- Lake retention time
Lake retention time (also called the
residence time of lake water, or the water age or flushing time) is a calculated quantity expressing themean time that water (or some dissolved substance) spends in a particularlake . At its simplest this figure is the result of dividing the lake volume by the flow in or out of the lake. It roughly expresses the amount of time taken for a substance introduced into a lake to flow out of it again. The retention time is especially important wherepollutant s are concerned.Global retention time
The global retention time for a lake (the overall mean time that water spends in the lake) is calculated by dividing the lake
volume by either the mean rate of inflow of alltributaries , or by the mean rate of outflow (ideally includingevaporation andseepage ). This metric assumes that water in the lake is well-mixed (rather than stratified), so that any portion of the lake water is much like any other. In reality, larger and deeper lakes are generally not well-mixed. Many large lakes can be divided into distinct portions with only limited flow between them. Deep lakes are generally stratified, with deeper water mixing infrequently with surface water. These are often better modeled as several distinct sub-volumes of water.Citation| url=http://www.hydromod.de/Eurolakes/results/D24.pdf| title=D24: Realistic Residence Times Studies| first=Kurt| last=Duwe| date = 2003-01-03 | series = Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas | publisher = EUROLAKES | accessdate = 2007-12-11]More specific residence times
It is possible to calculate more specific residence time figures for a particular lake, such as individual residence times for sub-volumes (e.g. particular arms), or a
residence time distribution for the various layers of a stratified lake. These figures can often better express thehydrodynamics of the lake. However, any such approach remains a simplification and must be guided by an understanding of the processes operating in the lake.Two approaches can be used (often in combination) to elucidate how a particular lake works: field measurements and mathematical modeling. One common technique for field measurement is to introduce a tracer into the lake and monitor its movement. This can be a solid tracer, such as a float constructed to be neutrally buoyant within a particular water layer, or sometimes a liquid. This approach is sometimes referred to as using a
Lagrangian reference frame . Another field measurement approach, using anEulerian reference frame , is to capture various properties of the lake water (including mass movement, water temperature,electrical conductivity and levels of dissolved substances, typically oxygen) at various fixed positions in the lake. From these can be constructed an understanding of the dominant processes operating in the various parts of the lake and their range and duration.Field measurements alone are usually not a reliable basis for generating residence times, mainly because they necessarily represent a small subset of locations and conditions. Therefore the measurements are generally used as the input for numerical models. In theory it would be possible to integrate a system of hydrodynamic equations with variable boundary conditions over a very long period sufficient for inflowing water particles to exit the lake. One could then calculate the traveling times of the particles using a Lagrangian method. However, this approach exceeds the detail available in current hydrodynamic models and the capacity of current computer resources. Instead, residence time models developed for gas and
fluid dynamics ,chemical engineering , and bio-hydrodynamics can be adapted to generate residence times for sub-volumes of lakes.List of residence times of lake water
"The residence time listed is taken from the infobox in the associated article."
Lake Location Basin countries Residence time Klingnauer Stausee Aargau Switzerland 0.13 days Lake Hévíz Hévíz Hungary 1 day (?) Lake Wohlen Canton of Berne Switzerland 2.1 days Lake St. Clair Canada, United States 7 days (2-30 days) Lake Arapuni North Island New Zealand 1 week Råcksta Träsk Sweden 2-3 weeks Lake Cristallina Ticino Switzerland 2-4 weeks Prospect reservoir Prospect, New South Wales Australia 30-40 days Sicklasjön Sweden 0.1 year Devils Lake Lincoln County, Oregon United States .15 years Lough Derg Ireland 0.15 years Lake Biel Switzerland 58 days Hacksjön Sweden 0.2 years Kamloops Lake British Columbia Canada ca. 0.2 years (20-340 days) Laduviken Sweden 3 months Trehörningen Sweden 0.27 years Lake Lesina Province of Foggia ,Puglia Italy 100 days (summer 306 days, winter 31 days) Hüttnersee Hütten, Canton of Zurich Switzerland 120 days Lake Lauerz Canton of Schwyz Switzerland 0.3378 years Sobradinho Brazil 0.35 years Magelungen Sweden 4-5 months Lappkärret Sweden 5 months Mettmenhaslisee Canton of Zurich Switzerland 180 days Egelsee Bubikon ,Canton of Zurich Switzerland 180 days Lac de Vouglans France 180 days Clinton Lake DeWitt County, Illinois United States 6 months Lake Coeur d'Alene Northern Idaho United States 0.5 years Kyrksjön Sweden 7 months Lake Silvaplana Switzerland c. 250 days Långsjön Sweden 9-10 months Lake Sarnen Switzerland 0.8 years Lake Lovozero Kola Peninsula ,Murmansk Oblast Russia 10 months Drevviken Sweden 10-11 months Judarn Sweden 11 months Khanka Lake Heilongjiang Province ,China andPrimorsky Krai ,Russia China, Russia 1 year Greifensee Switzerland 408 days Lake Zurich Switzerland 440 days Tegernsee Bavaria, Germany Germany 1.28 years Deer Creek Reservoir Utah United States 1.3 year Lake Walen Switzerland 1.4258 years Lake Murten Switzerland 1.6 years Oeschinen Lake Bernese Oberland Switzerland 1.61 years Ältasjön Sweden 1.8 years Faaker See Carinthia Austria 1.8 vears Lake Ossiach Carinthia Austria 1.8 vears Long Lost Lake Clearwater County, Minnesota United States 1.8 years Lake Thun Canton of Berne Switzerland 684 days Gömmaren Sweden 1.9 years Loch Lomond Scotland 1.9 years Türlersee Switzerland 730 days Lake Tutira Hawke's Bay New Zealand 2 years Pfäffikersee Switzerland 2.085 years Wilersee Canton of Zug Switzerland 2.2 years Lake Sils Switzerland 2.2 years Päijänne Finland 2.5 years Lake Erie Canada, United States 2.6 years Lake Brienz Canton of Berne Switzerland 2.69 years Ammersee Upper Bavaria Germany 2.7 years Trekanten Sweden 3.1 years Lake Champlain Canada, United States 3.3 years Lake Lucerne Switzerland 3.4 years Flathead Lake Montana United States 3.4 years Lake Hallwil Aargau Switzerland 3.9 years Flaten Sweden 4 years Lake Annecy France 4 years Lake Maggiore Italy, Switzerland Italy, Switzerland 4 years Lake Baldegg Switzerland 4.2 years Lake Constance Germany ,Switzerland ,Austria Germany, Switzerland, Austria, Liechtenstein 4.3 years Corey Lake Michigan United States 4.4 years Lake Como Northern Italy Italy, Switzerland 4.5 years Sea of Galilee Israel 5 years Sebago Lake Cumberland County, Maine United States 5.1 to 5.4 years Bay Lake Crow Wing County, Minnesota United States 4-7 years Lago di Mergozzo Piedmont Italy 6 years Lake Ontario Canada, United States 6 years Lago di Candia Province of Turin Italy 6 or 7 years Lac La Nonne Alberta Canada 6.5 years Ägerisee Canton of Zug Switzerland 6.8 years Moose Lake Alberta Canada 7.5 years Millstätter See Carinthia Austria 7.5 years Lake Lugano Ticino ,Lombardy Switzerland, Italy 8.2 years Lake Neuchâtel Switzerland 8.2 years Lake Orta Piedmont Italy 8.9 years Weissensee Carinthia Austria 9.2 years Quesnel Lake British Columbia Canada 10.1 years Lake Taupo North Island , New ZealandNew Zealand 10.5 years Wörthersee Carinthia Austria 10.5 years Lake Chelan Washington , USAUnited States 10.6 years Lake Geneva Switzerland, France 11.4 years Lake Wakatipu South Island New Zealand c. 12 years Higgins Lake Michigan United States 12.5 years Lake Zug Switzerland 14.7 years Lake Sempach Switzerland 16.9 years Skaneateles Lake United States 18 years Cayuga Lake United States 18.2 years Bear Lake Idaho /Utah United States 19.6 years Lake Huron Canada, United States 22 years Lake Garda Northern Italy Italy 26.8 years Crystal Lake Benzie County, Michigan United States 30 to 60 years Okanagan Lake British Columbia Canada 52.8 years Lake Ohrid the Republic of Macedonia,
Albania70 years Lake Michigan United States 99 years Clinton Lake Douglas County, Kansas United States 100 years Arendsee Saxony-Anhalt Germany 100 years Gull Lake Alberta Canada >100 years Crater Lake Oregon United States 157 years Lake Superior Canada, United States 191 years Caspian Sea Azerbaijan, Iran, Kazakhstan, Russia, Turkmenistan 250 years Lake Baikal Russia 350 years Lake Tahoe California ,Nevada United States 650 years Lakes Qaban Russia several thousand years Lake Poyang People's Republic of China 5,000 years Lake Vostok (Antarctica) 1,000,000 years References
ee also
*
External links
* [http://www.epa.gov/glnpo/atlas/gl-fact1.html EPA's Great Lakes Factsheet #1]
* [http://www.epa.gov/glnpo/atlas/index.html EPA's Great Lakes Atlas]
* - relationship between residence time of lakes of New Zealand andkoaro ,smelt andcommon bully populations.
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