shorter plant life
- Reduction in capacity to absorb carbon dioxide
- Fossil emissions in South America exceeds sequestration of carbon in the Amazon
Deforestation
Human activity - causes of change
- Predominantly for agriculture - 70% of deforestation occurs for cattle ranching.
- Between 2000 and 2007, the Amazon was deforested at a rate of 20,000km2 per year
- Brazil is the 6th polluter -75% of their emissions from deforestation and land use change
- Global temperatures are rising - which may disrupt the carbon and water cycle
Most significant human activity taking place.
Human activity Impacts - Water Cycle - Deforestation
- Fewer trees means less transpiration and evaporation occurs, so there is reduction in cloud formation and therefore rain.
- Moisture evaporated from deforested areas usually forms small cumulous clouds = no precipritation
not deforestation
Human activity Impacts - Water Cycle
- Extreme rainfall could lead to flash flooding as a result of less interception
- 15% less water can be held in the soil and it is more easily eroded = more run off
- There is an overall reduction is river discharge
Human activity Impacts - Carbon Cycle - Deforestation
- Forests absorb more solar radiation than pastural land and its average temperature is 8 degrees less - 24
- Carbon from deforestation is washed into the ground increasing the amount in soil and rivers
- Rate of photosynthesis declines
Where is the River Exe located
South-west of England, primarily in Devon. Its sources is in Exmoor- somerset. It flow 60 miles until it empties into the English channel at Exmouth.
River Exe - Upper Course description
Landscape: steep-sided valleys, over 500m abover sea level, dominated by moorland and peaty soils
River characteristics: narrow, shallow channel, vertical erosion
Land use: grazing, low population density, areas of conservation (Exmoor National Park)
Wimbleball reservoir
River Exe - Middle Course description
Landscape: less steep, valley widens and deepens
River characteristics: wider channel and more developed meander pattern, more lateral erosion and transportation
Land use: mixed agriculture, small settlements like Bampton and Tiverton, some deforestation
River Exe - Lower Course description
Exeter to Exmouth
Landscape: Gentle gradient, wide floodplain and river valley
River characteristics: large meander, wide deep channel with a slower flow.
Land use: urbanised in and around Exeter, floodplain used for housing, industry and transport.
Purpose and impacts
Wimbleball Reservoir
Purpose: water storage for east Devon and Exeter, maintains a consistent flow during dry periods
Impacts: reduces the risk of downstream flooding, regulates flow
Exmoor Mires Restoration Project
Goal: restore peatland bogs on Exmoor that were previously drained for agriculture
Impacts:
* reduced surface run-off and peak discharge
* Increased water storage
* Improved water quality and biodiversity
River Exe - Flood risk
High rainfall - Exmoor receive around 1300mm of rainfall anually.
Devonian sandstone = impermeable which means less infiltration and more run-off
