Water

• Systems


  Composed of: Inputs - Where matter or energy is added to the system, Outputs - Where matter or energy leaves the system, Stores - Where matter or energy builds up in the system, Flows - Where matter or energy moves in the system, Boundaries - Limits to the system (e.g. watershed)
• Open systems


  Systems that receive inputs and transfer outputs of energy or matter with other systems
• Closed systems

  Systems where energy inputs equal outputs
• Dynamic equilibrium


  When inputs equal outputs despite changing conditions
• Positive feedback


  A chain of events that amplifies the impacts of the original event
• Negative feedback


  A chain of events that nullifies the impacts of the original event, leading to dynamic equilibrium
• On a local scale the carbon and water cycles are both open systems, but on a global scale, they are closed systems
• Each of these systems contains flows/transfers, inputs, outputs and stores/components
• Inputs in the local water cycle

  • Precipitation

  
• Outputs in the local water cycle

  • Evapotranspiration
  • Streamflow
• Stores in the local water cycle

  • Groundwater
  • Soil Water
  • Rivers
  • Interception
  • Surface
• Flows in the local water cycle

  • Infiltration
  • Percolation
  • Throughflow
  • Surface Runoff
  • Groundwater Flow
  • Streamflow
  • Stemflow
• Water balance


  Used to express the process of water storage and transfer in a drainage basin system using the formula: Precipitation = Total Runoff + Evapotranspiration +/- Storage

  
• Factors impacting the local water cycle

  • Deforestation
  • Storm Events
  • Seasonal Changes
  • Agriculture
  • Urbanisation
• The soil water budget shows the annual balance between inputs and outputs in the water cycle

  
• There is a surplus of water in the winter months, after recharge of soil water in autumn
• The stores are depleting when evapotranspiration is greater than precipitation, leading to a deficit of soil water
• Maximum storage of water in the soil is field capacity
• Areas where water can be stored globally

  • Hydrosphere
  • Lithosphere
  • Cryosphere
  • Atmosphere
• Aquifers


  Underground water stores that are unevenly distributed globally, with shallow aquifers storing water for up to 200 years and deeper fossil aquifers storing water for up to 10,000 years
• Glaciers


  May store water for 20-100 years, feeding lakes that store water for 50-100 years
• Seasonal snow cover and rivers

  Store water for 2-6 months
• Soil water


  Acts as a more temporary store, holding water for 1-2 months
• Natural processes impacting the water cycle over time

  • Seasonal Changes
• Human impacts on the water cycle

  • Farming Practices
  • Land Use Change
  • Water Abstraction
• Flood hydrograph


  Used to represent rainfall for the drainage basin of a river and the discharge of the same river on a graph

  
• Factors affecting whether a flood hydrograph is flashy or subdued

  • Pastoral Farming
  • Deforestation
  • High Rainfall Intensity
  • Antecedent Rainfall
  • Impermeable Underlying Geology
  • High Drainage Density

  
• The carbon cycle occurs on a local scale in a plant, or sere such as the lithosere, which is a vegetation succession that occurs on bare rock
• Transfers in the global carbon cycle

  • Photosynthesis
  • Respiration
  • Combustion
  • Decomposition
  • Diffusion
  • Weathering and Erosion
  • Burial and Compaction
  • Carbon Sequestration
• Main carbon stores globally

  • Marine Sediments and Sedimentary Rocks
  • Oceans
  • Fossil Fuel Deposits
  • Soil Organic Matter
  • Atmosphere
  • Terrestrial Plants
• Carbon return to soil

  1. Diffusion

  2. Weathering and Erosion

  3. Burial and Compaction

  4. Carbon Sequestration
• Diffusion


  The oceans can absorb CO2 from the atmosphere, but this harms aquatic life by causing coral bleaching
• Weathering and Erosion


  Rock particles broken down and transferred to the ocean, where the carbon is used by marine organisms to create shells
• Burial and Compaction


  Sea shell fragments become compacted over time to form limestone and organic matter may form fossil fuels
• Carbon Sequestration


  Transfer of carbon from the atmosphere and can be both natural and artificial
• Main Carbon Stores (In order of magnitude)

  • Marine Sediments and Sedimentary Rocks - Lithosphere - Long-term
  • Oceans - Hydrosphere - Dynamic
  • Fossil Fuel Deposits - Lithosphere - Long-term but currently dynamic
  • Soil Organic Matter - Lithosphere - Mid-term
  • Atmosphere - Dynamic
  • Terrestrial Plants - Biosphere - Mid-term but very dynamic
• The lithosphere is the main store of carbon, with global stores unevenly distributed
• The oceans are larger in the southern hemisphere, and storage in the biosphere mostly occurs on land. Terrestrial plant storage is focussed in the tropics and the northern hemisphere
• Natural Processes


  1. Wildfires: Transfer carbon from biosphere to atmosphere as CO2 is released through burning. Can encourage the growth of plants in the long term

  2. Volcanic Activity: Carbon stored within the earth is released during volcanic eruptions, mainly as CO2 gas
• Human Impacts


  1. Fossil Fuel Use - Combustion transfers CO2 to the atmosphere from a long-term carbon sink

  2. Deforestation - Often used to clear land for farming/housing, rapidly releases carbon stored in plants using slash and burn techniques and interrupting the forest carbon cycle

  3. Farming Practices - Arable farming releases CO2 as animals respire. Ploughing can release CO2 stored in the soil. Farm machinery such as tractors may release CO2