Along the entire province, and on the eastern border, the Paraná River is found along with its islands and associated streams. This region is permanently changing; its entire landscape is modified by the rhythm of the flood and ebb tides. With rising tides, the river erodes and drags material; during the dry season, it creates sand banks where vegetation forms ‘forest in galleries’ with alders, willows, pacara earpod trees, laurels. Fauna: otter, yacare caiman, capybara, neotropic cormorant, dorado, spotted sorubim.