Freshwater Fishes of Iran
Introduction - Drainage Basins - Bejestan Highland
This basin comprises the drainages of the eastern highlands north of Birjand (32°53'N, 59°13'E) flanked by the Kavir basin to the west, the Lut and Sistan basins to the south, the Tedzhen to the north and the Afghan border to the east. The Tedzhen basin is separated by three ranges, from west to east, the Kuh-e Sorkh (35°30'N, 58°36'E) at 3017 m, the Kuh-e Bizak (35°11'N, 60°20'E) and the Kuh-e Khvaf at 2517 m east of Khvaf (34°33'N, 60°08'E). These receive snow in winter from moist Caspian Sea air. The highlands are relatively low compared with other parts of Iran and nowhere exceed 3000 m except for the Kuh-e Sorkh. The lowest points are in the sumps on the Afghan border at about 610 m. There are a number of minor sumps and the drainage patterns have been described as indeterminate. The total area is about 82,000 sq km. Tectonism commonly causes drainage disruptions (Krinsley, 1970).
The distinction of the western parts of the basin from the Kavir basin is somewhat arbitrary since the Kavir-e Namak near Bejestan (34°31'N, 58°10'E) lies at a similar level to the Kavir-e Bozorg and is separated by only a low rise in the land. This kavir receives intermittent streams from the east and north. The Bejestan basin does receive tributaries from Afghanistan but these are minor and do not begin to approach the input received by the Sistan and Tedzhen basins from the east. Streams drain mostly to the east, to three small terminal basins straddling the border; from north to south these are the Namakzar-e Khvaf, the Daqq-e Patargan and the Daqq-e Tondi.
The Lut basin to the south is separated by the drainage divide of the Birjand-Qa'in highlands, which trend north-west to south-east. Kuh-e Kalat is at 2605 m (34°18'N, 58°22'E) in the north-west and altitudes of 2779 m are reached in the south-east.
This whole basin has seasonal streams and a few springs with qanats a prominent feature. Water temperatures in qanats is 22-25°C year round and their is little fluctuation in water flow and chemical composition. Springs in contrast are influenced by the local geology and have a variable chemical composition, as well as being influenced by climate and pollution (Ruttner-Kolisko, 1964; 1966).
© Brian W. Coad (www.briancoad.com)