EQ1 The Water Cycle and Water insecurity 3.3.19
EQ1; What are the processes operating within the hydrological cycle from global to local
scale?
The Hydrological Cycle
Characteristics of the hydrological cycle
- Closed system; fixed amount of water in the world (1385 million km3)
- Driven by solar energy and gravitation potential
- Solar energy – More evaporation occurs as the global climate warms; more moisture
in the atmosphere; increase condensation & precipitation.
- Gravitational potential energy – keeps water moving through the system (inputs,
outputs, stores and flows). For example: Ice age- water is kept in the cryosphere as
snow and ice. Climate change has melted that, increasing sea levels. Smaller scale =
human water storage (reservoirs)
Polar Hydrology
- Freeze thaw seasonal differences
- Winter snow insulates ground- leading to 85% of solar radiation reflected
- Permafrost = impermeable surfaces
- Lakes & rivers are frozen
- Limited vegetation = reduces heat absorption
- Spring and summer thaw saturates land leading to rapid runoff and increases
evaporation.
- Seasonal freeze thaw cycle release gases (caused by decayed plants) trapped in the
ice, into the atmosphere.
- It is characterised by orographic or frontal precipitation and low humidity
- Annual precipitation less than 200mm – precipitation = rainfall
Tropical rainforest Hydrology
- Few seasonal differences
- Dense vegetation absorbs 75% of precipitation
- 50-75% of precipitation then returns by evaporation
- evapotranspiration cools the air – evapotranspiration = evaporation by vegetation
- rainforests generate their own rain (constantly recycling the same water)
- Limited surface infiltration or groundwater
- Deforestation reduces evaporation, thus reduces vapour and local rainfall
- Constant high temperatures
- It is characterised by convectional rainfall and high humidity
- Annual precipitation more than 2000mm
Cryosphere = areas of the earth where water is frozen into snow or ice
Stores = Reservoirs where water is held like the ocean
Fluxes = rate of flow between stores
Blue water = water stored in rivers, lakes, groundwater, in liquid form and is a visible part of
the hydrological cycle.
Green water = water stored in soil and vegetation, invisible part of the hydrological cycle.
EQ1; What are the processes operating within the hydrological cycle from global to local
scale?
The Hydrological Cycle
Characteristics of the hydrological cycle
- Closed system; fixed amount of water in the world (1385 million km3)
- Driven by solar energy and gravitation potential
- Solar energy – More evaporation occurs as the global climate warms; more moisture
in the atmosphere; increase condensation & precipitation.
- Gravitational potential energy – keeps water moving through the system (inputs,
outputs, stores and flows). For example: Ice age- water is kept in the cryosphere as
snow and ice. Climate change has melted that, increasing sea levels. Smaller scale =
human water storage (reservoirs)
Polar Hydrology
- Freeze thaw seasonal differences
- Winter snow insulates ground- leading to 85% of solar radiation reflected
- Permafrost = impermeable surfaces
- Lakes & rivers are frozen
- Limited vegetation = reduces heat absorption
- Spring and summer thaw saturates land leading to rapid runoff and increases
evaporation.
- Seasonal freeze thaw cycle release gases (caused by decayed plants) trapped in the
ice, into the atmosphere.
- It is characterised by orographic or frontal precipitation and low humidity
- Annual precipitation less than 200mm – precipitation = rainfall
Tropical rainforest Hydrology
- Few seasonal differences
- Dense vegetation absorbs 75% of precipitation
- 50-75% of precipitation then returns by evaporation
- evapotranspiration cools the air – evapotranspiration = evaporation by vegetation
- rainforests generate their own rain (constantly recycling the same water)
- Limited surface infiltration or groundwater
- Deforestation reduces evaporation, thus reduces vapour and local rainfall
- Constant high temperatures
- It is characterised by convectional rainfall and high humidity
- Annual precipitation more than 2000mm
Cryosphere = areas of the earth where water is frozen into snow or ice
Stores = Reservoirs where water is held like the ocean
Fluxes = rate of flow between stores
Blue water = water stored in rivers, lakes, groundwater, in liquid form and is a visible part of
the hydrological cycle.
Green water = water stored in soil and vegetation, invisible part of the hydrological cycle.
