River flow rates can have a dramatic effect on the difficulty of the Cruise, and, hence, upon the amount of communications traffic generated by boaters in trouble. Low water causes sand bar difficulties on the Green and a more difficult passage through “The Slide,” the one section of whitewater on the course, on the Colorado. High water at that time of year can mean difficulty with driftwood, particularly if a new peak has just been attained.
In the most successful cruises of recent years, flow rates on both rivers were between 20,000 and 25,000 cubic feet per second at the time of the Cruise.
The Green River flow rates are the ones measured at the town of Green River. The Colorado rates are measured at Cisco.
| Date | Green at Green River, UT |
Colorado at Cisco |
Cataract Canyon (below confluence) |
|---|---|---|---|
| 5-1 | 7,000 | 16,000 | 22,500 e |
| 5-2 | 6,400 | 17,000 | 23,000 e |
| 5-3 | 6,800 | 14,500 | 22,500 e |
| 5-4 | 7,800 | 13,500 | 21,000 e |
| 5-5 | 9,600 | 12,500 | 20,500 e |
| 5-6 | 10,000 | 12,500 | 23,000 e |
| 5-7 | 8,400 | 14,000 | 24,000 e |
| 5-8 | 7,600 | 15,500 | 22,500 e |
| 5-9 | 7,600 | 19,500 | 23,500 e |
| 5-10 | 8,500 | 22,400 | 28,500 e |
| 5-11 | 11,400 | 21,000 | 29,000 e |
| 5-12 | 15,000 | 20,000 | 32,500 e |
| 5-13 | 16,000 | 21,000 | 36,000 e |
| 5-14 | 14,000 | 21,000 | 36,000 e |
| 5-15 | 12,500 | 19,500 | 34,000 e |
| 5-16 | 12,000 | 19,000 | 32,000 e |
| 5-17 | 12,500 | 19,500 | 31,000 e |
| 5-18 | 12,000 | 19,000 | 31,000 e |
| 5-19 | 10,500 | 23,000 | 31,000 e |
| 5-20 | 10,500 | 26,500 | 34,000 e |
| 5-21 | 12,000 | 31,000 | 38,000 e |
| 5-22 | 16,000 | 37,000 | 45,000 e |
| 5-23 | 19,000 | 41,000 | 56,000 e |
| 5-24 | 21,000 | 42,000 | 62,000 e |
| 5-25 | 23,000 | 37,000 | 62,000 e |
| 5-26 | 24,000 | 29,500 | 56,000 e |
| 5-27 | 24,000 | 26,500 | 53,000 e |
| 5-28 | 22,500 | 26,000 | 51,000 e |
| 5-29 | 20,000 | 27,000 | 48,000 e |
| 5-30 | 18,500 | 29,000 | 47,000 e |
| 5-31 | 18,500 | 31,000 | 48,000 e |
| “e” = estimated | |||
The data above are from the daily Recreational River Report issued by the Colorado Basin River Forecast Center. These figures include estimated flow for Cataract Canyon and estimates for periods when a gauging station is out of service.
Additional information about the flow rates is available from CBRFC and from the US Geological Survey (USGS). The links below show nearly real-time data from the gauging stations at Green River and Cisco. In addition, the CBRFC chart shows a prediction of flow rates several days ahead and the USGS chart shows points for a 100-year median flow.
| River | CBRFC | USGS |
|---|---|---|
| Green (at Green River, UT) | GRVU1 Hydrograph | Green River Data |
| Colorado (at Cisco, UT) | CLRU1 Hydrograph | Cisco Data |