The Río Dulce begins at the Termas de Rio Hondo reservoir in the province of Santiago del Estero, which reservoir receives contributions from rivers that are born in the Calchaquíes summits in the province of Tucumán. El Dulce crosses the entire province of Santiago del Estero, having in the middle and lower part, almost no contact with the human being; and finally it flows into the important endorheic basin of the Mar Chiquita lagoon, in the province of Córdoba.
In the upper part,the water have transparents tones and sand bottoms, but in the summer season, it suffers from violent floods that dirty the water and change the course of the river, all this causes, that in its channel, there are large amounts of trees, which were deposited by the crescent.
The changing characteristics of the river and the warmth in the water temperature cause it to be the ideal habitat for large predatory fish such as Dorados (Salminus Brasilensis) and Tarariras (Hoplias Malabaricus). That, at the time of fishing they give unparalleled fighting. The Rio Dulce is one of the best places in Argentina for the practice the Golden Dorado Fishing in Driftboats with Lure, Fly, Live Bait or Spinning, since in its waters the Dorados and the Tarariras are found in abundance. And in its middle and upper section it has palisades, slides and ravines, all these are the places chosen for predatory fish to prey on their prey; so, when the sport fisherman sets near those places, the lures are strongly attacked