What the gauge reading measures
A water-level reading gives the height of the water in centimetres relative to the local zero of a particular hydrological station. That zero is fixed for the station; it is not sea level. So “−120 cm” means that the water is 120 centimetres below that gauge’s zero, not that the riverbed or water surface is 120 centimetres below the sea.
Why stations show different numbers
Each station has its own zero, and readings vary by location along the river. RHMZ, for example, gives the Bogojevo station’s zero elevation as 77.46 m above sea level. Compare the station name, date, daily change, and forecast—not isolated figures from different places. RHMZ publishes current observations and a short-term forecast separately, and operational readings can later be adjusted.
When low water matters
A low reading does not by itself give one universal “Danube depth.” Navigation depends on available depth on a particular reach, waterway restrictions, and a vessel’s permitted draught. In shallow water, barges carry less cargo or journeys become more difficult and costly. For hydropower, flow and how a plant is operated matter as well as the figure at one gauge.
Why this explainer was published
On July 25, N1 reported a reading down to −120 cm on the Bezdan–Apatin–Bogojevo stretch and described it as close to the 1909 historic minimum. In the same report, EPS director Dušan Živković said output at Đerdap 1 had fallen to one third, but that the company was prepared and expected stable supply. That was EPS’s position on the publication date, not a guarantee for the whole season.
Why it matters beyond river transport
N1 reported that shallower water was reducing barge loads, shifting some fuel and raw-material deliveries to road or rail. That can raise logistics costs. Lower hydropower output also changes the power system’s mix; it does not, on its own, mean that electricity restrictions have been announced.
What remains open
The central question is how long low water will last and what restrictions will apply on individual reaches. To understand the current situation, follow RHMZ’s daily observations and forecast, navigation notices, and separate statements from EPS and authorities on supply. One gauge reading should not be used to infer the state of the whole river or the risk of electricity restrictions.