Belle Fourche and Cheyenne River Basins (7)
January 2002

Snow
The Belle Fourche River Basin snow water equivalent (SWE) is much below average.. SWE is currently 40 percent of average snow pack; 20 percent of last years amount at this time. See Basin summary of Snow Course Data at the beginning of this report for a detailed listing.

Precipitation.
Precipitation, for the month of December was 20 percent of average in the Black Hills. Monthly percentages range from 10 to 154 percent. Year-to-date precipitation is 76 percent of average and 58 percent of last year's amount.

Reservoir.
Usable reservoir storage is generally above average in the basin. Angostura is currently storing 101 percent of average (97,800-acre feet), about 80 percent of capacity. Belle Fourche reservoir is storing 138 percent of average (124,600-acre feet), about 70 percent of capacity. Deerfield reservoir is storing 121 percent of average (14,900-acre feet), about 98 percent of capacity. Keyhole reservoir is storing 152 percent of average (154,600- acre feet), 80 percent of capacity. Pactola reservoir is storing 114 percent of average (52,400-acre feet), 95 percent of capacity. Shadehill reservoir is storing 104 percent of average (52,800-acre feet), 65 percent of capacity.

Streamflow
Water supply is estimated to be below normal this year. The following values reflect the 50 percent chance yields for the April through July runoff period. Deerfield Reservoir inflow is forecast at 3,100 acre feet (63 percent of average). Pactola is forecast at 9,100 acre feet (48 percent of average). 

==================================================================================================================================
                                              BELLE FOURCHE & CHEYENNE RIVER BASINS
                                               Streamflow Forecasts - January 1, 2002
==================================================================================================================================
                                              |  <<====== 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)
====================================================================|=======================|=====================================
DEERFIELD RESERVOIR Inflow           MAR-JUL      1.15      2.31    |     3.10        63    |      4.35      6.19           4.90
                                     APR-JUL      0.80      1.84    |     2.55        61    |      3.71      5.43           4.20
                                                                    |                       |
PACTOLA RESERVOIR Inflow             MAR-JUL       1.1       6.8    |     10.7        51    |      18.3        30             21
                                     APR-JUL       0.3       5.5    |      9.1        48    |      16.5        27           18.9
                                                                    |                       |
==================================================================================================================================
                  BELLE FOURCHE & CHEYENNE RIVER BASINS                 |          BELLE FOURCHE & CHEYENNE RIVER BASINS
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 1, 2002
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
ANGOSTURA                              122.1     97.8     85.4     96.4 |   BELLE FOURCHE               3        24        40
                                                                        |
BELLE FOURCHE                          178.4    124.6    132.4     90.6 |
                                                                        |
DEERFIELD                               15.2     14.9     15.0     12.3 |
                                                                        |
KEYHOLE                                193.8    154.6    158.7    101.7 |
                                                                        |
PACTOLA                                 55.0     52.4     54.0     45.8 |
                                                                        |
SHADEHILL                               81.4     52.8     41.5     50.7 |
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the table.

(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.
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