2012 Operations and 2013 Outlook for Hungry Horse and Como

Hungry Horse Forecasted and Actual Inflow for 2012

Forecast Month Forecast VolumeJan-Jul(% of average)

Forecast VolumeMay-Sep(% of average)

Jan 92 92

Feb 96 97

Mar 93 95

Apr 102 104

May 105 94

June 107 94

Actual 124 114

June-July runoff forecast was 880 kaf (92%). Actual June-July runoff was 1263 kaf (131%)

NWRFC ESP forecasts

• June 4, 2012 – June-July volume of 784 kaf (82%)

• June 15, 2012 – June-July volume of 951 kaf (99%)

• June 25, 2012 – June-July volume of 1040 kaf (108%)

• June 29, 2012 – June-July volume of 1173 kaf (122%)

• Actual - June-July volume of 1263 kaf (131%)

Flathead Basin

June 2012 Precipitation (% of average)

Precipitation

• Expected future precipitation used in runoff forecasts can vary dramatically from what actually happens

• June 2012 precipitation was over 200% of average (highest June total on record and 4 th highest month ever on record). 8 inches recorded at Hungry Horse Dam

• The result was much higher runoff in June than was forecasted

0.0

10.0

20.0

30.0

40.0

50.0

60.0

3520.00

3525.00

3530.00

3535.00

3540.00

3545.00

3550.00

3555.00

3560.00

3565.00

1-Mar-12 1-Apr-12 1-May-12 1-Jun-12 1-Jul-12 1-Aug-12 1-Sep-12

Flow (kcfs)

Forebay Elevation (ft)Hungry Horse Operations, 2012

Forebay (ft.)

Discharge (kcfs)

Inflow (kcfs)

CFMM (kcfs)

Reservoir surcharged 0.5 ft to limit discharge

Local Flood Control• Hungry Horse is operated to help keep the

Flathead River at Columbia Falls below 14 ft if possible.

• Flows can be reduced down to a minimum of 300 cfs if there is room in the reservoir to store

• The Flathead River at Columbia Falls can often exceed flood stage even with reduced flows depending on flow in the Middle and North Forks

Flathead River at Columbia Falls

• There were 12 days in 2012 when the daily average natural flow at Columbia Falls exceeded the flood flow of 51,800 cfs

• The actual regulated flow at Columbia Falls exceeded flood flow once for 13 hrs on June 27 with a peak stage of 14.18 ft or 2 inches above flood stage

Hungry Horse 2013 Outlook

• As of Oct 15, 2012, Hungry Horse was at elevation 3547.3 ft which is above average for this time of year but typical for years with the 10 ft. draft on September 30

• Currently releasing minimum flows

• Will continue to release minimum flows until flood control requires higher releases

Hungry Horse 2013 Outlook (cont.)

• NWRFC ESP water supply forecast (issued Oct 12) is around 90% of average for April-July inflow volume into Hungry Horse

• The first official operating forecast will be released in January 2013

4180.00

4190.00

4200.00

4210.00

4220.00

4230.00

4240.00

4250.00

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

Reservoir Elevation (ft)Como Operations (WY 2012)

2010 Forebay (ft) 2009 Forebay (ft) 2011 Forebay (ft) 2012 Forebay (ft)

Como 2013 Outlook• As of Oct 15, 2012, Como is at elevation

4200.8 ft which is average for this time of year

• NWRFC ESP water supply forecast (issued Oct 18) for the Bitterroot near Darby is around 70% of average for April-July runoff volume

• Como nearly always fills even in drier years. 2001 was the last year it did not fill but within 3 ft of full