World Wildlife Fund ( WWF ) identifies twelve major habitat types of freshwater ecoregions : Large lakes , large river deltas , polar freshwaters , montane freshwaters , temperate coastal rivers , temperate floodplain rivers and wetlands , temperate upland rivers , tropical and subtropical coastal rivers , tropical and subtropical floodplain rivers and wetlands , tropical and subtropical upland rivers , xeric freshwaters and endorheic basins , and oceanic islands .
The WWF speaks of seven major habitat types of freshwater ecoregions : Large rivers , large river headwaters , large river deltas , small rivers , large lakes , small lakes , and xeric basins .