The Danube at Orșova · 183 years of daily measurements
The Danube at low water, 1840–2026: how often the river has been this low
At Orșova, by the Iron Gates gorge on the Romanian–Serbian border, the Danube's flow has been measured every day since 1 January 1840. In the 183 years to 2022, no day between June and September fell below 1,440 m³/s. Romania's national hydrology institute (INHGA) reported 1,300 m³/s at Baziaș, where the river enters Romania, in August 2026 and 1,250 m³/s in September.
1,440
lowest June–September day in 183 years (31 August 2003, Orșova)
1,250
lowest flow in INHGA bulletins at Baziaș, 14 and 15 September 2026
77
days under 1,800 m³/s in 2026 by 2 October; 1947, the year with the most such days, had 77
INHGA bulletin figures are provisional and rounded to 50 m³/s, while the validated series is made of daily means. Two neighbouring gauges typically differ by 86 m³/s on a given day; the conclusions below rest on larger gaps.
What flow did you hear in the news?
Enter a Danube flow in cubic metres per second and pick a station and a time of year. See how many days have been that low: at Orșova since 1840, at Baziaș since 1976.
Example, with the values in the boxes:
Of the 22,326 days in June–September at Orșova (1840–2022), none had a flow of 1,300 m³/s or less.
No year out of 183 had a day that low.
Lowest day in June–September: 1,440 m³/s, 31 August 2003. The flow you entered is 140 m³/s lower.
The comparison is with validated daily means. A bulletin figure is provisional and rounded to 50 m³/s; differences under 100 m³/s are not meaningful.
183 years, month by month
Each row is a year, 1840 at the top to 2022 at the bottom; each column is a month. The colour is the lowest day of that month at Orșova. Dark red marks months when the Danube fell under 1,500 m³/s. The separate row below is 2026, from INHGA bulletins at Baziaș, June to October only.
The red sits almost entirely in winter and autumn. Only three summers had a day under 1,500 m³/s: 1852, 1907, 2003. In the 2026 row, August and September are in the same darkest class as the winters of 1858 and 1947.
Pick a year: its lowest day, days under 2,000 m³/s and mean flow.
- < 1,500
- 1,500–1,799
- 1,800–2,099
- 2,100–2,499
- 2,500–3,199
- 3,200–4,499
- 4,500–6,499
- ≥ 6,500
The lowest days are in winter; in summer the river had not fallen under 1,440
All 44 days with a flow of 1,300 m³/s or less fall in the cold months, December to March, in seven winters: 1858, 1864, 1866, 1893, 1902, 1954, 1985. The absolute minimum is 1,150 m³/s, on 11 January 1866.
Summer is different. The three lowest days between June and September are 1,440 m³/s (31 August 2003), 1,450 m³/s (1 August 1852), 1,460 m³/s (13 August 1907). The August 2026 value reported by INHGA at Baziaș, 1,300 m³/s, is 140 m³/s below the first of them (a different gauge; see the checks).
The lowest day between June and September has drifted down: the mean for 1840–1930 is 2,994 m³/s, for 1931–2022 it is 2,664 (Kendall trend τ = −0.19, p < 0.001). For mean annual flow no significant trend is detected over the same years (p = 0.75). The series comes from one gauge, so it cannot separate climate from changes to the channel and dams.
The lowest days in the series
| Flow, m³/s | Date | Period |
|---|---|---|
| 1,150 | 11 January 1866 | cold months |
| 1,170 | 10 January 1866 | cold months |
| 1,180 | 21 January 1985 | cold months |
| 1,190 | 4 March 1858 | cold months |
| 1,190 | 20 December 1902 | cold months |
| 1,200 | 20 January 1985 | cold months |
| 1,210 | 9 January 1866 | cold months |
| 1,220 | 9 January 1893 | cold months |
The lowest days from June to September
| Flow, m³/s | Date | Period |
|---|---|---|
| 1,440 | 31 August 2003 | June–September |
| 1,450 | 1 August 1852 | June–September |
| 1,460 | 13 August 1907 | June–September |
| 1,490 | 30 August 2003 | June–September |
| 1,490 | 2 September 2003 | June–September |
Dry years: how many days under 2,000 m³/s
By days under 2,000 m³/s, the driest years are 1947 (92 days), 1858 (71 days), 1908 (60 days), 1921 (55 days), 2003 (47 days). The year 2003 has 47; 2022 has 31.
In 2026, counting only 1 June to 2 October, INHGA bulletins give 82 days under 2,000 m³/s, more than any full year except 1947 (92). Under 1,800 m³/s there are 77 days, as many as all of 1947 (77). Under 1,500 m³/s there are 43 days; the full year 1858 has 59. These are running counts at Baziaș since the start of June, set beside full-year totals at Orșova. The year is not over, and the counts come from bulletin values rounded to 50 m³/s (strictly below the threshold).
Can 2026 be compared with 1866? Three checks
1. The operator's list is found in the series
On 17 August the manager of the Iron Gates hydropower plants (Hidroelectrica, Romania's state hydropower company) listed pre-regulation lows: 1,330 in 1947, 1,190 in 1902 and 1858, 1,150 in 1866 (Mediafax). The validated series gives 1,190 (1858), 1,190 (1902) and 1,150 (1866) exactly; for 1947, 1,330 m³/s on 27 October 1947 is the lowest autumn day, and the year's minimum is 1,310 in January. Three of four values match exactly, the fourth matches a specific day.
2. Two gauges that are not the same series
Baziaș (where the river enters Romania) and Orșova (at the Iron Gates) are separate measurements. Over 16,802 shared days since 1976 the mean ratio of Orșova to Baziaș is 0.9997, the daily correlation is 0.993 and that of annual minima 0.974, but the values are identical on only 3.2% of days and the usual gap is 86 m³/s (1.8%). Winter is worse: on 13 January 1985 Baziaș gives 1,400 and Orșova 1,840; on 21 January 1985 Baziaș gives 1,890 and Orșova 1,180. That is why winter minima are less certain than summer ones.
3. A test finds no step in the series at the 1971 dam
The generating units of Iron Gates I started between August 1970 and December 1971 (Hidroelectrica). Mean annual flow is 5,464 m³/s in 1840–1970 and 5,306 in 1971–2022 (p = 0.30); the average annual minimum is 2,145 and 2,225 (p = 0.38). The permutation test detects no difference between the means; that does not prove the dam had no effect. Day-to-day variation is 0.055 in 1940–1970, 0.105 in 1972–1989 and 0.059 in 1990–2022; the cause is not shown here.
Different sources give different minima. The same operator called 1,350 m³/s the lowest flow since the river was regulated; the validated series has 1,180 at Orșova (21 January 1985) and 1,400 at Baziaș (13 January 1985), both in January 1985. We do not know which series the operator has in mind.
How low flow relates to hydropower and shipping
In years of lower Danube flow, Romania's hydropower output was lower. Over the 33 years 1990–2022, Romania's hydroelectric output tracks mean annual flow at Orșova (r = 0.74): in the five driest years (1990, 1993, 2003, 2011, 2022) it averaged 13,349 GWh, in the five wettest (1999, 2005, 2006, 2010, 2013) 18,481 GWh; the dry years produced 28% less (an observed difference between the two groups). Across these 33 years, each 1,000 m³/s of extra mean annual flow at Orșova was associated with about 2,040 GWh more hydropower output a year. This is an association: output includes inland rivers and new plants, and the Danube shows how wet the year was, not what the Iron Gates alone produced.
Iron Gates I, shared by Romania and Serbia, produces on average 5,241 GWh a year on the Romanian side (Hidroelectrica). In August 2026 a Warsaw research institute (OSW) wrote that only about 25% of the 1,400 MW allocated to each country was operating.
The limit for nuclear plants is the water level at their intakes. At Paks, in Hungary, the pump intakes sit above the water although the volume would suffice (MVM, 30 July). At Cernavodă, Romania's nuclear plant, unit 1 was shut down in a controlled way on 28 July and unit 2 on 13 August 2026 (Nuclearelectrica, the plant's operator). A value from the series does not say when that happens: the link between flow and level depends on the channel. The Cernavodă story, with the emergency committee's plan triggered at 1.58 m in the intake basin, is in the piece “A navigation project promises cooling water for Cernavodă”
Shipping stops at depth. On 4 August 2026 Austria's infrastructure ministry and viadonau described cargo shipping on the Austrian Danube as largely at a standstill, with the fairway held at 2.0 m in the Wachau.
Summer 2026 against the record
Situation on 2 October 2026, after that day's INHGA bulletin.
Of the 122 INHGA bulletins between 1 June and 2 October (two are missing, 8 June and 29 September), 91 give a flow below the lowest value recorded in the 183 years on the same date, plus or minus three days. Against the whole month, 15 days in July, 21 in August and 17 in September fall below the lowest day of that month at Orșova; 19 of them are at least 100 m³/s lower, more than the usual gap between two gauges. The INHGA values are from Baziaș and these records from Orșova; against Baziaș's own 46 years, the days below the month's record number 8 in June, 16 in July, 26 in August, 17 in September and 2 in October (June has a high record there, 2,630 m³/s in 1993).
On 2 October INHGA gives 1,350 m³/s at Baziaș, steady, against the October long-term mean of 3,900. Its forecast: 1,350 for two more days, then a slight fall to 1,250 by 9 October. The lowest October flow in the series is 1,330 at Orșova (27 October 1947) and 1,580 at Baziaș (4 October 1992).
Romania's national emergency committee (CNSU) published a risk analysis on 28 September (Decision 23/2026). It forecasts a median of 1,185–1,200 m³/s at Baziaș on 10–13 October and a critical window at Cernavodă on 15–22 October. These are forecasts, not observations. On 25 September, Cristian Bușoi, a state secretary in Romania's Energy Ministry, said a restart of the plant could be discussed only towards mid-October, depending on how forecasts evolve.
- 2026, INHGA bulletins
- 183-year minimum (Orșova)
- 46-year minimum (Baziaș)
- median of 183 years
What the record cannot say
- The validated daily series stops on 31 December 2022. The years 2023–2025 have no days in this analysis, and 2026 comes from provisional bulletins.
- Flow is not level. Cernavodă and Paks stop at a water level; the numerical limits of the Cernavodă intake in 2026 are not public.
- The series does not say why. Channel, dams, rain and snow add up in one number a day. A 2015 study (Stagl and Hattermann, Water 7) projects, by its abstract, falling summer flow across the basin and falling autumn flow in the Middle and Lower Danube; it gives no figures for the Iron Gates.
- Winter minima are less certain than summer ones: two gauges can differ by hundreds of m³/s on the same January day.
Sources
Every number on the page comes from a source below or is calculated from them.
The series
Mean daily discharge at Orșova (1840–2022, 66,840 days, one missing) and Baziaș (1976–2022, the year 1989 is missing), data owned by INHGA, from the Global Runoff Data Centre, downloaded on 2 October 2026.
What is published
GRDC's terms forbid redistributing the data. The page publishes only derived statistics: each month's minimum, counts of days under a threshold, annual means and a few of the lowest days, with dates. The daily series cannot be rebuilt from them.
2026
The INHGA values at Baziaș are those of the daily bulletin Diagnosis and forecast for the Danube, for the 07:00–07:00 interval ending on the bulletin day, rounded by INHGA to 50 m³/s. The comparison with the validated series is approximate: the series differ as described under the checks.
Seasons and thresholds
Cold months are December to March. A day counts as under a threshold when strictly below it. The trend is Kendall over 183 years; differences before and after 1971 are tested by permutation (20,000 shuffles).
Hydropower
Eurostat, gross electricity production from hydro, Romania, all operators, GWh a year (nrg_ind_peh).
The code that computes every number on the page, the values read from the INHGA bulletins and the Eurostat data are published below. The GRDC series is free to request from GRDC, for stations 6742200 and 6742201, in daily format.
- The calculation code (Python)
- Values from the INHGA bulletins, 1 June–2 October 2026 (CSV)
- Eurostat data, hydro Romania (JSON)
Global Runoff Data Centre (GRDC), Koblenz
Mean daily discharge, Orșova 6742200, Baziaș 6742201, Zimnicea 6742500, Ceatal Izmail 6742900
Original data: INHGA. Downloaded 2 October 2026. Required citation: The Global Runoff Data Centre, 56068 Koblenz, Germany. Redistributing the data is not allowed; analysis and statistical products are.
Open the sourceINHGA, Romania's national hydrology institute
Hydrological diagnosis and forecast for the Danube, daily bulletins 1 June–2 October 2026
Flow at Baziaș, monthly long-term means, seven-day forecast.
Open the sourceEurostat
Gross electricity production from hydro, Romania, 1990–2024
Table nrg_ind_peh, in GWh.
Open the sourceMediafax
17 August 2026: pre-regulation lows quoted by the manager of the Iron Gates hydropower plants
Attributed to a named person; the operator's full series is not public.
Open the sourceHidroelectrica
The Iron Gates system: average annual output on the Romanian side
5,241 GWh a year.
Open the sourceOSW, the Centre for Eastern Studies, Warsaw
6 August 2026: drought in the Danube region deals a blow to electricity generation
Quoted: about 25% of the 1,400 MW allocated to each country was operating at the Iron Gates.
Open the sourceNuclearelectrica, via AGERPRES and AP
28 July and 13 August 2026: controlled shutdown of Cernavodă units 1 and 2
Statements quoted by AGERPRES (28 July) and the Associated Press (13 August).
Open the sourceCNSU emergency committee, via MonitorLegal
CNSU Decision 23/2026 of 28 September: the risk analysis
Forecast median at Baziaș and critical window at Cernavodă.
Open the sourceSpotmedia
25 September 2026: Cristian Bușoi on the Cernavodă restart
A reported statement, not the operator's technical schedule.
Open the sourceMVM Paks
30 July 2026: the Paks shutdown, pump intakes above the water level
Official statement.
Open the sourceBMIMI and viadonau, Austria
4 August 2026: shipping on the Austrian Danube
Cargo shipping largely at a standstill; fairway at 2.0 m in the Wachau.
Open the sourceStagl and Hattermann, Water 7(11), 2015
Impacts of climate change on the hydrological regime of the Danube and its tributaries
Only the abstract was checked.
Open the source