AQA Geography carbon and water cycle

Inputs into a drainage basin system

Precipitation:any water that falls to the surface of the Earth from the atmosphere including rain, snow and hail.

Types of rainfall (3)

Convectional - Due to heating by the sun, warm air rises, condenses at higher altitudes and falls as rain.

Relief - Warm air is forced upward by a barrier such as mountains, causing it to condense at higher altitudes and fall as rain.

Frontal - Warm air rises over cool air when two bodies of air at different temperatures meet, because the warm air is less dense and therefore lighter. It condenses at higher altitudes

Outputs in a drainage basin system (2)

• Evapotranspiration - Compromised of evaporation and transpiration. Evaporation occurs when water is heated by the sun, causing it to become a gas and rise into the atmosphere. Transpiration occurs in plants when they respire through their leaves, releasing water they absorb through their roots, which then evaporates.

• Streamflow - All water that enters a drainage basin will either leave through the atmosphere or through streams which drain the basin. These may flow as tributaries into other rivers or directly into oceans.

Flows in a drainage basin system (7)

• Infiltration - This is the process of water moving from above ground into the soil. Plants such as grass and trees create passages for water o flow into the soil.

• Percolation - Water moves from the ground or soil into porous rock or rock fractures.

• Throughflow - The movement of water through the soil layer towards a river channel or lake, occurring after infiltration.

• Surface runoff - Water flows above the soil when it is fully saturated or impermeable.

• Groundwater flow - Water moves through the rock layer.

• Streamflow - Water that moves through established channels.

• Stem flow - Flow of water that has been intercepted by plants or trees by any part of a plant.

Stores in the drainage basin system (5)

• Soil water - Water stored in the soil which is utilised by plants.

• Groundwater - Water that is stored in the pore spaces of rock.

• River channel - Water that is stored in a river.

• Surface storage - Water stored in puddles, ponds and lakes.

• Interception - Water intercepted by plants on their branches and leaves before reaching the ground.

The water balance

Express the process of water storage and transfer.

Precipitation - total runoff - evapotranspiration = change in storage

How does deforestation affect the water cycle?

There is less interception by trees so surface runoff and groundwater flow increases. The soil is no longer held together by roots, so soil water storage decreases. There are fewer plants so transpiration decreases.

How do storm event impact the water cycle?

Large amounts of rainfall quickly saturate the ground to its capacity. No more water can infiltrate the soil, increasing the surface runoff

How do seasonal events affect the water cycle?

Winter - snowfall and frozen ground, makes the soil impermeable so there is an increase in surface runoff. Vegetation dies in cold weather so there is less interception.

Summer - High evapotranspiration due to the increased temperature and more plant growth. So there will be more interception and lower discharge of rivers.

How does agriculture affect the water cycle?

• Livestock trample the ground and eat the grass, this compresses the soil and removes gaps for water to infiltrate.

• Ploughing for crops increases infiltration by creating looser soil, which decreases surface runoff.

• Irrigation greatly increases evapotranspiration, as water is moved to the surface.

How does urbanisation affect the water cycle?

• Creating roads and buildings which have impermeable surfaces that reduce infiltration and increase surface runoff, increasing flood risk.

• Green roofs and Sustainable Urban Drainage Systems(SUDS) use grass and soil to reduce the amount of impermeable surfaces, reduce urban flooding.

Percentages of global water stores.

Oceans contain 97% of total water stores.

2.5% of stores are freshwater of which 70% is glaciers, ice caps and ice sheets and 30% is groundwater.

Surface and other freshwater make up around 1% of global stores.

4 types of water stores

1. Hydrosphere - Any liquid water

2. Lithosphere - Water stored in the crust and upper mantle

3. Cyrosphere - Any water that is frozen

4. Atmosphere - Water vapour

Aquifers

Permeable rock or sand storing water underground, being a long term natural water store.

Features of a flood hydrograph (6)

• Discharge - The volume of water passing through a cross sectional point of the river at one point in time, measured in m3/sec (cumecs)

• Rising limb - The line on the graph that represents the discharge increasing.

• Falling limb - The line on the graph that represents the discharge decreasing.

• Lag time - The time between peak rainfall and peak discharge.

• Base flow - The level of groundwater flow.

• Storm flow - Compromised of overland flow and throughflow.

Flashy hydrographs features (4)

1. Short lag time

2. Steep rising and falling limb

3. Higher flood risk

4. High peak discharge

Subdued hydrograph features (4)

1. Long lag time

2. Gentle rising and falling limb

3. Lower flood risk

4. Low peak discharge

Natural factors which would cause a flashy hydrographs. (5)

• High rainfall intensity - higher discharge potential from the river.

• Antecedent rainfall - Rainfall that occurs the day before the studied event. Soil is already saturated so increase in surface runoff.

• Impermeable underlying geology - decreased percolation so greater levels of throughflow

• Small basin - rain reaches river faster

• Low temperatures - less evapotranspiration so greater peak discharge

Human factors which would cause a flashy hydrograph. (3)

• Urbanisation - more impermeable surfaces, so surface runoff increases.

• Pastoral farming - ground trampled so less infiltration, more surface runoff increases off

• Deforestation - less interception from trees, so water reaches river faster.

Transfers in the carbon cycle (8)

1. Photosynthesis

2. Respiration

3. Combustion

4. Decomposition

5. Diffusion

6. Weathering and erosion

7. Burial and compaction

8. Carbon sequestration

Photosynthesis in the carbon cycle

Living organisms convert carbon dioxide from the atmosphere and water from the soil, into oxygen and glucose using light energy. Plants are sequestering carbon dioxide and reducing the impacts of climate change.

Respiration in the carbon cycle

When plants and animals convert oxygen and glucose into energy which then produces water and CO2. During the night plants respire instead of photosynthesising.

Combustion

When fossil fuels and organic matter such as trees are burnt, they emit CO2 into the atmosphere, that was previously trapped inside them.

Decomposition

When living organisms die, they are broken down by decomposers which respire, returning CO2 into the atmosphere. Some organic matter is also added to the soil.

Diffusion

The oceans can absorb CO2 from the atmosphere, which has increased ocean acidity by 30% since pre industrial times.

Weathering and erosion

Rocks are eroded on land which releases stored CO2 into the ocean then later the atmosphere.

Carbonation weathering occurs when CO2 in the air mixes with rainwater which erodes rocks such as limestone. The carbon is moved through the water cycle and enters the ocean.

Burial and compaction

When shelled marine organisms die, their shell fragments fall to the ocean floor and become compacted over time to form limestone. Organic matter from vegetation and decaying n marine organisms are compacted over time to form fossil fuels deposits.

Carbon sequestration

A plant sequesters carbon when it photosynthesis and stores the carbon in its mass.

Factories use Carbon capture and storage (CCS). CO2 is captured and transported via pipeline to depleted gas fields and saline aquifers.

Advantages of Carbon Capture and Storage (CCS) (3)

1. Can be fitted to existing coal power stations

2. There is a demand for CO2 (carbonated drinks, plant growth, beer), so transports systems via pipelines already exist.

3. Potential to capture half the world’s CO2 emissions.

Disadvantages of Carbon Capture and Storage (CCS) (3)

1. High initial cost to build

2. Increases energy demand of power stations

3. May not be space to build onto old power stations

Climatic climax

The final stage of the sere where environmental equilibrium is achieved. The ecosystem is fully developed and it will not change dramatically as the equilibrium will counteract any change.

Carbon sink and source

Carbon sink - any store which takes in more carbon than it emits.

Carbon source - any store which emits more carbon than it stores.

Wildfires

Transfer carbon from biosphere to atmosphere as CO2 is released through burning. This burning can encourage the growth of plants in the long run.

Volcanic activity

Carbon stored within the Earth is released during volcanic eruptions, mainly as CO2 gas. Ash clouds can reduce the rate of photosynthesis, through blocking the sun radiation.

Deforestation

Often used to clear land for farming or houses, rapidly releases carbon stored in plants into the atmosphere using slash and burn techniques.

Farming practices

Pastoral farming releases CO2 as animals respire. Ploughing can release CO2 stored in the soil. Farm machinery such as tractors release CO2.

Radiative forcing

also known as climate forcing and is the difference between insolation (sunlight) absorbed by the Earth and energy radiated back to space.

Greenhouse effect

1. The greenhouse effect describes the natural balance between incoming and outgoing solar radiation in our atmosphere.

2. The various greenhouse gasses in our atmosphere such as carbon dioxide, methane, and halocarbons absorb a wide range of energy-including infrared energy (heat) emitted by the Earth—and then re-emit it.

3. The re-emitted energy travels out in all directions, but some returns to Earth, where it heats the surface.

Enhanced greenhouse effect

1. Caused by human activity adding extra greenhouse gases (like CO2) to the atmosphere.

2. Extra greenhouse gases disrupt Earth's energy balance, causing changes in temperature, usually warming (Radiative Forcing).

Causes of enhanced greenhouse effect

1. Fertilisers - They have direct greenhouse gas emissions from the soil, CO2 emissions from production and indirectly affects methane levels.

2. Deforestation - Carbon sinks are destroyed and CO2 is then released, often land is used for other purposes turning the area into a carbon source.

3. Urbanisation - By replacing vegetation and covering soils, the carbon cycle is affected. Cement releases CO2 during production and is a very important building material.

Impact of the carbon cycle on tropical rainforests. (2)

• High rates of photosynthesis and respiration in forests lead to greater humidity, cloud cover and precipitation.

• Deforestation reduces photosynthesis and respiration, reducing humidity, cloud cover and precipitations.

Impact of the carbon cycle on oceans. (2)

• Warmer oceans cause more phantom growth and through plankton chemical production, cause clouds to potentially form.

• Warm oceans store less CO2. This means higher temperatures could lessen the effects as ocean as carbon sinks. This sets up a positive feedback loop where the greenhouse effect is heightened further.

Permafrost feedback loop

Higher temperatures have started to melt permafrost. Organic matter trapped in the frozen ground are released as it is melted. The CO2 increases the temperature, further melting the permafrost.

Sea ice melting feedback loop

Ice reflect radiation from the sun, so less heat is absorbed by the surface. As the ice melts there is less reflection and more absorption by water. The warmer water further melts the ice.

Carbon fertilisation feedback loop

Higher temperatures and more CO2 cause a greater fertilisation in plants, so they absorb more CO2. This reduced the levels of CO2 in the atmosphere and the rates of warming and carbon fertilisation will decrease.

Wildfires feedback loop

Wildfires are more likely in hotter and drier climates created by global warming, which release large quantities of CO2 into atmosphere, which in turn then increases the warming effect.

Phytoplankton feedback loops. (2)

1. Higher CO2 levels cause phytoplankton to grow. CO2 is taken in through photosynthesis and levels decrease as a result, causing phytoplankton to decrease.

2. Higher temperatures cause phytoplankton to grow and photosynthesise quicker. Phytoplankton release substances that lead to the formation of clouds, meaning cloud cover increases. Radiation from the sun is therefore less able to reach oceans, reducing temperatures.