Buada Lagoon is a landlocked, slightly brackish, freshwater lake of Buada District in the island nation of Nauru. It occupies about . The lagoon is classified as an endorheic lake, meaning there is no outflow to other bodies of water such as oceans or rivers. The Buada Lagoon is the biggest and only true lake in Nauru, a small independent republic in Oceania consisting of a flat island of 21.3 km² in area. The lake lies in Nauru's Buada district, from which it gets its name. It is not a lagoon as such, in that the lake is not joined to the sea, but its water is slightly brackish. Freshwater is rare in Nauru, being present only in the form of a small phreatic zone, the Moqua Well (a small underground lake) and the Buada Lagoon, which is the most visible, rivers and streams being utterly absent from the country. The lake has traditionally been used for pisciculture, which saw the raising of milkfish for human consumption through the centuries, and even though this practice was given up in the 1960s, it has lately seen efforts to revive it, despite the lagoon's water pollution. Geography Geology and hydrology The Buada Lagoon, which is found in the southwest of the plateau that spreads over most of the central part of the island of Nauru, lies in the middle of a swampy depression of 12 hectares. This karstic bowl, dominated in the northwest by Command Ridge, the island's highest point, came about as a result of sagging of the ground, itself arising from dissolving coral limestone, the mineral that makes up a great part of the plateau's rocks in the form of pinnacles, among which phosphate ore, of a high level of purity, is found. The lagoon's basin, though, is the only region of the plateau where the ore, which was the mainstay of Nauru's economy through the 20th century, was never exploited. Oval in shape, with a length of roughly 280 m along a north-south axis and a width of about 140 m, and lying some 1,300 m from the seashore, the Buada Lagoon is shallow, with a depth of one or two metres on average, reaching five metres at its deepest, and its average surface level is near sea level. However, the lake’s levels can vary considerable as a result of the Buada Lagoon's endoreic state; it has no outlet