Lake retention time Totally Explained

Everything about Lake Retention Time totally explained

Lake retention time (also called the residence time of lake water, or the water age or flushing time) is a calculated quantity expressing the mean time that water (or some dissolved substance) spends in a particular lake. 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 where pollutants 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 all tributaries, or by the mean rate of outflow (ideally including evaporation and seepage). 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.

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 (for example particular arms), or a residence time distribution for the various layers of a stratified lake. These figures can often better express the hydrodynamics 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 an Eulerian 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	0000000.000 0.13 days
Lake Hévíz	Hévíz	Hungary	0000000.003 1 day (?)
Lake Wohlen	Canton of Berne	Switzerland	0000000.006 2.1 days
Lake St. Clair		Canada, United States	0000000.019 7 days (2-30 days)
Lake Arapuni	North Island	New Zealand	0000000.019 1 week
Råcksta Träsk		Sweden	0000000.048 2-3 weeks
Lake Cristallina	Ticino	Switzerland	0000000.058 2-4 weeks
Prospect reservoir	Prospect, New South Wales	Australia	0000000.096 30-40 days
Sicklasjön		Sweden	0000000.100 0.1 year
Devils Lake	Lincoln County, Oregon	United States	0000000.150 .15 years
Lough Derg		Ireland	0000000.150 0.15 years
Lake Biel		Switzerland	0000000.159 58 days
Hacksjön		Sweden	0000000.200 0.2 years
Kamloops Lake	British Columbia	Canada	0000000.200 ca. 0.2 years (20-340 days)
Laduviken		Sweden	0000000.250 3 months
Trehörningen		Sweden	0000000.270 0.27 years
Lake Lesina	Province of Foggia, Puglia	Italy	0000000.274 100 days (summer 306 days, winter 31 days)
Hüttnersee	Hütten, Canton of Zurich	Switzerland	0000000.329 120 days
Lake Lauerz	Canton of Schwyz	Switzerland	0000000.338 0.3378 years
Sobradinho		Brazil	0000000.350 0.35 years
Magelungen		Sweden	0000000.375 4-5 months
Lappkärret		Sweden	0000000.417 5 months
Mettmenhaslisee	Canton of Zurich	Switzerland	0000000.493 180 days
Egelsee	Bubikon, Canton of Zurich	Switzerland	0000000.493 180 days
Lac de Vouglans		France	0000000.493 180 days
Clinton Lake	DeWitt County, Illinois	United States	0000000.500 6 months
Lake Coeur d'Alene	Northern Idaho	United States	0000000.500 0.5 years
Kyrksjön		Sweden	0000000.583 7 months
Faaker See	Carinthia	Austria	0000000.650 7.8 months
Lake Silvaplana		Switzerland	0000000.685 c. 250 days
Långsjön		Sweden	0000000.792 9-10 months
Lake Sarnen		Switzerland	0000000.800 0.8 years
Lake Lovozero	Kola Peninsula, Murmansk Oblast	Russia	0000000.833 10 months
Drevviken		Sweden	0000000.875 10-11 months
Judarn		Sweden	0000000.917 11 months
Khanka Lake	Heilongjiang Province,China and Primorsky Krai, Russia	China, Russia	0000001.000 1 year
Greifensee		Switzerland	0000001.118 408 days
Lake Zurich		Switzerland	0000001.205 440 days
Tegernsee	Bavaria, Germany	Germany	0000001.280 1.28 years
Deer Creek Reservoir	Utah	United States	0000001.300 1.3 year
Lake Walen		Switzerland	0000001.426 1.4258 years
Lake Murten		Switzerland	0000001.600 1.6 years
Oeschinen Lake	Bernese Oberland	Switzerland	0000001.610 1.61 years
Ältasjön		Sweden	0000001.800 1.8 years
Long Lost Lake	Clearwater County, Minnesota	United States	0000001.800 1.8 years
Lake Thun	Canton of Berne	Switzerland	0000001.874 684 days
Gömmaren		Sweden	0000001.900 1.9 years
Loch Lomond		Scotland	0000001.900 1.9 years
Türlersee		Switzerland	0000002.000 730 days
Lake Tutira	Hawke's Bay	New Zealand	0000002.000 2 years
Pfäffikersee		Switzerland	0000002.085 2.085 years
Wilersee	Canton of Zug	Switzerland	0000002.200 2.2 years
Lake Sils		Switzerland	0000002.200 2.2 years
Päijänne		Finland	0000002.500 2.5 years
Lake Erie		Canada, United States	0000002.600 2.6 years
Lake Brienz	Canton of Berne	Switzerland	0000002.690 2.69 years
Ammersee	Upper Bavaria	Germany	0000002.700 2.7 years
Trekanten		Sweden	0000003.100 3.1 years
Lake Champlain		Canada, United States	0000003.300 3.3 years
Lake Lucerne		Switzerland	0000003.400 3.4 years
Flathead Lake	Montana	United States	0000003.400 3.4 years
Lake Hallwil	Aargau	Switzerland	0000003.900 3.9 years
Flaten		Sweden	0000004.000 4 years
Lake Annecy		France	0000004.000 4 years
Lake Maggiore	Italy, Switzerland	Italy, Switzerland	0000004.000 4 years
Lake Baldegg		Switzerland	0000004.200 4.2 years
Lake Constance	Germany, Switzerland, Austria	Germany, Switzerland, Austria, Liechtenstein	0000004.300 4.3 years
Corey Lake	Michigan	United States	0000004.400 4.4 years
Lake Como	Northern Italy	Italy, Switzerland	0000004.500 4.5 years
Sea of Galilee		Israel	0000005.000 5 years
Sebago Lake	Cumberland County, Maine	United States	0000005.250 5.1 to 5.4 years
Bay Lake	Crow Wing County, Minnesota	United States	0000005.500 4-7 years
Lago di Mergozzo	Piedmont	Italy	0000006.000 6 years
Lake Ontario		Canada, United States	0000006.000 6 years
Lago di Candia	Province of Turin	Italy	0000006.500 6 or 7 years
Lac La Nonne	Alberta	Canada	0000006.500 6.5 years
Ägerisee	Canton of Zug	Switzerland	0000006.800 6.8 years
Moose Lake	Alberta	Canada	0000007.500 7.5 years
Millstätter See	Carinthia	Austria	0000007.500 7.5 years
Lake Lugano	Ticino, Lombardy	Switzerland, Italy	0000008.200 8.2 years
Lake Neuchâtel		Switzerland	0000008.200 8.2 years
Lake Orta	Piedmont	Italy	0000008.900 8.9 years
Quesnel Lake	British Columbia	Canada	0000010.100 10.1 years
Lake Taupo	North Island, New Zealand	New Zealand	0000010.500 10.5 years
Wörthersee	west of Klagenfurt	Austria	0000010.500 10.5 years
Lake Chelan	Washington, USA	United States	0000010.600 10.6 years
Lake Geneva		Switzerland, France	0000011.400 11.4 years
Lake Wakatipu	South Island	New Zealand	0000012.000 c. 12 years
Higgins Lake	Michigan	United States	0000012.500 12.5 years
Lake Zug		Switzerland	0000014.700 14.7 years
Lake Sempach		Switzerland	0000016.900 16.9 years
Skaneateles Lake		United States	0000018.000 18 years
Cayuga Lake		United States	0000018.200 18.2 years
Bear Lake	Idaho/Utah	United States	0000019.600 19.6 years
Lake Huron		Canada, United States	0000022.000 22 years
Lake Garda	Northern Italy	Italy	0000026.800 26.8 years
Crystal Lake	Benzie County, Michigan	United States	0000045.000 30 to 60 years
Okanagan Lake	British Columbia	Canada	0000052.800 52.8 years
Lake Ohrid		the Republic of Macedonia, Albania	0000070.000 70 years
Lake Michigan		United States	0000099.000 99 years
Clinton Lake	Douglas County, Kansas	United States	0000100.000 100 years
Arendsee	Saxony-Anhalt	Germany	0000100.000 100 years
Gull Lake	Alberta	Canada	0000101.000 >100 years
Crater Lake	Oregon	United States	0000157.000 157 years
Lake Superior		Canada, United States	0000191.000 191 years
Caspian Sea		Azerbaijan, Iran, Kazakhstan, Russia, Turkmenistan	0000250.000 250 years
Lake Baikal		Russia	0000350.000 350 years
Lake Tahoe	California, Nevada	United States	0000650.000 650 years
Lakes Qaban		Russia	0002000.000 several thousand years
Lake Poyang		People's Republic of China	0005000.000 5,000 years
Lake Vostok		(Antarctica)	1000000.000 1,000,000 years

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