The Rio Uruguai (Uruguay River) is one of South America's great fishing rivers, forming part of the border between Rio Grande do Sul, Brazil and Argentina as it flows through the Northwest region of the state. The river is born from the confluence of the Rio Pelotas and the Rio Canoas, with the Pelotas originating in the Serra Geral Formation on the border between Santa Catarina and Rio Grande do Sul. From its headwaters, the river transitions from steep, rocky terrain marked by narrow channels, rapids, and waterfalls into a broad, powerful waterway that can reach widths of up to one kilometre in certain stretches. The river's depth is remarkable — in the Route region (Rota das Missões area of Northwest Rio Grande do Sul), a fissure in the ground causes depths exceeding 100 metres in places, while shallower areas near the banks provide calmer water. The climate of the region is humid subtropical (Cfa), characterized by rainfall well distributed throughout the year, which contributes to relatively stable flow conditions without the dramatic flood pulses seen in other parts of the La Plata basin.