Aquatic Habitat Response to 10825 Flow Alternatives

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Aquatic Habitat Response to 10825 Flow
Alternatives

• Bill Miller
• Miller Ecological Consultants, Inc.

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Objectives

• Recommend a target flow range for each river
  reach
• Review hydrologic data for each river reach
• Qualitatively evaluate the impact (positive or
  negative) from each alternative by river reach
• Make preliminary recommendations regarding
  release pattern and impacts to each reach

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Key physical processes and ecological responses

• Peak flows
• Natural timing is during snowmelt runoff
• Provide channel/habitat benefits
• Provide flows for benefits to riparian conditions
• Magnitude and duration determine the level of
  benefit
• Base flows -
• Provide conditions for benthic invertebrate
  production
• Provide conditions for feeding and growth of fish
• Provide sufficient over winter habitat
• Inter- and intra- annual variation are important
  factors for resulting ecological processes

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Hydrograph and ecological function
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Flow considerations by reach

• Populations (fish and invertebrates) in each
  reach determined by seasonal flow regime
• Primary time period of interest for this study is
  July October
• Determined target flows based on available
  hydrology and instream flow studies
• These flows were derived from the USGS gage
  records at selected gages.
• USGS mean monthly flow used to develop the range
• The lower value is based on 40 of the average
  monthly
• The upper value is 125 of the average monthly.

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Target Flow (cfs) Range by River Reach
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Alternative Analysis

• Characteristics common to all alternatives
• Higher than normal flows during the late summer
  can disrupt aquatic life cycles.
• The upper reaches of the Colorado River and the
  Fryingpan would likely have the most potential
  for changes to aquatic resources.
• As the river reaches get larger, the percent
  change with the 10825 water decreases and
  therefore, the impact to aquatic species should
  be less.

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Alternative A 10,825 delivered from Ruedi
Reservoir

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.

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Alternative A Summary and Recommendations

• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.

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Alternatives C1 C2- 5,412 from Ruedi and 5,412
from Sulphur Gulch or Buzzard Gulch

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.

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Alternatives C1 C2 Summary and Recommendations

• Maximum flows are less than Alternative A
• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.

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Alternative C3 8,125 from Ruedi (13,525 dry
years) and 2,700 from Williams Fork if reservoir
fills

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.
• Key characteristics of Colorado below the
  Williams Fork
• Low summer flows (lt100 cfs) reduce habitat area
• Flow targets from 120-250 best for young trout

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Alternative C3 Summary and Recommendations

• Fryingpan
• Maximum flows are nearly equal to Alternative A
• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.
• Colorado River
• Infrequent flow changes have a slight negative or
  no impact on the Colorado River below the
  Williams Fork

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Alternative C4 8,125 from Sulphur Gulch (13,525
dry years) and 2,700 from Williams Fork if
reservoir fills

• Key characteristics of Colorado below the
  Williams Fork
• Low summer flows (lt100 cfs) reduce habitat area
• Flow targets from 120-250 best for young trout

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Alternative C4 Summary and Recommendations

• Colorado River
• Infrequent flow changes have a slight negative or
  no impact on the Colorado River below the
  Williams Fork

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Alternative C5 5,412 from Ruedi and 5,412 from
Wolford Mountain Reservoir

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.
• Key characteristics of Colorado below the Muddy
  Creek
• 10825 flows are a minor contribution to total flow

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Alternative C5 Summary and Recommendations

• Fryingpan
• Maximum flows are less than Alternative A
• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.
• Colorado River downstream of Muddy Creek
• No change expected

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Alternative C6 5,412 from Buzzard Creek and
5,412 from Wolford Mountain Reservoir

• Key characteristics of Colorado below the Muddy
  Creek
• 10825 flows are a minor contribution to total flow

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Alternative C6 Summary and Recommendations

• Colorado River downstream of Muddy Creek
• No change expected

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Alternative C7 8,125 from Ruedi and 2,700 from
Granby

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.
• Key characteristics of Colorado below Granby
• Low summer flows (lt100 cfs) reduce habitat area
• Flow targets from 40-60 hypothesized as best for
  fish and macroinvertebrates
• Incremental increases beneficial to Colorado near
  Hot Sulphur Springs

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Alternative C7 Summary and Recommendations

• Fryingpan
• Maximum flows are nearly equal to Alternative A
• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.
• Colorado River downstream of Granby
• Extended summer base flow provides better
  conditions for invertebrates and fish
• Benefits extend to downstream of Williams Fork

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Alternative C8 2,700 from Ruedi 2,700 from
Granby and 5,412 from OMID/Green Mtn

• Key Characteristics of Fryingpan
• Flows greater than 125 cfs begin to impact
  juvenile trout.
• Flows greater than 250 cfs likely can cause local
  impact to invertebrates.
• Flows greater than 300 cfs impact fishing.
• Flow targets for best trout habitat should be
  less than 200 cfs.
• Key characteristics of Colorado below Granby
• Low summer flows (lt100 cfs) reduce habitat area
• Flow targets from 40-60 hypothesized as best for
  fish and macroinvertebrates
• Incremental increases beneficial to Colorado near
  Hot Sulphur Springs

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Alternative C8 Summary and Recommendations

• Fryingpan
• Maximum flows exceed 250 cfs for extended periods
  
• High flows (greater than 250 cfs) are detrimental
  to invertebrates, young of the year trout and
  juvenile trout.
• A long term release pattern of high flows in late
  summer could likely change dynamics of trout and
  invertebrate abundance.
• A smaller release over a longer period would be
  better for aquatic life.
• Colorado River downstream of Granby
• Extended summer base flow provides better
  conditions for invertebrates and fish
• Benefits extend to downstream of Williams Fork

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Alternative C9 8,125 from Sulphur Gulch and
2,700 from Granby

• Key characteristics of Colorado below Granby
• Low summer flows (lt100 cfs) reduce habitat area
• Flow targets from 40-60 hypothesized as best for
  fish and macroinvertebrates
• Incremental increases beneficial to Colorado near
  Hot Sulphur Springs

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Alternative C9 Summary and Recommendations

• Colorado River downstream of Granby
• Extended summer base flow provides better
  conditions for invertebrates and fish
• Benefits extend to downstream of Williams Fork

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Preliminary Summary
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Preliminary Recommendation

• Alternatives B, C5, C9 and possibly C8 show least
  impacts
• Alternatives C9 is most beneficial to upper
  Colorado River with no detrimental impacts
• Simultaneous release from all reservoirs starting
  in mid to late July.
• Increase in upstream reaches can benefit those
  areas most.
• Steady flows more beneficial than sequential
  sporadic increases below each reservoir.
• NOTE Subject to revision upon further analysis

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