Lagoa dos Barros is a freshwater lake covering approximately 92 square kilometers, situated within the Litoral Medio Basin on the Coastal Plain of Rio Grande do Sul (Planície Costeira do Rio Grande do Sul) in southern Brazil. Though located in a coastal region, it is not classified as a coastal lagoon because the local topography prevents any direct connection to the ocean — the basin instead drains through the Lagoa dos Patos. The lake is a vital resource for the surrounding region, particularly for irrigated rice agriculture, which draws heavily on its waters during the summer months. The surrounding landscape includes remnants of Atlantic forest, with the protected area known as Manuel de Barros Pereira covering approximately 24.61 hectares and recognized as a conservation zone under Santo Antonio da Patrulha law number 2549/1992. The municipality of Santo Antonio da Patrulha, which borders the lake, has a strong interest in preserving the ecosystem as a future freshwater supply for the city.