Land of lakes.

Canada has more lakes than any other country in the world; so many that we don't know exactly how many. If any body had an accurate count it should be Environment Canada. But, that federal department's website says only that: "There are an estimated two million lakes in Canada covering approximately 7.6% of Canada's land area." This is a much higher proportion of freshwater coverage than any other country. But, this abundance is a bit of an illusion. About 60 percent of Canada's fresh water drains north, while 85 percent of the population lives along the southern border with the United States.

Not surprisingly then, Canada is rich in fresh water. Our rivers discharge close to nine percent of the world's renewable water supply, while Canada has about half of one percent of the world's population.

Everybody knows about the Great Lakes; they make up the largest surface area of fresh water found in one place anywhere in the world. In addition, there are more than 31,000 freshwater lakes in Canada that are larger than three [km.sup.2] in area; about 560 are more than 100 [km.sup.2]. The official definition of a lake is: "Water bodies deep enough (greater than two metres) to contain water for long periods of time and to sustain fish during the winter by not freezing to the bottom." Then, of course, the boffins throw in an exception: "Some shallow water bodies, especially in the Arctic, are considered lakes simply because of their enormous surface area."

The major common factor is that lakes are bodies of fresh water: if the water is salty they become inland seas--Black Sea, Dead Sea.

Back to those boffins. People who study lakes have a fondness for jargon--words and phrases they use among themselves that the rest of us find a bit baffling. Here are a few:

* Allochthonous and autochthonous. Once a lake is formed it begins to fill up with sediments that will, eventually, cause the lake to disappear. Some of the sediment material comes by wind and erosion (allochthonous), and some from materials formed within the lake (autochthonous). As the sediments build up, marshes, meadows, and forests grow on what was once a lake. For the deepest lakes the process of filling with sediment takes millions of years to complete;

* Eutrophication. This describes concentration of nutrients, such as nitrogen or phosphorous, in a lake. When the concentrations are lowest the water is clear and is called oligotrophic. The grades march upwards through mesotrophic, eutrophic, to hypereutrophic. Slightly or moderately eutrophic water is good be cause it supports a complex web of plant and animal life. Hypereutrophic gives rise to masses of algae that consume oxygen leaving the water unable to support other life;

* Hydraulic retention time. This is the time required for all the water in a lake to pass through its outflow. The approximate retention times for the five Great Lakes are:

Lake Superior--191 years

Lake Michigan--99 years

Lake Huron--22 years

Lake Ontario--6 years

Lake Erie--2.6 years;

* Lentic. This word is applied to lakes because their waters are standing, or still, relative to rivers ("lotic" systems);

* Overturn. The sinking of surface water and rise of bottom water in a lake. This usually happens because of changes in air temperature in spring and fall, but can be the result of a storm. Lakes where this happens are called dimictic. In some lakes, called meromictic, the deepest water remains stagnant and never rises to the top;

* Thermal stratification.

Lake water nearest the surface is the warmest (in sum met anyway); this upper layer is called the epilimnion and the temperature is fairly uniform. The middle layer, or thermocline, is where there is a marked drop in temperature as you go deeper. The lowest level, or hypolimnion, is the coldest and, again, the temperature is fairly uniform.

There are a tonne more terms listed in a glossary at --http://www.nalms.org/ glossary/glossary.htm

Canadian provinces and territories
ranked by their freshwater surface area

Province /      Total area      Freshwater     % of juris-
 territory       (land +           area          diction
                  water)       ([km.sup.2])      covered
               ([km.sup.2])                     by fresh-
                                                  water

  Quebec        1,542,056        176,928           11.5
 Northwest      1,346,106        163,021           12.1
Territories
  Ontario       1,076,395        158,654           14.7
  Nunavut       2,093,190        157,077            7.5
 Manitoba         647,797         94,241           14.5
  Saskat-         651,036         59,366            9.1
  chewan
 Newfound-        405,212         31,340            7.7
   land
  British         944,735         19,549            2.1
 Columbia
  Alberta         661,848         19,531            2.9
   Yukon          482,443          8,052            1.7
   Nova            55,284          1,946            3.5
  Scotia
    New            72,908          1,458            2.0
 Brunswick
Prince Ed-          5,660            --             0.0
ward Island

Canada          9,984,670        891,163            8.9

Province /     % of total
 territory      Canadian
               freshwater
                  area

  Quebec          19.9
 Northwest        18.3
Territories
  Ontario         17.8
  Nunavut         17.5
 Manitoba         10.6
  Saskat-          6.7
  chewan
 Newfound-         3.5
   land
  British          2.2
 Columbia
  Alberta          2.2
   Yukon           0.9
   Nova            0.2
  Scotia
    New            0.2
 Brunswick
Prince Ed-        <0.1
ward Island

Canada           100.0

Source: Canada. Natural Resources Canada. The Atlas of Canada.
Facts About Canada: Land and Freshwater Areas, Ottawa,
1999.

FACT FILE

Freshwater lakes, rivers, and underground aquifers hold only 2,5% of the world's water, By comparison, saltwater oceans and seas contain 97.5% of the world's water supply.

FACT FILE

The most popular name for a lake in Canada is "Long"--there are 204 of them.