Corrections will be made in new versions accordingly. In 1991, the total cultivated area was estimated at 20.5 million ha, of which 17.5 million ha consisted of annual crops and 3.0 million ha consisted of permanent crops, mainly vineyards, fruit trees and olives. In the east, summers are hot and dry, winters are cold, rainy and snowy. Along the coastal area, a Mediterranean climate is dominant with long, hot, dry summers and short, mild, rainy winters.
Rainfall shows great differences from one region to another.
The most important hydrological basins in Turkey have been grouped in the Table below. In general, the streams vary greatly in their flow from season to season and year to year. For example, the Euphrates' annual flow at the border with Syria ranged from 15.3 km3 in 1961 to 42.7 km3 in 1963. Average annual surface runoff leaving the country is estimated at 60.4 km3, while almost 8 km3 flows in the interior basins. Groundwater flows to other countries are not known.