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TSANA

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Originally appearing in Volume V27, Page 348 of the 1911 Encyclopedia Britannica.
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TSANA , a See also:

lake of See also:North-See also:East See also:Africa, See also:chief See also:reservoir of the Abai or See also:Blue See also:Nile. Tsana lies between 11° 36' and 12° 16' N. and 37° 2' and 37° 40' E., filling a central depression in the Abyssinian See also:highlands. It is about 5690 ft. above the See also:sea, but from 2500 to 3000 ft. below the See also:mountain See also:plateau which encircles it. Its greatest length is 47 m., its greatest breadth 44 m., and it covers, approximately xtoo sq. m., having a drain-See also:age See also:area, including the lake See also:surface, of some 5400 sq. m. In shape it may be compared to a See also:pear, the See also:stem being represented by the escaping See also:waters of the Abai. The shores of the lake are well defined, generally See also:flat, and bordered by reeds, but at places the mountains descend somewhat abruptly into the See also:water. Elsewhere the See also:land rises in See also:gentle undulations, except at the mouths of the larger tributary streams, where are alluvial plains of considerable See also:size. At the See also:south-east end the lake forms a See also:bay about eleven See also:miles See also:long, and from three to eight miles across, and from this bay the Abai issues. The whole of the See also:coast-See also:line is considerably indented and, many narrow promontories jut into the lake. The See also:island of Dek (8 m. long by 4 broad) is in the south-western See also:part of the lake. Near it is the smaller island of Dega, whilst numerous islets fringe the shores. Lake Tsana is fed by three large See also:rivers and by many See also:petty streams.

The chief tributary is the Abai, which enters the lake at its south-See also:

west corner through a large See also:papyrus swamp. This See also:river, and the Abai or Blue Niie which issues from the lake, are regarded as one and the same stream and a current is observable from the inlet to the outlet. Next in importance of the affluents are the Reb and Gumara, which run in parallel courses and enter the lake on its eastern See also:side. The outlet of the lake is marked by openings in a rocky ledge, through which the water pours into a See also:lagoon-like expanse. Thence it issues by two or three channels, with a fall of about 5 ft. in a See also:succession of rapids. These channels unite within a couple of miles into one river—the Abai with a width of 65o ft. After passing a large number of rapids in the first sixteen miles of its course the Abai enters a deep See also:gorge by a magnificent fall—the Fall of Tis Esat—the water being confined in a channel not more than 20 ft. across and falling 15o ft. in a single leap. The gorge is spanned by a See also:stone See also:bridge built in the 17th See also:century. From this point the Abai makes its way through the mountains to the plains of See also:Sennar, as described in the See also:article NILE. The See also:average See also:annual rainfall in the Tsana catchment area is estimated at 3; ft., and•the See also:volume of water received by the lake yearly at 6,572,000,000 of cubic metres. More than See also:half of this amount is lost by evaporation, the amount discharged into the river being placed at 2,924,000,000 cubic metres. The seasonal alteration of the lake level is not more than 5 ft.

The See also:

rainy See also:season lasts from the beginning of See also:June to the end of See also:September. During this See also:period the See also:discharge from the lake is, it appears, little greater than in the dry season, the additional water received going to raise the lake level. Thus the rise in the Blue Nile, in its See also:lower course, would seem to be See also:independent of the See also:supply it derives from its source. Tsana has been identified with the Coloe Palus of the ancients, which although placed x 2° too far south by See also:Ptolemy was described by him as a chief reservoir of the See also:Egyptian Nile and the source of the Astapos, which was certainly the Blue Nile. In 1625 it was visited by the Portuguese See also:priest Jeronimo See also:Lobo, and in 1771 by See also:James See also:Bruce. Dr. Anton Stecker, in 1881, made a detailed examination of the lake, enabling the cartographers to delineate it with substantial accuracy. By the Portuguese of the 77th century the lake was styled Dambia, 1 Sven Hedin, Scientific Results of a See also:Journey in Central See also:Asia, 1899-5902, iii. 344 (See also:Stockholm, 1905-1907). and this name in the slightly altered See also:form of Dembea was in use until towards the See also:close of the 19th century. By many Abyssinians the lake is called See also:Tana, but the correct Amharic form is Tsana. See NILE and See also:ABYSSINIA, and the authorities there cited.

The See also:

British Blue See also:Book, See also:Egypt, No. 2, 1904, contains a See also:special See also:report (with maps) upon Lake Tsana by Mr C. See also:Dupuis, of the Egyptian See also:Irrigation Service. In the See also:Boll. See also:soc. geog. italiana for See also:December 1908 See also:Captain A. M. Tancredi gives the results (also with maps) of an See also:Italian expedition to the lake. (W. E. G.; F. R.

End of Article: TSANA

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