Ozanne
The Ozanne is a 46.0 km long French river, a tributary of the Loir, which is a tributary of the Loire.
Geography
The river spring is located at Perche-Gouët, Béthonvilliers at 222 m high at le Burail locality in le Bois de Beaumont.2 offshoots: la Suzanne ou Sainte-Suzanne et l'Ozanne de Dampierre ou Moranne ou Mozanne which join near Brou.
It flows into le Loir, right bank, 1 km north of Bonneval at 129 m high at Ouzenain.
Tributaries
The Ozanne has seven official tributaries :- ,, 3 km, in the two communes of Vicheres and Beaumont-les-Autels.
- , 0.9 km, in the two communes of Miermaigne and Beaumont-les-Autels.
- Seven branches of the Ozanne, for a total of 8.3 km in the six communes of Unverre, Brou, Yèvres, Dangeau, Moulhard and Luigny.
- The Sainte Suzanne,, 19.2 km in the five communes of Unverre, Authon-du-Perche, Charbonnières, Beaumont-les-Autels and Les Autels-Villevillon with two tributaries:
- * 4 km a branch of the Unverre.
- * The Sonnette,, 13.5 km in the five communes of Unverre, Charbonnières, Soize, La Bazoche-Gouet, and Les Autels-Villevillon.
- The Vallée d'Esse,, 10.1 km in the two communes of Unverre and Yèvres.
- The Vallée de Tronchet,, 8.8 km in the sole commune of Yèvres.
- The vallée de Montparentière,, 3.1 km in the commune of Yèvres.
- The vallée des Vollars,, 6.3 km in the three communes of Yèvres, Dangeau, and Gohory.
Watershed
The hydrological area of the Ozanne and its affluents is 278 km² wide, which is composed of farming land, of forests and semi-natural areas, artificial areas and damp areas.Hydrology
The Ozanne discharge was studied from 1973 to 2014 at Prémoteux, near Trizay-lès-Bonneval at 126 m high, very close to its meeting point with the Loir. The river watershed is of 268 km2.The river module at Trizay-lès-Bonneval is of 1.46 m3/s.
The river has minor seasonal discharge fluctuations, with high waters in winter: mean monthly flow of 2.71 and 3.61 m3/s, from December to March and low waters in summer, end of May to beginning of October, with a mean monthly debit drop of up to 0.235 m3 in August.
Low waters
However, the 3-day low-water volume can drop to a severe 0.044 m3/s during a dry five-year period.Floods
Floods can also be important.The maximal discharge recorded was 65.2 m3/s on January 22, 1995, while the maximal daily flow was 52.6 m3/s on April 10, 1983, which is expected to happen every 10 to 15 years on average. The maximal height was 1920 mm on January 14, 2004.