Lake Maracaibo

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Lake Maracaibo
Lake Maracaibo
Primary sources	Catatumbo River
Primary outflows	Gulf of Venezuela
Basin countries	Colombia Venezuela
Surface area	13,210 km²
Max depth	60.0 m
Water volume	280.00 km3
Surface elevation	0 m
Settlements	Maracaibo, Cabimas

Lake Maracaibo from space, August 1985. North is at the bottom left of the image. (STS-51-I)

Lake Maracaibo is a large brackish lake in Venezuela at 10°39'N 71°36'W. It is connected to the Gulf of Venezuela by a 55km strait on the northern edge of the lake, and fed by numerous rivers, the largest being the Catatumbo River. It is the largest lake in South America, at 13,210 km², and one of the oldest lakes on Earth. ^[1] ^[2]

Lake Maracaibo acts as a major sea route for to the ports of Maracaibo and Cabimas. The surrounding Maracaibo Basin contains large reserves of crude oil, making the lake a major profit center for Venezuela.^[2] A dredged channel gives oceangoing vessels access to the lake. The General Rafael Urdaneta Bridge (8.7 km long; completed 1962), spanning the lake's outlet, is one of the longest bridges in the world.

1 History
2 Fishing
3 Settlements
4 Subsiding Ground
5 Duckweed infestation
6 Notes
7 References

[edit] History

The first settlements on the lake were those of the Goajiro Indians, who speak an Arawakan language.

The first European to discover the lake was Alonso de Ojeda in 1499, on a voyage with Amerigo Vespucci. The port town of Maracaibo was founded in 1529 on the western side the lake.

In July of 1823, the lake was the site of Battle of Lake Maracaibo, an important battle in the Venezuelan War of Independence.

Oil production began in the surrounding basin in 1914, with wells drilled by Bataafsche Petroleum Me, a precessor of Royal Dutch Shell.

On April 6, 1964, at 11:45 pm, the supertanker Esso Maracaibo, loaded with 236,000 barrels of crude oil hit pier # 31 of the 2-year-old General Rafael Urdaneta Bridge that connects Maracaibo with much of the rest of Venezuela. The vessel had recently been loaded with oil, and lost steering due to a major electrical failure onboard, which lead to the collision. A 259 metre section of the bridge roadway fell into the water with a portion coming to rest across the tanker just a few feet from the ship's superstructure. The bridge damage lead to the deaths of seven people whose vehicles fell off of the damaged area. Amazingly, there was no loss of life or serious injury on the tanker. No oil spill occurred.

[edit] Fishing

As recently as 2000 Lake Maracaibo supported 20,000 fisherman. Pollution is ending this industry.[1]

[edit] Settlements

Several settlements built out on stilts over the lake - palafitos - still exist in the south and south-west, notably at Lagunetas.

These villages are cut off from modern amenities and supplies, and life there is hard. The populations are inbred and suffer from inherited disorders, particularly Huntington's disease, which is known by its old name El Mal de San Vito (St. Vitus' dance).

[edit] Subsiding Ground

Due to the massive volume of oil removed in the Maracaibo Basin, Lake Maracaibo has sunk, changing the geography of the region. In response, the Venezuelan government was forced to build an earthen dike around sub-sea-level Lagunillas to prevent encroachment by the waters. Many consider the dike to be a disaster in the waiting, with the potential of an earthquake causing soil liquifaction and submerging a large population.

[edit] Duckweed infestation

Green swirls on the lake are duckweed.

As of June 18, 2004, a large portion (18%) of the surface of Lake Maracaibo is covered by duckweed specifically Lemna . Although efforts to remove the plant have been underway since May, the plant, which can double its size every 48 hours, covers over 130 million cubic metres of the lake. The only way to remove the weed is to pull it out of the lake physically—no chemical or biological method has been found to treat the weed. The government has been spending $2 million monthly to clean the lake, and the state-run oil company Petroleos de Venezuela S.A. has created a $750 million cleanup fund. Current efforts are barely keeping up with the growth of the plant. The removal process has proven to be particularly difficult in the center of the lake where a specially equipped ship may be needed to pull the weed off the lake. More likely, however, the weed will simply run out of nutrients and the outbreak will die down on its own.

There is some mystery as to how the plant came to reside in the waters of Lake Maracaibo. According to scientists from the Institute for the Conservation of Lake Maracaibo (ICLAM), one of the government organizations charged with the care of Lake Maracaibo, the weed is probably native to the lake, but few studies have been conducted to confirm that suspicion. The prodigious growth of the freshwater marine plant is likely a self-purification mechanism. Others disagree, believing the type of duckweed to be native to Florida and Texas and thus the infestation is a result of its having been transported by ship.

Another point of uncertainty is why the scale of the outbreak is so great. Maracaibo is fed by both salt water from the Caribbean and fresh water from numerous rivers. The lighter fresh water floats on top of the heavier salt water, which forms a dense layer on the bottom. This set-up traps nutrients that have settled on the floor of the lake. In the spring of 2004, heavy rains disrupted the usual pattern. The sudden influx of fresh water stirred the layers, allowing nutrients to float to the top, where duckweed and other plants reside. These nutrients may have triggered the duckweed's rapid expansion. Additional sources of nutrients include untreated sewage discharge and fertilizers and other industrial waste flowing into the lake through rivers. (97 percent of the country's raw sewage is discharged without treatment into the environment.) Furthermore, chemicals used to clean up oil spills may have contributed to the duckweed problem. The lake basin hosts Venezuela's largest oil fields, and high concentrations of biodegradable dispersants that contain phosphorus and poliaspartic acid—a chemical used to increase nutrient uptake in crops—have been found, a veritable feast for the plants. Scientists at ICLAM disagree, saying that dispersants have been banned from the lake for years and, even if they were present, could not contain enough nutrients to support the current duckweed population.

Duckweed is not toxic to fish, but some scientists are concerned that it could suck oxygen out of the lake as it decays, asphyxiating large numbers of fish. Though officials say the weed hasn't harmed fish yet, it is putting a dent in the local fishing industry. The plant clogs the motors of small boats, making it impossible for fishers to launch their vessels. Duckweed further threatens the local ecosystem by choking out other plants as it shades large portions of the lake. In certain conditions, the weed may concentrate heavy metals and bacteria such as salmonella and Vibrio cholerae, the bacterium that causes cholera. Despite these problems, the weed may yet have some positive use; duckweed can be treated to be fed to poultry or to make paper.