The Medellín River called Porce River during most of its course, is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 that flows though the Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

n city of Medellín

Medellín

Medellín , officially the Municipio de Medellín or Municipality of Medellín, is the second largest city in Colombia. It is in the Aburrá Valley, one of the more northerly of the Andes in South America. It has a population of 2.3 million...

 and its metropolitan area

Metropolitan Area of Medellín

The Metropolitan Area of Medellín or the Metropolitan Area of the Aburrá Valley is a metropolitan area and subregion in the Colombian Department of Antioquia...

. For many years an organization called Mi Rio (My River) was involved in cleaning the river, trying to bring the river back to its prior glory and cleanliness.

For the river's first 60 km (37 mi), it is referred to as the Medellín and the Porce thereafter. It is a tributary of the Nechi River

Nechi River

Nechí River is a river of northwestern Colombia. It flows into the Cauca River. Nechí River rises in the municipality of Yarumal, and serves as a boundary between the municipalities of Antioquia, Campamento, Angostura, Anorí, Yarumal, Valdivia, Tarazá, Cáceres, Zaragoza, El Bagre, Caucasia and Nechí...

 which flows in turn into the Cauca River

Cauca River

The Cauca River is a river in Colombia that lies between the Occidental and Central cordilleras. Born in southwestern Colombia near the city of Popayán, it joins the Magdalena River near Pinillos in Bolívar Department, and the combined river eventually flows out into the Caribbean Sea. It has a...

.