The Cottbuser Ostsee (Cottbus Eastern Lake; dsb|Chóśebuski pódzajtšny jazor) is an artificial lake under development on the grounds of the former open-pit lignite mine near Cottbus, Brandenburg, Germany.
| Cottbus Eastern Lake | |
| Location: | northeast of Cottbus, Brandenburg, Germany |
| Coordinates: | 51.786°N 14.417°W |
| Type: | flooded former open pit lignite mine |
| Part Of: | Lusatian Lake District |
| Inflow: | Hammergraben (Spree) |
| Date-Built: | end of mining start of flooding |
| Date-Flooded: | begin of flooding end of flooding (planned) |
| Area: | (planned) |
| Depth: | NaNm (-2,147,483,648feet) (planned) |
| Max-Depth: | (planned) |
| Volume: | (planned) |
| Elevation: | above Normalhöhennull (planned) |
| Pushpin Map: | Germany |
| Pushpin Map Alt: | Location of the lake in Germany. |
When complete, it is to cover a surface area of 19km², making it one of the biggest artificial lakes in the country.[1] At a maximum depth of 30m (100feet) and an average depth of between and 3m (10feet) the lake is to have a total water volume of once flooding is complete. Until the lake is complete, the biggest artificial lake in Germany by surface area (likewise created by conversion of a former lignite mine) is Geiseltalsee which covers some . However, the water volume of Geiseltalsee is almost three times larger at . For comparison, Germany's largest lake, Lake Constance, covers at a depth of up to and contains some of water. The largest reservoir (i.e. an artificial lake created via a dam) in Germany by surface area is Forggensee in Bavaria with a surface area of and a maximum water volume of . However, this lake is reduced to a "rump" of surface area in winter.
The lake covers what used to be the open pit lignite mine "Tagebau Cotbus Nord" which produced a total of of coal during its operation from 1981 to 2015. The last coal was mined in December 2015 and subsequently work began on converting the mine into a lake.Flooding started in 2019[2] [3] but had to be interrupted several times due to low water levels in the nearby Spree River.[4] [5] The lake is to become part of the Lusatian Lake District, a chain of artificial lakes mostly the result of open-pit lignite mining.
The name - besides referring to the location of the lake to the East of central Cottbus - can be interpreted as a pun on the German name for the Baltic Sea, which is called "Ostsee" in German, the two words only being distinguished by their grammatical gender: "See" meaning "sea" in German is grammatically feminine, whereas "See" meaning "lake" in German is grammatically masculine.