RECLAMATION...Draft Reservoir to near Elevation 3617-3621 by March 31 – Preference to River Flow before reducing releases below 2000 cfs – Preference to Lake Level before increasing

Yellowtail Dam & Bighorn Lake Operating Criteria Review

Billings, MTSeptember 29, 2009

RECLAMATIONManaging Water in the West

WIND RIVER RANGE

OPERATING CRITERIA REVIEW GOALS

• Improve Overall Project Benefits

– Higher Lake Levels for Recreation and Fishery

– More Consistently Meet Desired Fishery Flow Targets

– Enhance Power Generation

– Improve Flood Control Operations

– More Transparent Methods for Operating Decisions

PROPOSED CHANGES

• Modified Reservoir Elevation Targets

• Revised Method for Calculating River Gains

• Improved Method for Forecasting Winter Gains

• Improved &Transparent Procedure for Setting Winter Release

• New Operating Procedure for Spring Runoff Season using Reservoir Operational Rule Curves

PROPOSED RESERVOIR TARGETS

Date Existing Proposed Difference _______ Targets Targets (feet)

Oct 31 3635 3638-40 +3-5 ft

Nov 30 3630 Eliminated

Mar 31 3605-14 3617-21 +7-13 ft

July 31 3640 3640 Same

November-March Gains

• Gains Prior to 1991 not used in Analysis

• New Method for Calculating Gains

• Nov-Mar Gain Forecast based on Correlation with Actual April-Oct Gains

Trend in Nov-Mar Gains 1968-2000Bighorn Lake Nov-Mar Gains

1968-2000

0

100000

200000

300000

400000

500000

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Gai

ns a

cre-

feet

Nov-Mar Release Calculation

• Water Balance Equation Used to Calculate Nov-Mar Release Rate Based On:

– Nov-Mar Release from Buffalo Bill and Boysen Reservoirs– Forecasted Nov-Mar River Gains– Draft Reservoir to near Elevation 3617-3621 by March 31– Preference to River Flow before reducing releases below

2000 cfs– Preference to Lake Level before increasing releases above

2500 cfs– Minimize reductions in River Release.

March 31 Reservoir Level Targets

River Release March 31 Target Elev.

Greater Than 2500 cfs 3620.6

2000-2500 cfs 3618.0

Less Than 2000 cfs 3616.7

Operational Rule Curves April-July

April-July Inflow HydrographsBighorn Lake April-July Inflow

02000400060008000

10000120001400016000

4/1

4/8

4/15

4/22

4/29 5/

6

5/13

5/20

5/27 6/

3

6/10

6/17

6/24 7/

1

7/8

7/15

7/22

7/29

Inflo

w C

FS

LD LQ Medium UQ UD Max

Bighorn Lake April-July Rule CurvesBighorn Lake Rule Curves

3600.0

3610.0

3620.0

3630.0

3640.0

3/31 4/

74/

144/

214/

28 5/5

5/12

5/19

5/26 6/

26/

96/

166/

236/

30 7/7

7/14

7/21

7/28

Lake

Ele

v. fe

et

Min Fill 28% Medium UQ UD Max

Bighorn Lake River ReleaseBighorn River Release

0

2000

4000

6000

8000

10000

120003/

31 4/7

4/14

4/21

4/28 5/

5

5/12

5/19

5/26 6/

2

6/9

6/16

6/23

6/30 7/

7

7/14

7/21

7/28

Riv

er F

low

CFS

Min Fill Medium UQ UD Max

RESULTSBased on 1988-2008 Model Study

Results Reservoir ElevationBighorn Lake Elev. Modified Criteria vs. Historic

1988-2008 Averages

360036053610361536203625363036353640

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

Lake

Lev

el fe

et

Modified Criteria Historic

Results River FlowsBighorn River below Afterbay Dam Modifed Criteria vs Historic

1988-2008 Averages

15002000250030003500400045005000


Dis

char

ge c

fs


Percent of Time Fishery Flows are MetBighorn River Fishery Flows 1988-2008

% of of Time above Fishery Flow Targets

0

20

40

60

80

100

1300 1500 2000 2500 3500

Perc

ent o

f Tim

e

Historic Modif ied Criteria

Power Generation

Yellowtail Dam Power Generation Modified Criteria vs. Historic 1988-2008

40.050.060.070.080.090.0

100.0

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

Gen

erat

ion

GW

H


Power Generation GWHs

Period Mod Criteria Historic Difference

Annual 780.1 762.2 +17.9

Dec-Feb 153.8 156.0 - 2.2

July-Aug 165.7 167.5 - 1.8

1988-2008 Compared to 1967-2008

Period Average Annual Inflow AF

1988-2008 1,992,619

1967-2008 2,343,002

1988-2008 (w/o 01-07) 2,327,807

Results Reservoir Elevation w/o 01-07

Bighorn Lake Elev. Modified Criteria vs. Historic1988-2008 (w/o 01-07) Averages

360036053610361536203625363036353640


Lake

Lev

el fe

et

Modif ied Criteria Historic

Results River Flows w/o 01-07Bighorn River below Afterbay Dam Modifed Criteria vs Historic

1988-2008 Averages (w/o 01-07)

15002000250030003500400045005000


Disc

harg

e cf

s


Results – Summary 1988-2008 Study Period

• Lake Levels– Jan-April 7-8 feet higher– May-June 3 feet higher– July-Dec 4-5 feet higher

• River Flows– 1,500 cfs + 8% of time, met 100% of time for study period– 2,000 cfs + 5% of time– 2,500 cfs + 5% of time– 3,500 cfs - 3% of time

• Power Generation +2% increase • Flood Control – Slight Improvement

Comparisons for 2009

2009 Bighorn Lake Nov-Mar River Release

River End of March Release Lake Elevation

Revised Criteria 2546 cfs 3623 ft

Actual 2450 cfs 3627 ft

Difference +96 cfs - 4 ft

Bighorn Lake Proposed Criteria vs. Actual 2009

Bighorn Lake Elevation 2009Modified Criteria vs. Acutal

3620

3625

3630

3635

3640

Oct Nov Dec Jan Feb MarEnd of Month

Elev

atio

n fe

et

Modified Criteria Actual

Bighorn River Proposed Criteria vs Actual 2009

Bighorn River Flow 2009Modified Criteria vs. Actual

22002300

24002500

26002700

2800

Oct Nov Dec Jan Feb MarEnd of Month

Disc

harg

e cf

s

Modified Criteria Actual

Bighorn Lake Elevation April- July 2009

Bighorn Lake Rule Curve vs Actual Operation 2009

3610.03615.03620.03625.03630.03635.03640.03645.03650.0

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Elev

atio

n fe

et

Rule Curve Reoperation Actual Top of Joint Use

Bighorn River April-July 2009Bighorn Lake Rule Curve Operation vs Actual 2009

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Dis

char

ge C

FS

Rule Curve Reoperation Actual

Bighorn Lake Forecasted Apr-July InflowBighorn Lake In flow April-Ju ly 2009

02000400060008000

1000012000140001600018000

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Inflo

w c

fs

Forecast

Bighorn Lake April-July Inflow Forecasted vs Actual

Bighorn Lake Inflow April-July 2009

02,0004,0006,0008,000

10,00012,00014,00016,00018,000

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Inflo

w c

fs

Actual Forecast

NRCS Apr-July Forecast

Rule Curve Inflow vs Actual 2009

Bighorn Lake Inflow April-July 2009

02,0004,0006,0008,000

10,00012,00014,00016,00018,000

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Inflo

w c

fs

Actual Forecast

2009 Rule Curve using Actual Inflow

Bighorn Lake Elevation for Forecast A-J Inflow with Rule Curves

3600

3610

3620

3630

3640

3/314/14

4/285/12

5/26 6/9 6/23 7/7 7/21

Elev

atio

n in

feet

Min Fill Max Forecast

LOOKING AHEAD TO 2010

River Release Nov-Mar 2010

• Planned Boysen Release - 900 cfs

• Planned Buffalo Bill Release – 390 cfs

• Forecasted Nov-Mar Gains - 244,000 acre-feet

• End of Oct. Lake Level – 3638-3639 ft

• Calculated River Release Rate - 2700-2800 cfs

• Expected End of March Lake Elev. - 3620.6 ft

Discussion & Questions


3610.03615.03620.03625.03630.03635.03640.03645.03650.0

4/1 4/84/1

54/224/29 5/65/135/20 5/2

7 6/3 6/10

6/17

6/24 7/1 7/87/157/22 7/2

9El

evat

ion

feet

Rule Curve Reoperation Actual Top of Joint Use

Bighorn Lake Rule Curve Operation2009

3610.0

3615.0

3620.0

3625.0

3630.0

3635.0

3640.0

3645.0

3650.0

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Elev

atio

n fe

et

Rule Curve Elevation ft Top of Joint Use


0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

4/1 4/8 4/15

4/22

4/29 5/6 5/13

5/20

5/27 6/3 6/10

6/17

6/24 7/1 7/8 7/15

7/22

7/29

Dis

char

ge C

FS

Rule Curve Reoperation Actual

Documents

RECLAMATION...Draft Reservoir to near Elevation 3617-3621 by March 31 – Preference to River Flow before reducing releases below 2000 cfs – Preference to Lake Level before increasing