# How is residence time calculated for a lake?

## How is residence time calculated for a lake?

residence time: Tr = V/I [T], a measure of the average time a molecule of water spends in a reservoir. The residence time defined for steady-state systems is equal to the reservoir volume divided by the inflow or outflow rate.

How long does water stay in a lake?

Storage in the water cycle

Reservoir Estimated residence time
Rivers weeks–months
Groundwater months–10,000 years
Glaciers 40–400 years
Lake 100 years

### Which lake has the longest residence time?

Africa’s Lake Tanganyika has the second longest water retention time….Lakes With the Oldest Water.

Rank 1 Lake Vostok Antarctica 13,300

Which Great lake has the shortest residence time?

Retention/replacement time of the Great Lakes (in years)*

Characteristic Retention/replacement time in years
Lake Superior 191
Lake Michigan 99
Lake Huron 22
Lake Erie 3

## What two factors determine the water residence time of a lake?

By definition, the residence time is the amount of material in the reservoir, divided by either the inflow or the outflow (they are equal when the reservoir is at equilibrium). If there are multiple inflows or outflows, then we use the sum of the outflows or inflows to determine the residence time.

What is residence time in water cycle?

The length of time water spends in the groundwater portion of the hydrologic cycle may be as little as days, or as much as 10,000 years or more. This is called “residence time.” For example: A raindrop may fall to the earth’s surface.

### How does a lake stay full?

For a lake to keep its water over time, it has to be replenished. The main way that water gets into reservoirs and man-made lakes is from the rivers and streams that were dammed to create them. Like man-made reservoirs and lakes, natural lakes may also be replenished by rivers and streams.

What is residence time in hydrology?

water cycle have different water residence times. Residence time is defined as the amount of water in a reservoir divided by either the rate of addition of water to the reservoir or the rate of loss from it. The oceans have a water residence time of 3,000 to 3,230 years;…

## How long does water stay in Lake Superior?

Each of the Great Lakes has a different retention time. Lake Superior’s retention time is much longer than the others: 194 years compared to just 75 years for Lake Huron, for example. Since the water mixes as it pours in and out, over the course of 194 years only half of the water in Lake Superior actually leaves.

What is a lake flushing time?

Lake residence time (also called the retention 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.

### Which Great lake has the longest retention time?

Lake Superior
Staff there used the example to explain how long water remains in Lake Superior. Its water retention/replacement rate is 191 years, by far the longest in the Great Lakes system. A later study pegged the retention time at closer to 173 years, but it’s still a big number.