Belle Fourche and Cheyenne River Basins
April 1997

Snow.
Snowpack in the Black Hills is above average for April 1. Snow water equivalent (SWE) is 131 percent of average and above the maximum SWE received at the beginning of April. This is 118 percent of what the figure was at this time last year. All reporting sites are measuring well above average, at this time. See the snow course basin summary at the beginning of this document for more details on specific sites.

Precipitation.
According to the 8 reporting sites, precipitation for March was 77 percent of average. Warren Peak reported in with 150 percent of average for the month. Year to date figures are also very high; the basin, as a whole, is 156 percent of average. The highest reporting site, as of April 1, is Warren Peak with 235 percent of average for the year.

Reservoir.
Reservoir storage is in good shape. Angostura is currently storing 110 percent of average (120,700 acre feet), Belle Fourche is 131 percent of average (172,100 acre feet), Deerfield is storing 108 percent of average (14,600 acre feet), Keyhole is storing 169 percent of average (181,900 acre feet), Pactola is storing 114 percent of average (53,500 acre feet), and Shadehill is storing 132 percent of average (83,500 acre feet).

Streamflow
Runoff could be well above average for the Black Hills if the current trend continues. Castle Creek is forecast at 131 percent of average flow (5,500 acre feet) for the April - July season. Rapid Creek is even higher at 132 percent of average (25,000 acre feet). Shortages of water should not be a problem this year in the basin. 

==================================================================================================================================
                                              BELLE FOURCHE & CHEYENNE RIVER BASINS
                                               Streamflow Forecasts - April 1, 1997
==================================================================================================================================
                                              |  <<====== 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)   APR-JUL      4.27      5.00    |     5.50       131    |      6.00      6.73           4.20
                                                                    |                       |
RAPID CREEK blw Pactola Dam (2)      APR-JUL      15.7        21    |       25       132    |        29        34           18.9
                                                                    |                       |
==================================================================================================================================
                  BELLE FOURCHE & CHEYENNE RIVER BASINS                 |          BELLE FOURCHE & CHEYENNE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1997
==================================================================================================================================
                                      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    120.7    111.6    110.1 |   BELLE FOURCHE               7       118       131
                                                                        |
BELLE FOURCHE                          178.4    172.1    181.4    130.9 |
                                                                        |
DEERFIELD                               15.2     14.6     14.7     13.5 |
                                                                        |
KEYHOLE                                193.8    181.9    147.7    107.6 |
                                                                        |
PACTOLA                                 55.0     53.5     54.0     46.8 |
                                                                        |
SHADEHILL                               81.4     83.5     64.4     63.1 |
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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 flow - actual flow may be affected by upstream water management.
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