The Hermance is a river that rises in France in Haute-Savoie

Haute-Savoie

Haute-Savoie is a French department in the Rhône-Alpes region of eastern France. It borders both Switzerland and Italy. The capital is Annecy. To the north is Lake Geneva and Switzerland; to the south and southeast are the Mont Blanc and Aravis mountain ranges and the French entrance to the Mont...

, between Machilly

Machilly

Machilly is a commune in the Haute-Savoie department in the Rhône-Alpes region in south-eastern France.-References:*...

 and Loisin

Loisin

Loisin is a commune in the Haute-Savoie department in the Rhône-Alpes region in south-eastern France.-References:*...

, and flows for 7 kilometres through the small valley from Hermance and the commune of Veigy-Foncenex

Veigy-Foncenex

Veigy-Foncenex is a commune in the Haute-Savoie department in the Rhône-Alpes region in south-eastern France.-References:*...

 where it marks the Swiss-French border on the last 6 kilometres of its course by bordering the communes of Anières

Anières

Anières is a municipality in the canton of Geneva in Switzerland.The inhabitants are known as "Aniérois".-History:Anières is first mentioned in 1179 as [Guillelmus] dasneres. It became an independent municipality in 1858 when it separated from Corsier.-Geography:Anières has an area, , of...

 and Hermance

Hermance

Hermance is a municipality of the Canton of Geneva, Switzerland.-History:Hermance is first mentioned in 1247 as intra Armentia. In 1271 it was mentioned as Eremencia.-Geography:...

 in Switzerland and Chens-sur-Léman

Chens-sur-Léman

Chens-sur-Léman is a commune in the Haute-Savoie department in the Rhône-Alpes region in south-eastern France.-World heritage site:It is home to one or more prehistoric pile-dwelling settlements that are part of the Prehistoric Pile dwellings around the Alps UNESCO World Heritage Site.-References:*...

 in France,
before flowing into Lake Geneva

Lake Geneva

Lake Geneva or Lake Léman is a lake in Switzerland and France. It is one of the largest lakes in Western Europe. 59.53 % of it comes under the jurisdiction of Switzerland , and 40.47 % under France...

.

Flood control and other river maintenance issues are regulated under the 1959 Hermance River Agreement.