Belle Fourche and Cheyenne River Basins (7)
June 2001

Snow.
The Belle Fourche River Basin is melted out as of June 1. See Basin summary of Snow Course Data at the beginning of this report for a detailed listing.

Precipitation.
Precipitation, for the month of May was 47 percent of average in the Black Hills. Monthly percentages range from 8 to 96 percent. Year-to-date precipitation is 83 percent of average and 93 percent of last year's amount.

Reservoir.
Usable reservoir storage is generally above average in the basin. Angostura is currently storing 98 percent of average (114,800-acre feet). Belle Fourche reservoir is storing 121 percent of average (184,500-acre feet). Deerfield reservoir is storing 111 percent of average (15,100-acre feet). Keyhole reservoir is storing 150 percent of average (169,900-acre feet). Pactola reservoir is storing 112 percent of average (54,300-acre feet), and Shadehill reservoir is storing 113 percent of average (77,800-acre feet).

Streamflow
Streamflow forecasts are below average as of June 1. Deerfield Reservoir inflow is forecast at 750 acre feet (42 percent of average). Pactola is forecast at 1,500 acre feet (17 percent of average). This is for the June July runoff period.

==================================================================================================================================
                                              BELLE FOURCHE & CHEYENNE RIVER BASINS
                                               Streamflow Forecasts - June 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)
====================================================================|=======================|=====================================
DEERFIELD RESERVOIR Inflow           JUN-JUL      0.18      0.52    |     0.75        42    |      1.30      2.11           1.80
                                                                    |                       |
PACTOLA RESERVOIR Inflow             JUN-JUL      0.03      0.90    |     1.50        17    |      5.01     10.17           9.00
                                                                    |                       |
==================================================================================================================================
                  BELLE FOURCHE & CHEYENNE RIVER BASINS                 |          BELLE FOURCHE & CHEYENNE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2001
==================================================================================================================================
                                      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    114.8    119.9    117.2 |   BELLE FOURCHE               1         0         0
                                                                        |
BELLE FOURCHE                          178.4    184.5    190.5    152.3 |
                                                                        |
DEERFIELD                               15.2     15.1     15.1     13.6 |
                                                                        |
KEYHOLE                                193.8    169.9    176.0    113.6 |
                                                                        |
PACTOLA                                 55.0     54.3     54.7     48.6 |
                                                                        |
SHADEHILL                               81.4     77.8     56.2     68.7 |
                                                                        |
==================================================================================================================================
 * 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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