Snow
As of May 1, the Belle Fourche River basin Snow Water Equivalent is 28 percent of normal (55 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 April was 92 percent of average in the Black Hills (186 percent of last April). Monthly percentages range from 97 to 237 percent. Year-to-date precipitation is 135 percent of average and 137 percent of last year's amount. Year to date percentages range from 111 to 170. This is from the 4 reporting stations.
Reservoir
Reservoir storage is above average in the basin. Angostura is currently storing 107 percent of average (121,100-acre feet). Belle Fourche reservoir is storing 126 percent of average (183,100-acre feet). Deerfield reservoir is storing 113 percent of average (15,300- acre feet). Keyhole reservoir is storing 170 percent of average (185,900-acre feet). Pactola reservoir is storing 116 percent of average (55,700-acre feet), and Shadehill reservoir is storing 119 percent of average (77,900-acre feet).
Streamflow
Black Hills water users should see average runoff during the May through July forecast period. The 50 percent chance runoff for Castle Creek below Deerfield Dam is estimated to be 100 percent of average (3,000 acre feet). The 50 percent chance runoff for Rapid Creek below Pactola Dam should be about 15,100 acre feet (100 percent of average).
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BELLE FOURCHE & CHEYENNE RIVER BASINS
Streamflow Forecasts - May 1, 1999
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| <<====== 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 MAY-JUL 1.03 2.20 | 3.00 100 | 3.80 4.97 3.00
| |
PACTOLA Reservoir Inflow MAY-JUL 0.1 9.0 | 15.1 100 | 21 30 15.1
| |
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BELLE FOURCHE & CHEYENNE RIVER BASINS | BELLE FOURCHE & CHEYENNE RIVER BASINS
Reservoir Storage (1000 AF) - End of April | Watershed Snowpack Analysis - May 1, 1999
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Usable | *** Usable Storage *** | Number This Year as % of
Reservoir Capacity| This Last | Watershed of =================
| Year Year Avg | Data Sites Last Yr Average
========================================================================|=========================================================
ANGOSTURA 122.1 121.1 120.7 113.7 | BELLE FOURCHE 4 55 28
|
BELLE FOURCHE 178.4 183.1 184.1 145.7 |
|
DEERFIELD 15.2 15.3 14.6 13.6 |
|
KEYHOLE 193.8 185.9 181.0 109.6 |
|
PACTOLA 55.0 55.7 53.8 47.9 |
|
SHADEHILL 81.4 77.9 72.3 65.2 |
|
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* 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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