Precipitation
Precipitation for the month of February was 90 percent of normal (67
percent of last year). Monthly percentages range from 5 to 305 percent of
average. The basin year-to-date precipitation is now 72 percent of average
(72 percent of last year). Year-to-date percentages range from 56 to 114
percent of average.
Reservoir
Current storage in Buffalo Bill Reservoir is 93 percent of average (82
percent of last year's storage) - the reservoir is about 56 percent of
capacity. Currently, about 362,500 acre-feet are stored in the reservoir
compared to 441,800 acre feet last year - normally the reservoir stores
about 391,200 acre feet at this time of the year. Detailed reservoir data
is shown on the following page and on the reservoir storage summary at the
beginning of this report.
Streamflow
The fifty percent yield (April through September period) for North Fork
Shoshone River at Wapiti is expected to be 285,000 acre-feet (55 percent of
average). South Fork of the Shoshone River near Valley is estimated to
yield of 120,000 acre-feet (45 percent of average), and South Fork above
Buffalo Bill Reservoir is expected to be 75,000 acre-feet (33 percent of
average). At the Buffalo Bill Reservoir, the fifty percent chance yield
for the Shoshone River is expected to be about 420,000 acre-feet (52
percent of average). The fifty-percent chance yield for the Clarks Fork of
the Yellowstone near Belfry, Montana is expected to be about 335,000 acre-
feet (57 percent of average).
==================================================================================================================================
SHOSHONE & CLARKS FORK RIVER BASINS
Streamflow Forecasts - March 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)
====================================================================|=======================|=====================================
NF SHOSHONE RIVER at Wapiti APR-SEP 244 270 | 285 55 | 315 358 520
| |
SF SHOSHONE RIVER nr Valley APR-SEP 94 110 | 120 45 | 142 175 269
| |
SF SHOSHONE RIVER abv Buffalo Bill APR-SEP 46 64 | 75 33 | 111 163 229
| |
BUFFALO BILL DAM Inflow (2) APR-SEP 338 386 | 420 52 | 481 572 804
| |
CLARKS FORK RIVER nr Belfry APR-SEP 283 313 | 335 57 | 373 428 590
| |
==================================================================================================================================
SHOSHONE & CLARKS FORK RIVER BASINS | SHOSHONE & CLARKS FORK RIVER BASINS
Reservoir Storage (1000 AF) - End of February | Watershed Snowpack Analysis - March 1, 2001
==================================================================================================================================
Usable | *** Usable Storage *** | Number This Year as % of
Reservoir Capacity| This Last | Watershed of =================
| Year Year Avg | Data Sites Last Yr Average
========================================================================|=========================================================
BUFFALO BILL 646.6 362.5 441.8 391.2 | SHOSHONE RIVER 7 61 53
|
| CLARKS FORK in WY 7 57 55
|
==================================================================================================================================
* 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.
To March 2001 Basin Outlook Report Contents Page