Functional flows:A practical strategy for healthy rivers

Stewart RoodUniversity of Lethbridge

Trees

Trout

Fundamental principle:

river ecosystemsrequire instream flow

Management:

Old:Minimum Flow for survivalInstream Objective – Flow target for human use & the environment

New (2006):Water Conservation Objective (WCO)

= Instream Objective + 10%; or 45% of natural flow

Science:

Instream Flow Needs – Flow amount and pattern required tosustain an organism

Environmental Flow Needs – Flows to sustain the aquatic and riparian ecosystems

AbEnv-IFN group: 85% of natural flow

Tennant (Montana) method

good poorOldman River – pre-Dam

1

2

3

4

5

6

0 10 20 30 40 50 60 70 80 90 100

% Discharge

Hea

lth

85%60%

45%

‘the proper way to do toast …… wait ‘til it burns, then 5 seconds less’

(Ogden Nash?)

St. Mary

another empirical approach

but … hysteresis

cond

ition

discharge

decline

recovery

conservation vs. restoration

Hydrograph components for:

1. Channel Formation

2. Riparian (Streamside) Community

3. Aquatic (Instream) Community

4. Water Quality

RiparianEcosystem

AquaticEcosystem

0

50

100

150

200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Scaled to the Bow River at Banff

1. High flows forChannel development

2. RiparianPost-flood ramping

for cottonwoodrecruitment

3. AquaticSufficient flow

for T & O2O2 under

ice

4. Water Quality

Winter AutumnSummerSpring

Dis

cha

rge

= F

low

Rat

e (m

3/s

)

BioScience 1997

… yes, but it’s not feasible to restore natural flow regimes …

0

50

100

150

200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Wet 1/4Normal 2/4Dry 1/4

Dis

cha

rge

= F

low

Rat

e (m

3/s

)High flows for

Channel development

RiparianPost-flood ramping

for cottonwoodrecruitment

TheParadox of Water Management

Demand is high when supply is low

Functional FlowsHigh flow functions occur

in high flow years

0

50

100

150

200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Dry 1/4

Dis

cha

rge

= F

low

Rat

e (m

3/s

)

RiparianSurvival

AquaticSufficient flow

for T & O2O2 under

ice

Water Quality

Uniform reduction to 45%= system stress

A management opportunity:Storage is proportionally greater in low flow years

Functional Flow= flow when most needed

Oldman River near MonarchJuly 1988 – pre-Oldman Dam

Insufficient flow = degraded system

Oldman River Dam Project

1991 increased minimum flows

1993 flow ramping

1995 flood

People cared

Validating the model

Oldman 1995

-7.5

-5

-2.5

0

2.5

5

7.5

Sta

ge

ch

an

ge

(cm

/da

y)

Month

-1

0

1

2

3

4

Sta

ge

ab

ove

ba

se (

m)

South Saskatchewan River 1995

May OctSepAugJulyJune

seeddispersal

2.5cm/daydecline

lethal

stressful

favorable

S. Sask.

Management:

Water Conservation Objective (WCO) 45% of natural flow

Functional Flows

1. Deliberately non-natural pattern

2. Support aquatic and riparian populations

3. Environmental benefit during wet years to compensate forEnvironmental stress during dry years

Science:

Instream Flow Needs – Flow to sustain an organism

Environmental Flow Needs – Flows to sustain aquatic and riparian ecosystems - The Natural Flow Regime

AbEnv-IFN group: 85% of natural flow

Different management objectives:

Condition Flow Objective Strategy Quantity

Dry 1/4 year

Low flow Survival

Sufficient late

summer flow

45%

Normal 2/4 years

Normal flow

Growth

Additional early

summer flow

60%

Wet 1/4 year

High flow Reproduction

High spring flow and gradual

recession

85%

1988

2008

Rejuvenatingthe Oldman

Decrepit population

Healthy population

River FishFirst

Nations Other

Truckee, NV Cui-ui sucker

Paiute - Partnership:Army COE – The Nature Conservancy

Oldman, AB x Peigan/Piikani

- Oldman River Dam controversy- Federal-Provincial jurisdiction

Bill Williams, AZ

- Compensate for environmental degradation

Kootenai, MT, ID, BC

Whitesturgeon

Kootenai - Channel & Floodplain reconstruction

Snake, ID x - Extensively dammed river, compensation- FERC relicensing

Bridge, BC x - Dept. Fish. & Oceans lawsuit

Duncan, BC x - Environmental benefit, without economic cost

Waterton, St. Mary, AB

x - Environmental benefit, without economic cost

Implementing Environmental & Functional Flows

Functional flows:A practical strategy for healthy rivers

Stewart RoodUniversity of Lethbridge