Lake Piso, also known as Lake Pisu and Fisherman's Lake, is an oblong tidal

Tide

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

 lagoon

Lagoon

A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...

 in Grand Cape Mount County

Grand Cape Mount County

Grand Cape Mount is a county in the northwestern portion of the West African nation of Liberia. One of 15 counties that comprise the first-level of administrative division in the nation, it has five districts. Robertsport serves as the capital with the area of the county measuring...

 in western Liberia

Liberia

Liberia , officially the Republic of Liberia, is a country in West Africa. It is bordered by Sierra Leone on the west, Guinea on the north and Côte d'Ivoire on the east. Liberia's coastline is composed of mostly mangrove forests while the more sparsely populated inland consists of forests that open...

, near the town of Robertsport

Robertsport

Robertsport, also known as Roberts Port and Robert's Port, is a town in western Liberia, about 10 miles from the Sierra Leone border. It is named after Joseph Jenkins Roberts, the first president of Liberia....

. At an area of 103 km² (40 sq mi), it is the largest lake in Liberia. Its name originates from a local term meaning "pigeon's hole" – a reference to the flocks

Flock (birds)

A flock is a group of birds conducting flocking behavior in flight, or while foraging. The term is akin to the herd amongst mammals. The benefits of aggregating in flocks are varied and flocks will form explicitly for specific purposes...

 of pigeons that once came to Lake Piso for water.

Hydrology and geology

The brackish water

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"...

 lake borders the Cape Mount peninsula

Peninsula

A peninsula is a piece of land that is bordered by water on three sides but connected to mainland. In many Germanic and Celtic languages and also in Baltic, Slavic and Hungarian, peninsulas are called "half-islands"....

, and is connected to the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 by a narrow inlet

Inlet

An inlet is a narrow body of water between islands or leading inland from a larger body of water, often leading to an enclosed body of water, such as a sound, bay, lagoon or marsh. In sea coasts an inlet usually refers to the actual connection between a bay and the ocean and is often called an...

 known locally as the "bar mouth". Various rivers empty into Lake Piso, including Mole Creek and Mafa River, which discharges at the 'bar mouth'. There are a number of islands in the lake, including Massatin Island, which offered a haven for some Liberians during the Liberian Civil War

Liberian Civil War

The First Liberian Civil War was an internal conflict in Liberia running from 1989 until 1996. The conflict killed over 200,000 people and eventually led to the involvement the Economic Community of West African States and of the United Nations...

.

History

During World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, Lake Piso functioned as a military base

Military base

A military base is a facility directly owned and operated by or for the military or one of its branches that shelters military equipment and personnel, and facilitates training and operations. In general, a military base provides accommodations for one or more units, but it may also be used as a...

 for Allied

Allies of World War II

The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 seaplane

Seaplane

A seaplane is a fixed-wing aircraft capable of taking off and landing on water. Seaplanes that can also take off and land on airfields are a subclass called amphibian aircraft...

s.

Lake Piso overflowed its banks at least twice in 1998, causing heavy flooding in Garwular District. Flooding in August 1998 occurred due to a blockage of the narrow inlet connecting the lake to the Atlantic Ocean, damaging some homes.
Additional flooding in September and October, brought about by heavy rains, affected over twenty settlements, causing at least ten deaths, leaving thousands homeless, and forcing others to leave their homes.
The floods led the government of Liberia to declare the area a "disaster zone".

On December 13–14, 2002, the Papa Friends 2000 capsize

Capsize

Capsizing is an act of tipping over a boat or ship to disable it. The act of reversing a capsized vessel is called righting.If a capsized vessel has sufficient flotation to prevent sinking, it may recover on its own if the stability is such that it is not stable inverted...

d in Lake Piso, at the confluence

Confluence

Confluence, in geography, describes the meeting of two or more bodies of water.Confluence may also refer to:* Confluence , a property of term rewriting systems...

 of the lake and Mafa River. The overcrowded wooden ferry

Ferry

A ferry is a form of transportation, usually a boat, but sometimes a ship, used to carry primarily passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate on regular, frequent, return services...

 was transporting approximately 200 passengers, most returning from the funeral of a local footballer. Only 15 people were rescued; the rest drowned and were recovered or presumed dead.

A nature reserve

Nature reserve

A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...

 was designated near Lake Piso in 1999 and, as of 2004, the Lake Piso wetland

Wetland

A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

s, covering an area of 76091 ha (761 km²), were Liberia's only designated wetland of international importance

Ramsar list of wetlands of international importance

This is the list of wetlands of international importance as defined by the Ramsar Convention for the conservation and sustainable utilization of wetlands, recognizing the fundamental ecological functions of wetlands and their economic, cultural, scientific, and recreational value.The Convention...

.

Human activity

The area near the lagoon is the homeland of the Vai

Vai (ethnic group)

The Vai are a Manden ethnic group that live mostly in Liberia and small minority live in south-eastern Sierra Leone. The Vai are known for their indigenous syllabic writing system, developed in the 1820s by Duala Bukele and other tribal elders. Over the course of the 19th century, literacy in the...

 people.

Human activity in Lake Piso includes fishing

Fishing

Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....

 and water sports such as swimming, canoeing

Canoeing

Canoeing is an outdoor activity that involves a special kind of canoe.Open canoes may be 'poled' , sailed, 'lined and tracked' or even 'gunnel-bobbed'....

 and water skiing

Water skiing

thumb|right|A slalom skier making a turn on a slalom waterski.Waterskiing is a sport where an individual is pulled behind a boat or a cable ski installation on a body of water, skimming the surface.-History:...

. Prior to the outbreak of the First Liberian Civil War, the lagoon was a popular travel destination for tourists.

High-quality diamond

Diamond

In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...

s have been mined from the rivers that discharge into Lake Piso where "igneous intrusions provide potentially rich structural traps".