A framework for setting flow and allocation limits - Nelson

1. A framework for setting flow and allocation limits - Nelson Joe Hay 15 december 2016

2. A bit about me • Resident in the Maitai catchment • Freshwater Biologist, Cawthron Institute for last 13 years (last 5 ½ yrs as a contractor) • Member of FoM • Maitai FMU group member • Involved in research and provide advice to councils and other stakeholders throughout NZ • Mainly relating to water allocation management and freshwater fish

3. Flow is A defining feature of streams • Flow a “master variable” in streams. • Influences many aspects of stream ecology, including: • Channel form • Transport of sediment, nutrients and food down a river system • and the distribution and behaviour of organisms.

4. What flow features need attention?

5. Flow requirements of different species Slow water species Fast water species

6. Determining environmental flow needs – where do we start? • Identify instream values • Define instream management objectives • Focus on critical values • those that have highest value and highest flow needs • in larger rivers these are typically salmonids and birds • Focus on critical flow related environmental requirements (attributes) • physical habitat (space) • fish passage • food • water quality (temperature, oxygen, etc.) MFE 1998 - Flow Guidelines for Instream Values

7. NPS-FM water quantity objectives • 1. To safeguard life-supporting capacity, ecosystem processes and indigenous species including their associated ecosystems in sustainably managing the taking, using, damming, or diverting of fresh water. • 2. To avoid any further over-allocation of water and phase out existing over-allocation. • 3. To improve and maximise the efficient allocation and use of water. • 4. To protect the significant values of wetlands and outstanding freshwater bodies.

8. Key Components of flow management (required by NPS-FM) • Minimum flow is the flow at which abstraction must be restricted or cease • Provides refuge for instream values during periods of low flow • Allocation limit is the rate (or volume) that water can be extracted • Protects instream values by controlling length of low flow period and maintaining some flow variability • Maintains reliability of supply to abstractors

9. Environmental flow regime

10. Two main Instream flow assessment methods • Historical flow methods • Habitat methods

11. Habitat methods Brown trout adult feeding habitat preferences Suitability Suitability Depth Velocity Suitability Substrate index Habitat

12. Historical flow methods Historical flow method Biological response Flow

13. Habitat methods vs historical flow methods Historical flow method Biological response Habitat method Flow

14. Technical Assessment methods • Historical flow methods • Generalised habitat modelling • Hydraulic habitat modelling • Water quality modelling • Ecohydraulics modelling • ++ many more Assume status quo is best Assume linear response to flow Non-specific Easily applied Assumes habitat (or WQ) is limiting Non-linear flow response Linked with specific values Data hungry Expensive Controversial

15. Protection levels • Risk management • High value then accept minimal risk • minimum flow provides 90-100% habitat retention at naturalised MALF • allocation limit 10-20% of MALF • Lower value then accept more risk • minimum flow provides 70-80% habitat retention at naturalised MALF • allocation limit 20-30% of MALF

16. Common Approach in other regions • Historical flow methods to guide broad-scale flow management decisions • Detailed instream habitat analysis for rivers with very high values and/or large flow alteration • Protection levels based on risk assessment • Allocation limits set based on security of supply

17. Other considerations • Flow statistics – 7Day or 1Day • Naturalising flow statistics • Minimum flow equals cease take • Restriction trigger and number of steps • Security of supply • Supplementary allocation (high flow harvesting) • Scaling limits within catchments • Cumulative allocation Consented and permitted

18. Recommended framework • Historical flow approach across all classes (except Maitai and Roding where habitat modelling available) • Where naturalised flow statistics are not available, set more conservative interim limits • Minimum flow equals % of naturalised 7Day MALF High value sites 90-100% Lower value sites 70-80% • Allocation limit equals % of 7Day MALF High value sites 10-20% Lower value sites 30% • Minimum flow equals cease take

19. Whangamoa FMU Collins River

20. Flow recorder site Flow record not influenced by abstraction 6 species of native fish recorded Moderate sized stream Collins River at Drop

21. Collins River at Drop

22. Collins River– Security of supply

23. Wakapuaka FMU Wakapuaka River @ Hira

24. Flow recorder site Flow record influenced by abstraction upstream (including Teal and Lud) 8 species of native fish recorded Locally important trout fishery, of high local value Large stream Wakapuaka River at Hira

25. Wakapuaka River at Hira

26. Wakapuaka River at Hira

27. Stoke FMU Orphanage Stream

28. Flow recorder site Flow record influenced by small permitted abstraction 11 species of native fish recorded Small stream Orphanage Stream at Ngawhatu

29. Orphanage Stream at Ngawhatu

30. Or 80% of MALF minimum flow? Depends on mgmt. objectives. Orphanage Stream at Ngawhatu

31. Maitai FMU Todds Valley Stream

32. Synthesised flow record Flow record influenced by large volume abstraction 7 species of native fish recorded Small stream Potential peak permitted take exceeds low flows Todds Valley Stream at SH6

33. Todds Valley Stream at SH6

34. Or 100% of current MALF? Since flow statistics already influenced by proportionally large abstraction Todds Valley Stream at SH6

35. Maitai FMU Maitai River

36. Flow recorder site Flow record influenced by large abstraction upstream (municipal supply) 11 species of native fish recorded Large stream Habitat modelling undertaken for upper and middle reaches Maitai River at Avon Terrace

37. Maitai River at Avon Terrace

38. Maitai River at Avon Terrace