Large paleochannels are widespread in the surroundings of Lake Nero, they are larger than modern ones. Their presence indicates an increased river run-off in the past and a likely impact on changes in lake level. The study of paleochannels was carried out using hydro-morphological analysis and drilling cores. The results showed that their sizes are to 1.5-3 times larger than modern analogues. At the time of their formation, river discharges exceeded recent ones, the lake was in regression. The paleochannels north of the Rostov belong to the Ustye paleoriver, which had previously flowed into the Nero with a level below 91 m a.s.l. Further study of the river paleochannels will help to better understand the reasons for the change of Nero Lake level.