Lake Titicaca
Lake Titicaca 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.
Overview
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 across at the narrowest point. The larger subbasin, Lago Grande, has a mean depth of and a maximum depth of. The smaller subbasin, Wiñaymarka, has an average depth of and a maximum depth of. The overall average depth of the lake is.
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, 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, 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".
Name
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 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.
Stanish argues that the logical explanation for the origin of the name Titicaca is a corruption of the term thakhsi cala, which is the 15th- to the 16th-century name of the sacred rock on the Isla del Sol. Given the lack of a common name for Lake Titicaca in the 16th century, the Spaniards are thought to have used the name of the site of the most important indigenous shrine in the region, thakhsi cala on the Isla del Sol, as the name for the lake. In time and with usage, this name developed into Titicaca.
Locally, the lake goes by several names. The southeast quarter of the lake is separate from the main body and the Bolivians call it Lago Huiñaymarca and the larger part Lago Chucuito. The large lake also is occasionally referred to as Lago Mayor, and the small lake as Lago Menor. In Peru, these smaller and larger parts are referred to as Lago Pequeño and Lago Grande, respectively.
Highest lake
With a surface area of and an elevation of, Lake Titicaca is often called the highest navigable lake in the world. That claim is generally considered to refer to commercial craft. Numerous smaller lakes around the world are at higher elevations, such as the crater lake of Ojos del Salado, which at an elevation of is the overall highest lake in the world, and the Lake Puma Yumco, which at an elevation of is the highest large lake in the world. For many years, the largest vessel afloat on Lake Titicaca was the 2,200-ton, SS Ollanta. Today, the largest vessel is most likely the similarly sized train barge/float Manco Capac, operated by PeruRail.Ecology
Lake Titicaca is home to more than 530 aquatic species.The lake holds large populations of water birds and was designated as a Ramsar Site on August 26, 1998. It has also been designated an Important Bird Area, in both Bolivia and Peru, by BirdLife International because it supports significant populations of many bird species. Several threatened species such as the huge Titicaca water frog and the flightless Titicaca grebe are largely or entirely restricted to the lake.
In addition to the threatened Titicaca grebe, some of the birds associated with water at Titicaca are the white-tufted grebe, Puna ibis, Chilean flamingo, Andean gull, Andean lapwing, white-backed stilt, greater yellowlegs, snowy egret, black-crowned night-heron, Andean coot, common gallinule, plumbeous rail, various ducks, wren-like rushbird, many-colored rush-tyrant, and yellow-winged blackbird.
File:Bird on the Uros islands.jpg|thumb|Andean coot among totora sedges|leftThe Titicaca orestias has likely become extinct due to competition and predation by the introduced rainbow trout and the silverside Odontesthes bonariensis. In addition to the Titicaca orestias, native fish species in the lake's basin are other species of Orestias, and the catfish Trichomycterus dispar, T. rivulatus, and Astroblepus stuebeli. The many Orestias species in Lake Titicaca differ significantly in both habitat preference and feeding behavior. About 90% of the fish species in the basin are endemic, including 23 species of Orestias that only are found in the lake.Titicaca is home to 24 described species of freshwater snails and less than half a dozen bivalves, but in general these are very poorly known and their taxonomy is in need of a review. The lake also has an endemic species flock of amphipods consisting of 11 Hyalella.
Reeds and other aquatic vegetation are widespread in Lake Titicaca. Totora sedges grow in water shallower than, less frequently to, but macrophytes, notably Chara and Potamogeton, occur down to. In sheltered shallow waters, such as the harbour of Puno, Azolla, Elodea, Lemna and Myriophyllum are common.
Geology
The Tinajani Basin, in which Lake Titicaca lies, is an intermontane basin. This basin is a pull-apart basin created by strike-slip movement along regional faults starting in the late Oligocene and ending in the late Miocene. The initial development of the Tinajani Basin is indicated by volcanic rocks, which accumulated between 27 and 20 million years ago within this basin. They lie upon an angular unconformity which cuts across pre-basin strata. Lacustrine sediments of the Lower Tinajani Formation, which are exposed within the Tinajani Basin, demonstrate the presence of a pre-Quaternary, ancestral Lake Titicaca within it between 18 and 14 million years ago. Little is known about the prehistory of Lake Titicaca between 14 Mya and 370,000 BP because the lake sediments dating to this period lie buried beneath the bottom of Lake Titicaca and have not yet been sampled by continuous coring.The Lake Titicaca drilling project recovered a 136-m-long drill core of sediments from the bottom of Lake Titicaca at a depth of and at a location just east of Isla del Sol. This core contains a continuous record of lake sedimentation and paleoenvironmental conditions for Lake Titicaca back to about 370,000 BP. For this period of time, Lake Titicaca was typically fresher and had higher lake levels during periods of expanded regional glaciation that corresponded to global glacial periods. During periods of reduced regional glaciation that corresponded to global interglacial periods, Lake Titicaca had typically low lake levels.
Lacustrine sediments and associated terraces provide evidence for the past existence of five major prehistoric lakes that occupied the Tinajani Basin during the Pliocene and Pleistocene. Within the northern Altiplano, these prehistoric lakes were Lake Mataro at an elevation of, Lake Cabana at an elevation of, Lake Ballivián at an elevation of, Lake Minchin at an elevation of, and Lake Tauca at an elevation. The age of Lake Mataro is uncertain—it may date back to the Late Pliocene. Lake Cabana possibly dates to the Middle Pleistocene. Lake Ballivián existed between 120,000 and 98,000 BP. Two high lake stands, between 72,000 and 68,000 BP and 44,000–34,000 BP, have been discerned for Lake Minchin within the Altiplano. Another ancient lake in the area is Ouki. The high lake levels of Lake Tauca have been dated as having occurred between 18,100 and 14,100 BP.