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2.1. What is a Watershed?
Everyone in Nova Scotia lives in
a watershed. A watershed is an area of land that is drained
by a particular river or stream or other body of water. Some
people call watersheds river basins. You may not live anywhere
near a stream but you most definitely live in a watershed area. |
For most of
us, water is something we take for granted. When we turn on
our taps it is there and after we use it, it disappears mysteriously.
We swim in it, we drink it, we bathe in it, and cook with it,
but rarely do we understand where the water has come from and
where it goes. Water is not only useful to us, but also necessary
for our survival.
More and more of late we have come to realize that we need to
take more care with this precious supply of fresh water. In
order to do that we must understand how water systems are interconnected
within the watershed system.
Much of the watershed is invisible to you because it lies beneath
the earth's surface. The part of a watershed you can see is
the land on which snow and rain fall and the places where surface
water collects. In the soil and rock, underground water flows
through channels following the slope of the ground or bedrock.
Sometimes this water comes to the surface in springs and seeps,
and bubbles up to become a streambed. |
WATER FACTS
-A healthy human can go without food for a month, but will die
in less than a week without fresh water.
-Although we always seem to have an endless supply of water,
97% of the earth's water is seawater.
-If all of the earth's water could fit into a gallon jug, only
a tablespoon of it would be fresh or 1 % of the earth's water
supply.
-Another 2% of the earth's water is contained in glaciers and
ice-caps.
-Two-thirds of the world's fresh water is found beneath the
ground.
-In Canada, there's 37 times more groundwater than surface water.
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Stream drainage
follows the lowest areas of land, so watersheds drain from
a high point in the land to a lower point in the land or to
the sea. In the Cape Breton Highlands you can stand on a ridge
in the middle of two watersheds - one river on one side drains
eventually into the Gulf of St. Lawrence and the river on
the other side of the ridge drains into the Bras d'Or Lakes.
There are many cases in Nova Scotia were the headwater marshes
are shares by two watersheds. |
The size of a watershed can vary tremendously
depending on the lay of the land and the soil and rock conditions
of the area. Sometimes we may be talking about a small watershed
area connected by a small stream that flows to the coast.
Bigger rivers in our province, like the St. Mary's or Margaree
rivers, drain a much larger watershed area. A big watershed
area like the St. Mary's is really a collection of smaller
systems put together called sub-watersheds.
In Nova Scotia there are about 1200 watersheds emptying into
salt water. These small watersheds combine together to form
76 major watersheds in our province.
When the settlers first came to Nova Scotia they relied on
the watershed to give them much of what they needed to live.
Some First Nations even identified themselves with particular
river systems. These peoples understood that networks of brooks,
streams, rivers, and lakes were a special sort of community
to which they belonged and where all things were interconnected.
Today in our modern world we have lost this feeling of interconnectedness.
We sometimes forget that something that is done many miles
away from us can have a profound effect on the ecology of
our area. We think of water as coming from our taps, we don't
envision the huge surface and groundwater systems that connect
all flowing water together and from where all of our water
comes. |
SOME WATERSHED!
Some watersheds in other areas of Canada are huge.
The watershed of the Mackenzie River (Canada's largest river),
for example, contains seven provincial and territorial boundaries
and involves three provinces, two territories and the federal
government in its management. The water collected from this
huge area drains into the Beaufort Sea.
Surprising as it may seem, about 60% of Canada's freshwater
drains north into the Arctic Ocean and Hudson's Bay.
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As an example, water flows
differently over forested land than it does over cleared land
and paved roads. Imagine the effect of the paved cities, towns,
and highways on the flow of water and imagine what gets washed
into the water when it runs over all of our human-made world.
We will cover some of the impacts of this later but just as
one example, think of the impact of road salt on our water systems.
Each winter, tons of salt are put on our highways to help us
travel more safely. When the salt melts the snow and ice the
briny water flows into our streams and what is left washes in
with spring rains. Care is now taken in most areas to keep the
salt out of our wells and town water supplies. |
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