Modeling the Boise Reservoir System

with Climate Change

Leslie Stillwater, Pacific NW Region

Picture Source: CIG (2007)

Intergovernmental Panel on Climate Change Scenarios (Year 2040)

Approach• T and P Adjustments obtained from

Climate Impacts Group• T and P Adjustments applied to NWS Extended Streamflow

Prediction Model to produce daily local inflows (WY1949-1996)

• Each Climate Scenario was compared to the No Adjustment Scenario to produce daily local gain adjustments

• Daily local gain adjustments were aggregated into monthly gain adjustments for input to the Snake River revised BA monthly planning model (WY1949-1996)

• Daily gain adjustments were applied to the Daily Boise Operations Model (WY1949-1996)

Average Unregulated Daily Flows at Lucky Peak Damfor Scenarios with

Temperature Adjustments Only

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

1-O

ct

1-N

ov

1-D

ec

1-Ja

n

1-F

eb

1-M

ar

1-A

pr

1-M

ay

1-Ju

n

1-Ju

l

1-A

ug

1-S

ep

cfs

No Adjustment

echam T

giss T

ipsl T

Average Unregulated Daily Flows at Lucky Peak Damfor Scenarios with

Temperature and Precipitation Adjustments

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

1-O

ct

1-N

ov

1-D

ec

1-Ja

n

1-F

eb

1-M

ar

1-A

pr

1-M

ay

1-Ju

n

1-Ju

l

1-A

ug

1-S

ep

cfs

No Adjustment

echam TP

giss TP

ipsl TP

Average Unregulated Daily Flows at Lucky Peak Damfor ipsl Scenarios with

Temperature Only and Temperature and Precipitation

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

1-O

ct

1-N

ov

1-D

ec

1-Ja

n

1-F

eb

1-M

ar

1-A

pr

1-M

ay

1-Ju

n

1-Ju

l

1-A

ug

1-S

ep

cfs No Adjustment

ipsl T

ipsl TP

Boise System Maximum StorageProbability of Exceedance

300000

400000

500000

600000

700000

800000

900000

1000000

11000000

.00

0.0

50

.09

0.1

40

.18

0.2

30

.27

0.3

20

.36

0.4

10

.45

0.5

00

.55

0.5

90

.64

0.6

80

.73

0.7

70

.82

0.8

60

.91

0.9

51

.00

No Adjustecham Tgiss Tipsl T

Boise System Maximum StorageProbability of Exceedance

300000

400000

500000

600000

700000

800000

900000

1000000

11000000

.00

0.0

50

.09

0.1

40

.18

0.2

30

.27

0.3

20

.36

0.4

10

.45

0.5

00

.55

0.5

90

.64

0.6

80

.73

0.7

70

.82

0.8

60

.91

0.9

51

.00

No Adjustecham TPgiss TPipsl TP

Comments on the Monthly Planning Studies

• Assumptions drive the study results– A2 IPCC scenarios (aggressive emissions)– T and P results are scalable to PN Region and to the Boise

Basin– Present level diversions– Present level groundwater influences

• Your point of view influences how you interpret results

• We addressed uncertainties by employing results from a range of IPCC models

Monthly Planning Study Results

• Probability of Refill is not significantly impacted by the Climate Change scenarios studied

• Present level Deliveries are not significantly impacted by the Climate Change scenarios studied

Daily Operations Studies

• COE Water Control Manual is followed

• Each hydrology year (WY1949-1996) starts with

Nov 2001 reservoir contents

• Starting on Jan 1, perfect forecast (Apr – July) ->

Apr 1 space requirements (rule curves)

• Starting on Jan 1, perfect forecast (Jan – Apr) -> release to get to Apr 1 space requirements

• After Apr 1, go to the rule curves every 2 weeks with perfect forecasts

• Measure of success is discharge < 7,200 cfs at Glenwood Bridge

No Adjustment

1970/1971

Apr 1 Space (AF)

required = 950,150

achieved = 885,780

Echam T

1970/1971

Apr 1 Space (AF)

required = 664,530

achieved = 663,780

Giss T

1970/1971

Apr 1 Space (AF)

required = 822,790

achieved = 820,390

Ipsl T

1970/1971

Apr 1 Space (AF)

required = 588,970

achieved = 582,100

Echam TP

1970/1971

Apr 1 Space (AF)

required = 784,410

achieved = 613,210

Giss TP

1970/1971

Apr 1 Space (AF)

required = 834,650

achieved = 831,930

Ipsl TP

1970/1971

Apr 1 Space (AF)

required = 852,310

achieved = 244,280

No Adjustment

1970/1971

Apr 1 Space (AF)

required = 950,150

achieved = 885,780

Comments on the Daily Operations Studies

• Assumptions drive the study results– A2 IPCC scenarios (aggressive emissions)– T and P results are scalable to PN Region and to the Boise

Basin– Historic groundwater influences not removed – Starting storage conditions of Nov 2001 (historic median)– Perfect forecasts

• We addressed uncertainties by employing results from a range of IPCC models

Daily Operations Study Results

• Reliable forecasts will be even more critical• Early forecasts (prior to Jan 1) will be required• Drawdown needs to start before Jan 1• Space requirements need to start earlier than Apr 1• Maintaining 55% space in Lucky Peak and Arrowrock

may not be possible• Glenwood Bridge discharge Jan – Apr will be higher• Glenwood Bridge discharge > 7,200 cfs can be

anticipated if the wettest scenario is realized