Precipitation
Reservoir
Streamflow
The 50 percent chance runoff is expected to be 42 to 56
percent above average for the April through September
runoff period. Yellowstone at Corwin Springs has a 50
percent chance of yielding about 3,000,000 acre feet (55
percent above normal). Yellowstone near Livingston has a
50 percent chance of yielding about 3,500,000 acre feet (56
percent above normal). Madison River near Grayling has a
50 percent chance of yielding about 690,000 acre feet (42
percent above normal). See the following page for detailed
runoff volumes.
================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS Streamflow Forecasts - April 1, 1997 ================================================================================================================================== | <<====== Drier ====== Future Conditions ======= Wetter =====>> | | | Forecast Point Forecast | ==================== Chance Of Exceeding * ====================== | Period | 90% 70% | 50% (Most Probable) | 30% 10% | 30-Yr Avg. | (1000AF) (1000AF) | (1000AF) (% AVG.) | (1000AF) (1000AF) | (1000AF) ====================================================================|=======================|===================================== YELLOWSTONE at Lake Outlet APR-SEP 1026 1100 | 1150 145 | 1200 1274 792 | | YELLOWSTONE RIVER at Corwin Springs APR-SEP 2786 2913 | 3000 155 | 3087 3214 1937 | | YELLOWSTONE RIVER near Livingston APR-SEP 3256 3401 | 3500 156 | 3599 3744 2241 | | MADISON RIVER near Grayling (2) APR-SEP 626 664 | 690 142 | 716 754 486 | | ================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS | UPPER YELLOWSTONE & MADISON RIVER BASINS Reservoir Storage (1000 AF) - End of March | Watershed Snowpack Analysis - April 1, 1997 ================================================================================================================================== Usable | *** Usable Storage *** | Number This Year as % of Reservoir Capacity| This Last | Watershed of ================= | Year Year Avg | Data Sites Last Yr Average ========================================================================|========================================================= ENNIS LAKE 41.0 28.2 29.6 33.2 | MADISON RIVER in WY 9 130 163 | HEBGEN LAKE 377.5 234.4 255.8 246.6 | YELLOWSTONE RIVER in WY 11 114 158 | ================================================================================================================================== * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow will exceed the volumes in the table. The average is computed for the 1961-1990 base period. (1) - The values listed under the 10% and 90% Chance of Exceeding are actually 5% and 95% exceedance levels. (2) - The value is natural flow - actual flow may be affected by upstream water management.