The Tercero River (, 'Third River'), also known as Ctalamochita, is the river in Córdoba Province of Argentina. It originates in the Sierras de Córdoba near Cerro Champaquí and Calamuchita Valley, in an area of annual precipitation of between 600 and 1000 mm. Leaving the valley, it reaches the plains where four dams have been constructed, called Cerro Pelado Dam, Arroyo Corto Dam, Embalse Río Tercero — with 54.3 km2 built in 1936 — and Piedras Moras, which serve as flow regulators and produce hydroelectricity. The reservoirs created by the dams are also used for tourism and recreation, including water sports and fishing. It has a water flow of 27.17 m3/s, and flows 307 km before reaching the Carcarañá River. The river navigable for small- to medium-sized boats as it flows through the plains. It flows eastward into the Humid Pampas, which has an average rainfall of 730 mm per year. It joins the Saladillo River (also called the Cuarto River) to form the Carcarañá River, a tributary of the Paraná River. Among the most important cities on the path of the Tercero are Río Tercero, Villa María, Villa Nueva, Bell Ville and Leones. The word Ctalamochita (from which the term Calamuchita derives) seems to be a mixture of the Native American term ctala or tala, meaning "important tree", and a deformation of the Spanish mucho or muchito, finally meaning "area of many trees". The name Tercero became more common since the 18th century, being the third of five rivers counting from Córdoba city. Of them, the Tercero and the Cuarto (fourth) are the only ones to reach, indirectly, the Paraná River, being therefore tributaries to the Río de la Plata Basin.

Bridges

The river has the following bridges from Piedras Moras dum to the Carcarañá River: