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Archive for Lakes

Vegetation Index of Ghana, Togo, Benin and Nigeria

10.3N 4.6E

November 30th, 2009 Category: Climate Change, Lakes

Nigeria, Benin, Togo & Ghana - November 17th, 2009

Nigeria, Benin, Togo & Ghana - November 17th, 2009

This FAPAR image stretches along the coast of Africa, from Ghana (left), across Togo and Benin, to Nigeria (right). FAPAR stands for Fraction of Absorbed Photosynthetically Active Radiation, which corresponds to the  area’s vegetation index.

In FAPAR images, the color spectrum over land runs from red (1.0), to green, to yellow and white (0.0), while bodies of water, such as Lake Volta in Ghana  (lower left) and Lake Kainji in Nigeria (center), generally appear blue.

High photosynthetic activity is present in dark red regions, such as those along the coast here. Green areas are also productive. Yellow to white areas, on the other hand, indicate a low degree of photosynthetic activity. Here, the more photosynthetically active green areas gradually give way to less activa yellow and white zones as one approaches the drier Sahel, south of the Sahara desert.

Mount Nemrut and Arms of Lake Van, Turkey – November 30th, 2009

38.6N 42.9E

November 30th, 2009 Category: Image of the day, Lakes, Volcanoes

Turkey - November 24th, 2009

Turkey - November 24th, 2009

Lake Van is one of the largest endorheic lakes in the world and the largest lake in Turkey, located in the far east of the country in the Van district. It is a saline and soda lake, receiving water from numerous small streams that descend from the surrounding mountains. Here, the Nemrut Volcano can also be seen west of the lake, partially covered with snow.

The lake’s average depth is 171 metres (560 ft) with a maximum recorded depth of 451 metres (1,480 ft). The western portion of the lake is deepest, with a large basin deeper than 400 m (1,300 ft) lying northeast of Tatvan and south of Ahlat. This deeper section of the lake appears navy blue here.

The eastern arms of the lake, on the other hand, are shallower and appear greenish from sediments and algae. The Van-Ahtamar portion, southeast, shelves gradually, with a maximum depth of about 250 m (820 ft) on its northwest side where it joins the rest of the lake. The Erciş arm, northeast, is much shallower, mostly less than 50 m (160 ft), with a maximum depth of about 150 m (490 ft).

Over 100 species of phytoplankton have been recorded in the lake including flagellates, diatoms, bacteria, cyanobacteria, green algae and brown algae. Thirty-six species of zooplankton have also been recorded including Rotatoria, Cladocera and Copepoda in the lake.

Sobradinho Reservoir on the São Francisco River, Brazil

9.6S 41.5W

November 29th, 2009 Category: Lakes, Rivers

Brazil - November 15th, 2009

Brazil - November 15th, 2009

Sobradinho Lake is one of the largest artificial reservoirs in the world, with an area of 4,214 square kilometres (1,627 sq mi). It lies along the São Francisco River, in the Brazilian state of Bahia.

The Sobradinho Dam, built in 1977 and one of four hydroelectric plants along the course of the river, has storage capacity of 34.1 billion m3 of water.

The lower end of the reservoir appears tan in color, as it is filled with sediments where the São Francisco River spills into it. The color appears more greenish where the river exits after flowing through the dam.

Sediments Clouding Lake Erie, Canada and USA – November 28th, 2009

42.0N 81.3W

November 28th, 2009 Category: Image of the day, Lakes, Rivers

USA - November 8th, 2009

USA - November 8th, 2009

The waters of Lake Erie (below) are clouded by tan sediments, particularly along the upper shoreline to the left, while those of Lake Ontario (above) are much clearer with the exception of a small stretch along the southern shore.

Lake Erie is the fourth largest lake (by surface area) of the five Great Lakes in North America. It is the southernmost, shallowest, and smallest by volume of the Great Lakes, and therefore also has the shortest average water residence time. Lake Erie drains via the Niagara River and Niagara Falls into Lake Ontario.

It is bounded on the north by the Canadian province of Ontario, on the south by the U.S. states of Ohio, Pennsylvania, and New York, and on the west by the state of Michigan.

Steppe-like Plains of Argentine Patagonia

38.6S 68W

November 27th, 2009 Category: Lakes, Rivers

Argentina - October 6th, 2009

Argentina - October 6th, 2009

The landscape of Argentine Patagonia appears mostly tan and brown in color, as it is for the most part a region of vast steppe-like plains. These plains rise in a succession of abrupt terraces about 100 metres (330 ft) at a time. In the hollows of the plains are ponds or lakes of brackish and fresh water.

Several such lakes can be seen in the upper left quadrant, near the Neuquén River (above) and the Limay River (below). All of these are artificial: the reservoir to the south was created by the El Chocón Dam, the two to the north are part of the Cerros Colorados Complex, and the final one to the east is Pellegrini Lake.