The water cycle

• What % of Earth's surface is water? 

  72%
• whats the distribution of water?

  97% oceans, 3% freshwater

  79% ice and glacier, 20% groundwater, 1% easily accessible

  52% lakes, 38% soil moisturE, 1% living organism, 1% rivers, 8% water vapour
• What is the cryosphere? Where can water be stored? Recall the five cryospheric water stores. Locations?

  Where water is 'locked up' and frozen into snow or ice. Ice sheets; ice caps; alpine glaciers; sea ice; permafrost. 
• What is the impact if ice sheets melt?

  66+m sea level rise
• Hydrosphere?

  A discontinuous layer of water at or near the Earth's surface. 
• Lithosphere?

  The solid outer layer of Earth, consisting of the crust, the outermost layer of the mantle (asthenosphere) and soil (pedosphere). 
• Atmosphere?

  A layer of gases that surround Earth. 
• Biosphere?

  Total sum of all living matter
• Cloud formation:

  1. water evaporates from the earths surface due to solar energy heating it up
  2. it cools and condenses once it rises to form water droplets and ice crystals
  3. due to the presence of hygroscopic materials like dust and salt, a cloud droplet forms
  4. once there is too much water vapour for the air to hold, it precipitates
  5. warm air holds more moisture
• Precipitation?Types?

  Mositure that forms in the atmosphere and falls to the Earth. 

  Relief- warm air rises and is pushed up by a barrier like a mountain, it cools and condenses at higher altitudes and it precipitates

  Convectional - warm air rises and cools and condenses at higher altitudes (dew point)

  Frontal- different air masses of different temperatures and densities meet, the warm less dense air rises above the cooler sinking air where it cools and condenses at higher altitudes and then it precipitates
• Factors that influence precipitation?

  Solar energy; availablity of water; temperature; humdity; altitude; relief. 
• What is ablation? What is accumulation? What is sublimation? 

  Ablation: Loss of ice mass

  Accumulation: Build up of ice mass

  Sublimation: Ice directly changing into water vapour
• What factors influence the rate of evaporation?

  Solar energy; availablity of water; wind speedl temperature; humdity; albedo. 
• What is latent heat? 

  Energy absorbed or released by a substance during a change in its physical state. 
• What is a drainage basin? What type of system?

  A single river basin bounded by its own watershed and the sea. Open system
• Recall three stores within the drainage basin system. 

  Interception; vegetation; surface; soil; groundwater. 
• Define infiltration. What factors can affect the rate?

  Downwards movement of water from the surface into the soil. Influenced by soil porosity and gravity
• Define percolation. 

  Downwards movement of water within rock, under the soil surface. 
• What is groundwater flow?

  The slow movemnet of water through underlying rocks. 
• What is overland flow?

  The tendency of water to flow horizontally across the surface when rainfall has exceeded infiltration capacity. 
• What is stemflow?

  Precipitation that reaches the ground through flowing down stems or stalks of vegetation. 
• What is throughfall?

  Precipitation that reaches the ground directly through gaps in the vegetation e.g., leaves, twigs and stems. 
• What is interception? How may this vary? Precipitation that falls on vegetated surfaces and is temporarily stored. 

  hardwood tropical trees can store 58% of water however needle leaf trees for example in Oregon, USA only temporarily store 22%
• What is throughflow? What factors can affect the rate? The movement of water down-slope through the subsoil under the influence of gravity. 
• What is the water balance?

  The long-term balance between the inputs and outputs in the drainage basin system. 
• What is potential evapotranspiration? The amount of water that could be evaporated or transpired from an area, if there was sufficient water available. 
• What is a storm hydrograph? What are the key components? A graph of discharge of a river over the time period when then normal flow of the river is affected by a storm event. 
• Define lag time. 

  The difference in time between peak rainfall and peak discharge (peak of flood). 
• What is discharge? How is it measured? Movement of water in a channel. 
• Recall three physical factors that can impact a hydrograph. Gradient; precipitation (antecedent, type, quantity and intensity); tributaries; confluence; basin size and shape; soil saturation
• Recall three human factors that can impact a hydrograph.

  Impermeable ground; drainage density (sewerage); floodplain development; management; deforestation.
• What is the differene between an urban and rural hydrograph?Generally, urban storm hydrographs respond to the event in a 'flashy' manner, but rural areas respond 'slowly'. 
• Why is there reduced interception in winter?

  Deciduous trees lose their leaves. 
• What is a river regime?The variability in discharge throughout the course of a year. Recall three factors that impact a rivers regime. Climate; vegetation coverage; land use; precipitation; soil; geology. 
• How can urbanisation impact the hydrological cycle?

  Decreased vegetated surfaces (interception and infiltration); increased impermeable surfaces (overland flow and runoff)
• What is water abstraction? 

  Removal of water resources from stores e.g., rivers, lakes and groundwater.