National Academies Press: OpenBook

Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem (1999)

Chapter: Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts

« Previous: Appendix D: Record of Decision (1996)
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

Appendix E
Table II-7 Summary Comparison of Alternatives and Impacts

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
This page in the original is blank.
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

Table II-7. — Summary Comparison of Alternatives and Impacts

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

WATER

Streamflows (1,000 acre-feet)

Annual streamflows

Median annual release

8,753

8,573

8,559

8,559

Monthly streamflows (median) Fall (October)

568

568

568

568

Winter (January)

899

899

899

899

Spring (May)

587

587

592

592

Summer (July)

1,045

1,045

1,045

1,045

Hourly streamflows can be found in table 11-2.

SEDIMENT

Riverbed sand (percent probability of net gain)

After 20 years

50

49

53

61

After 50 years

41

36

45

70

Sandbars (feet)

Active width

44 to 74

47 to 77

33 to 53

28 to 47

With habitat maintenance flows

 

 

 

41 to 66

Potential height

10 to 15

10 to 16

7 to 11

6 to 10

With habitat maintenance flows

 

 

 

9 to 14

FISH

Aquatic food base

Limited by reliable wetted perimeter

Same as no action

Minor increase

Moderate increase

Native food

Stable to declining

Same as no action

Same as no action

Same as no action

Non-native warmwater and coolwater fish

Stable to declining

Same as no action

Same as no action

Same as no action

Interactions between native and non-native fish

Some predation and competition by non-natives

Same as no action

Same as no action

Same as no action

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

Trout

Stocking-dependent

Same as no action

Same as no action

Increased growth potential, stocking-dependent

 

Modified Low Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

WATER

Streamflows (1,000 acre-feet)

Annual streamflows

 

 

 

 

 

Median and annual release

8,559

8,559

8,559

8,554

8,578

Monthly streamflows (median)

 

 

 

 

 

Fall (October)

568

568

568

492

699

Winter (January)

899

899

899

688

703

Spring (May)

592

592

592

1,106

699

Summer (July)

1,045

1,045

1,045

768

699

Hourly streamflows can be found in table 11-2.

SEDIMENT

Riverbed sand (percent probability of net gain)

After 20 years

64

69

71

71

74

After 50 years

73

76

82

82

100

Sandbars (feet)

 

 

 

 

 

Active width

24 to 41

24 to 41

10 to 19

16 to 29

0

With habitat maintenance flows

41 to 66

 

 

37 to 60

 

Potential height

6 to 9

6 to 9

3 to 5

4 to 7

0 to 1

With habitat maintenance flows

9 to 14

 

 

8 to 13

 

FISH

Aquatic Fish Base

Potential major increase

Potential major increase

Major increase

Major increase

Major increase

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

Modified Low Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

Native Food

Potential minor increase

Potential minor increase

Uncertain potential minor increase

Uncertain potential minor increase

Uncertain potential minor increase

Non-native warmwater and coolwater fish

Potential minor increase

Potential minor increase

Potential minor increase

Potential minor increase

Potential minor increase

Interactions between native and non-native fish

Potential minor increase in warm, stable microhabitats

Potential minor increase in warm, stable microhabitats

Potential minor increase in warm, stable microhabitats

Potential minor increase in warm, stable microhabitats

Potential minor increase in warm, stable microhabitats

Trout

Increased growth potential, stocking-dependent

Increased growth potential, stocking-dependent

Increased growth potential, possibly self-sustaining

Increased growth potential, possibly self-sustaining

Increased growth potential, possibly self-sustaining

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

VEGETATION

Woody plants (area)

New high water zone

No net change

0 to 9% reduction

15 to 35% increase

23 to 40% increase

With habitat maintenance flows

 

 

 

0 to 12% increase

Species composition

Tamarisk and others dominate

Tamarisk and others dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Emergent marsh plants

New high water zone

 

 

 

 

Aggregate area of wet marsh plants

No net change

Same as no action

Same as or less than no action

Same as or less than no action

WILDLIFE AND HABITAT

Riparian habitat

See vegetation.

 

 

 

Wintering waterfowl (aquatic food base)

Stable

Same as no action

Same as no action

Potential increase

ENDANGERED AND OTHER SPECIAL STATUS SPECIES

Humpback chub

Stable to declining

Same as no action

Same as no action

Same as no action

Razorback sucker

Stable to declining

Same as no action

Same as no action

Same as no action

Flannelmouth sucker

Stable to declining

Same as no action

Same as no action

Same as no action

Bald eagle

Stable

Same as no action

Same as no action

Potential increase

Peregine falcon

No effect

No effect

No effect

No effect

Kanab ambersnail

No effect

Some incidental take

Some incidental take

Some incidental take

Southwestern willow flycatcher

Undetermined increase

Same as no action

Same as no action

Same as no action

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

Modified Low

Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

VEGETATION

Woody plants (area)

New high water zone

30 to 47% increase

30 to 47% increase

45 to 65% increase

38 to 58% increase

63 to 94% increase

With habitat maintenance flows

0 to 12% increase

 

 

0 to 12% increase

 

Species composition

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Tamarisk, coyote willow, arrowweed, and camelthorn dominate

Emergent marsh plants

New high water zone

 

 

 

 

 

Aggregate area of wet marsh plants

Same as or less than no action

Same as or less than no action

Less than no action

Less than no action

Less than no action

WILDLIFE AND HABITAT

Riparian habitat

See vegetation.

 

 

 

 

Wintering waterfowl (aquatic food base)

Potential increase

Potential increase

Potential increase

Potential increase

Potential increase

ENDANGERED AND OTHER SPECIAL SPECIES

Humpback chub

Potential minor increase

Potential minor increase

Uncertain potential minor increase

Uncertain potential major increase

Uncertain potential minor increase

Razorback sucker

Potential minor increase

Potential minor increase

Uncertain potential minor increase

Uncertain potential minor increase

Uncertain potential minor increase

Flannelmouth sucker

Potential minor increase

Potential minor increase

Uncertain potential minor increase

Uncertain potential major increase

Uncertain potential minor increase

Bald eagle

Potential increase

Potential increase

Potential increase

Potential increase

Potential increase

Peregrine falcon

No effect

No effect

No effect

No effect

No effect

Kanab ambersnail

Some incidental take

Some incidental take

Some incidental take

Some incidental take

Some incidental take

Southwestern willow flycatcher

Same as no action

Same as no action

Same as no action

Same as no action

Same as no action

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

CULTURAL RESOURCES

Archeological sites (Number affected)

Major

(336)

Major

(336)

Potential to become major (263)

Moderate

(Less than 157)

Traditional cultural properties

Major

Same as no action

Potential to become major

Moderate

Traditional cultural resources

Major

Same as no action

Same as no action

Increased protection

AIR QUALITY

Regional air quality

Total emissions (thousand tons)

 

 

 

Sulfur dioxide

1,960

Same as no action

Slight reduction

Slight reduction

Nitrogen oxides

1,954

 

 

 

RECREATION

Fishing Angler activity

Potential danger

Same as no action

Same as no action

Moderate improvement

Day rafting Navigation past 3-Mile Bar

Difficult at low flows

Same as no action

Negligible improvement

Major improvement

White-water boating Safety

High risk at very high and very low flows

Same as no action

Negligible improvement

Minor improvement

Camping beaches (average area at normal peak stage)

Less than 7,720 square feet

Same as no action

Same as no action

Minor increase

Wilderness values

Influenced by range of daily fluctuations

Same as no action

Minor increase

Moderate increase

Economic benefits Change in equivalent annual net benefits (1991 nominal $ million)

0

0

0

+0.4

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

Present value (1991 $ million)

0

0

0

+4.6

 

Modified Low

Fluctuating Flow

Interim Low

Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady

Flow

CULTURAL RESOURCES

Archeological sites (Number affected)

Moderate

(Less than 157)

Moderate

(Less than 157)

Moderate

(Less than 157)

Moderate

(Less than 157)

Moderate

(Less than 157)

Traditional cultural properties

Moderate

Moderate

Moderate

Moderate

Moderate

Traditional cultural resources

Increased protection

Increased protection

Increased protection

Increased protection

Increased protection

WILDLIFE AND HABITAT

Regional air quality

Total emissions (thousand tons)

 

 

 

Sulfur dioxide

Slight reduction

Slight reduction

Slight reduction

Slight reduction

Slight reduction

Nitrogen oxides

 

 

 

 

 

RECREATION

Fishing Angler safety

Moderate improvement

Moderate improvement

Major improvement

Major improvement

Major improvement

Day rafting Navigation past 3-mile bar

Major improvement

Major improvement

Major improvement

Major improvement

Major improvement

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

Modified Low Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

White-water boating

Safety

Minor improvement

Minor improvement

Moderate improvement

Potential to become major increase

Major improvement

Camping beaches

(average area at normal peak stage)

Minor increase

Minor increase

Major increase

Potential to become major increase

Major increase

Wilderness values

Moderate to potential to become major increase

Moderate to potential

to become major

increase

Major increase

Major increase

Major increase

Economic benefits

Change in equivalent annual net benefits (1991 nominal $ million)

+3.7

+3.9

+3.9

+4.8

+2.9

Present value (1991 $ nominal million)

+43.3

+45.6

+45.6

+55.0

+23.5

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

 

No Action

Maximum Powerplant Capacity

High Fluctuating Flow

Moderate Fluctuating Flow

POWER

Annual economic cost

1991 nominal $ million

 

 

 

 

 

Hydrology

 

0

-1.5

2.1

54.0

Contract rate of delivery

 

0

0

2.5

36.7

Present value (1991 $ million)

 

 

 

 

 

Hydrology

 

0

-17.3

24.3

624.5

Contract rate of delivery

 

0

0

28.9

424.5

Wholesale rate

 

18.78

18.78

19.38

22.82

(1991 mills/kWh)

 

 

 

(+3.2%)

(+21.5%)

Retail rate (1991 mills/kWh)

70% of end users

 

No change

No change

No change to slight decrease

No change to slight decrease

23% of end users

 

No change

No change

Slight decrease to moderate increase

Slight decrease to moderate increase

7% of end users (weighted mean)

 

64.1

64.1

64.6 (+0.8%)

69.7 (+8.8%)

NON-USE VALUE

No data.

 

 

 

 

 

Modified Low Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

POWER

Annual economic cost

1991 nominal $ million

Hydrology

15.1

36.3

65.9

88.3

69.7

Contract rate of delivery

44.2

35.6

68.7

123.5

85.7

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×

 

Modified Low Fluctuating Flow

Interim Low Fluctuating Low

Existing Monthly Volume Steady Flow

Seasonally Adjusted Steady Flow

Year-Round Steady Flow

Present value (1991 $ million)

 

 

 

 

 

Hydrology

174.6

418.7

761.4

1,021.2

805.0

Contract rate of delivery

511.2

411.7

794.6

1,428.4

991.2

Wholesale rate

23.16

23.18

25.22

28.20

26.78

(1991 mills/kWh)

(+23.3%)

(23.4%)

(34.4%)

(+50.2%)

(+42.6%)

Retail rate (1991 mills/kWh)

70% of end users

No change to slight decrease

No change to slight decrease

No change to slight decrease

No change to slight decrease

No change to slight decrease

23% of end users

Slight decrease to moderate increase

Slight decrease to moderate increase

Slight decrease to moderate increase

Slight decrease to moderate increase

Slight decrease to moderate increase

7% of end users (weighted mean)

70.5 (+10.0%)

70.2 (+9.6%)

72.9 (+13.8%)

75.8 (+18.4%)

74.5 (+16.3%)

NON-USE VALUE

No data.

 

 

 

 

Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 189
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 190
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 191
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 192
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 193
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 194
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 195
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 196
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 197
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 198
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 199
Suggested Citation:"Appendix E: Table II-7 Summary Comparison of Alternatives and Impacts." National Research Council. 1999. Downstream: Adaptive Management of Glen Canyon Dam and the Colorado River Ecosystem. Washington, DC: The National Academies Press. doi: 10.17226/9590.
×
Page 200
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The Grand Canyon Monitoring and Research Center began long-term planning at its inception and, in May 1997, produced a Long-Term Monitoring and Research Strategic Plan that was adopted by stakeholder groups (the Adaptive Management Work Group and the Technical Work Group) later that year. The Center then requested the National Research Council's (NRC) Water Science and Technology Board to evaluate this plan.

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