Related by context. Frequent words. (Click for all words.) 52 watersheds 52 groundwater 51 aquifer 50 aquifers 50 reservoirs 49 hydro dams 49 headwaters 48 underground aquifers 48 headwater 48 underground aquifer 48 groundwater basin 47 irrigators 47 groundwater pumping 47 river basins 47 basin 46 polluted groundwater 46 freshwater mussels 46 river basin 46 Ogallala Aquifer 45 rivers 45 migratory fish 45 watercourse 45 freshwater wetlands 45 groundwater recharge 45 basins 44 Nile basin 44 bottomlands 44 aquatic ecosystem 44 weirs 44 freshwater 44 wetland habitat 44 Waitaki River 44 Upper Klamath 44 aquatic ecosystems 43 Aquifer 43 Middle Fork 43 Salinity 43 irrigated agriculture 43 hydropower 43 sewage lagoons 43 dams 43 Edwards Aquifer 43 Treatment Plant 43 Snake River dams 43 catchment 43 tributaries 43 reservoir 43 riparian 43 Groundwater 43 streambed 43 freshwater lakes 43 streambeds 43 lakes 42 bottomland 42 mainstem 42 wetland 42 Water Conservancy 42 Catchment 42 Great Lakes 42 aquatic habitat 42 Great Lakes basin 42 hydropower dams 42 lamprey 42 aquatic habitats 42 fragile ecology 42 catchments 42 waterbodies 42 wetlands 42 wetland habitats 42 freshwater ecosystems 42 spawning beds 42 waterways 42 NRDs 42 diking 42 transboundary 41 Friant Dam 41 contaminated groundwater 41 endangered salmon 41 wellfield 41 arid regions 41 Klamath Basin 41 River basin 41 navigable waterways 41 Didymo 41 streamflows 41 wildlife habitat 41 gasfields 41 hydroelectric dams 41 Irrigation District 41 estuary 41 Delta smelt 41 trout fishery 41 Penobscot River 41 Coho salmon 41 Basin 40 water 40 Snake River 40 Asian republics 40 Eel River 40 rangelands 40 salinity