Cuyo
The river continues south-southeast to cross the east of San Juan Province, were it receives the waters of tributaries Jáchal River and San Juan River (the latter itself fed by the Mendoza River). As it gets closer to the provinces of Mendoza and San Luis, it reaches a deeper area where it created the Lagunas de Guanacache lagoons, currently almost dried out.
Leaving the lagoon areas the river is called Desaguadero ("outlet") and becomes the natural limit between Mendoza and San Luis provinces. From Mendoza it receives the tributaries Tunuyán, Diamante and Guandacol before reaching the parallel 36°S to then enter La Pampa Province. Shortly after it receives from the west the tributary Atuel River; the overflows of both rivers in that area form the Bañados del Atuel.
Read more about this topic: Desaguadero River