Water and carbon cycle

• Dynamic equilibrium 


  Inputs equals outputs despite changing condition.
• Local: drainage basin 


  Outputs: evapotranspiration, evaporation, and runoff into ocean/river

  inputs: precipitation
• Types of rainfall 


  Convectional: warm air rises, condenses, and falls as rain

  Orographic: warm air forced upwards by mountains, causing it to condense and fall as rain

  Frontal: warm air rises over cool air (the warm air is less dense so it rises), condenses at higher altitudes and falls as rain
• Outputs at a drainage basin

  Evapotranspiration, evaporation, and stream flow
• Drainage Basin Flows 


  Infiltration, percolation (water moves from soils to permeable rocks), through flow, surface runoff, groundwater flow, stem flow
• Stores in drainage basins

  Soil water, groundwater, interception, surface storage
• The water balance 


  Precipitation= total runoff + evapotranspiration +\- storage

  dependent upon climate and seasonal change
• Changes to the water cycle: deforestation 


  Less interception so surface runoff increases. Soil water Storage decreases as soil roots removed. Transpiration decreases from fewer Plants.
• Agriculture 


  Trampling of ground, reducing infiltration (pastoral farming)

  Arable: ploughing increases infiltration and decreases surface runoff, reduces lag time and increases flood risk

  irrigation can lead to groundwater depletion
• Urbanisation 


  Leads to impermeable services and reduce infiltration, but increases surface runoff, reducing lag time and increasing flood risk

  Sustainable urban drainage systems: use grass and soil to reduce impermeable services, helping to tackle urban flooding
• Water budget graph 


  Field capacity: maximum possible level of storage of storage of water in soil

  
• Percentages of water stores

  Oceans contain 97% of the earth’s water

  2.5% is fresh water and 69% of that is in the cyrosphere and 30% is groundwater
• The inter-tropical convergence zone 


  Unstable weather occurs when Ferrel and Hadley cells meet and moves by the jet stream, this causes the changeable weather in the uk

  
• Human impact to water cycle on a global scale

  Water abstraction: reduces volume of water in surface stores. increases in dry seasons.

  human abstraction from aquifers is often greater as an output than as an input
• Flood hydrograph 


  Represents rainfall for the drainage basin of a river and the discharge of the river

  
• labels on the flood hydrograph

  Discharge: volume of water passing through a cross sectional point of the river at any one point in time

  lag time: time between peak rainfall and peak discharge

  flashy hydrograph: short lag time and high peak discharge, occurring during a storm event

  subdued hydrograph: long lag time and low peak discharge
• Cryospheric processes in the water system

  Accumulation and ablation change the amount of water stored as ice.

  Inputs are greater than outputs during periods of global cold.
• Carbon stores on earth

  Lithosphere: 99.9% stored in sedimentary rocks and 0.004% is stored in fossil fuels.

  Atmosphere: 0.001%

  Hydrosphere: 0.04%

  Biosphere: 0.004%

  Cyrosphere: 0.1%
• Flows #1: carbon cycle

  Photosynthesis: carbon stored in the atmosphere to biomass. Carbon dioxide and water into glucose and oxygen. Carbon passed through the food chain and released through respiration and decomposition.

  Combustion: carbon stored in biomass to the atmosphere through burning. Wildfires cause carbon flow.

  Ocean uptake and loss: CO2 dissolved directly from the atmosphere to oceans and then taken up by organisms (Plankton). Also transferred from ocean to atmosphere when carbon rich water rises and releases CO2.
• Flows #2: carbon cycle


  Sequestration: carbon is captured and held in sedimentary rocks or as fossil fuels. Dead fauna and flora fall to the ocean floor and is compacted. Sequestered until it is burnt.

  Weathering: chemical weathering transfers carbon from the atmosphere to the hydro and biosphere. Atmospheric carbon reacts with water vapour to form acid rain and dissolves rock when it falls. Molecules may be washed to the sea and react with CO2 to from calcium carbonate, used by sea creatures.
• Carbon budget


  The difference between the inputs in a subsystem and outputs of carbon. The balance determines whether it acts as a carbon sources (releases more carbon) or a carbon sink (absorbs more carbon).
• Positive feedback in the water cycle

  Temperatures rises, evaporation increases, amount of water vapour in atmosphere increases, and greenhouse gases.
• Negative feedback in the water cycle

  Temperature rises, evaporation increases, amount of water vapour in atmosphere increases causing more cloud cover, increased cloud cover reflects more of sun's energy back to space, and temperatures fall.
• Positive feedback in the carbon cycle

  Temps rise, plant respiration increases, amount of CO2 in the atmosphere increases, and the greenhouse effect increases.
• Negative feedback in the carbon cycle

  CO2 in the atmosphere increases, extra CO2 causes plants to increase growth, plants remove and store more CO2 from atmosphere, and amount of CO2 reduces in the atmosphere.
• Humans trying to influence the carbon cycle

  There is now more than 40% atmospheric carbon than in 1750.

  The Intergovernmental Panel on Climate Change set up by the UN and states that countries need to reduce CO2 emitted by human activities.
• Amazon rainforest 


  Covers 40% of the South American landmass,

  Up to 1 million plant species, over 500 mammal species, and over 2000 species of fish.
• Amazon rainforest: water cycle

  • Wet air blown from the Atlantic towards the Amazon. High evaporation which increases precipitation
  • Dense canopy so interception is high, less water in rivers as it flows more slowly
  • Species adapted to high humidity and frequent rainfall
• Amazon rainforest: Carbon cycle

  • Vegetation and soils store carbon, a carbon sink
  • Increasing CO2 has led to increasing productivity such as photosynthesis and respiration- increase in biomass
  • Sequestration increases, more important as a carbon store
  • Trees growing more quickly, but dying younger- may not be as an effective carbon sink in future
• Attempts to limit human factors in the rainforest #1

  Selective logging: less damaging as it only fells some trees and the forest structure is kept.

  Canopy remains and soil isn't exposed, means regenerative forests
• Limits on the rainforest #2


  Replanting: a project in Peru replanted over 115 acres of forest between 2016 and 2019.

  Same tree type needs to be replanted, so variety of trees is kept

  Carbon and water cycle returns to dynamic equilibrium
• Limits on rainforest #3

  Environmental law: band excessive logging and control land use

  e.g. the Brazilian Forest Code says that landowners have to keep 50-80% of their land as forest.
• Limits on rainforest #4:

  Protection: national parks and nature reserves set up e.g. Central Amazon Conservation Complex was set up in 2003 Brazil and protects biodiversity in an area of 49 000km^2 while allowing local people to use forests in sustainable ways