Why do many Siberian rivers, covered with ice in winter, have no water under them?

This phenomenon is quite common not only in Siberia. The nature of this phenomenon is that precipitation increases in the autumn period, the level of rivers does not fall below its usual level. Over time, frosts hit, which fetter the river with a thick layer of ice. Let’s remember that the temperature in Siberia can drop down to -40 degrees in winter. The layer of ice can even exceed a meter thickness. After that, precipitation ceases to fall in liquid form until spring, the inflow of water into rivers decreases and, accordingly, the water level falls. An air gap is formed.