The Water Cycle

Water Distribution and Stores

• Surface water includes tundra, flat, treeless Arctic area with frozen subsoil, glacial areas and alpine areas;
• Tundra is located quite far North, especially around Greenland’s coast, throughout Russia, into Norway, Sweden and Finland. Northern Canada and the state of Alaska are both also predominantly tundra areas.
• Glacial areas would predominantly be Greenland in the Northern Hemisphere, and Antarctica in the Southern Hemisphere.
• Alpine areas are found in Western Canada, as well as the Himalayas in central Asia. In South America, the Andes are an example of Alpine, and it spreads into Chile. In Europe, there are the Alps, as well as some Alpine areas on the west coast of Norway.
• Groundwater can be divided into the major groundwater basin, and local/shallow aquifiers;
• Major groundwater basin is spread throughout North America, Northern India, East Europe, West Russia and some parts of West Asia like Saudi Arabia.
• Local/shallow aquifiers are predominantly found in Canada, as well as in Norway, Sweden and Finland.
• There are some in Africa such as Ghana and the Ivory Coast, South America and North-East Russia.
• Lakes are collections of fresh water in hollows on the land surface. Generally, they are classified as lakes if they are bigger than two hectares.
• If smaller than this, then it is a pond. Most lakes are found in the Northern hemisphere, at higher latitudes, like in North America and Canada. It is estimated that Canada has 31,752 lakes.
• There are also lakes in Northern Europe, Norway, Sweden, Finland and in central Africa like Lake Malawi. The largest lake is the Caspian Sea.
• Hydrosphere is a discontinuous layer of water at or near the Earth’s surface.
• It includes all liquid and frozen surface waters, groundwater held in soil and rock, and atmospheric water vapour.
• There are various forms/stores of water on the Earth. Collectively, all this water together is called the hydrosphere.
• It is estimated that around 97% of the hydrosphere is the oceanic water.
• The remaining 3% is fresh water, cryospheric water, terrestrial water and atmospheric water.

Cryospheric Water

• The cryosphere is where water is solid in snow or ice. It occurs when water has been subject to temperatures below -1⁰. The cryosphere makes up 1.7% of all the water on Earth.
• It is a very important component of the Earth’s hydrospheric system, as snow/ice reflects the Sun’s heat, which in turn helps to regulate the Earth’s temperature.
• Ice is a tightly bonded substance formed from water when temperatures go below the freezing point.
• Snow is precipitation of ice crystals. Ice can be found in liquid water, like in frozen parts of the ocean for example surrounding the Arctic and Antarctica or frozen lakes/rives normally in polar regions.
• Sea ice forms when oceanic temperatures drop below freezing. Glaciers are thick, land ice masses which form after a great amount of snowfall. When glaciers move into the ocean, they can become ice shelves or ice bergs.
• Cryospheric water is commonly found in the North Pole (Arctic) and the South Pole (Antarctica) and Greenland, which is just a thick ice sheet.

Terrestrial Water

• This is basically just water on the ground. It is split into various classes: surface water, ground water, soil water and biological water.
• Surface water is free-flowing water, including rivers, lakes and wetlands. Rivers are both a store and transfer of water.
• They hold 0.0002% of all water on Earth and include the Amazon River in South America. A lake is a collection of fresh water found in hollows on the land surface.
• In general, it is classed as a lake if it is over two hectares. If not, it is a pond. Canada is extremely abundant in lakes, with 31,752 of them. An example of a lake is the Caspian Sea on the boundary between Europe and Asia.
• Wetlands are areas of marsh, fen or peatland which have water covering the surface for certain periods of time. They tend to support a range of aquatic and terrestrial wildlife.
• Ground water collects in underground rock pores.
• For example, in the Kola Peninsula, North Russia, there is a store of hot, mineralised water 13km down.
• Soil water is held together with air in the upper unsaturated layers of the land. It affects the climate, flood control, erosion and water quality.
• Biological water encompasses any water stored in biomass, mainly vegetation. The store of biological water is affected by vegetation cover, as areas of dense rainforest will store more water than deserts.
• The process of transpiration results in a loss of water from biomass. Certain plants are adapted a store lots of water, more than others, such as the cactus which has many adaptational features that allow it to store lots of water due to its climate.

Atmospheric Water

• In the atmosphere, water can exist as solid, liquid or gas. About 0.001% of Earth’s water is stored in the atmosphere. Much of it is stored as clouds, visible masses of water droplets/ice crystals.
• There is also lots of water vapour in the atmosphere, which helps regulate temperature by absorbing, reflecting and scattering solar radiation. Major contributory processes the atmospheric water is evaporation (90%) and transpiration (10%).

Oceanic Water

• Around 96.5% of Earth’s total water is stored in the oceans. Covering 72% of the Earth’s surface, oceans have an average depth of 3,682m, and supply 90% of the water that evaporated into the hydrological cycle.
• The ocean water contains dissolved salts that make it saline – 35,000 ppm of salt.

Reservoir and Residence Times