Why are there no permanent streams along much of the eastern Caspian Sea coast?

The eastern coast of the Caspian Sea is characterized by a desert climate, which is the primary reason for the complete lack of permanent streams along that shoreline, with the notable exception of the Atrak River in southern Turkmenistan.12

This region experiences high temperatures, with summer air temperatures reaching as high as 111 °F (44 °C), and receives the least amount of annual precipitation compared to other areas surrounding the sea. The combination of these arid conditions and high evaporation rates prevents the formation of consistent, year-round watercourses.21