Streamflow
All the following forecasts are the 50 percent chance runoff for the April
through September runoff period. Yellowstone at Lake Outlet has is expected
to yield about 960,000 acre feet (121 percent of normal). Yellowstone at
Corwin Springs will yield about 2,385,00 acre-feet (123 percent of normal).
Yellowstone near Livingston will yield about 2,775,000 acre-feet (124
percent of normal). Hebgen lake inflow is estimated to be 580,000 acre feet
(119 percent of normal). See the following page for detailed runoff volumes.
================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS Streamflow Forecasts - April 1, 1999 ================================================================================================================================== | <<====== 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 837 910 | 960 121 | 1010 1083 792 | | YELLOWSTONE RIVER at Corwin Spgs. APR-SEP 2143 2287 | 2385 123 | 2483 2627 1937 | | YELLOWSTONE RIVER near Livingston APR-SEP 2531 2676 | 2775 124 | 2874 3019 2241 | | HEBGEN LAKE Inflow APR-SEP 503 549 | 580 119 | 611 657 486 | | ================================================================================================================================== UPPER YELLOWSTONE & MADISON RIVER BASINS | UPPER YELLOWSTONE & MADISON RIVER BASINS Reservoir Storage (1000 AF) - End of March | Watershed Snowpack Analysis - April 1, 1999 ================================================================================================================================== 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 31.0 29.6 33.2 | MADISON RIVER in WY 8 145 126 | HEBGEN LAKE 377.5 258.3 262.4 246.6 | YELLOWSTONE RIVER in WY 9 137 121 | ================================================================================================================================== * 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. (D) - The operational measurement of flow at this point has been discountinued.