01 · Before the reservoir
Where did old Orșova stand?
The 1939 map shows the Cerna branching through a floodplain 500 to 700 metres wide, bordered by terraces. Orșova, Jupalnic and Tufări had grown on the floodplain and low terraces. The Cerna’s old mouth lay 4 kilometres downstream of its present position.
The old town site is under water. The drawing keeps only the relationships between river, floodplain, terraces and the two town sites. The paper publishes a topographic map of the floodplain, with roads and building symbols; this schematic does not digitise them. The studies consulted do not list, building by building, what was demolished or left standing.
02 · 1966–1974
First the town moved. Then the reservoir rose.
The planning report places the move from the old site between 1966 and 1974, 3 kilometres north, on the fourth terrace. The new town brought old Orșova together with Jupalnic, Tufări and Coramnic.
The town hall gives the new town’s terrace an elevation of 110 to 130 metres; land below 70 metres, including the floodplain and three lower terraces, was covered by the reservoir. In 1970 the new town’s street network was almost 16 kilometres long.
Zaharia writes that the reservoir filled in stages from February 1970 to November 1971. The 2021 paper says the Iron Gates I reservoir reached its operating level in 1972. The drawing raises the water for orientation; it does not assign intermediate water levels to this place. The sources do not give the day the main street went under.
What do the 30 metres mean?
In the 2021 paper, Nistor and his co-authors write that upstream of the dam the water rose by about 30 metres, and the river turned into a lake. They place the dam about 900 kilometres from the mouth of the Danube. The gulf lies between kilometres 953 and 955. The rise and the gulf are not the same place.
Liliana Zaharia, in 2010, prints two wordings in one study. The abstract says the water level rose by as much as 27 metres in the vicinity of the dam. Further down, a sentence about the navigable channel says the water rose by 30 metres behind the dam. The two figures stay side by side. They are not averaged.
How deep is the Cerna Gulf?
The same 2021 paper measures the gulf. It covers almost 500 hectares, reaches a depth of 24 metres, and is almost 3.4 kilometres long and about 1.4 kilometres wide. The depth map's scale runs down to 23.6 metres. Those are two wordings of one drawing.
The sounding was made on 29 March 2017 and 25 October 2017 with a Garmin GPSMAP 298, on 33 transects 100 metres apart, a point every 10 metres, 5,551 points in all. The sounder sat 0.30 metres under the surface. The daily level, from the River Administration of the Lower Danube, was 68.744 metres in March and 69.444 metres in October. The March day was given a further 0.7 metre correction so the two days share a reference, plus 0.224 metres for the Sulina to Constanța difference. The 24 metres belong to the gulf at those levels, not to a named day of a full pool.
The 2013 environmental report for the town plan gives the same water other dimensions. The Cerna enters the Danube through a gulf 5 kilometres long, 2 kilometres wide and 22 to 23 metres deep. The report also calls the place the Orșova gulf. The two descriptions stay side by side.
69.5 − 48 = 21.5
Zaharia prints the maximum retention level as 69.5 metres above sea level, citing Aquaproiect 1992. The military maps redrawn in the 2021 paper, at 1 to 20,000 from 1939 and 1 to 25,000 from 1952, have contours every 10 metres, and the printed heights include 48, 50 and 70 metres. Subtracting gives 21.5 metres. The 48 metre point is not a street, and 21.5 metres is not the 2017 sounding.
How much mud lies on the old town?
The paper says the old town of Orșova, in the western part of the gulf, is covered with a sediment layer 5 to 6 metres thick. On the opposite side the thickness reaches 12 metres. Toward the Danube, sediment covers a compact strip up to 14 metres thick and more than 500 metres wide. The 5 to 6 metres on the town are mud, not the column of water.
Zaharia has another 5 to 6 metres. Hers is a water depth for the whole reservoir, from 5 to 6 metres out to 110 metres. The two pairs do not add.
Where are the 110 metres?
Zaharia writes that the reservoir's depth runs from 5 to 6 metres to 110 metres, and that the maximum is a pit beside the Tabula Traiana. She cites a 2003 paper. The greatest width she prints, 4.6 kilometres, is at Moldova Veche. She names Orșova among the wide basins of the gorge. The 110 metre pit is not the Cerna Gulf.
Ada Kaleh and the gorge have their own pages, Ada Kaleh and the Iron Gates. This one is the bank at the mouth of the Cerna.