Orne (river)

The Orne is a river in Normandy, within northwestern France. It is 170 km long. It discharges into the English Channel at the port of Ouistreham. Its source is in Aunou-sur-Orne, east of Sées. Its main tributaries are the Odon and the Rouvre.

Geography
The Orne flows through the following departments and towns:


 * Orne (named after the river): Sées, Argentan
 * Calvados: Thury-Harcourt, Saint-André-sur-Orne, Caen, Ouistreham

Its longest tributaries are, from source to mouth:
 * Don
 * Ure
 * Cance
 * Udon
 * Baize
 * Rouvre
 * Noireau
 * Laize
 * Odon

Name
The name of the Orne in Normandy, which is referred to as the Olinas by Ptolemy, is a homonym of Fluvius Olne, the Orne saosnoise in Sarthe, which Xavier Delamarre traces back to the Celtic olīnā (elbow).

Hydrology and water quality
The waters of the Orne are typically moderately turbid and brown in colour. Its pH level has been measured at 8.5 at the town of St. Andre sur Orne where summer water temperatures approximate 18 C. Electrical conductivity of the water has been measured at 30 microsiemens per centimeter.