Related by context. Frequent words. (Click for all words.) 53 hydrological cycle 52 groundwater aquifers 52 aquifers 51 nonrenewable resources 50 millenniums 49 Aquifers 49 icecaps 48 millennia 48 underground aquifers 48 magma chamber 48 Arctic permafrost 47 salination 47 Fossil fuels 47 freshwater 46 irrigated agriculture 46 desalinated 46 melting glaciers 46 ecologies 46 freshwater ecosystems 46 mineral salts 46 oceans 46 millenia 45 wetland ecosystems 45 atmospheric methane 45 seabeds 45 glaciers melt 45 indigenous cultures 45 oceanic crust 45 clathrates 45 acidified 45 marine sediments 45 rivers lakes 44 magmas 44 reservoirs 44 replenished 44 overexploitation 44 underground aquifer 44 Melting glaciers 44 seawater 44 carbonic acid 44 metabolised 44 peat bogs 44 glacier melt 44 glacial melt 44 biota 44 meltwater 44 tailing ponds 43 refilled 43 acidifying 43 glaciers 43 finite resource 43 fertile soils 43 artesian wells 43 biodegrading 43 Toxic chemicals 43 acidic soils 43 constantly replenished 43 water 43 overexploited 43 Earth ozone layer 43 oxygenating 43 earths 42 overfishing pollution 42 Cyanobacteria 42 ecosystems 42 cenotes 42 erupting volcanoes 42 groundwater extraction 42 groundwater 42 aquifer 42 whale blubber 42 Hydraulic fracturing 42 sulphates 42 upwellings 42 hypochlorite 42 methane hydrates 42 melting glacier 42 overpumping 42 retreating glaciers 42 plate tectonics 42 bauxite ore 42 Great Artesian Basin 42 methane hydrate 42 biodegrades 41 hydrocarbon fuels 41 streambeds 41 Volcanic eruptions 41 pasteurisation 41 Omo River 41 lavas 41 lithosphere 41 melting snowpack 41 rivers 41 deplete oxygen 41 vast quantities 41 ancient Mayans 41 tooth enamel 41 underground caverns 41 Soil erosion 41 rampant deforestation 41 marine reptiles