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Reading a river (kawa)
Learn to read an opponent's river (kawa): the order of their discards reveals their progress, their likely shapes, and which tiles are safe.
The principle
The river, or kawa, is the ordered sequence of a player's discards, read left to right and top to bottom. Every tile laid down is a decision: it records what the player judged useless at that moment. Following this chronological order, rather than seeing the river as a mere pile, is the foundation of all defensive reading.
Rule and example
The start of the river gives clues, never proof. Early honor or terminal discards are compatible with central development, but also with many other plans. A middle tile discarded late may simply have become redundant and does not prove tenpai.
What changes
Distinguish tedashi, a discard from the hand, from tsumogiri, discarding the draw. A run of tsumogiri only shows that the draws were not kept; it proves neither a frozen hand nor tenpai. Every tile in that player's river is still genbutsu against their ron, while suji reduces some ryanmen risk without excluding other waits.
Mistake to avoid
The river gives probabilities, not certainties: a player can break a pair late or set a trap. Always cross-check your kawa reading with the timing of the riichi and the genbutsu available before pushing a doubtful tile. Read well, a river turns random defense into reasoned discarding.
Rules references
- Tenhou rulesReference profile used for game mechanics and scoring.
- WRC Rules 2025International rules compared whenever their options differ from Tenhou.