Belle Fourche and Cheyenne River Basins (7)
January 1999

Snow
As of January 1, the Belle Fourche basin is 42 percent of normal Snow Water Equivalent (48 percent of 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 December was 75 percent of average in the Black Hills (58 percent of last year). Monthly percentages range from 35 to 100 percent. Year-to-date precipitation is 209 percent of average and 171 percent of last year's amount. Year to date percentages range from 163 to 315. This is from the 4 reporting stations.

Reservoir
Reservoir storage is in good shape. Angostura is currently storing 115 percent of average (111,100 acre feet). Belle Fourche reservoir is storing 184 percent of average (166,700 acre feet). Deerfield reservoir is storing 116 percent of average (14,300 acre feet). Keyhole reservoir is storing 180 percent of average (176,800 acre feet). Pactola reservoir is storing 112 percent of average (51,500 acre feet), and Shadehill reservoir is storing 114 percent of average (57,800 acre feet).

Streamflow
Black Hills water users could see below average runoff during the March through July forecast period. The 50 percent chance runoff for Castle Creek below Deerfield Dam is 217 percent of average (10,630 acre feet). The 50 percent chance runoff for Rapid Creek below Pactola Dam should be 49,000 acre feet (235 percent of average). 

==================================================================================================================================
                                              BELLE FOURCHE & CHEYENNE RIVER BASINS
                                               Streamflow Forecasts - June 1, 1998
==================================================================================================================================
                                              |  <<====== 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)
====================================================================|=======================|=====================================
CASTLE CREEK blw Deerfield Dam (2)   JUN-JUL      0.52      0.87    |     1.10        61    |      1.33      1.68           1.80
                                                                    |                       |
RAPID CREEK blw Pactola Dam (2)      JUN-JUL      2.19      4.76    |     6.50        72    |      8.24     10.81           9.00
                                                                    |                       |
==================================================================================================================================
                  BELLE FOURCHE & CHEYENNE RIVER BASINS                 |          BELLE FOURCHE & CHEYENNE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 1998
==================================================================================================================================
                                      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    119.6    121.0    117.2 |   BELLE FOURCHE               2         0         0
                                                                        |
BELLE FOURCHE                          178.4    171.8    186.9    152.3 |
                                                                        |
DEERFIELD                               15.2     15.2     15.1     13.6 |
                                                                        |
KEYHOLE                                193.8    178.8    184.0    113.6 |
                                                                        |
PACTOLA                                 55.0     54.9     55.7     48.6 |
                                                                        |
SHADEHILL                               81.4     71.0     66.7     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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