The Water Withdrawal Assessment Process

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The Water Withdrawal Assessment Process

• Context within regional water policy discussions
• Aquatic ecosystems now a priority user
• No Adverse Resource Impact
• Ground- Surface-water connections recognized
• Groundwater Conservation Advisory Council
• Convened by the legislature
• Broadly representative of societal water use
  interests
• Charged with definitions, design of science-based
  process and screening tool, and guidance on
  policy
• National science review panel

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The Flow Regime Paradigm -- There is a
geography of flow regimes -- Fish species are
adapted to habitats controlled by certain
quantities of, and variability in, river flows
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Michigan rivers naturally have different flow
regimes, and thus different habitat conditions,
biological communities, sensitivity to
disturbance, and potential for fishery management
.
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Michigan Streams by Flow
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Midwest Streams by Flow
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Stressful, low flow period
Index Flow
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The Water Withdrawal Assessment Process

• Groundwater Stream Flow
  Fish Populations

Feeds
Supports

• Three Models Interact within the impact
  assessment model
• Withdrawal Model - How much water is in the
  aquifer, is being withdrawn, and from where and
  how it will affect stream flow
• Streamflow Model - How much water is flowing in
  the stream during summer low flow periods
• Fish Impact Model - What fish are in the stream
  and what is the likely effect of removing water
  on those groups of fish

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The Water Withdrawal Assessment Process

• This is the process that the user goes though
  to see whether the proposed withdrawal is OK or
  is likely to cause an adverse effect on fish
  populations
• Screening Tool The Automated Analysis within
  the model based on general, state-wide data for a
  given withdrawal
• Site Specific Analysis Same process but using
  professional evaluation of site-specific data on
  flow, geology or fish

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1. The Withdrawal Model

• Model needs to know how much water is in the
  local aquifer
• Automatically determines where the nearest
  streams are.
• Apportions the withdrawal effect between streams
• Calculates the likely reduction in flow due to
  the proposed withdrawal

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Characteristics of the Withdrawal Model

• Distance Matters
• A well adjacent to a river will very quickly get
  water either from water that would have gone to
  the river or directly from the river
• A well farther from a river will get more water
  from storage and require a longer time to affect
  the stream
• Geology and Soil Matters
• Clay soils are tight and water does not move
  easily
• Sandy soils are porous and water flows quickly

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2. The Streamflow Model

• Need to Know How Much Flow is in any Stream
  Segment
• Index flow low flow period in the year
• Look at the segments where we know the flow (132
  stream gauges in the State) and extrapolate these
  to the streams that are not gauged
• Major Factors Used
• Drainage Basin Size
• Forest Cover
• Geology and Soils
• Precipitation

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Stressful, low flow period
Index Flow
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• Major Factors in the Analysis
• The geographic database contains info for 11,000
  distinct watersheds and streams
• Info on watershed location, size, geology and on
  stream flow, temperature, and fish populations
• Resulting maps closely match field experiences

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3. The Fish Response Model

• What fish populations live where in the streams
  and how do they respond to flow reductions in the
  summer (at low flow)

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Fish habitat optima identified- Low-flow yield,
catchment area, and July mean temperature- 82
most common species
Smallmouth bass
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Each fish species has a habitat optimum and
suitability curve.
For 60 fish species we determined these for 1)
Catchment area, 2) summer base-flow yield, and 3)
July mean temperature.
We assigned scores of 4, 3, 2, 1, 0
(respectively) to each 0.5 standard deviation
increment away from the optimum for that habitat
variable.
Optimum Habitat
4 represents best conditions 4 is 0.5 SD
3 is 0.5 to 1.0 SD
2 is 1.0 to 1.5 SD
Abundance
1 is 1.5 to 2.0 SD
0 is gt 2.0 SD
Habitat Gradient (Flow or Temperature for
instance)
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Characteristic
Thriving
2X state median
Above state median
Below state median
Abundance
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We grouped Michigan streams into types and
developed response models using an average of
20 specific segments per type
X
20 Cold Sm Rivers
Cold
Cold Trans
Cool
20 Warm Streams
Warm
Streams
Lg Rivers
Sm Rivers
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All River Segment Types
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What Can the Fish Curves Tell Us About
Functional Impairment?
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What Can the Fish Curves Tell Us About
Functional Impairment?
Baseline or existing condition
Some density changes in fish
Some replacement of sensitive species
Notable replacement by tolerant species
Tolerant species dominant ecological functions
altered
Severe alteration of ecological structure and
function
Interpretive criteria from Davies and Jackson 2006
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Interpreting the Fish Curves
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Characteristic Fish
Gradient of increasing risk
Thriving Fish
Adverse Resource Impact
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Cold Streams
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