water courses water courses regulation 91 hydrology 33 water pollution 33 hydrology of rivers 30 water management 28 flood control 26 more ... environment protection 24 řeky 23 floods 20 water flow rate 17 regulace řek 17 channels 16 river basin 15 stream restoration 15 hydrogeography 14 hydraulic structures 14 sewerage 14 anti-pollution protection of water 14 sediments 14 water reservoirs 14 ecology 13 vodní stavby 13 water structures 11 ecosystems 10 history 10 water quality 10 waterways 10 rain water separators 9 dams 9 less ...