Related by context. Frequent words. (Click for all words.) 72 aquifers 70 groundwater 68 underground aquifers 67 underground aquifer 67 aquifer 61 reservoirs 60 water 59 groundwater recharge 59 reservoir 58 Groundwater 57 watersheds 56 Ogallala Aquifer 56 Aquifer 55 contaminate groundwater 55 contaminated groundwater 55 lakes 54 arsenic contamination 54 treated effluent 54 contaminants 53 irrigate crops 53 total dissolved solids 53 nitrates 53 headwaters 53 wells 53 ponds 53 freshwater 52 septic systems 52 soils 52 Creek tributary 52 lake 52 dissolved solids 51 basin 51 streamflows 51 sediment 51 rivers 51 groundwater pumping 51 Nitrates 51 sandy soils 51 Athabasca River 51 lakebed 51 contaminate drinking 50 river basins 50 basins 50 potable 50 groundwater contamination 50 lagoons 50 wastewater 50 waterbodies 50 septic tanks 50 saltwater intrusion 50 streambed 50 Reservoirs 49 rivers lakes 49 Great Lakes basin 49 streambeds 49 drainage basin 49 fecal coliform bacteria 49 artesian 49 effluent 49 nitrate 49 streamflow 49 irrigated agriculture 49 geologic formations 49 chloramine 49 sediments 49 arsenic 49 naturally occurring bacteria 49 brackish water 49 wetlands 49 fecal contamination 49 River basin 49 river basin 49 Raw sewage 48 fecal bacteria 48 freshwater lakes 48 Contaminants 48 ash ponds 48 brackish 48 Upper Klamath 48 potable water 48 fertile soils 48 glacial lakes 48 creek 48 contaminant 48 meltwater 48 livestock manure 48 seepage 47 dissolved oxygen levels 47 Edwards Aquifer 47 snow melt 47 lakes rivers 47 fecal coliform 47 tributaries 47 tritium 47 contamination 47 chlorinate 47 Sediment 47 borewells 47 Soil moisture 47 watercourse 47 catchments