Related by context. Frequent words. (Click for all words.) 80 aquifers 75 aquifer 74 groundwater 60 reservoirs 59 Groundwater 55 water 55 river basin 55 headwaters 54 freshwater 53 watersheds 52 river basins 52 rivers lakes 52 rainwater 51 rivers 51 snowmelt 50 tributaries 50 potable 50 silt 50 soils 50 reservoir 49 basin 49 wastewater 49 septic tanks 49 irrigators 49 sediment 48 irrigate 48 sewage 48 River basin 48 nitrates 48 effluent 48 hydrological 47 basins 47 wetlands 46 leachate 46 reverse osmosis 46 untreated sewage 46 floodplains 46 floodplain 46 brine 46 coal seams 46 sediments 46 snowpack 45 polluted 45 septic systems 45 topsoil 45 potable water 45 lakes rivers 45 irrigation 45 fracking 44 lakes 44 megalitres 44 flood plain 44 irrigated 44 raw sewage 44 nitrate 44 methane 44 flood plains 44 catchments 44 catchment 44 sedimentation 44 wells 44 dams 43 groundwater contamination 43 riverbed 43 creeks 43 landfills 43 sewage treatment 42 contaminants 42 rainwater harvesting 42 salinity 42 Water Resources 42 arsenic 42 arable land 42 sandy soil 42 desalination plants 42 evaporation 42 desalination 42 rainfall 42 seawater 42 waterways 42 estuaries 42 cistern 42 wastewater treatment 42 stormwater 42 drinkable water 42 magma 42 estuary 41 phosphorus 41 aqueduct 41 watershed 41 lagoons 41 cropland 41 carbon dioxide 41 coal seam 41 pollutants 41 stormwater runoff 41 methane gas 41 wetland 41 River Basin 41 farmland 41 quarries