The river begins in the highlands of the Huarochirí Province in the Lima Region and its mouth is located in Callao, near Jorge Chávez International Airport.

[2] The name Rímac is from the Quechua word rimaq, meaning "speaker, speaking",[3] leading to it being nicknamed El Río Hablador ("the talking river").

Parallel to the Rímac River runs the Central Highway and a railway line, which starting from the port of Callao, reaches the city of La Oroya in the department of Junín, to later divide into two (one to the south and the other to the north), but not before going through the Abra de Anticona, better known as Ticlio, located at 4840 mamsl.

On its margins, in the part of the mountains, several tourist restaurants, vacation and recreation centers can be found, as well as a series of clubs, which serve as escape points for the people of Lima in the cold and humid winters.

The "maximum discharge in 24 hours", which occurred in the Rímac river and registered at the Chosica station, amounts to 385 m³/s (in 1941) and was only repeated on another occasion with 380 m³/s (in 1955) (since there was a record of less than 120 years, the risks of extrapolating are high).

[6] The decrease in the flow of the Rímac during the dry season, in addition to the constant growth of Lima, prevented a good supply of drinking water in the city.

For this reason, in 1962 the Peruvian government carried out the water transfer project from the Marcapomacocha lagoon, which belongs to the Mantaro river basin, through a 10-kilometre siphon-shaped tunnel at 4,000 mamsl that crosses several glaciers.