A second dam, immediately south of the village of Kozarovychi [uk], was built to stop the reservoir from inundating more of the Irpin river basin.

The lands around the Irpin were the heartland of Kyivan Rus, and the chronicles mention the river in connection with several important historic events, such as the Battle on the Irpin River of 1321 in which the Grand Duke of Lithuania Gediminas (Gedemin) allegedly gained control over the lands of what is now central Ukraine.

The river also defended Kyiv from German invasion during World War II.

[5][6] Ukrainian troops also opened the Kozarovychi dam on the second day of the invasion, to flood the Irpin basin, including houses in Demydiv.

The flooding effectively created a shallow lake that prevented Russian vehicles from advancing across it.