Flooded grasslands occur in two areas of northern South America, the Guayaquil flooded grasslands of western Ecuador and the Orinoco flooded grasslands of northeastern Venezuela. The Guayaquil flooded grasslands expand along the Guayas River Basin and are a tropical freshwater marsh formation. The Orinoco flooded grasslands exist within a matrix of forest and savanna systems and form along the north delta of the Orinoco River, which is the second largest river in the Neotropics. Grass species that exist here are classified as tall and tropical, though alterations to the wetland hydrology (due to dam projects) has created a saline environment that is affecting species composition.