Functional flows: A practical strategy for healthy rivers Stewart Rood University of Lethbridge

1. Functional flows: A practical strategy for healthy rivers Stewart Rood University of Lethbridge

2. Fundamental principle: river ecosystems require instream flow Trees Trout

4. Science: Instream Flow Needs – Flow amount and pattern required to sustain an organism Environmental Flow Needs – Flows to sustain the aquatic and riparian ecosystems AbEnv-IFN group: 85% of natural flow Management: Old: Minimum Flow for survival Instream Objective – Flow target for human use & the environment New (2006): Water Conservation Objective (WCO) = Instream Objective + 10%; or 45% of natural flow

5. Tennant (Montana) method Oldman River – pre-Dam good poor 85% 60% 45%

6. another empirical approach St. Mary ‘the proper way to do toast … … wait ‘til it burns, then 5 seconds less’ (Ogden Nash?)

7. conservation vs. restoration decline recovery but … hysteresis condition discharge

8. Riparian Ecosystem Aquatic Ecosystem Hydrograph components for: 1. Channel Formation 2. Riparian (Streamside) Community 3. Aquatic (Instream) Community 4. Water Quality

9. Scaled to the Bow River at Banff 1. High flows for Channel development 2. Riparian Post-flood ramping for cottonwood recruitment Discharge = Flow Rate (m3/s) 3. Aquatic Sufficient flow for T & O2 O2 under ice 4. Water Quality Winter Spring Summer Autumn

10. BioScience 1997 … yes, but it’s not feasible to restore natural flow regimes …

11. Functional Flows High flow functions occur in high flow years The Paradox of Water Management Demand is high when supply is low Wet 1/4 Normal 2/4 Dry 1/4 High flows for Channel development Riparian Post-flood ramping for cottonwood recruitment Discharge = Flow Rate (m3/s)

12. A management opportunity: Storage is proportionally greater in low flow years Dry 1/4 Uniform reduction to 45% = system stress Functional Flow = flow when most needed Riparian Survival Discharge = Flow Rate (m3/s) Aquatic Sufficient flow for T & O2 O2 under ice Water Quality

13. Oldman River near Monarch July 1988 – pre-Oldman Dam Insufficient flow = degraded system

14. Oldman River Dam Project 1991 increased minimum flows 1993 flow ramping 1995 flood People cared

15. 350 300 Recruitment Box 250 survivable stage decline (2.5 cm / day) 200 River stage above base (cm) 150 potential recruitment band 100 50 seed release 0 MAY JUN JUL AUG SEP Month

16. Validating the model

17. S. Sask. Oldman 1995

18. 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 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 for Environmental stress during dry years

19. Different management objectives:

20. Decrepit population 1988 Rejuvenating the Oldman 2008 Healthy population

22. Implementing Environmental & Functional Flows

23. Functional flows: A practical strategy for healthy rivers Stewart Rood University of Lethbridge