Lake Titicaca

Lake Titicaca (/tɪtɪˈkɑːkə/; Spanish: Lago Titicaca [ˈlaɣo titiˈkaka]; Quechua: Titiqaqa and Aymara: Titiqaqa) is a large lake in the Andes mountains on the border of Bolivia and Peru. It is often called the highest navigable lake in the world. It is often listed as a freshwater lake, though its waters are slightly brackish. Titicaca is the largest lake in South America, both in terms of the volume of water and surface area. It is the 18th largest lake in the world. It has a surface elevation of 3,812 m (12,507 ft).

The lake is located at the northern end of the endorheic Altiplano basin high in the Andes on the border of Peru and Bolivia. The western part of the lake lies within the Puno Region of Peru, and the eastern side is located in the Bolivian La Paz Department.

The lake consists of two nearly separate subbasins connected by the Strait of Tiquina, which is 800 m (2,620 ft) across at the narrowest point. The larger subbasin, Lago Grande (also called Lago Chucuito), has a mean depth of 135 m (443 ft) and a maximum depth of 284 m (932 ft). The smaller subbasin, Wiñaymarka (also called Lago Pequeño, "little lake"), has an average depth of 9 m (30 ft) and a maximum depth of 40 m (131 ft). The overall average depth of the lake is 107 m (351 ft).

Five major river systems feed into Lake Titicaca. In order of their relative flow volumes, these are Ramis, Coata, Ilave, Huancané, and Suchez. More than 20 other smaller streams empty into Titicaca. The lake has 41 islands, some of which are densely populated.

Having only a single season of free circulation, the lake is monomictic, and water passes through Lago Huiñaimarca and flows out the single outlet at the Río Desaguadero, which then flows south through Bolivia to Lake Poopó. This only accounts for about 10% of the lake's water balance. Evapotranspiration, caused by strong winds and intense sunlight at high altitude, balances the remaining 90% of the water loss. Its waters are slightly brackish, with UNESCO reporting its salinity as ranging from 5.2-5.5 parts per 1000. It is nearly a closed lake.

Since 2000, Lake Titicaca has experienced constantly receding water levels. Between April and November 2009 alone, the water level dropped by 81 cm (32 in), reaching the lowest level since 1949. This drop is caused by shortened rainy seasons and the melting of glaciers feeding the tributaries of the lake. Water pollution is also an increasing concern because cities in the Titicaca watershed grow, sometimes outpacing solid waste and sewage treatment infrastructure. According to the Global Nature Fund (GNF), Titicaca's biodiversity is threatened by water pollution and the introduction of new species by humans. A 2011 United Nations report found alarming concentrations of cadmium, arsenic, and lead in various parts of the lake. In 2012, the GNF nominated the lake "Threatened Lake of the Year".

Given the various Indigenous groups that occupied the Lake Titicaca region, it likely lacked a single, commonly accepted name in prehistoric times and at the time the Spaniards arrived.

The terms titi and caca can be translated in several ways. In Aymara, titi can be translated as either puma, lead, or a heavy metal. The word caca (kaka) can be translated as white or grey hairs of the head and the term k’ak’a can be translated as either crack or fissure, or alternatively, comb of a bird. According to Weston La Barre, the Aymara considered in 1948 that the proper name of the lake is titiq’aq’a, which means gray, discolored, lead-colored puma. This phrase refers to the sacred carved rock found on the Isla del Sol. In addition to names including the term titi and/or caca, Lake Titicaca was also known as Chuquivitu in the 16th century. This name can be loosely translated as lance point. This name survives in modern usage in which the large lake is occasionally referred to as Lago Chucuito.