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Watersheds

Drainage basins


A watershed, or drainage basin, is a unit of land from which all water collected and stored is funnelled to drain into a body of water such as a lake or river. It takes many tiny drops of water flowing together to develop into a creek, then a larger stream, to ultimately fill a lake or form a major river, such as Canada’s largest, the Mackenzie River. A river functions as an organized network, including its own recharge area upstream, and drainage channel and mouth further downstream. In each individual watershed, water flows from high to low, from upstream to downstream. Ultimately a river or river system delivers that water back to the ocean.

  1. Drought – A drought is a normal, recurrent phenomenon which occurs when a region experiences a prolonged period of time of inadequate water supply, lasting from months to years, even decades. Most often drought is caused when precipitation amounts are far below average. Droughts can cause widespread and long-term damage to biodiversity and agricultural practices resulting in food shortages. Drought can also trigger mass human and animal migration. Prolonged drought in western Canada during the “Dirty 30s” caused widespread suffering and both agricultural and economic disaster.
  2. Flood - Like droughts, flood are a naturally occurring phenomenon. Flooding is a result of a temporary overflow of water that escapes its usual boundaries. While small-scale flooding occurs frequently along riverbanks or lakeshores, from time to time a significant flood happens as a result of a severe storm such as a hurricane in Canada’s Maritime region, or rapid melting of the winter snowpack. People living in a region threatened by flood will often take measures to hold the water back to protect their land, homes and businesses.
  3. Water shortages – A water shortage is the result of human demand exceeding available supply of potable water, often as a result of water over-allocation from a single source, or from excessive pollution of a water source required for human use.
  4. Internal or non-contributing drainage (endorheic) – Internal or non-contributing drainage basins are closed basins that retain water but do not drain via rivers or other outflow mechanisms, as normal basins do. Water contained in such a closed, or terminal basin only leaves that basin via evaporation or seepage, whereby the water flows through soil pores. The bottoms of these lakes are usually lined with dissolved salts that are left behind as the lake evaporates - salt pans. Saskatchewan’s spring-fed Little Manitou Lake is an example of an internal basin, with a salt content of 180 g/L that lets bathers float effortlessly.


Synopsis

This piece describes the impact of floods and droughts throughout Canadian history. Users can select from a menu of thumbnails, with each description supported by full-colour and black and white imagery.











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