The city receives its fresh water via a long aqueduct from the now besieged city of Kherson.
But since April, the tap has stopped.
Satellite images and geodata obtained by the BBC now show that the water pipeline was probably deliberately destroyed when the area came under Russian control.
Several experts told the BBC that the damage could not possibly have been there by accident but appeared to come from deliberately placed explosives.
- Bread and canned food are the only things I eat.
Soon it will already be winter and it is scary, says 70-year-old Mykolajiv resident Anna Bilousova.
See the long queues for both water and food in Mykolajiv in the video above.