-->
More than 12 thousand years ago Europe and North America were
ice deserts. The woods, didn't rustle,
the rivers, didn't flow. Ice laid from the horizon to the horizon. Huge blocks
of ice, moving to the south, swept away everything on the way, pulled down the
mountains, moving titanic stones and ploughed deep hollows of the improbable
sizes. When the glacier receded, on its borders remained so-called moraines,
borders from stones, sand, gravel.
The
basin of the Great Lakes was formed at the time of ice age. When the glacier
started to thaw, behind these blockages in deepening where ice laid, the lakes
have arisen.
Now on the USA and Canada boundary are five big lakes,
connected with each other by the short rivers, forming together the biggest
congestion of fresh water on Earth. Lake Erie, lake Huron, lake Michigan, lake
Ontario, lake Superior. Common area of these lakes, are 246.000 km2.
When glaciers receded, lakes received a drain to the Atlantic Ocean through St.
Laurent’s river. On coast of these lakes situated the largest industrial port
cities of the USA and Canada. The basin of the Great Lakes – one of the largest
water catchment system on a planet; the pool contains 18 % of stocks of fresh
water. Due to very strong maintenance of this pool, by the USA and Canada,
pollution of surface and underground water has began. Oxygen level in the lakes
decrease considerably, the amount of mercury and various poisonous substances
exceeded limits and this became the reason of mass death of fishes.
The
biggest part of pollutants was dumped into the Great Lakes. Believing that the
ecological system of lakes is capable for self-recreation, throughout the 18th
and 19th centuries, lakes were often used as sewage, rubbish pits.
Especially clear such "destination" of the lake,
became noticeable with rapid growth of the industry and the population of the
cities. The polluted sewage water, corpses of the died animals rather often
were dumped to the river, it was distinctive feature of that time. People
didn't bare in mind that the river flows further and, respectively, along on a
river course, water already will be polluted or poisoned. This kind of
treatment of unique ecological system of the Great Lakes started to change in
the 20th century. Change in that relation happened due to the people who
realized and estimated importance of availability of pure fresh water and
understood, how water can influence health (rendering both positive, and a
negative effect). However, owing to rapid development of the industry and
negligent attitude of many people, polluted became not only the Great Lakes,
but also the adjacent rivers, and also inflows of lakes. On account of such
amount of pollutants, Lake Erie became practically "dead". But
already since the end of 1980 it was possible to reach reduction of volume of
toxic substances for 82 %, and in a consequence of it declared earlier «the
dead lake» became the world's largest area of production of a perch. But even
such large reduction didn't give completely desirable result. Toxic substances
arrived to these lakes together with sewage and acid rains in a very big
volume. It also became the reason that Canada was the first who signed the
Kyoto Protocol on regulation of emissions in the atmosphere of green house
gases for the industrial enterprises. But despite this according to experts,
the Great Lakes, which remain the main source of fresh water in Canada, could
face other environmental problems.
So, a global warming can cause reduction of lakes level on
1 m by the middle of the XXI century, what can lead to serious ecological
consequences. Shortage of water can raise the question about necessity of a
transfer of a part of a rivers drain or fencing of lake waters that creates
threat to steady use of water resources. Experts forecasted, that frequency of
large floods which occurred earlier to periodicity of 1 time in 500 years,
within the XXI century will increase in 10 times. Deficiency of water in the
USA and Canada already started. People in America for irrigation of the
territories were using underground waters. Reduction of underground water
stocks involves increase of water consumption from superficial sources what the
Great Lakes are, in particular. At the same time sharply growth of the cities
and an intensification of agriculture led to large-scale growth of excess of
pesticides, fertilizers, herbicides and other chemical preparations which in
turn a direct or indirect way get to the Great Lakes. In additives to it on
coast of lakes there are largest port cities as Chicago and Toronto. It is also
one of significant reasons of pollution of lakes, as large port always dense
populated and as we know the more people, the garbage they produce. Moreover,
during traffic of all boats and ships chance of leakage of petrol and others
combustible to these lakes is increase.
Deterioration of characteristic of water of lakes as a
result of activity of the human being, forced him to find a way of improvement
of lakes. In this sense the history of Great American Lakes is indicative. Its
condition have been improved as a result of the carried-out events, but it is
quite early to speak about good ecological condition of these lakes, as this
program are expected to continue for several decades.
We must take care of lakes, since they are
integral part of a landscape and live cell of nature. What beauty has given to
us by these lakes! And how much our
nature would paled if these lakes suddenly disappeared?!
