Ecological Flow Requirements

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