Ouzoum

The Ouzoum or Ouzom  is a left tributary of the Gave de Pau, in the Southwest of France, between the Génie longue and the Béez. It is 33.3 km long.

It flows into the Gave in Nay, upstream from Pau.

Name
Historical graphies were oscillating between the voiced -s- and the unvoiced -ss-: Oson (1441), Osom, Osson, Ozon (1538), le Lozon (1581), l ' Ouson (1585).

This name could be related with the Pyrenean hydronym Ousse.

Geography
The valley of the Ouzoum is separated in two distinct parts by a 9 km long narrow pass. The villages in the upper part of the valley (Arbéost and Ferrières) belong to the Hautes-Pyrénées and have relationships with the Val d'Azun, on the other side of the mountain. On the other hand, the lower part of the valley, close to Pau, is Béarnese (Pyrénées-Atlantiques).

The Ouzoum rises at Cap d’Ouzom ("head of Ouzom") at 1131 m above sea level in the Litor Circus dominated by the Grand Gabizos at 2692 m. This circus is in relation with the Val d'Azun through the Col du Soulor at 1474 m and with the Ossau Valley through the Aubisque Pass at 1709 m.

After the basin of Ferrières, the Ouzoum flows through a narrow pass bordered by steep limestone slopes. The valley widens after Arthez-d'Asson.

Its hydrographic regime is pluvio-nival.

Départements and towns

 * Hautes-Pyrénées: Arbéost, Ferrières
 * Pyrénées-Atlantiques: Asson, Arthez-d'Asson, Igon, Nay.