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 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 Habitat
Suitability
Suitability
Depth
Velocity
Suitability
Substrate index
Habitat

12. Historical flow methods
Biological response
Flow

13. Habitat methods vs historical flow methods
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 % 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
Also cover a few other key points.
Ideally be based on naturalised MALF, but that this may not be possible at this stage for most streams in Nelson due to a lack of abstraction records.
That although minimum flows and allocation volumes can be calculated for a given point in the catchment (i.e. the flow recorder site), that these numbers need to be scaled to other parts of the catchment.
That permitted activity abstractions should be quantified and included in the allocation block, and cease to be permitted activities once catchments are fully allocated. Without this provision the permitted activity takes can cumulatively overwhelm the total consented allocation, especially in small stream, as seems to have happened in Nelson.

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 %
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
the approach I’m proposing we take here (i.e. base minimum flows on a proportion[probably in the order of 70-90%] of the 7 day MALF, and allocation volume also on a proportion [probably in the order of 10-30%] of the 7 day MALF.

19. Whangamoa FMU Collins River Mean Median 7 Day MALF
Collins at Drop Structure
542
220
63.6
Existing minimum flow
63.6
Existing consented allocation
Existing potential peak permitted abstraction

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

21. Collins River at Drop
The key thing I am seeking feedback and discussion on is the % levels used for setting the minimum flow and allocation volume. This is based on risk management, with greater level of risk of adverse ecological effects at higher allocation levels and lower minimum flows. I would like to know what level of ecological risk is acceptable to the stakeholders involved in the FMU and Iwi Group meetings.
Also, the duration and frequency of the minimum flow has potential impacts on abstractors (i.e. it defines the duration and frequency of abstraction restriction, when they are shut off). Increasing frequency and duration of the minimum flow also increases the risk of adverse ecological effects. So I am keen to hear whether there are particular frequencies of durations of flow restrictions that are not acceptable to the stakeholders.

22. Collins River– Security of supply

23. Wakapuaka FMU Wakapuaka River @ Hira Mean Median 7 Day MALF
Wakapuaka at Hira
1344
733
306
Existing minimum flow
245
Existing consented allocation
=16
Existing potential peak permitted abstraction
47.4

24. Wakapuaka River at Hira
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

25. Wakapuaka River at Hira

26. Wakapuaka River at Hira

27. Stoke FMU Orphanage Stream Mean Median 7 Day MALF
Orphanage at Ngawhatu 78 25
4.8
Existing minimum flow
None specified
Existing consented allocation
Existing potential peak permitted abstraction
0.1

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

29. Orphanage Stream at Ngawhatu

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

31. Maitai FMU Todds Valley Stream Mean Median 7 Day MALF Todds at SH6 36
28.6 14
3.8
Existing minimum flow
2.3
Existing consented allocation
0.8
Existing potential peak permitted abstraction
8.1

32. Todds Valley Stream at SH6
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

33. Todds Valley Stream at SH6

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

35. Maitai FMU Maitai River Mean Median 7 Day MALF Maitai at Avon Tce
2416
882
358
Existing minimum flow
35.8
Existing consented allocation
=314.8
Existing potential peak permitted abstraction
=19

36. Maitai River at Avon Terrace
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

37. Maitai River at Avon Terrace

38. Maitai River at Avon Terrace