Rivers 56 History 26 Dissertations, Academic (Ph.D) 21 Water 17 Ecology 16 Hydrology 15 River 15 Stream ecology 14 Literature 13 Water resources development 13 Dams 12 Geography 12 India 12 Computer networks 11 Human ecology 11 Mathematics 11 Computer security 10 Fiction 10 Novel 10 Lakes 9 Religion 9 River, stream ecology 9 Thesis (Ph.D)-Zoology 9 Voyages and travels 9 Water quality 9 Watershed management 9 Operating systems (Computers) 8 Pollution 8 American fiction 7 Aquatic ecology-- Fresh water ecology-- Pond ecology-- Limnology 7