Kawa (River/Discards) - Reading Opponent Discards

What is Kawa?

Kawa (River) is the area where each player’s discards are placed during the game. The name comes from how tiles flow like a river as they’re discarded in sequence. Reading the kawa is essential for both offense (predicting waits) and defense (finding safe tiles).

River Layout

Standard arrangement:
1  2  3  4  5  6  ← Row 1 (turns 1-6)
7  8  9  10 11 12 ← Row 2 (turns 7-12)
13 14 15 16 17 18 ← Row 3 (turns 13-18)

*Riichi declaration tile placed sideways
*6 tiles per row is standard

River Components

Element	Description	Importance
Discards	Tiles thrown away	High
Order	Sequence matters	High
Riichi tile	Placed sideways	High
Called tiles	Removed from river	Medium

Reading the River

What Rivers Reveal

Information from rivers:
1. Safe tiles (genbutsu)
   - Already discarded = 100% safe
   - Against that player

2. Relatively safe tiles
   - Suji theory
   - Kabe (wall) theory

3. Hand tendencies
   - Flush possibilities
   - Yaku predictions

River Patterns

Pattern	Likely Hand	Alert Level
Few honors	Yakuhai or Kokushi	High
Few terminals	Chanta-type	Medium
One suit missing	Flush hand	High
All middle tiles	Tanyao	Low

Defense Using Rivers

Genbutsu (Safe Tiles)

Genbutsu importance:
1. 100% safe
   - Same tile already discarded
   - Furiten prevents ron

2. Top priority
   - Against riichi, use genbutsu
   - Multiple options = choose wisely

3. Check all rivers
   - Don't miss any
   - Especially toimen's (far away)

Defensive Tactics

Situation	Check	Action
Riichi called	Genbutsu count	Use genbutsu
Multiple riichi	Shared genbutsu	Safe for all
Late game	River length	Consider flow

River Arrangement Rules

6 tiles per row
- Standard format
- Left to right
Riichi tile sideways
- Marks declaration
- Don’t move it
Called tiles removed
- Order remains in memory
- Gaps show timing
Keep it neat
- Everyone can see
- No rearranging

Advanced River Reading

Early River (Turns 1-6)

What to observe:
- Unwanted tile types
- Honor tile cutting order
- Hand direction clues

Mid River (Turns 7-12)

Observation	Meaning
More safe tiles	Player is cautious
Normal progression	Building hand
Same suji	May be stuck

Late River (Turns 13+)

Tenpai indicators
Desperate discards
Fold signals

Riichi and Rivers

Reading Riichi Player’s River

Before riichi:
- Clean river = likely good wait
- Messy river = lucky tenpai
- Flush tendency = flush wait

Pre-riichi River	Inference	Danger
Clean	Good shape	High
Scattered	Random tenpai	Medium
Suit-heavy	Flush hand	Very High

Sutehai: Discarded tiles
Genbutsu: Safe tiles
Suji: Suji theory
Riichi: Declaration tile sideways

Summary

The kawa (river) is where discards are placed, and reading it is fundamental to mahjong strategy. Genbutsu (same tiles as in the river) are 100% safe, making river awareness crucial for defense. Watch discard patterns to predict opponents’ hands, and always check all four rivers - especially when riichi is called. “Mastering the river is mastering mahjong.”