Water Supply and Utilization Report
Bighorn River Basin
Wyoming Area Office
This report concerns the operation of Reclamation facilities in the Shoshone and Wind/Bighorn River Basins. Reclamation defines a water year as the time period of October 1 through September 30. Water year is abbreviated in this report as W.Yr. Other organizations furnished information for the Water Supply and Utilization Report. Their cooperation is greatly appreciated.
Bighorn River Basin Inflow
May inflow was above average at Bull Lake and Buffalo Bill Reservoirs.
| May Inflow |
May Historical Inflow |
Accumulated Inflow (October-May) |
|||||||
| Reservoir | W.Yr. 2007 |
30 Yr. Avg.1 |
% of Avg. |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
W.Yr. 2007 |
30 Yr. Avg.1 |
% of Avg. |
|---|---|---|---|---|---|---|---|---|---|
| Bull Lake | 36.1 | 27.7 | 130 | 35.3 | 41.9 | 17.8 | 57.0 | 47.5 | 120 |
| Boysen | 85.9 | 125.0 | 69 | 70.6 | 187.7 | 69.5 | 315.4 | 450.0 | 70 |
| Buffalo Bill | 177.1 | 153.7 | 115 | 198.8 | 178.7 | 71.9 | 325.1 | 302.5 | 107 |
| 1 Average is based on the 1977-2006 period. | |||||||||
Bighorn River Basin
Reservoir Inflow
May
Bighorn River Basin Outflow
Releases from Bull Lake, Boysen and Buffalo Bill Reservoirs were below average during May.
| May Outflow |
May Historical Outflow |
Accumulated Outflow (October-May) |
|||||||
| Reservoir | W.Yr. 2007 |
30 Yr. Avg.1 |
% of Avg. |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
W.Yr. 2007 |
30 Yr. Avg.1 |
% of Avg. |
|---|---|---|---|---|---|---|---|---|---|
| Bull Lake | 11.0 | 14.8 | 74 | 17.2 | 8.1 | 18.3 | 29.9 | 34.5 | 87 |
| Boysen | 65.9 | 93.3 | 71 | 65.7 | 117.3 | 63.0 | 280.2 | 508.0 | 55 |
| Buffalo Bill | 100.2 | 106.9 | 94 | 113.9 | 63.0 | 103.4 | 203.7 | 288.6 | 71 |
| 1 Average is based on the 1977-2006 period. | |||||||||
Bighorn River Basin
Reservoir Outflow
May
Bighorn River Basin Storage
Storage at the end of May was above average at Buffalo Bill Reservoir. Bull Lake, Boysen, and Pilot Butte Reservoirs recorded below average storage at the end of May.
| Reservoir | Total Storage End of May |
End of May Historical Storage |
Total Conservation Storage Capacity |
Percent of Capacity |
||||
|---|---|---|---|---|---|---|---|---|
| W.Yr. 2007 |
30 Yr. Avg.1 |
% of Avg. |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
|||
| Bull Lake | 78.2 | 90.2 | 87 | 91.7 | 139.0 | 61.1 | 152.5 | 51 |
| Boysen | 483.0 | 555.4 | 87 | 549.1 | 701.6 | 453.5 | 741.6 | 65 |
| Buffalo Bill | 562.5 | 427.12 | 132 | 557.5 | 598.3 | 442.4 | 646.6 | 87 |
| Pilot Butte | 21.2 | 27.6 | 77 | 20.7 | 32.0 | 18.3 | 33.7 | 63 |
| 1 Average is based on the 1977-2006 period. | ||||||||
| 2 This does not reflect a long term average because in 1992 the capacity of the reservoir was increased to approximately 646,565 acre-feet as a result of raising the dam. The average used here reflects data from 1993 through 2006. | ||||||||
Bighorn River Basin
Reservoir Storage
End of May
Bighorn Snowpack Water Content
The tables shown below display the Snotel stations used in the development of the April - July snowmelt runoff forecasts displayed on page six of this report.
| June 1 snow-water content |
Comparative June 1 snow-water content |
|||||
| Watershed | W.Yr. 2007 |
30 Yr. Avg.2 |
% of Avg. |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
|---|---|---|---|---|---|---|
| Bull Lake Reservoir | 0.33 | 5.10 | 6 | 0.0 | 4.0 | 0.5 |
| Boysen Reservoir | 0.94 | 7.36 | 13 | 2.3 | 4.4 | 3.0 |
| Buffalo Bill Reservoir | 2.63 | 13.70 | 19 | 5.7 | 5.5 | 6.8 |
| Boysen Reservoir Watershed | Buffalo Bill Reservoir Watershed |
| SWE in inches1 | SWE in inches1 |
| Snotel Stations (Elevation) |
Water Content |
30 Yr. Avg.2 |
Snotel Stations (Elevation) |
Water Content |
30 Yr. Avg.2 |
|---|---|---|---|---|---|
| Burroughs Creek (8,750) | 0.0 | 3.4 | Blackwater (9,780) | 10.1 | 24.7 |
| Hobbs Park (10,100) | 1.0 | 10.1 | Evening Star (9,200) | 2.7 | 26.7 |
| Kirwin (9,800) | 0.0 | 5.5 | Marquette (8,760) | 0.0 | 4.2 |
| Little Warm (9,620) | 0.0 | 1.9 | Sylvan Lake (8,420) | 0.0 | 11.4 |
| Togwotee Pass (9,580) | 5.6 | 21.9 | Sylvan Road (8,120) | 0.0 | 0.0 |
| Townsend Creek (8,700) | 0.0 | 1.7 | Togwotee Pass (9,580) | 5.6 | 21.9 |
| Younts Peak (8,350) | 0.0 | 7.0 | Younts Peak (8,350) | 0.0 | 7.0 |
| Watershed Average | 0.94 | 7.36 | Watershed Average | 2.63 | 13.70 |
| Bull Lake Reservoir Watershed |
| SWE in inches1 |
| Snotel Stations (Elevation) |
Water Content |
30 Yr. Avg.2 |
|---|---|---|
| Elkhart Park (8,400) | 0.0 | 3.3 |
| Hobbs Park (10,100) | 1.0 | 10.1 |
| Little Warm (9,620) | 0.0 | 1.9 |
| Watershed Average | 0.33 | 5.10 |
| 1 SWE (Snow Water Content is the amount of water in the snowpack expressed in inches) | ||
| 2 Average is based on the 1971-2000 period | ||
Bighorn Water Supply Forecast
The June 1, 2007, water supply forecast indicates below average April - July runoff can be expected as shown below. The water supply forecasts are based on the snowpack at the Snotel stations displayed on page five of this report, along with precipitation and soil moisture data.
| Forecast Points |
June 1, 2007 Forecast of April-July Runoff3 |
30 Yr. April-July Runoff Avg.2 |
Most Probable % of Avg. |
Comparative Actual April - July Runoff |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Reasonable Minimum1 |
Most Probable |
Reasonable Maximum1 |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
W.Yr. 2003 |
|||
| Bull Lake Reservoir |
90 | 100 | 120 | 138.8 | 72 | 121 | 155 | 117 | 110 |
| Wind River above Bull Lake Creek |
175 | 200 | 250 | 401.6 | 50 | 282 | 387 | 294 | 302 |
| Boysen Reservoir |
175 | 225 | 300 | 551.3 | 41 | 201 | 589 | 321 | 262 |
| Buffalo Bill Reservoir |
360 | 410 | 500 | 640.1 | 64 | 546 | 513 | 387 | 668 |
| 1 The probability is estimated to be 9 chances in 10 that the actual volume will fall between the reasonable minimum and reasonable maximum. | |||||||||
| 2 Average is based on the 1977-2006 period. | |||||||||
| 3 Actual Inflows are as Follows: | |||||||||
| April (kaf) | May (kaf) | ||||||||
| Bull Lake | 2.8 | 36.1 | |||||||
| Wind River above Bull Lake Creek | 17.5 | 70.7 | |||||||
| Boysen | 31.4 | 85.9 | |||||||
| Buffalo Bill | 40.9 | 177.1 | |||||||
| Forecast Points |
June 1, 2007 Forecast of April-July Runoff Chance of Exceeding |
30 Yr. April-July Runoff Avg.1 |
|||||
|---|---|---|---|---|---|---|---|
| 95% | 75% | 50% | % of Avg |
25% | 5% | ||
| Bull Lake Reservoir |
90 | 96 | 100 | 72 | 108 | 120 | 138.8 |
| Wind River above Bull Lake Creek |
175 | 190 | 200 | 50 | 220 | 250 | 401.6 |
| Boysen Reservoir |
175 | 205 | 225 | 41 | 256 | 300 | 551.3 |
| Buffalo Bill Reservoir |
360 | 390 | 410 | 64 | 447 | 500 | 640.1 |
| 1 Average is based on the 1977-2006 period. | |||||||
Bighorn River Basin Generation
Generation was average or greater at all powerplants except Boysen and Buffalo Bill Powerplants.
| May Gross Generation |
May Historical Generation |
Accumulated Gross Gen. (October-May) |
|||||||
| Powerplant | W.Yr. 2007 |
Avg. | % of Avg. |
W.Yr. 2006 |
W.Yr. 2005 |
W.Yr. 2004 |
W.Yr. 2007 |
Avg. | % of Avg. |
|---|---|---|---|---|---|---|---|---|---|
| Boysen1 | 5.0 | 6.7 | 75 | 5.4 | 8.6 | 4.6 | 20.5 | 40.0 | 51 |
| Pilot Butte2 | 0.2 | 0.2 | 100 | 0.9 | 0.3 | 0.0 | 0.2 | 0.5 | 40 |
| Heart Mtn.3 | 2.5 | 2.2 | 114 | 3.2 | 0.0 | 1.2 | 3.4 | 3.3 | 103 |
| Buffalo Bill3 | 7.8 | 10.1 | 77 | 9.5 | 7.3 | 10.1 | 13.2 | 29.0 | 46 |
| Shoshone3 | 2.7 | 2.0 | 135 | 2.2 | 2.1 | 2.0 | 12.6 | 12.3 | 102 |
| Spirit Mtn.4 | 2.2 | 1.9 | 116 | 2.8 | 0.6 | 2.9 | 3.3 | 3.0 | 110 |
| 1 Average is based on the 1977-2006 period. | |||||||||
| 2 Average is based on the 1990-2006 period. | |||||||||
| 3 Average is based on the 1993-2006 period. | |||||||||
| 4 Average is based on the 1995-2006 period. | |||||||||
Bighorn River Basin
Gross Generation
May
