From OpenStreetMap Wiki
This is used to described different types of waterways. When mapping the way of a river, stream, drain, canal, etc. these need to be aligned in the direction of the water flow. See the page titled Waterways for an introduction on its usage.
|waterway||river||For narrow rivers which will be rendered as a line. For larger rivers see also waterway=riverbank (Other languages).|
|waterway||riverbank||Used for larger rivers in addition to waterway=river, to define an area between the opposite riverbanks. See water=river for alternative tagging.|
|waterway||stream||A naturally-formed waterway that is too narrow to be classed as a river. An active, able-bodied person should be able to jump over it if trees along it aren't too thick.|
|| A natural, dry (ephemeral) riverbed that contains water only during times of heavy rain or simply an intermittent stream, in semi-arid areas. Also known as a "Wash" in the deserts of America.
It has been recommended to stop using this tag. For intermittent waterways use waterway=river/waterway=stream + intermittent=yes. For valleys natural=valley.
|| Dry stream bed - negative forms of erosion relief formed by the activity of temporary streams.
Don't use this tag. For intermittent waterways use waterway=stream + intermittent=yes. For valleys use natural=valley.
Man made waterways
|waterway||canal||An artificial open waterway used for transportation, waterpower, or irrigation.(Other languages).|
|waterway||drain||An artificial waterway for carrying storm water or industrial discharge.|
|waterway||ditch||A small to moderate depression created to channel water.|
|waterway||fairway||A navigable route in a lake or sea marked by buoys. (Note: conflicts with seamark:type=fairway)|
|waterway||dock||An 'enclosed' area of water used for building or repairing ships.|
|waterway||boatyard||Boat yard – a place for constructing, repairing and storing vessels out of the water.|
Barriers on waterways
|waterway||dam||A wall built across a river or stream to impound the water. A dam normally does not have water flowing over the top of it.|
|waterway||weir||A barrier built across a river, sometimes to divert water for industrial purposes. Water can still flow over the top.|
|waterway||waterfall||A waterfall, use in combination with natural=cliff|
|waterway||lock_gate||To mark the position of gates at each end of a lock. Alternatively, for smaller locks use a single lock=yes node in the middle of the lock.|
Other features on waterways
|waterway||turning_point||A place to turn the driving direction for vessels, where the boats are longer than the river/canal is wide. Use maxlength=* to denote the maximum length of the vessel.|
|waterway||water_point||A place to fill fresh water holding tanks of a boat.|
|waterway||fuel||A place to get fuel for boats.|
Some additional attributes for waterways
|intermittent||yes||Indicates that the waterway does not have a permanent flow (i.e. is sometimes/often dry).|
|seasonal||yes, spring, summer, autumn, winter, wet_season, dry_season||Indicates that a waterway has a seasonal (yearly cyclic) flow.|
|lock||yes||()||A lock is used for moving boats between waterways at two different levels. Can tag either the section of the way between the gates (detailed) or just a single node in the waterway (less detailed).|
|mooring||yes, private, no||A length of bank where boats are explicitly permitted to moor. maxstay=* should be used for timing information.|
|service||transportation, water_power, irrigation||A waterway=canal may have one (or more; separate with semicolons) uses.|
|tunnel||culvert||()||For streams passing under a road in culverts use tunnel=culvert+layer=-1 on the section of stream passing under the road. Don't use either of these tags for streams passing under bridges.|
|waterway||user defined||All commonly used values according to Taginfo|