The lake turns to be the head of the Charest River which, a priori, flows south-west over 1.5 kilometers in the territory of Notre-Dame-de-Montauban until the limit of Saint-Ubalde.

In Saint-Ubalde’s territory, the river flows through the rows Saint-Paul, Saint-Achilles and Sainte-Anne, going gradually away from the boundaries of the Lac-aux-Sables.

In his course in Saint-Ubalde, the river recovers waters of fews lakes, including Sainte-Anne and "à la Perchaude" (perch).

The shape of the lake Charest resembles to a pear which is raising his hat, and the top facing north.

Streets "Des Écureuils" (Squirrels), "du camping" et "Saint-Paul" are surrounding Charest lake.