About the data: the Danube at Budapest

2 November 2026

The Danube page follows the river at the Vigadó tér gauge in Budapest: where the water stands, where it comes from, how it compares with 65 years of records and where it might go next. This page explains where each number comes from and what is measured, what is modelled and what is drawn.

The water level

Every level is a reading of the Vigadó tér gauge (OVF station 1026, DanubeHIS HU442027, Danube km 1646.5): centimetres above the gauge's zero, which lies at 94.97 m above the Baltic Sea (95.0 m in the older EOMA system). Zero is only the mark the gauge counts from; the river is still about three metres deep there at 0 cm.

1961 to 2023: the validated daily mean levels from DanubeHIS, the Danube hydrological information system of the ICPDR and the national hydrological services. Since 2024: their provisional hourly readings, averaged per day.

Every night the site's data job adds the newest hours from OVF's open data portal (data.vizugy.hu), the same anonymous access the portal gives every visitor. The page then lays the last hours on top live, fetched by the site's own server at most once an hour. Recent values are provisional and can still be corrected.

The timeline shows monthly averages; each event shows its official peak or lowest reading, which an average smooths out. The record high is 891 cm (9 June 2013), the record low −2 cm (1 October 2026). Each nightly build checks the events against the data and keeps a report with it.

The cross-section

The drawing is Vigadó tér looking upstream: Buda on the left, Pest on the right, the Chain Bridge behind. Heights are to scale, from the embankments' measured heights; the river's width is shortened and the riverbed is approximate (about 3 to 3.5 m of water on average at 0 cm, deeper in the main channel).

Above 600 cm the lower quays close; above 650 cm tram 2 is suspended. The marks I, II and III on the gauge are OVF's flood alert levels at Budapest: 620, 700 and 800 cm.

From level to flow: the rating curve

OVF also publishes the river's flow at the gauge, in cubic metres a second. The two are tied together by the riverbed, so the site fits the gauge's rating curve to their hourly readings since 2024: Q = 0.0203 × (h + 290)^1.84, with h in cm and Q in m³/s. It matches the published flow to within about 1 %. At 0 cm about 690 m³/s passes the city; at 600 cm, when the quays close, about 5,400.

It is refitted every night, so a shift in the riverbed would show.

The map

The basin, rivers, lakes and borders come from Natural Earth; the relief from the Mapzen terrain tiles (in Europe EU-DEM, produced using Copernicus data and information funded by the European Union). The basin above Budapest was traced from the terrain and checked against the official area, about 183,500 km².

The river dots show GloFAS, the river model of the Copernicus Emergency Management Service, through Open-Meteo: its flow at 18 points, from the last week to a week ahead. A dot's size is that flow against the model's own record for the same place and time of year since 1997 (the median of the days within 15 days of the date): a medium dot is usual, a small yellowish one unusually low, a large one a flood. Comparing the model with itself cancels most of its bias; against the measured flow at Budapest it runs about 28 % high.

The Hungarian gauges upstream (Esztergom, and the Budapest gauge itself) carry their latest measured level from OVF. The weather marks are live, from Open-Meteo. Flood wave is an example of how a flood travels, not a forecast.

The forecast

The forecast card shows OVF's official forecast for the Vigadó tér gauge, from its open data, with the uncertainty OVF states: a value every six hours, averaged per day here. The site's data job fetches it every night.

Every night's forecast is kept, by how many days ahead it looked, and checked against the gauge's daily average once that day has passed. The page shows the average error so far, a day ahead and as far ahead as the forecast reaches, and marks what the forecast had said the day before beside what happened.

A forecast of the site's own is planned: a machine-learning model trained on the basin's weather (what has fallen and what is forecast), the river's current levels and the season, tested on years it has never seen and compared with OVF's.

Photos

Historical photos come from Fortepan, a community archive of photographs from Hungary, licensed CC BY-SA 3.0 and credited with each one: fortepan.hu

Sources and licences

DanubeHIS (ICPDR) and the national hydrological services, www.danubehis.org, licensed CC BY-NC-SA 4.0. The site's data file built from it is shared under the same licence, for non-commercial use.

Országos Vízügyi Főigazgatóság (OVF), open data: data.vizugy.hu

GloFAS v4, Copernicus Emergency Management Service, through Open-Meteo, open-meteo.com, licensed CC BY 4.0. Weather: Open-Meteo, CC BY 4.0, and ERA5, Copernicus Climate Change Service.

Natural Earth, public domain, www.naturalearthdata.com. Terrain: Mapzen terrain tiles; EU-DEM, Copernicus.