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ECOLOGICAL FLOW
REQUIREMENTS: WHY BOTHER!
Jack Imhof
Director of Conservation Ecology
Trout Unlimited Canada
Ecological Flow Requirements Workshop, GRCA
October 27, 2011
What is it?
• Definition – A holistic look at natural flow regimes that support healthy aquatic ecosystems.
• Flow has been described as the master variable driving river health (Poff et al. 1997)
How Seriously Do People Take Their
Watersheds These Days?
In British
Columbia,
they can
be
found….
Problem Statement
• We are placing more
and more demands
on our water
resources
• Realize that our
rivers and their
watersheds are in
various stages of
deterioration
• Do we want to go
here?
Some of the Management Issues
• DEMAND
– More people placing more demand on the watershed and its rivers
• SCALE
– Use can be both distributed (eg. water abstraction for irrigation) or centralized (e.g. hydro-electric or flood control) or a combination of both
• COMPLEXITY
– Each watershed is unique with complex features so application of management solutions is complicated
– One target does not fit all problems
“Clearly half of the peak discharge will not
move half of the sediment, half of the
migration motivational flow will not move half
of the fish, and half of an overbank flow will
not inundate half of the floodplain.”
Poff et al. (1997)
No Simple Solution
IT’S A COMPLEX ENVIRONMENT FOR
ENGINEERS AND OTHER PROFESSIONALS
Important Considerations
• Aquatic ecosystems, their plants and animals
have evolved to cope with water flow
regimes and their stochastic events
• Human uses tend to be seasonal or chronic
(e.g.): – agriculture, aggregate extraction, hydro-electric, golf
course irrigation, commercial water taking, municipal
water supplies and urbanization to mention a few
• This places an un-natural burden on
ecosystem functioning
Ecological Concepts and Design
Principles
• Spatial and Temporal Scales are important
• Species in rivers and their corridors have likely co-
evolved to the pattern and dynamics of the ENTIRE
flow regime and the river’s forms and patterns
• Aquatic animals are extremely mobile
• Habitat does not just occur longitudinally, it occurs
laterally (channel elasticity) AND vertically
(groundwater and Hyporheic zone)
Pathways within the watershed • Two Key Pathways: Hydrologic and
Ecologic
• Hydrologic pathways describe how and where water flows over and through the landscape
• Creates the unique characteristics of each watersheds groundwater and surface water regimes
• Ecologic pathways drive ecological process in the valley that create opportunities for plants and animals
• These regimes drive the flow regime, sediment regime, nutrient regime and thermal regime
Longitudinal Habitat
Use operates as
several Nested
scales (e.g.
migration, feeding,
reproduction).
At the watershed scale
hydrology creates
opportunities for migration
and movement
The reach creates the
habitat form and supply, the
site provides specific
hydraulic features used
moment by moment.
From: Newbury and Gaboury 1993
Longitudinal
Connectivity
Traditionally we viewed
aquatic ecosystems as
many small pieces on the
landscape.
We now realize that
animals travel great
distances as part of their
HOME territories.
From Fausch et al. (2002)
Major Ecologically Related Design
Stages – Linking Habitat to Physical
Features and Processes
BASEFLOW (FISHERIES)
BASEFLOW (FISHERIES)
BANKFULL BANKFULL
RIPARIAN
RIPARIAN
VALLEY
VALLEY
FOUR MAJOR DESIGN STAGES
2-3x ANNUALLY
1:1.5YR RETURN
1:2-20YR RETURN
1:100YR RETURN
NATURAL RIVER VALLEY
FOR NATURAL CHANNEL/VALLEY MANAGEMENT
The interplay
of flow stages
on the
morphology of
the channel
and floodplain
create and
refresh
ecological
features and
processes
Channel Elasticity and Habitat
• Stream move laterally over the course of the year providing different habitats for various species (e.g. reproduction; flood refugia, feeding areas, etc.)
Groundwater:
Surface Water
Interactions
These interactions are
complex but need to be
understood as part of
Ecological Flow
Requirements since they
drive many ecological
processes
Major
discharge
areas
Key Flow Regime Building Blocks • Low Flow Regime – minimum living space controlling
maximum population size
• Channel Forming Flow – maintenance of channel structure and habitat
• Flushing Flows – periodic cleansing of seasonally accumulated materials (silts, algae, etc.)
• Migratory/Reproductive Flows – connectivity and reproductive capability
Up, down, and lateral mobility Food accumulation Food circulation Cover
Sediment re-sorting Detritus accumulation
Pools/glides (inherited) uniform 60 Partitioned states 40 shear planes 5 eddy trains 10 V & H circulation 25
MODERATE (Recurring, persistent, pattern inherited, locally-varied)
connectivity Aeration Continuity
Trickles, seepage (inherited) mixed states 100
Thermal and light refugia (over-summer and over-winter)
Storage Persistence Groundwater storage
Pools (inherited) still 95 (stratified) wind circulation 5
LOW (recurring, long term. Pattern inherited, locally-varied)
Benthic insolation, Oxygen, Food concentration, Reproduction, Refugia, Fish passage
Transparency Aeration Local scour
Riffles/runs (inherited) mixed state 100 convergence 20 separation 5 V & H rotation 55/20
Cover development Detritus transport Spawning bed development Nursery habitat creation
Meander migration, Bank erosion, Pointbar construction, Substrate partitioning, Sediment transport, Debris accumulation, Floodplain saturation
Alternating thalweg 100 Helical circulation 80 (meandering) Plunging profile 80 Swifts/rapids 20
HIGH (short term, pattern and channel forming, gradually-varied)
BIOTIC FUNCTION ABIOTIC FUNCTION FORM(a) %(b) FLOW
Natural Flow Regime components provide important biotic and abiotic
Cause:Response forms and functions (from Newbury, pers. Comm.)
Lowflow in Context
• Lowflow is only one state that
aquatic animals must cope with;
• Considerations for changes in
lowflow volumes:
– Stream Order
– Stream Location
– Stream Form
– Time of year and duration
– Species and life stage
The Formative flows
cumulatively adjust the
shape and structure of
the channel.
The structure and
shape of the channel at
lowflow confines the
flow and controls the
relative quality of
habitat for fish.
Bankfull/Lowflow Linkage
Different stream forms will hold low and high flows
differently and therefore respond differently to changes in flow regime
Simple cause:effect relationships are rare when
examining the impact of a stressor on a natural
system.
The response of animals in the river may be dictated
by the interplay of a variety of variables operating
together and disturbance patterns happening over
time.
The response will also be coloured by the time of
year, state conditions at that time of year and the
stage or state in the animal or populations life cycle.
Framework and Tool Considerations • All sizes will NOT fit all – therefore need a
flexible Framework that is holistic, hierarchical and adaptive.
• Tools that should be considered:
– Stream Form Classification
– Valley Classification (e.g. ALIS/MNR)
– Flow Regime analysis
– Drainage network characteristics
– Groundwater:Surface Water Linkages
– Development of Cause:Response Relationships
– Benthic and Fish Community Characterization
Ecological Assessment Framework
• Framework that incorporates a examination of the system, that has scale and is adaptive (from Bradford 2008)
The process of developing
an integrated context
begins with selecting the
spatial hierarchy that helps
to integrate the sciences.
Implementation will occur
at several scales, selected
to be the most appropriate
to the issue.
With EFR design will likely
occur at watershed and
reach level
Context Setting
Considerations for Framework Application
• Type of water abstraction or flow modification (e.g. water abstraction vs hydro-electric)
• Geophysical characteristics of the watershed
• Location in the drainage network
• Valley type and stream form
• Level of Human Modifications already existing
• Balancing Flow Regime Management with Stochastic Events important to ecological reset
• Be willing to test and learn (Adaptive Approach)
Valley Wall Valley
Wall
A Major Outcome of Re-establishing
Ecological Flows
Re-establishing
functional stream
corridors provide more
opportunities for more
complex trophic
structures where
nutrients can be cycled
and stored in long-lived
organisms (e.g. shrubs,
trees, fish) leading to
healthier system and
better water quality
EFR and Natural Infrastructure
• EFR is a major step in rehabilitating a watershed’s Natural Infrastructure
• Unrealistic to think that we can return systems to historical conditions;
• The key is to try to return the landscape, flow regime, stream corridors and their land:water linkages to a healthy, functional state for people and environment
• We re-build this infrastructure by developing Ecological Flow Requirements and a semblance of Natural Flow Regime.
So…Why Bother? • Aquatic ecosystems are topographically unique in
occupying the lowest position in the landscape,
thereby integrating catchment-scale processes
(Naiman et al. 2002)
• EFR is a key component in Watershed and Water
Resource Management aimed at improving the
quality and resiliency of a Watershed’s Natural
Infrastructure
• If we don’t better manage our systems, we will
temporarily have a high standard of living in a
degraded environment….this is NOT a long-term
sustainability option
So, Let’s Move Forward • Let’s begin to determine the steps needed to
imbed current and emerging science into water resource management for EFR
• Will it be easy?.....NO, but…
“WE CANNOT SOLVE TODAY’S
PROBLEMS WITH THE SAME LEVEL
OF THINKING THAT CREATED
THEM.”
Albert Einstein
“WE CANNOT SOLVE TODAY’S
PROBLEMS WITH THE SAME LEVEL
OF THINKING THAT CREATED
THEM.”
Albert Einstein
MOVING FORWARD
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