Further south, separating the department from San José Department to the west, is the stream Arroyo de la Virgen, a tributary of Santa Lucia River. The later forms the south border of the department, separating it from Canelones Department, with its tributaries flowing through the south part of the department. From east to west, these are: Arroyo Chamaré and Arroyo Casurá, both of which are part of the east border of the department, Arroyo Chamizo, Arroyo de Arias and the Santa Lucia Chico River, with Arroyo de Pintadito as its tributary. A dam in the course of the Santa Lucia Chico River near 25 de Mayo and Cardal forms the Paso de Severino Reservoir.