Lake Mandrensko or Lake Mandra is the southernmost of the Burgas Lakes

Burgas Lakes

The Burgas Lakes or Burgas Wetlands are a group of coastal lakes of varying saltiness located around the Bulgarian city of Burgas in the proximity of the Black Sea...

, located in the immediate proximity of the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

 and close to Burgas

Burgas

-History:During the rule of the Ancient Romans, near Burgas, Debeltum was established as a military colony for veterans by Vespasian. In the Middle Ages, a small fortress called Pyrgos was erected where Burgas is today and was most probably used as a watchtower...

. Being 8 km long and 1.3 km wide at maximum, as well as having an area of 38.84 km², it was a brackish

Brackish water

Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...

 natural lake until 1963, when it was turned into a reservoir with the construction of a dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 to secure fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 for the large Neftochim Burgas oil refinery

Oil refinery

An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...

. The rivers Izvorska, Fakiyska, Sredetska

Sredetska

Sredetska is a river in eastern Bulgaria. It is 69 km long with a catchment area of 985 km2. It empties into the Black Sea through Lake Mandrensko near Burgas....

 and Rusokastrenska flow into the lake.

Parts of Lake Mandrensko are designated protected area

Protected area

Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...

s inhabited by a number of locally and globally endangered species of fish and birds.