Water renewal time
The water renewal time , also called dwell time , dwell time or water exchange time , describes in hydrology the time in which the entire body of water in a stagnant body of water is theoretically exchanged once by inflowing and outflowing water. It is calculated as the quotient of the mean volume and the mean discharge . The values range from a few days for lakes with a strong flow to many years for bodies of water without runoff. Waters with a residence time of less than three days are considered flowing waters. In practice, however, the water exchange does not take place homogeneously: The exchange of substances that sink into the hypolimnion (e.g. phosphorus in the form of biomass) is therefore much slower than the theoretical renewal rate would suggest.
For example, the water renewal time shows how quickly a lake recovers from pollution. A long water renewal period promotes the warming of the water in summer.
Examples
- Almsee : 10 days
- Hallstätter See : 6 months
- Traunsee : 1 year
- Lake Constance : 4.5 years
- Starnberger See : 21 years
- Pulvermaar : 70 years
- Lake Tahoe : 650 years
Individual evidence
- ↑ Federal Office for Water Management (Hrsg.): Atlas of the natural lakes of Austria with an area ≥ 50 ha. Morphometry - Typing - Trophy. As of 2005. Series of publications by the Federal Office for Water Management, Volume 29, Vienna 2008, p. 9 ( PDF; 9 MB )
- ↑ Pulvermaar , Seenatlas, State Office for the Environment Rhineland-Palatinate