its drainage basin. Thus, for an average flow of before the Mayenne's confluence with the Oudon, the yearly minimum flow can range from very low ( at Laval) to very high (flash floods with flows of at Laval and more than at Chambellay). The flow of the Mayenne has been observed for a period of 44 years (1965-2008) at Chambellay, situated upstream of the confluence with the Sarthe, and just upstream from where the Oudon joins the Mayenne. At this location, the drainage basin of the river is out of a total of , which is less than three-quarters of the entire drainage basin (71.5%), and also does not include the flow of the Oudon, the Mayenne's principal tributary. The average yearly flow at Chambellay is , which corresponds to over if the rest of the drainage basin were included. Tributaries The main tributaries of the Mayenne are, from source to mouth: Varenne Colmont Ernée Jouanne Vicoin Oudon References External sources River Mayenne (River Maine) and River Oudon, with maps and details of places, ports and moorings, by the author of Inland Waterways of France, Imray Navigation details for 80 French rivers and canals (French waterways website section) Rivers of France Rivers of Mayenne Rivers of Maine-et-Loire Rivers of Orne Rivers of Normandy Mayenne