| 100% | DES | 3 | ___ Moines River (tributary of the Mississippi) |
| 76% | YAZOO | 5 | Tributary of the Mississippi |
| 73% | ARKANSAS | 8 | Major tributary of the Mississippi |
| 73% | REDRIVER | 8 | Colorful tributary of the Mississippi |
| 71% | OHIO | 4 | Longest west-flowing tributary of the Mississippi |
| 71% | MARNE | 5 | Tributary of the river Seine |
| 71% | GILA | 4 | Tributary of the Colorado River |
| 71% | EBOLA | 5 | Tributary of the Congo River |
| 71% | OSAGE | 5 | Tributary of the Missouri River |
| 68% | PASHA | 5 | Tributary of the Svir River in NW Russia |
| 68% | YARROW | 6 | Tributary of the River Douglas skirting Chorley, Lancashire |
| 68% | DERWENT | 7 | Tributary of the River Trent upon which Derby stands |
| 68% | CHERWELL | 8 | Tributary of the River Thames that flows through Oxford |
| 67% | OTTAWA | 6 | Chief tributary of the St. Lawrence River |
| 67% | GILA | 4 | Much depleted tributary of the Colorado River |
| 67% | IRTYSH | 6 | Main tributary of the Ob River in Russia |
| 66% | KAMA | 4 | Tributary of the Volga River upon which Perm and Solikamsk stand |
| 66% | ZUNIS | 5 | Dwellers along a tributary of the Little Colorado River |
| 66% | ITASCA | 6 | Lake —, source in Minnesota, US, of the Mississippi River |
| 65% | WHOTHEHELLKNOWS | 15 | Left tributary of the Vitim River in Irkutsk Oblast, Russia |
| 65% | MORAVA | 6 | Central European river, tributary of the Danube |
| 63% | WHARFE | 6 | Tributary of the River Ouse in West and North Yorkshire upon which Ilkley stands |
| 63% | IOWA | 4 | The Mississippi and Missouri rivers form parts of its border |
| 62% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with Belarus and Ukraine |
| 62% | BRENT | 5 | Major tributary of the River Thames rising in the London Borough of Barnet |
| 62% | MOHAWK | 6 | Largest tributary of the Hudson River in the state of New York, US |
| 62% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with both Belarus and Ukraine |
| 61% | REDDEER | 7 | City in S Alberta, Canada, on a major tributary of the South Saskatchewan River |
| 60% | PLATTE | 6 | — River, tributary of the Missouri in Nebraska, US, upon which Fremont stands |
| 59% | OHIO | 4 | River that joins the Mississippi in the southeast corner of the 43-Across |