El "Junco" Lagoon :: San Cristóbal Island

In town you can hire a car or bus to carry the group to El Junco. During the winter, January to April, there are often heavy rains. During the rainy season there may be fog. Also one can get to El Progreso and then walk from there, if the group is very active. The walk from Progreso may last for 1 1/2 to 2 hours (depending on the group). From Port Baquerizo Moreno to El Progreso is about a 30-minute drive. 

The area of El Junco has established limits. However, to date, residents have not respected the National Park's boundaries and livestock are often found in areas of the park. 

The high area of San Cristobal has many farms and ranches, so it is common to find cattle in the lagoon and surrounding areas. There is a lot of introduced guava that has spread thanks to the cattle and competes with Miconia robinsoniana, Melastomatacea endemic to Galapagos. Moreover, in recent years another introduced plant, Rubus nivea (blackberry) is causing more problems than the guava, it is a highly aggressive plan.

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El Junco Lagoon has an area of 60,000 m2 and its volume is 360,000 m3, equivalent to 9 million gallons of water. Its diameter is 270 m. and its maximum depth is 6 m. It is fed only by rainwater, in periods of drought it decreases to 1 m. and when there are heavy rains it increases its level until it overflows forming a stream. In 1978, it grew till it gave off 5400 gallons per hour. In 1982-83 the river coming down from the top destroyed everything in Puerto Baquerizo Park. Similar damage was caused during the El Niño of 1998. 

The lagoon is located 19 kilometers from Port inside a small crater, which in turn lies within the caldera of a large volcano, now extinct and hard to distinguish without geological knowledge.

According to studies conducted in 1966 by Dr. Paul Colinvaux, sediment at the bottom of the lagoon have a thickness of 16 m. Using radiocarbon analysis it has been discovered that 3 m of the top layer were deposited during the last 10,000 years, while the other 13 m were deposited during dry spells over a period of 38,000 years, giving a total sediment age of 48,000 years. The implications of this information for scientists are very important, because Dr. Colinvaux believes that the climate of Galapagos went through a dry period caused by glacial advances in the Northern Hemisphere, beginning 48,000 years ago and ending 10,000 years ago. An organic band, deposited at the maximum depth of red mud seems to have been deposited at times so remote that it cannot be analyzed by the radiocarbon method, i.e. it must be greater than 48,000 years (Colinvaux 1984). It is now accepted that the Laguna El Junco is from the end of the last glaciations in the northern hemisphere. (For more information read the article THE GALAPAGOS CLIMATE: Present and Past, written by Paul Colinvaux, Key Environments, "GALAPAGOS".

In 1966 there were no fish nor was the presence of nitrate in the lagoon, in 1977 it had fish and nitrates. The increase in nitrates is perhaps due to the presence of cattle, or the fish, which are a species of mullet, probably introduced by locals. 

The name of the lake comes from a type of plant that is common in the surrounding area, known as "junco". Eleocharis mutates and is member of the Cyperacea family. 

In 1990, the black fly, Simulium bipunctata, was introduced to San Cristobal Island. Its arrival on the island is causing many problems, especially the farmers who live above 300 m. high. The female of this species is a bloodsucker and its venom is extremely strong, in some cases it has caused the death of animals and humans when they have been stung by many of these dipterans. These flies are also vectors of diseases such as onchocerciasis, a disease that presents itself as subcutaneous tumors, which, if it affect the eyes can cause partial or total blindness.

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