How to understand Danube water levels

The levels of the Danube waters are measured against a reference level specific to each locality. It is easy to imagine that the depths cannot be taken as a reference as the depths may differ greatly even for a small area.

The level of the Danube is measured against a reference level and the reference level for a certain locality is in the table below expressed in centimeters compared to the level of the Black Sea. If you want to find out the level of the Danube compared to the level of the Black Sea for a certain locality, add the level on that day (expressed in centimeters) with the value of the reference level for that locality. For example, for Tulcea, the reference level is 56 centimeters. A level of 200 cm in Tulcea means that the Danube has a level of 200 + 56 cm compared to the level of the Black Sea.