1. Instream flow assessment in New Zealand

2. Flow assessment framework Morphology Evaluate for changes in flow Water quality Methods and parameters DO Temperature NH3 Biological evaluation Water quality suitability Flow regime requirements Methods Flushing flow analysis (shear stress) Fluctuating flow habitat analysis Sediment deposition Habitat suitability Velocity/depth Hydraulic geometry 2d models Stage/Discharge Water surface profile Flow assessment based on flow response curves of biological indicators

3. Instream habitat Habitat suitability is a widely used concept e.g., angling and hunting No suitable habitat - no fish Suitable habitat - maybe..

4. Three basic life requirements for fish and benthic invertebrates that live in flowing water Velocity Depth Cover

5. New Zealand adult brown trout (Hayes & Jowett 1994) Suitability Depth (m)Velocity(m/s) 0.00.30.60.91.21.50.00.40.81.21.62.0 0.0 0.2 0.4 0.6 0.8 1.0 Adult brown trout (Raleigh et al. 1984) Suitability Depth (m)Velocity(m/s) 0.00.30.60.91.21.5 0.00.40.81.21.62.0 0.0 0.2 0.4 0.6 0.8 1.0

6. Velocity (m/s) Offset (m) Depth (m) 0 4 8 12 16 20 0.0 0.4 0.8 1.2 1.6 2.0 -2.00 -1.25 -0.50 0.25 1.00 5.3 m 3 /s 11 m 3 /s Prediction of depth and velocity Predicted water level and depth Predicted velocity Level at 5.3 m 3 /s Level at 11 m 3 /s

7. Habitat quality across river 1 m 3 /s 6 m 3 /s 11 m 3 /s

8. Weighted usable area (m 2 /m) Discharge (m 3 /s) 0510152025 0 2 4 6 8 10 Maximum Point where habitat begins to reduce sharply Usable habitat summed over reach for each flow

9. 6 1 2 3 4 5 NZ case studies

10. River flows are affected by : –Hydroelectric diversion, –Hydroelectric flow control, or –Irrigation diversion Studies between 1979 and 2001 Trout, benthic invertebrate, and native fish goals

11. 1.Description of river and flows 2.Habitat analysis and flow recommendation 3.Before and after photographs 4.Biological response For each project:

12. Lake fed river - natural mean flow 450 m 3 /s River diverted for hydropower generation in 1976 Minimum flow of 0.3 m 3 /s since dam construction Waiau River Hydroelectric diversion

13. WUA (m 2 /m) Discharge (m 3 /s) 051015202530 0 5 10 15 20 25 30 Adult brown trout Food production Maximum habitat at >15 m 3 /s Sharp drop as flow goes below 10 m 3 /s Goal: Trout and food production Summer flow Winter flow

14. Before: flow about 1 m 3 /s After: flow about 16 m 3 /s Minimum flow of 12-16 m 3 /s since August 1997

15. Flow (m 3 /s) 1 10 100 1000 Before After minimum flow 1 year Waiau River

16. Numbers of trout (>20 cm) 0 50 100 150 200 250 199619971998199920002001 Brown and rainbow trout per km BeforeAfter minimum flow

17. Brown and rainbow trout densities ranked nationally River (300+ reaches in descending order) Trout (> 20 cm) per km Waiau River 0 50 100 150 200 250 300 350 Before After

18. Monowai River Controlled flow to hydroelectric plant Lake fed river - mean flow 13.8 m 3 /s Dam at lake controls flow to downstream power station Minimum flow of near zero, usually each night

19. WUA (m 2 /m) Discharge (m 3 /s) 0246810 0 5 15 Food production Maximum habitat at 5-7 m 3 /s Sharp drop as flow go below 3 m 3 /s Maximum Sharp drop Goal: Invertebrate abundance and diversity

20. 1-JAN-95 1-JUL-95 0 5 10 15 20 Flow (m 3 /s) 1-JAN-92 1-JUL-92 BeforeAfter minimum flow Minimum flow since July 1994

21. 0 200 400 600 800 1000 19911992199319941995199619971998 Density (no m -2 ) 0 5 10 15 20 25 Taxon richness (no per sample) After minimum flow increased to 6 m 3 s -1 Invertebrate abundance doubled Number of species doubled Density Taxon richness Invertebrate abundance and diversity Before

22. Ohau River Hydroelectric diversion Lake fed river - mean flow 80 m 3 /s Flow diverted for hydropower in 1979 Minimum flow of near zero

23. WUA (m 2 /m) Discharge (m 3 /s) 051015 0 5 10 15 20 Adult brown trout Food production Maximum Habitat analysis indicated excellent adult trout and food producing habitat at 10 m 3 /s Goal: High quality brown trout fishery

24. Before: Flow < 1 m 3 /s After: Flow 10 m 3 /s Minimum flow of 10-14 m 3 /s since 1994

25. Failed to meet expectations Trout present, but not many Reasons unknown Food ? Recruitment? Flow too high?

26. Tekapo River Hydroelectric diversion Lake fed river - mean flow 90 m 3 /s Lake flow diverted in 1978 leaving 10 m 3 /s from tributaries

27. Excellent adult trout spawning and food producing habitat at >10 m 3 /s 0 10 20 30 05101520 Discharge (m 3 /s) WUA (m 2 /m) Trout spawning Food production Habitat begins to drop sharply Goal: High quality trout fishery

28. Just below dam Zero flow 45 km downstream Flow 10 m 3 /s

29. Tekapo River Before diversion (flow 90 m 3 /s) –Not mentioned in angling surveys –Some trout spawning After diversion (flow c. 10 m 3 /s) –Up to 240 brown and rainbow trout (> 20 cm) per km –More than 200 juvenile brown and rainbow trout per km

30. 0 50 100 150 200 250 300 350 River (300+ reaches) Brown and rainbow trout (> 20 cm) per km Brown and rainbow trout densities ranked nationally Before? After

31. Moawhango River Hydroelectric diversion Natural mean flow 9.3 m 3 /s In 1991, all water was diverted to another river system

32. WUA (m 2 /m) Discharge (m 3 /s) Goal: benthic invertebrate community composition 012345 0 3 6 9 12 15 Deleatidium Zelandoperla decorata Aoteapsyche Hydrobiosis parumbripennis Maoridiamesa Orthocladinae Tanytarsus vespertinus Maximum Sharp drop Sharp reduction at flows < 0.8 m 3 /s

33. After 0.52 m 3 /s Before 0.06 m 3 /s Minimum flow of 0.6 m 3 /s since June 2000

34. 0 10 20 30 40 Deleatidium Orthocladiinae Aoteapsyche Tanytarsus Pycnocentrodes Maoridiamesa Zelandoperla Ostracods Lymnaea Elmidae Oligochaeta Potamopyrgus Percentage of total Before (1997) After (2002) Desirable species Undesirable species

35. Waipara River Diversion for irrigation Small gravel-bed river Mean flow 2.5 m 3 /s

36. WUA (m 2 /m) Discharge (m 3 /s) 0.00.10.20.30.40.50.6 0 2 4 6 8 Common river galaxias Longfin eel (<300 mm) Upland bully Torrentfish Bluegill bully Common bully Sharp drop Goal: maintain native fish population Habitat for a species with “intermediate” velocity preference begins to decline sharply at 0.12 m 3 /s

37. Dec 1998-May 1998 Dry summer Less than recommended minimum (0.12 m 3 /s) for 36% of time Dec 1999-May 2000 Wet summer Less than recommended minimum ( 0.12 m 3 /s) for 11% of time

38. Effect on Fish Population Beginning of summer 1 10 100 1000 Upland bullies Canterbury galaxias Torrentfish Bluegill bullies Fish per 100 m End of summer Dry 1998/99 summer 1 10 100 1000 Upland bullies Canterbury galaxias Torrentfish Bluegill bullies Fish per 100 m Wet 1999/00 summer

39. Conclusion This is all the NZ data on biological response to flow changes Flow assessments were based on habitat requirements 5 out of 6 were successful The outcomes don’t support commonly held views that more flow is better and that all aspects of a natural flow regime are important

40. Thank you