Water

• What is the Hydrosphere?

  A layer of water at or near the Earth's surface. It includes all liquid and frozen surface waters, groundwater held in soil & rock and atmospheric water vapour

  
• What is the Biosphere?

  The total sum of all living matter. The biological component of Earth systems (the others being atmosphere, hydrosphere and lithosphere)

  
• What is the Cryosphere?

  The cryosphere is the frozen water part of the Earth system. One part of the cryosphere is ice that is found in water. This includes frozen parts of the ocean, such as waters surrounding Antarctica and the Arctic

  
• What is the Atmosphere?

  The envelope of gases surrounding the Earth. Water can be found in the atmosphere mainly in the form of water vapour and some liquid water (cloud & rain droplets) and ice crystals

  
• What is the Lithosphere?

  The crust & uppermost mantle; this constitutes the hard & rigid outer layer of the Earth. It is this layer which is split into a number of tectonic plates

  
• What is Oceanic Water?

  The water contained in the Earth's oceans and seas but not including such inland areas such as the Caspian Sea
• What is Terrestrial Water?

  This consists of groundwater, soil moisture, lakes, wetlands and rivers
• Water on Earth:

  1. Water on the Earth's surface is the hydrosphere. Estimated = 1.338 x10^9 km3
  2. Approximately 97% is oceanic water
  3. Fresh water (the other 3%) is locked up inland in:

  • Cryosphere Water - inland ice, glaciers, & permafrost
  • Terrestrial Water - groundwater, lakes, soil, etc
  • Atmospheric Water

  
• Water on Earth:

  • 12,900km3 of water vapour are found in the atmosphere. This is only 0.4% of water but has huge effects on human life
  • The amount of water in these stores is in a constant state of dynamic equilibrium which changes diurnally (every 24 hours) and geologically (millions of years)
• Stats about Water Stores: (Oceanic Water)

  • Covers approx 72% of Earth Surface
  • Contains 97% of Earth's water
  • Salts in the Water allow it to stay liquid below 0C
  • Seas are alkaline but the pH is falling due to increased atmospheric carbon
• Stats about Water Stores: (Cryospheric Water)

  • Sea Ice: doesn't raise sea levels when it melts as its made from sea water
  • Ice Sheets: A mass of glacial land ice more than 50,000km2
  • Greenland & Antarctica contain 99% of freshwater
  • Alpine Glaciers: Thick layers of ice on land
  • Permafrost: When melted, releases CO2 & methane
• Stats about Water Stores: (Terrestrial Water)

  • Rivers: Store & transfer water
  • Lakes: Greater than 2 hectares, Majority in the Northern Hemisphere
  • Wetlands: Marsh areas, can support aquatic & terrestrial species
  • Soil Water: The exchange of water & heat energy between land surface & atmosphere
  • Biological Water: All water stored in biomass, depends on vegetation type
• Stats about Water Stores: (Atmospheric Water)

  • Most common is a gas (water vapour) which absorbs, reflects and scatters solar radiation
  • Increase in vapour means an increase in temperature
• What is the Water Cycle?

  • The continuous movement of water on, above & below the surface of the Earth
  • Closed system as there is a fixed amount of water on Earth
  • Changes state dependant on temperature
• Water Cycle:

  
• What is Evaporation?

  The process of turning water from liquid into vapour
• What is Evapotranspiration?

  The process by which water is transferred from the land to the atmosphere by evaporation from the soil & other surfaces and by transpiration from plants
• What is Transpiration?

  The exhalation of water vapour through the stomata
• What is Condensation?

  The conversion of a vapour or gas to a liquid
• What is Surface Runoff?

  The flow of water occurring on the ground surface
• What is Precipitation?

  Rain, snow, sleet, or hail that falls to or condenses on the ground
• What are the Inputs of the Water Cycle?

  Precipitation (rain, snow, sleet, hail)
• What are the Outputs of the Water Cycle?

  • Evaporation
  • Transpiration
  • Evapotranspiration
• What are the Stores of the Water Cycle?

  • Liquid Water (lakes, oceans, rivers)
  • Cryosphere (ice caps, glaciers)
  • Water in Biomass
• How do Clouds form?

  1. The atmosphere is full of gas particles known as water vapour. There are also tiny particles called aerosols (salts & dusts)
  2. Water vapour & aerosols bump into each other. When the air is cooled some of the water vapour sticks to the aerosols - this is condensation
  3. Warmer air holds more water vapour. Clouds form when air rises, becomes saturated & can't hold more water. Either amount of water in air has increased or air has cooled to dew point
  4. Water droplets group together, become heavy & fall as raindrops. If air is cold, ice crystals remain frozen & fall as snow
• Types of Rainfall: Frontal Rainfall

  1. Areas of warm & cool are blown towards each other
  2. The lighter, less dense air (warm) & is forced to rise over the denser cold air
  3. Frontal rain produces a variety of clouds, bringing mid/heavy rain

  
• Types of Rainfall: Relief Rainfall

  1. The prevailing winds picks up moisture by the sea
  2. Warm, moist air is forced to rise before cooling & condensing, forming clouds
  3. Air drops down over the mountain & warms. It increases the amount of water it can hold, meaning little rainfall occurs (rain-shadow effect)

  
• Types of Rainfall: Convectional Rainfall

  1. The surface of the Earth is heated by the Sun
  2. The warm air is heated by the surface. It rises, then cools & condenses
  3. Convection produces cumulonimbus clouds (heavy, dark, & towering storms) which produce heavy rain, thunder & lightning

  
• What forms does Water exist on Earth in?

  • Liquid Water
  • Solid Ice
  • Gaseous Water Vapour

  Energy (in the form of latent heat) is either absorbed or released depending on the process

  
• • Solid -> Liquid = melting
  • Solid <- Liquid = freezing
  • Liquid -> Gas = evaporation
  • Liquid <- Gas = condensation
  • Solid -> Gas = sublimation
  • Solid <- Gas = deposition

  
• Phases of Water: What causes Rate changes?

  • solar energy
  • availability of water
  • humidity of air (more humid = closer to saturation point = less evaporation)
  • temperature of air (warmer air can hold more water than cold air)
• What is Residence Times?

  The amount of water in a store / either the rate of addition of water to the store or the rate of loss from it
• Why does Soil have a low Residence Time? (4 reasons)

  1. Water in the Soil quickly percolates into bedrock
  2. Be transpired by plants into the atmosphere
  3. Transferred into rivers by throughflow
  4. Be evaporated into the atmosphere
• How do Cryospheric Processes affect the amount of water stored in Ice?

  • It fluctuates massively (ice ages & interglacial periods)
  • Short term: snow accumulates & adds to the mass of the glacier or ice sheet
  • Climate warming has led to ice stores shrinking. Example of Positive Feedback
  • As glaciers melt, sea levels rise which could destabilise ice shelves causing more calving & further melting
• What is the dew point?

  The temperature at which water vapour in the air turns into liquid water
• How does Condensation cause Precipitation?

  1. The temperature of the air is reduced to the dew point E.g. When cold winter's nights - heat radiates away from Earth - ground gets cooler
  2. When air rises it cools. As it cools it expands (adiabatic cooling) this can occur when air is forced over hills.

  • ^^ this is called the orographic effect
• What is a Drainage Basin?

  • The area that supplies a river with its supply of water. This includes water found below the water table as well as soil water & any surface flow.
  • They are cascading systems - a series of open systems that link together so the output of one is the input of the next
• Drainage Basin:

  
• Effect of Vegetation on the Drainage Basin:

  • Vegetation intercepts precipitation
  • Depends on species & density (i.e. needle-like leaves intercept 22% whereas the Tropical Rainforest intercepts 58%)
  • Thus lots of intercepted water is evaporated back into the atmosphere
  • Water can make its from tree leaves -> ground (called throughflow) or down the stems of plants (called stemflow)
• Ground of the Drainage Basin :

  • Water soaks into ground by infiltration, the rate of this process is the infiltration rate
  • Movement of water is controlled by gravity, capillary action & soil porosity (coarse, textured soils are most porous i.e. not rainforests)
  • Pores can be made larger by plant roots or burrowing worms
  • ^^ increases the amount of macro and micro channels in the soil