Streamflow
Runoff in this basin will be well below average. Irrigation water shortages can be expected from all direct diversions.
All the following forecasts are the 50 percent chance runoff for the June through September runoff period. Yellowstone
at Lake Outlet is expected to yield about 275,000 acre feet (40 percent of normal). Yellowstone at Corwin Springs will
yield about 700,000 acre-feet (47 percent of normal). Yellowstone near Livingston will yield about 800,000 acre feet (47
percent of normal). Hebgen lake inflow is estimated to be 120,000 acre feet (39 percent of normal). See the following
page for detailed runoff volumes.
================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS Streamflow Forecasts - June 1, 2001 ================================================================================================================================== | <<====== 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 JUN-SEP 263 270 | 275 40 | 287 306 691 | | YELLOWSTONE RIVER at Corwin Spgs. JUN-SEP 625 670 | 700 47 | 765 860 1484 | | YELLOWSTONE RIVER near Livingston JUN-SEP 601 719 | 800 47 | 881 999 1721 | | HEBGEN Reservoir Inflow JUN-SEP 109 115 | 120 39 | 132 149 307 | | ================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS | UPPER YELLOWSTONE & MADISON RIVER BASINS Reservoir Storage (1000 AF) - End of May | Watershed Snowpack Analysis - June 1, 2001 ================================================================================================================================== 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 36.6 32.1 35.8 | MADISON RIVER in WY 6 0 0 | HEBGEN LAKE 377.5 349.1 355.5 309.8 | YELLOWSTONE RIVER in WY 8 16 8 | ================================================================================================================================== * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume 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 volume - actual volume may be affected by upstream water management.