Lesson 14- The water cycle in the tropical rainforest

Question 1

Why does it rain a lot in the amazon?

Answer 1

There is low pressure on the equator which means we have rising air, lots of evaporation and therefore lots of convectional rain.

-However, the location of the ITCZ (Inter tropical convergence zone) this is where the Hadley cells meet and where we get the most rainfall.
-It varies throughout the year due to changes in solar radiation as the earth rotates around the sun.

Question 2

Amazon general facts

Answer 2

• It sits within the Amazon River basin, covers some 40% of the South America
• 1000 species of bird, 60,000 species of plants, 10 million species of insects
• 20 million people
• 2.1 million square miles
• Home to almost 20% of species on Earth

Question 3

Vegetation in the Amazon

Answer 3

• The Amazon contains around 300 billion trees, which store 1/5th of the planets biomass carbon store.
• Very high NPP (net primary productivity) - the rate at which plants accumulate energy in the form of organic matter taking into account the energy used in respiration.
• The high temperatures and high rainfall mean fast-growing trees form a dense canopy.

Question 4

Soil in the Amazon

Answer 4

• Tropical latosols are not fertile.
• There is significant leaching (draining away of soluble materials) due to the high precipitation resulting in poor nutrients.
• The top 15-20cm of the soil is nutrient rich leaf litter.
• Deep soils due to rapid chemical weathering of the bedrock.

Question 5

What is rainfall recycling like in the Amazon

Answer 5

• Average rainfall is 2300 mm/yr and 50% is recycled
• High humidity drives local convectional rainfall.
• The dense canopy means that interception rates are high
• Rates of evapotranspiration are also high (50% all water is evaporated).
• Water is effectively recycled within the tropical forest system before it ever reaches the river / ground.

Question 6

What happens to water that isnt intercepted in the amazon?

Answer 6

• Water enters the Amazon River and its tributaries.
• Discharge of water into the Atlantic Ocean by the Amazon about 1/5th of the total discharge into the oceans ofall oftheworld’s rivers.
• Water may output into the Atlantic Ocean via the Amazon river

Question 7

Inputs in the water cycle of amazon?

Answer 7

• Water vapour from the Atlantic Ocean (heated by the sun, evaporated, cooled, condensed into clouds) blown by trade winds towards the Amazon

Question 8

Outputs in the water cycle of the amazon?

Answer 8

• The Amazon river flows into the Atlantic Ocean (30% of all rain).
• Evaporation exports water vapour to other places.

Question 9

What are the flows in the water cycle in the amazon?

Answer 9

• Precipitation
• Evapotranspiration
• Run-off

Question 10

Flows of water cycle in the amazon- Precipitation

Answer 10

• Precipitation- High average annual rainfall. Rainfall fairly evenly distributed throughout the year though short drier seasons occur in some places.
• High intensity, convectional rainfall. Interception by forest trees is high. Intercepted rainfall accounts for a high proportion of evaporation.

Question 11

Flows of the water cycle in the amazon- Evapotranspiration

Answer 11

• High rates due to high temperatures, abundant moisture and dense vegetation. Strong evaporation- precipitation feedback loop.
• Most evaporation is from intercepted moisture from leaf surfaces. Moisture lost in transpiration is derived from the soil via tree roots.

Question 12

Flows of the water cycle in the amazon- Run-off

Answer 12

• Rapid run-off due to high rainfall, intensive rainfall and well-drained soils.

Question 13

What are the stores in Amazon?

Answer 13

• Atmosphere
• Soil/groundwater
• Vegetation

Question 14

What are the stores in the Amazon- Atmosphere

Answer 14

• High relative humidity (the amount of water vapour present in air as a percentage of the amount needed to saturate it at the same temperature).

Question 15

What are the stores in the Amazon- Soil/groundwater

Answer 15

• Abundant rainfall and deep soil leads to significant water storage in soils and aquifers.

Question 16

What are the stores in the amazon- vegetation

Answer 16

• Absorbs and stores water from the soil and releases it through transpiration.

Question 17

What are the physical factors affecting the stores and flows of water in the amazon?

Answer 17

• Geology
• Relief
• Temperate

Question 18

Physical factors affecting the stores and flows of water cycle in the amazon- Geology

Answer 18

• Impermeable catchments have minimal water storage capacity, resulting in rapid run-off (large parts of the Amazon Basin are an ancient shield area comprising of impermeable, crystalline rocks).
• However chemical weathering does leave deep soils, allowing water to infiltrate. Other areas have permeable and porous rocks such as limestone and sandstone store rainwater.

Question 19

Physical factors affecting the stores and flows of water cycle in the amazon-Relief

Answer 19

• Most of the Amazon Basin comprises of extensive lowlands- overland flow and throughflow.
• In the West, the Andes create steep catchments with rapid run-off. Annual widespread inundation across flood plains.

Question 20

Physical factors affecting the stores and flows of water cycle in the amazon- Temperature

Answer 20

• High temperatures generate high rates of evaporation.
• Convection is strong, leading to high atmospheric humidity, and intense precipitation.

Question 21

Human factors affecting the stores and flows of the water cycle in the amazon

Answer 21

• Deforestation
• Cattle ranching

Question 22

Human factors affecting the stores and flows of the water cycle in the amazon- Deforestation

Answer 22

• Deforestation in the Amazon averaged around 17,500km2/yr between 1970 and 2013.
• Since 1970 almost 1/5th of the primary forest has been destroyed or degraded, though in recent years rates of deforestation have slowed.

Question 23

Human factors affecting the stores and flows of the water cycle in the amazon- Cattle ranching

Answer 23

• Cattle ranching accounts for over 60% of deforestation in the Amazon.
• Beef has become an important export for Brazil; 80% of its beef is farmed in the Amazon

Question 24

How does deforestation affect the water cycle?

Answer 24

1) Evapotranspiration
2) Cloud formation
3) Forest albedo
4) Precipitation
5) Interception
6) Total-run off
7) Run-off speeds
8) Risk of flood
9) Water stored in biomass
10) Water stored in soils
11) Water stored in atmosphere

Question 25

How deforestation affects the water cycle- Evapotranspiration

Answer 25

Decrease due to fewer trees so less transpiration and evaporation, this means less clouds and more droughts.

Question 26

How deforestation affects the water cyle- Cloud formation

Answer 26

Formation- decrease due to less evapotranspiration so less water vapour adiabatically expanding and cooling to dew point.

Question 27

How deforestation affects the water cycle- Forest albedo

Answer 27

(Proportion of sunlight reflected)- decrease due to darker soil surfaces exposed which absorb more sunlight compared to green trees. Ground temperatures increase.

Question 28

How deforestation affects the water cycle- Precipitation

Answer 28

Decrease due to less interception and evapotranspiration and so less recycling to form precipitation.

Question 29

How deforestation affects the water cycle- Interception

Answer 29

Decreases as fewer trees

Question 30

How deforeststion affects the water cycle- Total run-off

Answer 30

Decreases due to less precipitation

Question 31

How deforestation impacts the water cycle- Run-off speeds

Answer 31

Increases due to less interception and more overland flow

Question 32

How deforestation impacts the water cycle- Risk of flood

Answer 32

Increase due to less interception, soil could become saturated without tree roots taking up water, leading to saturated overland flow.

Question 33

How deforestation impacts the water cycle- Water stored in biomass

Answer 33

* Water stored in biomass- decrease due to less vegetation.

Question 34

How deforestation impacts the water cycle- Water stored in soils

Answer 34

* Decrease because although there is less interception and water taken up by roots, there is less vegetation and hence less leaf litter. * Less humus reduced the capacity of the soil to absorb water, so infiltration capacity is low.

Question 35

How deforestation impacts the water cycle- Water stored in atmosphere

Answer 35

* Decrease due to less evapotranspiration and reduced cloud formation.

Question 36

Natural rainfall recycling

Answer 36

1) Precipitation falls 2) Most is intercepted by trees and through stem flow  3) A small amount reaches the ground and infiltrates the soil  4) Some is used by plants and through transpiration returns to the atmosphere.  5) About ¼ evaporates almost immediately and returns to the atmosphere.

Question 37

Deforestation rainfall recycling

Answer 37

1) Precipitation falls.  2) Most reaches the ground immediately with little vegetation to intercept the rainfall, leading to high surface runoff increasing flooding risk. 3) Less evapotranspiration, so the atmosphere is less humid and rainfall decreases. 4) When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought. These have been made worse by deforestation.

Question 38

Impact of deforestation on the water cycle-Flooding case study -impacts

Answer 38

* Flooding of the Madeira River, the largest tributary of the Amazon River * The watershed covers over 900,000km2, 80% of which is in Bolivia. * Torrential flows of water flooded Bolivia’s lowlands before heading to Brazil. * 60 people died and 68,000 families were evacuated. * Outbreaks of cholera and leptospirosis. * The BR-364 road that crosses the rainforest was impassable, cutting off communities and causing shortages of food and fuel.

Question 39

Impacts of deforestation on the water cycle- Flooding case study -causes

Answer 39

* Deforestation in Bolivia and Peru on the steep lower slopes of the Andes– 2000-2012, * 30,000km2 of Bolivian rainforest was cleared for subsistence farming and cattle ranching. * Reduction in water storage and accelerated run-off 27 times more than normal. * 50% rain falling on grassland goes directly into rivers. * At Porto Vehlo the river reached record levels, 20m above normal. * Deforestation breaks rainfall recycling cycle and can lead to permanent climate change.

Question 40

Small scale water cycle in the rainforest -convectional rainfall

Answer 40

* Sun overhead throughout the year * To protect themselves from the heat, the plants release water. * The water evaporates from the surface of their leaves * This causes the plants to cool down (i.e. when you exercise and sweat this is our adaptation to help cool down). * The moist air rises and forms huge cumulonimbus clouds (nimbus = Latin for rain). * At some stage, the energy is too much as released in torrential downpours as convectional rainfall

Question 41

Large scale water cycle in the rainforest -how inputs and outputs leave the system

Answer 41

1) Moist air is brought from the Atlantic ocean to south America by the so-called ‘trade winds’, that blow from East to West. 2) The closer these are to the equator, the warmer they are. 3) When the air reaches the area where the sun shines most strongly, the hot moist air rises and forms clouds. 4) Once it has rained, some of the water is brought back to the Atlantic by river