Rivers History 45 Regulation 28 Environmental aspects 24 Stream ecology 18 Description and travel 16 Water 16 más ... Law and legislation 15 Social aspects 13 Inland navigation 11 Stream conservation 10 Dams 9 Harbors 9 Salmon fishing 9 Stream restoration 9 Travel 9 Water resources development 9 Environmental conditions 8 Navigation 8 Canoes and canoeing 7 City planning 7 Drainage 7 Geology 7 Geomorphology 7 Hydrology 7 Mountains 7 Pollution 7 Water-supply 7 Canals 6 Economic aspects 6 menos ...