Related by context. Frequent words. (Click for all words.) 54 groundwater 52 contaminate groundwater 50 contaminating groundwater 49 underground aquifers 47 aquifers 47 contamination 47 contaminate drinking 47 perchlorate contamination 47 arsenic contamination 47 groundwater pumping 46 aquifer 45 polluted groundwater 45 pollute groundwater 45 USGS 44 contaminants 44 groundwater recharge 44 groundwater contamination 44 streamflow 43 chlordane 43 contaminated 43 hydrologists 43 Geological Survey 43 aquifer recharge 42 hydrologic 42 GBRA 42 underground aquifer 42 exceedances 42 desalinated 42 Hydrologists 41 Soil samples 41 Groundwater 41 streamflows 41 hydrogeologist 41 Geologic Survey 41 groundwater basin 41 Geological Survey USGS 41 perchlorate 41 seepage 41 evapotranspiration 40 contaminant 40 atmospheric methane 40 Floridan Aquifer 40 hydrogeological 40 water 40 soils 40 trace amounts 40 naturally occurring radioactive 40 nitrates 40 hydrology 40 hydrological cycle 39 Edwards Aquifer Authority 39 fracking fluids 39 contaminating 39 sediment 39 arsenic 39 methane hydrates 39 Perchlorate 39 aerosol particles 39 sedimentation 39 mountain snowpack 39 saltwater intrusion 39 contaminate 39 radionuclides 39 Contaminants 39 harmful contaminants 39 subsurface 39 fecal contamination 39 arid regions 39 MtBE 39 soil borings 38 Ogallala Aquifer 38 reservoirs 38 hydrogeology 38 radioactive contaminants 38 reinjection 38 irrigate crops 38 dissolved oxygen levels 38 leaching 38 evaporation ponds 38 depletion 38 contaminated groundwater 38 toxicants 38 biota 38 iodide 38 trichlorethylene TCE 38 treated effluent 38 irrigated farmland 38 salinity 38 percolation 38 Edwards Aquifer 38 mg l 38 toxic byproducts 38 sulfates 37 radioactive contamination 37 nitrate 37 Toxic chemicals 37 sediments 37 arsenic mercury 37 radionuclide 37 fecal bacteria 37 Nature Geoscience