The Manas Lake area is characterized by arid climate with hot summers; the average annual precipitation of merely 63.7 millimetres (2.51 in), as compared to the average annual evaporation of 3,110.5 millimetres (122.46 in); which means that without an inflow of water from outside, the lake's water level can drop very quickly.

These two rivers flow from the Tian Shan into the Dzungarian Basin in Hutubi and Changji Counties; nowadays, they disappear in the desert a long distance away from the Manas Lake, but in the period under consideration they would merge and reach the Alan Nur.

[3] Even though the Manas River flowed into the Alan Nur, the lake now known as the Manas Lake existed as well; it was fed primarily by streams coming from the northern rim of the Zhungarian Basin[1] (i.e., from the Saur Mountains); this is indicated by old alluvial fans still existing at the pertinent locations.

The Manas River Irrigation District had been fully in that area by 1962; the system was designed to use up to 1.36 cubic kilometres (0.33 cu mi) of water per year.

[4] [5][6] Consequently, the Alan Nur, whose water surface still occupied the area of 238 square kilometres (92 sq mi) in the 1950s, had completely dried up by the 1960s.

[1] According to Chinese researchers, the recent history of the Manas Lake and its neighbors can be divided into two stages.