Belle Fourche and Cheyenne River Basins (7)
February 2000

Snow.
The Belle Fourche River basin has 68 percent of normal SWE. The basin SWE is 86 percent of what it was last year. See Basin summary of Snow Course Data at the beginning of this report for a detailed listing.

Precipitation.
Precipitation, for the month of January was 75 percent of average in the Black Hills (44 percent of last January). Monthly percentages range from 65 to 285 percent. Year-to-date precipitation is 80 percent of average and 40 percent of last year's amount. Year to date percentages range from 70 to 92. This is from the 3 reporting stations.

Reservoir.
Reservoir storage is above average in the basin. Angostura is currently storing 111 percent of average (108,900-acre feet). Belle Fourche reservoir is storing 171 percent of average (172,900-acre feet). Deerfield reservoir is storing 116 percent of average (14,900-acre feet). Keyhole reservoir is storing 175 percent of average (172,300-acre feet). Pactola reservoir is storing 118 percent of average (54,000-acre feet), and Shadehill reservoir is storing 47 percent of average (23,300-acre feet).

Streamflow
Streamflow forecast are below average as of February 1. Deerfield Reservoir inflow is forecast at 2850 acre feet (58 percent of average). Pactola is forecast at 10500 acre feet (50 percent of average). This is for the March - July forecast period. 


==================================================================================================================================
                                              BELLE FOURCHE & CHEYENNE RIVER BASINS
                                               Streamflow Forecasts - February 1, 2000
==================================================================================================================================
                                              |  <<====== 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      0.25      1.65    |     2.85        58    |      4.05      5.83           4.90
                                                                    |                       |
PACTOLA RESERVOIR Inflow             MAR-JUL       1.0       3.3    |     10.5        50    |      17.7        28             21
                                                                    |                       |
==================================================================================================================================
                  BELLE FOURCHE & CHEYENNE RIVER BASINS                 |          BELLE FOURCHE & CHEYENNE RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 2000
==================================================================================================================================
                                      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    108.9    116.1     98.1 |   BELLE FOURCHE               5        86        68
                                                                        |
BELLE FOURCHE                          178.4    172.9    167.1    101.4 |
                                                                        |
DEERFIELD                               15.2     14.9     14.5     12.8 |
                                                                        |
KEYHOLE                                193.8    172.3    177.4     98.7 |
                                                                        |
PACTOLA                                 55.0     54.0     51.9     45.8 |
                                                                        |
SHADEHILL                               81.4     23.3     55.5     49.1 |
                                                                        |
==================================================================================================================================
 * 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.
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