Short answer
A tributary adds water to a larger river. A distributary branches off a main river and carries water away, commonly through a delta. Look at flow direction at a junction rather than the channel’s size or name. 1 2
A tributary joins a main channel; a distributary splits from it. The arrows point in opposite network directions.
On this page
At a glance
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| Question | Tributary | Distributary |
|---|---|---|
| At junction | Joins main channel | Splits from main channel |
| Typical location | Throughout a drainage network | Often near a delta or fan |
| Network effect | Channels converge | Channels diverge |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Tributary. A stream or river that flows into a larger channel. 1
Distributary. A channel that branches away from a main stream and carries water outward, commonly across a delta. 1
Key differences
The terms describe how channels connect. A small channel joining the Mississippi is a tributary; a delta channel carrying Mississippi water toward the Gulf is a distributary. Some networks split and rejoin, so one reach may need contextual description. 1 2
How to tell them apart
Follow the water downstream. If it enters the larger channel, label the incoming channel tributary. If it leaves the main channel toward a separate downstream route, label the branch distributary. 1 2
Where they overlap
Both are flowing-water channels and may transport sediment, flood or change course. They can occur within the same river basin. 1 2
Edge cases
Braided rivers split and rejoin repeatedly. Tidal flows may reverse direction temporarily, so use the system’s ordinary downstream pattern. 1 2
Why the distinction exists
Hydrologists and geographers distinguish converging drainage from diverging delivery of water and sediment. 1 2
Common misconceptions
A distributary is not merely a smaller tributary. Its direction relative to the main channel is reversed. 1 2
Examples
The Missouri joins the Mississippi as a tributary. A channel diverging through a river delta toward the sea is a distributary. 1 2
Sources
Sources checked October 3, 2026.
- NOAA Fisheries — Glossary: Watershed Restoration Research Terms. Tributary; Distributary.
- National Park Service — Delta Landforms. River mouths and sediment deposition.