The number of lakes of Iran due to its geological status is relatively high. Some of these lakes are permanent and some of them are dry in most days of the year. Among the most important permanent lakes in Iran, besides the Caspian Sea, one can mention the lakes of Urumia, Bakhtegan, Jazmourian, Parishan, Maharlou, Zaryar and Hamoun. Iran is a part of the semi-arid and arid lands of Asia with relatively low annual rainfall. Hence, its lakes are low and often in the dug out of the earth. However, some of Iran's lakes, such as the lakes of Tar and Gohar, are on the high. Persistent Iranian lakes are mostly restricted to the northwest and southwestern Iran. In arid and desert areas, the lakes are seasonal and terminal and have salt water. In Iran there are 28 natural lakes and 9 lakes formed by the dam construction.