Precipitation
Precipitation across the basin was much below average for last month.
Monthly precipitation, for the basin, was 70 percent of average (63 percent
of last year). February percentages range from 49 to 108 percent of
average. Water-year-to-date precipitation is 58 percent of normal for the
Snake River basin (77 percent of last year at this time) Year-to-date
percentages range from 43 to 81 percent of average.
Reservoir
Current storage compared to average for the three storage reservoirs in the
basin is as follows: Grassy Lake -116 percent of average (12,800 acre feet
compared to 12,500 last year), Jackson lake - 133 percent of average
(638,300 acre feet compared to 653,500 acre feet last year), and Palisades
Reservoir -65 percent of average (695,600 acre feet compared to 1,247,100
acre feet last year).
Streamflow
The most probable, 50 percent chance April through September runoff yield
forecast is below average for the basin. The Snake near Moran is expected
to yield 590,000 acre-feet (68 percent of normal). Yield from the Snake
River above Palisades Reservoir is estimated to be 1,820,000 acre-feet (68
percent of normal). The 50 percent chance yield near Heise is expected to
be 2,550,000 acre-feet (63 percent of normal). Pacific Creek at Moran is
expected to yield about 111,000 acre-feet (67 percent of average). Greys
River above Palisades Reservoir is estimated to yield 235,000 acre-feet (61
percent of normal). Salt River near Etna is estimated to have a yield of
235,000 acre-feet (59 percent of normal).
================================================================================================================================== SNAKE RIVER BASIN 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) ====================================================================|=======================|===================================== SNAKE near Moran (1,2) APR-SEP 411 534 | 590 68 | 646 769 869 | | SNAKE above Palisades (2) APR-SEP 1459 1674 | 1820 68 | 1966 2181 2671 | | PALISADES RESERVOIR INFLOW (1,2) APR-SEP 1677 2167 | 2390 64 | 2613 3103 3763 | | SNAKE near Heise (2) APR-SEP 1934 2301 | 2550 63 | 2799 3166 4049 | | PACIFIC CREEK at Moran APR-SEP 76 97 | 111 67 | 125 146 166 | | GREYS above Palisades APR-SEP 161 205 | 235 61 | 265 309 388 | | SALT near Etna APR-SEP 128 192 | 235 59 | 278 342 399 | | ================================================================================================================================== SNAKE RIVER BASIN | SNAKE RIVER BASIN 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 ========================================================================|========================================================= GRASSY LAKE 15.2 12.8 12.5 11.0 | SNAKE above Jackson Lake 9 65 57 | JACKSON LAKE 847.0 638.3 653.5 481.0 | PACIFIC CREEK 3 65 63 | PALISADES 1400.0 695.6 1247.1 1063.1 | GROS VENTRE RIVER 3 80 62 | | HOBACK RIVER 6 71 62 | | GREYS RIVER 5 66 61 | | SALT RIVER 5 66 65 | | SNAKE above Palisades 29 68 60 | ================================================================================================================================== * 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.