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Where do rivers come from?

23 November 2010 No Comment

I always wondered as a child where do creeks begin and where do they end. Etobicoke creek, Humber River, Grand River – these are all rivers and creeks of my childhood, but I had no idea where the water was coming from or going to. It wasn’t until I started working at BC Hydro that I began to appreciate hydrology – the study of water movement throughout the Earth.

There are two important geographical features that determine how water makes its way into the oceans

  1. Continental Divide
  2. Drainage Basin

The Continental Divide

Have you ever wondered why the border between Alberta and British Columbia is not a straight line ?

The basis for the border is the Great Continental Divide, which is a series of highest peaks in the Rocky Mountain range that separates water that flows east and west. Mount Robson, the highest peak in the Canadian Rockies, is an example of a mountain on the Great Divide that lies on the border of BC-AB. When rain falls on Mount Robson, you can imagine that half of the rain flows west to the Pacific, and remainder flows east to the Arctic/Hudson Bay.

There are other continental divides in North America, which you can see in the map below.

Drainage Basin

Most of the precipitation that falls on the surface of the Earth travels from small creeks, into tributaries, into a main stem river, and finally into the ocean. The entire area of interconnected creeks, tributaries, and rivers is called the drainage basin.

Below are some of Canada’s most important economical and historical river basins:

Mackenzie River Basin

The Mackenzie River collects water from the river systems in Northern Alberta and the great lakes in North West Territories. I had a road trip from BC to AB in 2010 and was able to see the Athabasca Glacier, the starting point of the Athabasca River which ultimately drains in the Arctic Ocean via the Mackenzie River.

Fraser River Basin

The Fraser River is one of the most important river systems for the salmon fisheries in the Pacific Ocean. When salmon return to spawn in the Fraser River they enter at the mouth in Vancouver, and swim upstream to their place of birth in this drainage system. Hydroelectric generation is present on a number of river systems in BC (notably the Peace River and Columbia River), but there have never been any dams constructed on the main Fraser River for fear of environmental damage.

Adams River Salmon run in October 2010

Columbia River Basin

The Columbia River Basin is the most hydroelectrically system in the world. Mica. Revelstoke. Duncan. Grand Coulee.

Prior to many of these dams being constructed settlements in this basin often experienced destructive flooding from the snow packs melting in the spring.

St Lawrence River Basin

Endoheic Basins

Endoheic basins area the ares in the world that do not drain directly into the ocean. Typically an endoheic basin will have its own internal drainage system that is not connected to an ocean bound river. Streams in an endoheic basin collect sediments, deposit them to lower elevations, and the water finally evaporates. This is the reason why you have salt lakes. Two famous salt lakes include the Dead Sea in the Middle East and Salt Lake in the Great Basin.

Hopefully this post has helped you appreciate the complexity of the Earth’s hydrological cycle. Some rivers and creeks may seem small, insignificant at a microscopic level, but collectively these river systems are what makes life flourish in so many corners of the world!

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