Agenda of Maori Committee

	Agenda Item	Action	Person Responsible	Due Date	Status Comment
1.	Marae Water issues – A Verbal Update by Mr Des Ratima	Meeting with CE and Chairman	LL/VM	24 June	Verbal update at 24 June meeting
2.	Future of Maori Committee	A workshop to be held	VM/MH	24 June	Verbal update of workshop discussions
3.	Healthy Homes Presentation	Meeting with Regional CEs	LL/VM	24 June	Update at 24 June meeting

HAWKE’S BAY REGIONAL COUNCIL

Maori Committee

Tuesday 24 June 2014

SUBJECT: River Gravel Update

Reason for Report

1. This report is to update the Maori Committee on progress with the Review of Riverbed Gravel Management. This is review being managed by the Engineering Section as part of the Gravel Management Project (Project 369).

Background

2. Gravel extraction forms an integral part of ongoing flood protection to both the Heretaunga and Ruataniwha Plains scheme areas, with gravel being extracted such that the flood capacity of the schemes is maintained, and the potential for the rivers to undermine edge protection is minimised.

3. The Hawke’s Bay river-borne gravel resource is increasingly under pressure for construction use particularly in the proximity of the Heretaunga Plains where the transport cost to the main centres is significantly less than gravel sourced further away.

4. The majority of the easily accessible rivers are now effectively managed through the process of targeted gravel extraction. However gravel stocks are limited in many of the areas closest to the market and as a result pressure is placed on gravel extractors to win their resource at greater distances (eg Ruataniwha Plains rivers) from their markets putting pressure on their competitiveness.

5. With the understandable reluctance to source gravel from further afield due to the high transport costs there is a risk that gravel management for flood control purposes in these areas will become an expense on scheme ratepayers that may be unaffordable.

6. In addition there is increasing concern being expressed by the public that river gravel extraction is aggravating coastal erosion, particularly in Haumoana and Te Awanga. More research being undertaken to fully understand and manage the potential effects.

7. The Asset Management section believes it is imperative for Council to have an effective framework for the ongoing management of the gravel resource within the region, supported by robust science and processes. This was the subject of a paper to Council on 09 November 2010 where a scoping report was presented that outlined the issues and proposed a way forward.

8. The scoping report identified the issues associated with the current management of the region’s river bed gravel resource that when completed would:

8.1. Improve Council’s understanding of riverbed gravel transport and the impact of gravel extraction on flood protection works and coastal processes.

8.2. Enable Council to review its management regime for assessing the gravel resource and for managing its extraction.

8.3. Examine the future demand for the resource working with the extraction industry.

8.4. Inform co-management discussions with regard to the gravel resource and its management with Treaty Claimant Groups.

9. The scoping report adopted by Council included a prioritised programme of work that could be accommodated in a 6 year time span. This 2013/2014 financial year is the third year of the programme. Completion is programmed for 2016/2017.

10. In order to carry out the review and obtain a wide view of community concerns and ideas on the gravel resource a number of meetings have been arranged, (and are ongoing) to discuss the issues. A separate meeting was held with the key people in the gravel supply industry to hear their views as they have a different perspective on the resource than other interested parties. These meetings with the industry are continuing as they are a vital part of gravel management.

11. A meeting has been held with DOC, Fish & Game and the TLA’s. A hui was widely advertised and held at Kohupatiki Marae to inform and discuss with hapu associated with the rivers the issues relating to gravel management. In addition a number of specialists working in the fields of coastal and river gravel processes have been interviewed for their expert knowledge.

12. HBRC has a number of responsibilities that have a direct bearing on the management of gravel resources in the region:

12.1. It has the jurisdiction to manage and authorise activities in riverbeds

12.2. It has the jurisdiction to manage and authorise activities in the coastal area

12.3. It has responsibility for flood control and protection of assets.

13. There is an ongoing demand for gravel and aggregate for a range of activities in the roading and construction industry. There is a need to balance the allocation of gravel between supply demand and the need to maintain the flood capacity of flood protection schemes. This balance should also take account of the environmental effects of gravel extraction, Māori views and the river ecology.

14. Extensive flood protection schemes have been established throughout the Heretaunga Plains and the Ruataniwha Plains, managed by HBRC. These schemes are currently designed and constructed to a standard (1% Annual Exceedance Probability, AEP). This standard is maintained through maintenance of the channel carrying capacity and design riverbed levels.

15. The main population areas and therefore gravel demand are on the Heretaunga Plains. However the gravel resources are spread between the Northern area, Heretaunga Plains and Ruataniwha Plains. As noted above there is a tension between the gravel supply and the gravel demand areas due to the extra transport costs. This has implications for HBRC’s management of the flood protection schemes as too high a cost to extract the gravel may result in gravel extractors preferring to establish land based sources. HBRC currently has little ability to manage these land based areas, although land based mining is covered in the Hastings District Plan.

16. There is uncertainty over the potential effects of riverbed gravel extraction, specifically in relation to the following aspects:

16.1. Long-term riverbed morphology

16.2. Long-term riverbed gravel supply from the high country

16.3. Sediment supply to the coast and the effect on coastal stability

16.4. Riverbed ecology and biodiversity

16.5. Sites and issues of significance to tangata whenua.

17. The review includes work to investigate and/or quantify these effects and determine what further work, if any is needed to provide HBRC with robust information necessary to manage the gravel resource as well as confirming or otherwise whether the current management regime and processes are appropriate for long term sustainability. The information will improve the understanding of gravel transport and therefore also enhance the understanding for other interested parties.

18. The review is divided into 13 separate but related issues that require investigation. The order presented in the table below begins with the highest priority first and some of the later issues are dependent on the outcome and/or data from the earlier studies. Rough order costs to carry out the work have been assigned to each issue. In addition there are annual costs associated with Tangata Whenua involvement and a steering group.

	Issue	Total Indicative cost	Stage	Current Status
1	Hydrological Review	$40,000	Stage 1	Complete
2	Gravel Supply & Transport	$110,000		In Progress
3	Gravel Resource Inventory	$60,000
4	Implications for Flood Protection	$40,000
5	Gravel Demand & Forecast	$30,000
6	Gravel Monitoring & Resource Availability	$40,000
7	In-stream Ecological Effects	$75,000	Stage 2	In Progress
8	Riverbed Birds & Flora	$45,000		In Progress
9	Tangata Whenua Values	$20,000		Ongoing
10	Effectiveness of Beach-raking	$40,000	Stage 2	Complete
11	RMA Issues	$30,000	Stage 3 (RMA issues sooner)
12	Allocation & Financial Mechanisms	$30,000	Stage 3 (RMA issues sooner)
13	Riverbed Gravel Management Plan	$75,000	Final Stage
	Total	$635,000
	Tangata Whenua consultation	$10,000/year		Ongoing
	Steering Group	$10,000/year		Ongoing

19. The terms of reference for the review were to consider the costs spread over a number of years at about $100,000 per year. This of course is subject to a suitable source of funding and could be expanded or reduced to suit. At present 6 years is the time period considered. A work programme has been prepared to enable each of these issues to be studied and reported on in a final report by 2017.

20. Possible options for funding the work were discussed with gravel extractors and Council. The option chosen to fund the work is from increased Resource Management charges currently levied on a per cubic metre rate on all river bed gravel extracted. With the previous level of extraction averaging approximately 600,000 cubic metres per annum this required an increase of the levy charged from $0.60/m³ to approximately $0.80/m³.

21. In the past year gravel extraction from the region’s rivers has reduced significantly as the market demand has dropped off. There are two consequences of this if the trend continues;

21.1. The lesser consequence is that funding to continue the research will need to be topped up from another source or the programme will need to be extended. This latter action is least preferred owing to the urgent nature of some of the issues.

21.2. The more serious consequence with reduced demand is that gravel build-up in the rivers will be a problem for the flood protection system. Already some river reaches in the Ruataniwha Plains (e.g. Makaretu River) have excessive gravel deposits causing problems.

22. Staff will give a short presentation to Councillors outlining the research done to date, highlighting some of the more pertinent findings and provide some comment on future work.

Decision Making Process

23. This paper is to update Council on a programme of work that has already been approved and as such no decisions are required to be made. Likewise there are no recommendations to consider.

Recommendation

1. That the Maori Committee receives the report “Gravel Resource Review: Update”.

Mike Adye

Group Manager Asset Management

Attachment/s

There are no attachments for this report.

Ahuriri Estuary Contact Recreation and Food Gathering Report

Attachment 1

2 Methods for assessing contact recreation and food gathering risk

2.1 Contact recreation

“Contact recreation” includes any activity that causes people come into contact with water where a reasonable risk of inhaling or ingesting water exists. At times, the suitability of water for recreation may be compromised by the presence of human or animal faecal material resulting from land run-off, discharges or from natural populations of animals or birds. During these events, water may contain pathogens from this faecal matter. The risk of contracting illnesses such as gastro-enteritis, respiratory illnesses, Hepatitis A, giardiasis, cryptosporidiosis, campylobacterosis, and salmonellosis increases as the risk of exposure to pathogenic organism increases (MfE and MoH, 2003).

From an aesthetic point of view, water clarity can be an important consideration for people undertaking recreational activities. Although not as important in marine waters which tend to be naturally more turbid, freshwater recreation choice can be influenced by visual clarity.

Visual clarity (determined by black disk visibility), is not generally measured in marine or estuarine waters. Turbidity, a measure of the amount of light scattered or absorbed by particles in the water, is more commonly used in New Zealand coastal water quality monitoring programmes. An inverse relationship can generally be demonstrated between turbidity and visual clarity. Generally, if turbidity meets the requirements for aquatic ecosystems, it is likely to meet the aesthetic value for contact recreation as well.

High algal biomass can influence aesthetic values associated with contact recreation. High algal biomass may reduce the visual clarity of the water by making it more turbid, or by changing the colour of the water, creating ‘murky’ or discoloured water. Human health risk associated with contact recreation may be increased if toxic species are present. Increased nutrient inputs from either land or marine sources can influence (increase) algal biomass growth rates.

Current guidelines for the attributes associated with contact recreation are detailed in Table 2-1.

Table 2-1: Current water quality guidelines associated with contact recreation.

cfu = colony forming units, NTU = Nephelometric turbidity units, BD = black disk.

Attribute	Guideline value¹		Source	Value
Attribute	Satisfactory	Unsatisfactory/ Unacceptable	Source	Value
Enterococci (cfu/100 mL)	<280 cfu/100 mL	>280 cfu/100 mL	(MfE and MoH, 2003)	Human health
Turbidity (NTU)	0.5-10 NTU	>10 NTU	(ANZECC, 2000)	Aquatic ecosystems
Visual clarity (BD)	>1.6 m	<1.6 m	(MfE, 1994)	Aesthetic and safety
Chlorophyll a (g/m³)	<4 µg/L	>4 µg/L	(ANZECC, 2000)1	Aquatic ecosystems
Toxic algal species (cells/mL)	Absent	Present	‑	Human health and aquatic ecosystems

¹These guidelines refer to ANZECC 2000 for South-Eastern Australia which is used in the absence of New Zealand specific estuarine guidance.

2.2 Food gathering

With the exception of overlying water quality, comparatively little information or guidance exists around the risk associated with recreational harvesting of shellfish and fish. Export food safety guidelines are applied in the absence of recreational specific guidelines; however it is acknowledged that this appears to be an area for further work or development.

For shellfish gathering the attributes likely to compromise the ability to collect shellfish include contamination by faecal material that may contain pathogens. Additionally, the ability of shellfish and fish to accumulate contaminants such as trace metals and other industrial and stormwater related toxins, means that these parameters are also used to assess risks associated with food gathering.

Current guidelines for the attributes associated with shellfish/fish gathering are detailed in Table 2-2.

Table 2-2: Current guideline values associated with water and shellfish quality.

MPN = Most Probable Number.

Attribute	Guideline		Source	Relevance
Attribute	Satisfactory	Unsatisfactory/ Unacceptable	Source	Relevance
Faecal coliforms in overlying waters	Seasonal median < 14 MPN/100mL < 10% of samples < 43MPN/100mL	Seasonal median > 14 MPN/100mL > 10% of samples > 43MPN/100mL	(MfE and MoH, 2003)	Human Health
Toxic algal species in overlying waters	Not present	Present	Nil	Human Health and Aquatic Ecosystems
E. coli in shellfish flesh	Median < 230 MPN/100g and < 10% of samples < 700 MPN/100g	Median > 230 MPN/100g and > 10% of samples > 700 MPN/100g	(NZFSA, 1995)	Human Health
Trace metals	Below FSA guidelines	Above FSA guidelines		Human Health

Ahuriri Estuary Contact Recreation and Food Gathering Report

Attachment 1

3.3 Current state

3.3.1 Faecal bacteria

National guidelines identify concentrations at which the risk of illness associated with contact recreation is no longer considered acceptable (MfE and MoH, 2003). This allows the public to be informed of the health risks, and make informed decisions regarding their exposure to these risks (see Appendix A for an explanation of these guidelines).

The results of routine sampling at the Pandora Pond, the most popular site within the estuary, has provided good quality information regarding the risks associated with contact recreation at this site. The pond is partially enclosed by a barrier arm, creating a hydrodynamic environment that favours exchange of water on the incoming tide (refreshed with saltwater), rather than the outgoing tide (refreshed with freshwater) (Eyre, 2009). These characteristics suggest that this area is likely to be protected from faecal contamination arising from freshwater inflows outside of the pond.

Pandora Pond has been monitored as part of Councils Recreational Water Quality Monitoring programme since 1996. Since the 2008/09 season, the indicator has remained enterococci, allowing trends over time to be established from this date.

During 2012/13, the pond was sampled for enterococci (as an indicator of faecal contamination), electrical conductivity (as a proxy for salinity), turbidity and temperature. During this period the site achieved 90% compliance with MfE and MoH (2003) guidelines, indicating that for 18 out of the 20 weeks sampled, the risk of illness associated with contact recreation at this site was low. For two weeks however, elevated levels of bacteria (>280 cfu/100 mL) meant that the risk of illness was considered ‘unacceptable’ (Figure 3-1). Both of these occasions occurred after periods of significant rain (11 mm 24^th and 25^th December and 9 mm 7^th January), indicating that surface runoff can impact water quality at this site. Given the hydrodynamic regime described above, localised sources should be investigated to determine their role in elevated bacterial concentrations following rainfall events.

Figure 3-1: Levels of bacterial indicator Enterococci at Pandora Pond, Ahuriri during the 2012/2013 recreational season.

Weekly monitoring provides important information regarding the current state of water quality within Pandora Pond. However, the timing of such information limits our ability to assess the public health risk associated with contact recreation because much of the information only becomes available after the period of risk has occurred. This situation arises because the results of analysis only become available 24-36 hours after the samples are collected – during this period, the risk associated with contact recreation is unknown and individuals may be exposed to elevated concentrations of pathogenic organisms. To overcome this limitation, the 2003 guidelines incorporate an approach that couples historical data with a catchment risk assessment to generate a ‘Suitability for Recreation Grade’ (SFRG). The SFRG is designed to provide a general indication of recreational water quality of a water body at any time, rather than in response to the result from a single sampling event.

A suitability for recreation grade for Pandora Pond was generated at the completion of the 2012/13 season:

§ A moderate catchment risk was obtained, indicating potential contamination from sources such as stormwater, rural runoff, birds, land drainage and boat mooring

§ A microbiological assessment category of ‘C’ was obtained, indicating that elevated bacteria concentrations can occur at times

§ Pandora Pond achieved a ‘Fair’ SFRG.

This grading indicates that the area is generally suitable for swimming, although caution should be taken if there has been heavy rainfall, or if the water appears discoloured (MFE and MOH, 2003).

3.3.2 Clarity/Turbidity

Turbidity within the estuary has been assessed for a number of discrete projects over the last decade. The most comprehensive data record exists for the period between 1995 and 1998. These data characterise the water quality of the Ahuriri Estuary and the inflows to the estuary. These data were compared with the results from a previous survey (Hooper (1989)) in Fenton (1997).

The turbidity in waterways flowing in to the Ahuriri Estuary generally exceed guidelines for New Zealand lowland streams (5.4 NTU (ANZECC, 2000); Figure 3-2, left). At times, and within certain sub-catchments, turbidity can be extremely high; however they appear to be somewhat buffered within the estuary with only a few sites exceeding guidelines for marine and estuarine waters (Figure 3-2, right). Typically higher turbidity values are observed in the upper reaches of the estuary (Quarantine and Watchmen Rd), with elevated values at sites in proximity to incoming waterways (e.g. Low level bridge, Tyne Street). In general turbidity in the mid to lower estuary is within, or close to, guideline values for aquatic ecosystems (10 NTU). These values are unlikely to negatively impact on contact recreation except during periods of heavy rainfall, when turbidity may transiently reach values of 130 NTU.

Figure 3-2: Turbidity measured in inflows to the Ahuriri Estuary and within the Ahuriri Estuary n=4-37 Red line = ANZECC trigger levels for aquatic ecosystems for freshwater (left) and estuaries (right).

Figure 3-3: Turbidity levels at Pandora Pond, Ahuriri Estuary between 1999 and 2013. n=20 per annum

The data described above was collected mainly during the period 1995-98, with more recent data restricted to the Pandora Bridge site. The Pandora Pond however has consistently been monitored for turbidity since 1999 as part of the Recreational Water Quality Monitoring programme. With the exception of 2004, no significant increase or decrease in turbidity has been observed (Figure 3-3).

Therefore, the turbidity at the Pandora Pond site does not appear to have significantly changed since 1998.

3.3.3 Algae

Algae, both macroscopic (large, found on the sediment surface), and microscopic (small, plants found within the water column and on the sediment), are normal constituents of a healthy estuarine ecosystem. In areas of high nutrient loading however, algal numbers or cover can become excessive, causing nuisance growths in terms of visual amenity, as well as negatively influencing sediment quality and water chemistry.

Macroalgae

The largely channelised nature of the Ahuriri Estuary minimises the likelihood of prolific algal growths. In depositional areas (where flow is less rapid or obvious), algal growth has generally been restricted to small patches of ephemeral species (e.g. Ulva sp.) during the spring/summer period, persisting at times through to autumn.

Given the nature of the estuary and the moderate sediment nutrient concentrations, prolific algal growth that would adversely affect contact recreation within the lower estuary area (more commonly used for contact recreation) is unlikely.

Chlorophyll a

A few previous studies have detailed the nutrient status of the Ahuriri Estuary waters. These identified that inflows to the estuary have delivered high concentrations of both phosphorus and nitrogen into the main, ‘true’ estuary (Fenton, 1997, Hooper, 1989). Although the estuary has previously been described as eutrophic (Hooper, 1989, Knox, 1979), the decrease in phosphorus concentrations measured between 1989 and 1997 and currently indicate that the trophic state of the waters may have decreased more recently. Conversely, nitrogen concentrations (particularly ammoniacal nitrogen) appear to have increased over the period 1989 – 2013 (Fenton, 1997, Hooper, 1989). The current trophic status of estuarine waters, including the contributions of nutrients from various inflows and land-uses should be investigated further.

That said, chlorophyll a concentrations on estuarine sediments were assessed as part of a specific water quality study in 1998 and 2000 (Figure 3-4). These data can provide important information regarding the relative nutrient status of inflows to the estuary. This work highlighted the role of inflows in determining overall quality of estuarine water.

Figure 3-4: Sediment chlorophyll a concentrations in the Ahuriri Estuary between 1998 and 2000.

More recently, sampling in the Ahuriri Estuary has been undertaken as part of:

§ the Nearshore Coastal Water Quality Monitoring Programme (at Pandora Bridge),

§ the Estuarine Water Quality Monitoring programme to support policy development (at six locations between Watchman Rd and Pandora Bridge) (waters),

§ the Estuarine Ecological Monitoring Programme (sediments collected at multiple locations across the estuary).

The waters of the upper estuary appear to be fairly eutrophic, consistent with the findings of previous reports. However by approximately the middle of the estuary, chlorophyll a levels have dropped below trigger levels, indicating that dilution and flushing from marine waters is moderating nutrient concentrations and algal growth (Figure 3-5).

Figure 3-5: Chlorophyll a levels of water samples taken within the Ahuriri Estuary between March and April 2013 (Ahuriri 1-6), and 2006-2013 (Ahuriri at Pandora). Redline = ANZECC trigger value for south-east Australian estuaries.

From a contact recreation perspective, waters of the Ahuriri Estuary are unlikely to support algal growth to an extent that would impair contact recreation. This assessment excludes the periodic and transient blooms which can significantly increases chlorophyll a concentrations and reduce visual clarity. Such events are infrequently reported for the Ahuriri Estuary.

Harmful algal blooms (HABs)

Harmful algae blooms (and associated marine biotoxins) occur infrequently in Hawke Bay and estuarine areas. These are defined as species that may release toxins (e.g. Gymnodinium catenatum, Pseudonitzchia, Karenia, Dinophysis) which can be harmful if ingested via water or contaminated shellfish, resulting in serious illness. Additionally, species may be present in bloom numbers that do not produce toxins, but cause irritation to the eyes or skin. These blooms may also have environmental impacts, such as depletion of dissolved oxygen concentrations in the water column.

Marine biotoxins were routinely monitored by the Public Health Unit on behalf of the Food Safety Authority until recently, when this function was transferred to the Ministry of Primary Industry (MPI). During autumn 2005 and 2006, significant parts of the Hawke’s Bay coastline were closed due to the presence of marine biotoxins. In August 2012, a large and persistent bloom of Akashiwo sanguine (red tide) was observed along most of the east coast of the North Island, and in the following month a bloom of Pseudo-nitzschia spp. (produces the neurotoxin domoic acid) was observed off Napier; this bloom also included the red tide, Mesodinium rubrum. During these times, contact recreation would have been discouraged along coastal beaches or estuaries affected by these organisms.

3.4 State of the Ahuriri Estuary for contact recreation

Based on information derived from various monitoring programmes operated by Hawke’s Bay Regional Council, the Ahuriri Estuary may be considered as “fair” for contact recreational purposes (see appendix one). This grading indicates that:

§ Ahuriri Estuary waters are generally suitable for swimming.

§ Elevated bacteria concentrations can occur at times.

§ Caution is required during periods of heavy rain or when the water appears discoloured.

Faecal contamination of the estuary is associated with stormwater inflows, runoff from rural land uses and direct deposition of faeces by the high numbers of birds for which the estuary is valued. Throughout the summer period when water quality monitoring indicates an elevated risk of illness due to high numbers of faecal bacteria, the Regional Council work in collaboration with the Public Health Unit of the Hawke’s Bay District Health Board to inform the public of the risk through signage and media releases.

Sewage discharges may cause infrequent problems; these are not considered to be a persistent problem.

Should the community express a desire for improved water quality, application of techniques such as faecal source tracking would be useful in identifying the sources of faecal indicator organisms, which in turn would allow management strategies to be targeted on these sources.

Other water quality metrics, such as visual clarity and algal growth do not generally impair recreational values.

Ahuriri Estuary Contact Recreation and Food Gathering Report

Attachment 1

8 References

ANZECC (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality 2000. ANZECC and ARMCANZ (eds), Australian and New Zealand Environment and Conservation Council, Australia.

Ataria, J., Tremblay, C., Tremblay, L., Black, M., Kaukau, M., Kemp, R. and Mauger, J. (2008) He Moemoea mo Te Whangaui-a-Orotu: A vision plan.

Black, M. and Ataria, J. (2008) Napier Estuary Literature Review, p. 31, Landcare Research, Lincoln, New Zealand.

Bolton-Ritchie, L., Greenfield, S., Madarasz-Smith, A., Milne, J., Stevenson, M. and Walker, J. (2013) Recreational Water Quality: A practitioner's discussion on the limitations of the 2003 national guidelines.

Chague-Goff, C., Nichol, S.L., Jenkinson, A.V. and Heijnis, H. (2000) Signatures of natural catastrophic events and anthropogenic impact in an estuarine environment, New Zealand. Marine Geology 167, 285-301.

Comerty, P.S., D.A. (1996) A directory of wetlands., p. 395, Department of Conservation, Wellington.

ESR (2004) Ahuriri cockle results, p. 1, ESR, ESR.

Eyre, T.M. (2009) The Sediment Dynamics of Ahuriri Estuary, Napier, New Zealand, University of Waikato & Universitat Bremen, Hamilton, New Zeland.

Fenton, J.A. (1997) Ahuriri Estuary Water Quality: Review of water quality in the estuary and catchment area, p. 69, Blue Tear Environmental, Napier, New Zealabnd.

HBRC (2012) Hawke's Bay Regional Coastal Environment Plan, HBRC.

Henriques, P.R., Binmore, H., Grant, N.E., Anderson, S.H., Duffy, C.A.J. (1990) Coastal Resource Inventory First Order Survey: Hawke's Bay Conservancy, p. 78 + Department of Conservation, Wellington.

Hooper, G. (1989) Ahuriri Estuary Water Quality Study, p. 37 +, Hawke's Bay Regional Council.

Kilner, A.R. and Akroyd, J.M. (1978) Fish and Invertebrate Macrofauna of the Ahuriri Estuary, Napier, p. 79, Ministry of Agriculture and Fisheries, Wellington, New Zealand.

Knox, G.A. (1979) Ahuriri Estuary: An Environmental Study, p. 84, University of Canterbury, Christchurch, Canterbury.

Lee, J.W. (1977) Hawke's Bay Harbour Board's Proposal to Dredge Humber Street Pond. Board, H.s.B.C. (ed), p. 9, Wellington, New Zealand.

MfE (1994) Water Quality Guidelines No. 2. Environment, M.f.t. (ed), Ministry for the Environment, Wellington, New Zealand.

MfE and MoH (2003) Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas, Ministry for the Environment, Wellington.

NZFSA (1995) Microbiological Limits for Food. Authority, F.S. (ed).

Rycroft, C. (2000) Napier Inner Harbour & Lower Ahuriri Estuary Point Source Discharges, p. 17, Hawke's Bay Regional Council, Napier, New Zealand.

Smith, S. (2010) Monitoring of benthic effects of stormwater discharges at sites in the Ahuriri Estuary: 2010 Survey, p. 52.

Smith, S. (2011) Fate, transport and extent of sediment associated trace metal contaminants in Napier urban waterways: Purimu Stream and County Drain, p. 39.

Strong, J. (2005) Antifoulant and trace metal contamination of the sediments from the Napier Inner Harbour., p. 30, EAM Ltd, Napier.

Appendix A Assessing microbiological water quality for contact recreation

The “Microbiological water quality guidelines for marine and freshwater areas” (MfE and MoH, 2003) were developed to improve the communication of risk to recreational water users. In a departure from earlier assessments of recreational water quality, the 2003 guidelines required two related activities to be undertaken in order to assess suitability for recreational use:

§ risk grading, allowing a Sanitary Inspection Category to be assigned to the water body and associated catchment, and

§ allocation of a Microbiological Assessment Category, using routine monitoring data.

Combining these indices allows an overall Suitability for Recreation Grade to be assigned, which is the basis for informing the public regarding health risks associated with recreation at a particular location.

Significant monitoring is required to classify recreational water. A minimum of 20 data should be acquired over the recreation season. Ideally the classification should be based on data collected over a five year period. The classification makes use of 95th percentile concentration values.

Weekly Monitoring

The MfE and MoH (2003) guidelines also identify two tiers of surveillance activity. These actions are based on maintaining the risks of infection below identified thresholds. A “traffic light” coding system is used:

§ in surveillance mode (green), where concentrations of indicator organisms in individual samples remain below specific thresholds, routine monitoring continues.

§ where the surveillance concentration threshold is exceeded by a single sample result:

− alert (amber) or

− action (red) monitoring modes commence.

§ sampling frequency increases (to daily), the source of pollution is investigated and warning signs may be erected.

The monitoring thresholds for fresh and saline waters associated with these “traffic light” are detailed in Table A-1.

Table A‑1: Status levels and management actions associated with measured faecal indicators and illness risk. Source MfE&MoH, 2003

Colour code	Status	Marine waters (enterococci /100 mL)	Freshwaters *(E. coli* /100 mL)**	Action
Green	Surveillance	All results <140	All results <260	Continue routine weekly monitoring
Amber	Alert	Single sample result >140	Single sample result >260	Increase to daily sampling, identify source of contamination
Red	Action	2 consecutive sample results >280	Single sample results >550	Increase to daily sampling, identify source of contamination, erect signs, inform public

Suitability for Recreation Grade (SFRG)

In order to grade a recreational water body, two activities must occur:

§ the Microbiological Assessment Category (MAC) must be established from existing or collected microbiological data; definitions for the different categories are given in Table 4-3

§ the Sanitary Inspection Category (SIC) must be established (classifications are Very High, High, Moderate, Low or Very Low; these refer to risk of contamination and are determined for a specific water body by using the SIC flow chart provided in the guidelines (MfE and MoH, 2003).

The Suitability for Recreation Grade (SFRG) provides five grades (very poor to very good) that summarise the potential health risk associated with primary recreation (such as swimming or surfing) at a site. The process for generating a SFRG is summarised schematically in Figure A-1.

Figure A‑1: Suitability for recreation grade schematic.

The grades can then be used to communicate typical risk of contact recreation in a specific water body to water uses as described in Table A-2.

Table A‑2: Explanation of suitability for recreation grades.

SFRG	Description*
Very Good	The site has generally excellent microbial water quality and very few potential sources of faecal pollution. Water is considered suitable for swimming for almost all of the time.
Good	The site is considered suitable for swimming for most of the time. Swimming should be avoided during or following heavy rain.
Fair	The site is generally suitable for swimming, but because of the presence of significant sources of faecal contamination, extra care should be taken to avoid swimming during or following rainfall or if there are signs of pollution such as discoloured water, odour, or debris in the water.
Poor	The site is susceptible to faecal pollution and microbial water quality is not always suitable for swimming. During dry weather conditions, ensure that the swimming location is free of signs of pollution, such as discoloured water, odour or debris in the water, and avoid swimming at all times during and for up to three days following rainfall.
Very Poor	The site is very susceptible to faecal pollution and microbial water quality may often be unsuitable for swimming. It is generally recommended to avoid swimming at these sites.

* from http://www.mfe.govt.nz/environmental-reporting/fresh-water/suitability-for-swimming-indicator/suitability-swimming-indicator.html).

The Tukituki, Waitangi and Ahuriri Assessment of the Extent of Saltwater Influence in Hawke's Bay Estuaries

Attachment 2

1 Introduction

Estuaries form a transition zone (ecotone) between saline and fresh waters. Over tidal cycles, saline water moves through estuaries and river mouth openings, the larger the tidal coefficient (amplitude of the tide), the further the saltwater pushes inland. Due to the density differences between saltwater and freshwater, the saltwater often moves upstream in the form of a wedge, with the denser saltwater pushing underneath the fresh. Temperature differences between cooler seawater and river water reinforce density differences during the summer period. As the freshwater flow decreases, the wedge becomes longer and sharper, as flow increases, the wedge becomes shorter and blunter until the freshwater pushes the saltwater back toward the estuary mouth. In addition to flow, the extent of saltwater influence in estuaries is affected by four processes that determine the influence of physical characteristics of an estuary on the tidal wave (Rijn 2010). These are:

§ amplification (or shoaling) of the tidal wave as it is compressed as the width and depth of the estuary decrease (convergence)

§ reduction in the velocity of the tidal wave due to bottom friction

§ deformation of the tidal wave leading to high tide occurring as a sharp transient event, whereas low tide occurs as a long, smooth event

§ partial reflection of the tidal wave by abrupt changes in the depth of the estuary or at the landward end of the estuary (in the absence of a river).

Other meteorological factors can also affect the extent of saltwater influence. Strong winds can push the salt water in shallow estuaries. Strong onshore winds and large swells can create a ‘storm surge’ effect where the sea level, and hence tide level, is higher than it normally would be. Similarly, low barometric pressure can cause an increase in water depth – tide heights are estimated for a standard, 1013 hectopascals (hPa) pressure, and for every decrease in pressure by of 1 hPa below the standard, tide height may be expected to increase by about 1 cm^{^[1]}.

Estuaries are highly productive areas (P. Meire (2005)) driven by the constant supply of nutrients provided by freshwater inputs. This productivity is not realised in an especially large diversity of species but rather through large numbers of individuals and a high biomass. These species include both freshwater and marine species living at the maximum extent of their distribution areas, as well as estuary-specific species. The distribution of species has been highly correlated with salinity (J. Maes 1998). This high productivity results in a high biomass of algae and phytoplankton, which in turn attract a large number of invertebrates, fish and birds. Retaining the natural balance in these areas is important to maintain the feeding and reproductive cycles of many species.

Additionally, the extent of saltwater penetration into rivers can have some important implications for jurisdictional issues, claims under the Foreshore and Seabed Act (2004), and administration of the Resource Management Act (1991).

The extent of saline penetration in most New Zealand estuaries and rivers is largely unknown. Within Hawke’s Bay, extensive work has been undertaken to describe these zones, so that change driven either by Council managed activities (such as those regulated through the resource consent process), or natural events (e.g. climate change, change in shape and extent of the estuary following an unusual hydrological event) may be detected. The current report provides a specific benchmark or reference point in time against which change over time may be assessed.

1.1 Project objectives

This project will:

§ Describe the spatial extent of Hawke’s Bay estuarine and riverine transition areas;

§ Monitor transition zones over time to provide an understanding of temporal change;

§ Provide information regarding transitional zones to better target monitoring of activities that may affect flora and fauna in these areas.

1.2 Statutory context

Hawke’s Bay Regional Council (HBRC) has a responsibility under the Resource Management Act (1991) for the sustainable management of the coastal area. Sections 6 and 7 of the RMA outline the matters of national importance, and include the ‘preservation of natural character’ and ‘Maintenance and enhancement of the quality of the environment’.

HBRC has demonstrated commitment to increasing knowledge regarding the region's coastal resources by funding investigation of estuarine processes (including saltwater influence) over the life of the current long-term plan (Level of Service Statement, LTCCP 2009-2019).

2 Methodology

Odyssey conductivity loggers (manufactured by Dataflow Systems Pty. Ltd.) were deployed in selected estuaries in order to collect time series data that describe changes in salinity at fixed points in the estuaries and to provide a spatial characterisation of the saline transition zone. Water was classified as fresh, brackish or salt as according to the Venice Classification System (Table 2‑1).

Table 2‑1: The Venice Classification System.

Salinity (ppt)	Conductivity (mS/cm)	Classification
< 0.5	1.2	Fresh water
0.5 – 30	1.2 – 46	Brackish water
>30	>46	Salt water

2.1 Site selection

Prior to logger deployment, an initial survey of the estuary was conducted. Firstly, aerial or satellite photos were inspected to see if there was an indication of where the deeper channels may lie. Secondly, a physical reconnaissance of the estuary was conducted at high tide, on a large tidal coefficient, by either kayak or boat. Using a field conductivity meter, the extent of saltwater influence at the time of survey was ascertained in order to guide placement of the loggers. A survey of the types of shoreline vegetation gave further indications regarding the extent of saltwater penetration.

Once the initial survey was completed, conductivity loggers were deployed at the pre-determined sites on the estuary. The location of the sites was determined by several factors:

§ Existence of previous conductivity data.

§ Water depth: the dense salt water moves up the channel that defines the deepest parts of the estuary (thalweg); to ascertain the maximum extent of saltwater influence, the loggers need to be deployed in the thalweg, where practicable.

§ Proximity to areas of interest such as tributaries and potential Inanga spawning sites.

§ Distance from the estuary mouth: placement of the loggers at even distances from the estuary mouth allows for better interpolation of the data.

§ Location of suitable attachment points. The loggers were attached in a variety of ways: to manmade structures (bridges/whitebait stands); to logs and root systems; anchored by concrete blocks both freestanding and tethered to the bank. Loggers were attached approximately 30 cm above the river bed in locations where they were permanently covered by water.

2.2 Deployment

The loggers were deployed under low flow conditions with high tidal coefficients (spring tides) which are believed to be the optimum conditions for determining the maximum extent of the saltwater influence. The loggers were deployed in the Tukituki Estuary once, and the larger Ahuriri and Waitangi Estuaries twice. This was because of the size and complexity of the latter two estuaries. Each deployment encompassed at least two periods of spring tides that coincided with low flows. A tide was designated a spring tide when the depth of water under high water conditions exceeded 1.7 meters.

While every effort was made to map the maximum extent of the saltwater influence, the many influencing variables involved means that it is possible the saline water could intrude further into these estuaries than was observed during the periods of study. Events such as large swells, strong onshore winds and low barometric pressure can create ‘storm surge’ conditions where tidal height dramatically exceeds the forecast height, leading to an increase in the extent of saltwater influence. The present study is considered to describe the typical extent of saltwater influence.

Similarly, it is not possible to map the ultimate minimum extent of saltwater influence, because river conditions necessary (e.g. flood conditions with high velocity flows) would probably lead to loss of loggers.

The extent of saltwater influence recorded during this investigation has been mapped on an estuary by estuary basis. The current report details work completed on the Tukituki, Waitangi and Ahuriri Estuaries (see Figure 2-1).

Figure 2-1: Map showing the location of estuaries within Hawke's Bay.

The red points denote the estuaries that have been included in this study to date, the yellow points are estuaries that will be mapped during future surveys.

2.3 Data analysis

The data retrieved from the conductivity loggers was analysed using ArcGIS. Data were interpolated to provide a conductivity gradient for each estuary at the time of maximum and minimum saltwater influence.

Spearman correlations were determined using Statistica V.11. These allow the influence of tidal height and flow/rainfall on conductivity readings to be determined at sites where saline or brackish water was recorded. The amount of data available for the correlations was restricted by the tidal height information. The tide data utilised^{^[2]} gives only the time of the point of lowest and highest tide, whereas the conductivity and flow data were collected at 15 minute intervals. Therefore the median conductivity and flow values for a six hour period (three hours either side of the tide time) were calculated and these values were used for the correlations rather than the raw data.

Tidal influx is often delayed in estuarine systems relative to the adjacent coastline. Typically the delay for the tidal wave to reach a point in an estuary increases with distance from the estuary mouth. This delay was accounted for at each logger site by first examining the conductivity and tide height data graphically to ascertain any lag between peak conductivity readings and time of high tide. Where necessary, the high tide time was then adjusted to be synchronised with peak conductivity readings. This temporal adjustment was confirmed using the Spearman correlation - adjustment was accepted if the adjusted tide time provided a higher correlation coefficient (r).

The correlation coefficient (r) describes the relationship between conductivity and either flow or tide height. The correlation coefficient can have a value of between 1 and -1. A negative value means that as either flow or tidal height increase, conductivity tends to decrease. A positive value means that as flow or tidal height increases, conductivity tends to increase also. The closer the correlation coefficient is to either 1 or -1, the stronger the relationship. The p value describes whether this relationship is statistically significant. The relationship is significant when p < 0.05.

3
Tukituki Estuary

The Tukituki River is the fourth largest river in the region in terms of average flows. (Hume 2013), determined that residence times of waters within the estuary are short and characterised the estuary as essentially an extension of the river that is tidally influenced. The river bed within the estuary is predominantly gravel, with a relatively steep gradient.

Conductivity loggers were deployed at five sites (Figure 3-1) in the Tukituki Estuary between 24/01/12 and 24/02/12. These loggers were attached to concrete blocks placed on the river bed.

The initial survey indicated that saltwater intruded as far as site 3 (1.8 m tide). The logger at site 4 was placed in the thalweg where there was rapid flow and was not expected to log any saline or brackish water. Bankside vegetation could not be used as an indicator of the extent of saltwater influence because the area is highly modified and characterized by introduced grasses, willows and poplars. The saline and fresh water appeared to be highly stratified, with the saltwater confined to the thalweg and minimal mixing with the upper freshwater layer. Visual observations of the water clarity appeared to be the best indicator of saline water, which was much more turbid than the freshwater.

Figure 3-1: Tukituki estuary logger deployment sites.

The hydrographic flow site at Red Bridge, approximately 10 km upstream of the estuary was used to estimate river flow (m³/sec) data at the estuary. There is limited inflow between the Red Bridge site and the river mouth.

The loggers were deployed during a period of low flow (~ 12 m³/sec) that lasted for two and a half weeks before the flow increased to over 50 m³/sec on the 20/02/12. The loggers were retrieved three days later because of concerns they would be buried by gravel or swept away. The logger at site 0 malfunctioned, however field observations at this site indicated that it would be subject to saltwater under all conditions. Sites 3 and 4 recorded brackish water at certain periods, and sites 1 and 2 recorded saltwater the majority of the time. Further observations were taken during periods of low flow (~ 5 m³/sec) at the ‘Field Observation Site’ using a field meter. Conductivity readings of 36 mS/cm (brackish – saltwater) were recorded here in 1.2 m water depth. Of particular interest at this site was a localized phytoplankton bloom of Cryptomenas sp. collected from the saline part of the water column (see Appendix 1 for laboratory report).

3.1 Results

ArcGIS was used to interpolate the data from the Odyssey loggers and generate graphical images of the maximum (Figure 3-2) and minimum (Figure 3-3) extent of the saltwater influence in the Tukituki Estuary. The maximum extent of saltwater influence was approximately 1 km from the estuary mouth. At present the upper extent of the saltwater influence is bounded by a steep riffle, approximately 100 metres downstream from Black Bridge.

Figure 3-2: Maximum extent of saltwater influence in the Tukituki Estuary.

Figure 3-3: Minimum extent of saltwater influence in the Tukituki Estuary.

The median conductivity was correlated with the median flow data and tidal height (Table 3-1). The estuarine stretch of the Tukituki River is relatively short and straight – accordingly, there is little tidal delay and it was only necessary to adjust the data at Site 4 (Table 3-1).

Table 3-1: Spearman correlation coefficients for the Tukituki Estuary sites.

Figures shown in bold are statistically significant (p<0.05).

	Site	Period of Deployment	Tidal delay	Conductivity vs. Flow	Conductivity vs. Tide height
UPSTREAM	4	24/01/12 – 24/02/12	+ 2 hrs	-0.586	0.101
	3	24/01/12 – 24/02/12	0 hrs	-0.676	0.105
	2	24/01/12 – 24/02/12	0 hrs	-0.616	0.393
DOWNSTREAM	1	24/01/12 – 24/02/12	0 hrs	-0.478	0.469

Flow was significantly negatively correlated with conductivity at all sites (Table 3-1). These correlations are quite high for the natural environment and suggest a strong relationship between an increase in flow and a decrease in conductivity. The increase in flow required to reduce the influence of saltwater to all sites was quite similar (between 35 and 45 m³/s) (see Figure 3-4). Tide height had a strong positive correlation with conductivity at the lower sites but no relationship at the upstream sites (Table 3-1). This suggests flow limits conductivity at the upstream sites, while both flow and tide height have a combined influence closer to the estuary mouth.

The increasing influence of saltwater closer to the estuary mouth can be seen in Figure 3-5. At the upstream sites (3 & 4), only brackish water was present on the largest tidal coefficients with corresponding low flows. As might be expected, salinity was highest at the sites closest to the mouth, and the point of highest salinity more frequently coincided with the high tide.

Site 4		Upstream
Site 3
Site 2
Site 1		Downstream

Figure 3-4: Scatter plot of median flow (X) and median conductivity (Y) for the Tukituki Estuary.

The Tukituki, Waitangi and Ahuriri Assessment of the Extent of Saltwater Influence in Hawke's Bay Estuaries

Attachment 2

4 Waitangi Estuary

The Waitangi Estuary is the common mouth of the Tutaekuri River (north), Ngarururo River (centre) and Clive River (south), and is the only multi-river estuary in Hawke’s Bay. The rivers feeding into the Waitangi Estuary have been extensively modified. Each river channel appears to have characteristics that effect the extent of saltwater influence uniquely.

Conductivity loggers were deployed within the Waitangi Estuary from the 18/12/12 to the 24/01/13 and from the 27/02/13 till the 16/04/13 (Figure 4-1). The loggers were deployed using a variety of methods, including attachment to concrete blocks, whitebait stands, logs and the Brookfields Bridge. Despite efforts to conceal the loggers, several were lost due to vandalism.

The initial survey of the estuary found saltwater penetration 100 metres downstream of site 1T on the Tutaekuri River, to site 2N on the Ngarururo River and to site 1C on the Clive River. Similar to the Tukituki Estuary, the banks of the Waitangi are highly modified with only replanted remnants of native vegetation, and the waters are similarly stratified, making it difficult to visually determine the extent of saltwater influence. Once again water clarity provided a better indication of the saline content of the water. On retrieval of the loggers on the 16/04/13, a large phytoplankton bloom was observed around logger site 3N. The bloom was dominated by Cryptomonas sp, which can be fresh or saltwater species (see Appendix 1 for laboratory report). This bloom was confined to the saline part of the water and may therefore be a saline species.

Figure 4-1: Waitangi estuary logger deployment sites.

Red points denote sites were logger data was correlated against flow and tide height; white points denote sites of previous logger deployment

During the primary period of deployment there was one rain event around the 26/12/13 that increased flows in all the rivers. The second period of deployment was during extreme low flow conditions. The purpose of the primary deployment was to coarsely identify the extent of saline penetration into the estuary. The second deployment focused on the areas of furthest extent of saline water found during the primary deployment to increase the resolution at this level.

The different physical attributes of these rivers (e.g., depth of thalweg, meanders, flow etc.) mean that the saltwater influence into each is different. The estuary was treated as a single system for the GIS interpolation but correlations were conducted separately for each river.

The maximum extent of saltwater influence in the Waitangi Estuary was approximately 5.2 km in the Ngarururo River), 2.5 km in the Tutaekuri River and 4.1 km into the Clive River (Figure 4-2).

Figure 4-2: Maximum extent of saltwater influence in the Waitangi Estuary.

The minimum extent of saltwater influence in the Waitangi Estuary was shorter in the Tutaekuri and Ngarururo arms than the Clive River (Figure 4-3). This is likely due to the larger catchments and greater flows of water in the former that exert a greater pressure on the salt water, particularly during rainfall events .

Figure 4-3: Minimum extent of saltwater influence in the Waitangi Estuary.

4.1 Clive River

The Clive River is the southern-most arm of the Waitangi Estuary. The Clive River follows the original path of the Ngarururo River prior to its channelization. The flows in the Clive River are much smaller than would typically be found in a river channel of this size. As a consequence, flows in the Clive River are slower than the other rivers; this creates a depositional environment – as a consequence, the river bed is characterised by soft sediments and extensive macrophyte growth. Flow measurements from a hydrographic site in the Awanui Stream (one of the tributaries of the Clive River) were used as a proxy for flow conditions in the Clive River.

The maximum extent of saltwater influence in the Clive River was 4.1 km from the mouth.

Data from loggers collected during both periods of deployment were correlated against median flow and tide conditions (Table 4-1).

Table 4-1: Spearman Correlation Coefficients for Clive River sites.

Figures shown in bold are statistically significant (p<0.05).

	Site	Period of Deployment	Tidal delay	Conductivity vs. Flow	Conductivity vs. Tide height
UPSTREAM	3 C	27/02/13– 16/04/13	+ 3 hrs	-0.578	0.047
	2 C	27/02/13– 16/04/13	+ 3 hrs	-0.757	0.093
DOWNSTREAM	1 C	18/12/12- 24/01/13	0 hrs	-0.766	0.213

Flow had a significant negative correlation with conductivity at all sites (Table 4-1). This suggests a strong relationship between an increase in flow and a decrease in conductivity. Towards the estuary mouth a higher flow is required to reduce the influence of saltwater (see Figure 4-4). Tide height had a weak positive correlation with conductivity at Site 1C but no relationship at the upstream sites (Table 4-1). This suggests flow is the deciding factor limiting conductivity at all sites, however at the estuary mouth tidal height additionally has a small positive influence on conductivity levels. At all sites the periods of highest conductivity were associated with the period of highest tidal coefficient (Figure 4-5).

Site 3C		Upstream
Site 2C
Site 1C		Downstream

Figure 4-4: Scatter plot of median flow (X) and median conductivity (Y) for the Clive River.

Site 3C		Upstream
Site 2C
Site 1C		Downstream
Tide Height Median Flow Median Conductivity

Figure 4-5: Line plot of tide height with associated median conductivity (Y1) and median flow (Y2) readings.

Note the different flow values (Y2) between the sites 3C and 2C and the site 1C, corresponding to different periods of deployment.

4.2 Ngarururo River

The Ngarururo River forms the central arm of the Waitangi Estuary. It generally contributes the greatest flow of the three rivers which flow into the Waitangi Estuary. Where the river enters the estuary it is channelised with a deep thalweg. The bed of the estuary is mainly comprised of river gravels.

The hydrographic site at Fernhill was used to measure flow (m³/sec). Flows from 2 – 26 m³ /sec were recorded (annual mean = 33.12 m³/sec). Conductivity data collected from the Odyssey loggers was correlated against flow and tide height (Table 4-2).

The maximum extent of saltwater influence in the Ngarururo River was 5.1 km from the estuary mouth.

Table 4-2: Spearman Correlation Coefficients for Ngarururo River sites.

Figures shown in bold are statistically significant (p<0.05).

	Site	Period of Deployment	Tidal delay	Conductivity vs. Flow	Conductivity vs. Tide height
UPSTREAM	3 N	27/02/13– 16/04/13	+ 3 hrs	-0.563	0.146
	2 N	18/12/12- 24/01/13	+ 2 hrs	-0.247	0.479
	1 N	18/12/12- 24/01/13	0 hrs	-0.289	0.716
DOWNSTREAM	0	18/12/12- 24/01/13	0 hrs	-0.288	0.645

Flow and tidal height have significant negative and positive correlations respectively with conductivity (Table 4-2). Flow had a higher negative correlation at the most upstream site (3 N), suggesting that the influence of flow on the extent of saltwater influence increased with distance from the river mouth. Similarly, the flow rate required to reduce saltwater influence at the lower sites was much higher than that at the upper sites (Figure 4-6). The lower sites had a higher positive correlation with tide height, suggesting that at these sites an increase in tide height had a more important influence on conductivity than flow. At all sites the periods of highest conductivity were associated with the period of highest tidal coefficient (Figure 4-7).

Site 3N		Upstream
Site 2N
Site 1N
Site 0		Downstream

Figure 4-6: Scatter plot of median flow (X) and median conductivity (Y) for the Ngaruroro River.

Site 3N		Upstream
Site 2N
Site 1N
Site 0		Downstream
Tide Height Median Flow Median Conductivity

Figure 4-7: Line plot of tide height with associated median conductivity (Y1) and median flow (Y2) readings.

Note the different flow values (Y2) between the site 3N and the other sites corresponding to different periods of deployment.

4.3 Tutaekuri River

The Tutaekuri River forms the northern arm of the Waitangi Estuary. The Tutaekuri River is the shallowest of the three rivers running into the Waitangi Estuary and the bed is predominantly clean river gravels.

The hydrographic site at Puketapu was used as a proxy for flows into the estuary. Flows ranging between 3 – 25 m³/sec were recorded during the period of logger deployment (annual mean = 11.66 m³/sec).

The maximum extent of saltwater influence in the Tutaekuri River was approximately 2.9 km from the mouth.

Several of the loggers placed in the Tutaekuri River malfunctioned, and the data from these loggers failed quality control checks. Therefore data from only two loggers were used in the assessment.

Table 4-3: Spearman Correlation Coefficients for Tutaekuri River sites.

Figures shown in bold are statistically significant (p<0.05).

Site

Period of Deployment

Tidal delay

Conductivity vs. Flow

Conductivity vs. Tide height

UPSTREAM

27/02/13– 16/04/13

+ 3 hrs

-0.088

0.308

DOWNSTREAM

18/12/12- 24/01/13

0 hrs

-0.288

0.645

Tide height was positively correlated with conductivity at both sites (Table 4-3). This suggests a strong relationship between an increase in tide height and conductivity at site 0, and a moderate relationship at site 1T (Figure 4‑8).

Conductivity was negatively correlated with flow at the downstream site only (Table 4-3). It was expected that the saline wedge would act similarly in the Tutaekuri River as was observed in the other rivers, with the negative correlation of conductivity with flow increasing in an upstream direction. However no significant correlation between flow and conductivity was observed - therefore the scatterplot of flow (X) and conductivity (Y) has not been plotted for this river.

Site 1T		Upstream
Site 0		Downstream

Figure 4‑8: Line plot of tide height with associated median conductivity (Y1) and median flow (Y2) readings.

Note the different flow values (Y2) between the two sites indicating different periods of deployment.

5 Ahuriri Estuary

In a region dominated by alluvial flood plain river mouths, the Ahuriri Estuary (Te Whanganui-a-Orotu) represents one of the few tidal lagoon estuaries in Hawke’s Bay. With an area of 470 ha it is also the region’s largest estuary. Unlike the other estuaries, this estuary also has large areas of associated wetlands (approx. 175 ha) (Madarasz-Smith, 2013).The Ahuriri Estuary also differs from the other estuaries in the area as there are no large riverine inputs. The bed of the estuary comprises of mainly soft sediments and the water depth is generally much shallower than the other estuaries reported here.

Figure 5-1 shows the sites of logger deployment within the estuary. Placement of the loggers was informed by conductivity data collected at a limited number of sites during previous investigations on the estuary (HBRC unpublished) and an initial survey of bankside vegetation. The initial survey of the Ahuriri Estuary used the extent and location of native vegetation, especially the raupo (Typha orientalis) as an indicator of the maximum extent of the saltwater influence.

Figure 5-1: Ahuriri estuary logger deployment sites.

Red points denote sites where logger data was correlated against flow and tide height.

Conductivity loggers were deployed in the Ahuriri Estuary (Figure 5-1) for two periods, first between the 17/08/12 and the 25/09/12 and then between the 23/04/13 and the 6/06/13. During the first deployment, several of the loggers malfunctioned and the data gathered from these loggers failed quality control checks and were therefore not used in the assessment. The second period of deployment was at the end of an extended period of drought. Loggers were attached to existing structures and warratahs driven into the soft sediment.

There was no operational flow site within the Ahuriri Estuary during the time of logger deployment so rainfall at a nearby site (Newstead) was used as a proxy for flow in the estuary. There were two periods of low rainfall during the time of deployment but these seemed to have little effect on conductivity measurements (Figure 5-4).

5.1 Ahuriri Estuary Results

ArcGIS was used to interpolate the logger data and generate graphical images of the maximum (Figure 5-2) and minimum (Figure 5-3) extent of saltwater influence in the Ahuriri Estuary. The maximum extent of saltwater influence into the Ahuriri Estuary was approximately 9.2 km (Figure 5-2).

Figure 5-2: Maximum extent of saltwater influence in the Ahuriri Estuary.

The ArcGIS interpolation for the minimum extent (Figure 5-3) utilised data collected during previous surveys of the estuary and shows the saline water pushed back almost to the mouth of the estuary.

Figure 5-3: Minimum extent of saltwater influence in the Ahuriri Estuary.

Conductivity was not significantly correlated with rainfall at any of the sites (Table 5-1). Due to this lack of correlation the scatter plots of conductivity (Y) and rainfall (X) have not been plotted.

Table 5-1: Spearman Correlation Coefficients for Ahuriri Estuary sites.

Figures shown in bold are statistically significant (p<0.05).

	Site	Period of Deployment	Tidal delay	Conductivity vs. Rainfall	Conductivity vs. Tide height
UPSTREAM	3	23/04/13 – 06/06/13	+ 6 hrs	- 0.089	0.279
	2	23/04/13 – 06/06/13	+ 6 hrs	0.103	0.312
	1	23/04/13 – 06/06/13	+ 3 hrs	0.005	0.339
DOWNSTREAM	0	23/04/13 – 06/06/13	+ 3 hrs	-0.011	0.338

At all sites, conductivity was positively correlated with tide height (Table 5-1). This suggests that tide height is the significant factor influencing the extent of saltwater influence in the Ahuriri Estuary. There was less variation in conductivity readings between the low and high tides (Figure 5-4) than the Tukituki and Waitangi Estuaries due to a higher degree of vertical mixing through the water column, and much smaller inflows of freshwater into the estuary.

Site 3		Upstream
Site 2
Site 1
Site 0		Downstream
Tide Height Median Flow Median Conductivity

Figure 5-4: Line plot of tide height with associated median conductivity (Y1) and median rainfall (Y2) readings.

6 Discussion

The data collected from the Tukituki, Waitangi and Ahuriri Estuaries indicate that the individual estuaries have different salinity regimes, driven largely by their physical characteristics and the magnitude of freshwater inflows.

Data from the Tukituki Estuary indicate that it is the most stratified of the three estuaries. The correlations suggest that flow is the dominant force governing the extent of saltwater influence, with all conductivity values at all sites displaying a stronger relationship with flow than tide height (Table 3-1). Under the conditions encountered, the Tukituki acted as a classic ‘saline-wedge’ estuary (Pritchard, 1989), with the salt water pushing up under the fresh water with little mixing between the two layers. Since flow appears to be the dominant force influencing the extent of saltwater influence at this site, any changes in flow are likely to affect the extent of saltwater influence. However, the relatively steep gradient of the upper Tukituki Estuary appears to act as a physical barrier as the estuary bed rapidly rises above sea level. The bed of the estuary is dynamic and this physical barrier can move up or downstream in responses to changes to the river bed following flood events. During the initial survey it was hoped to use bankside vegetation as an indicator of the extent of saltwater influence; the strong stratification and limited mixing of fresh and saline water has little impact on the vegetation, which only comes into contact with the surface freshwater layer. This is evident in the fact that willows are present almost down to the estuary mouth.

As a common mouth for three river systems, the characteristics of the extent of saltwater influence in the Waitangi Estuary were different in each of the rivers. The Clive River is highly stratified and acted as a ‘saline-wedge’ estuary where flow had a stronger correlation with conductivity than tide height (Table 4-1). In the Ngarururo River although both flow and tide height appeared to strongly influence the extent of saltwater influence (Table 4-2), the water still appeared stratified. The Tutaekuri River, as the shallowest of the three arms of the Waitangi Estuary, did not appear to be as stratified as either the Clive or Ngarururo arms. For the Tutaekuri arm, tide height was significantly correlated with conductivity (Table 4-3). As for the Tukituki Estuary, the Waitangi Estuary is susceptible to changes in low flows affecting the maximum extent of saltwater influence, however, this extent is also bounded by the physical barrier of the river beds rising above sea level.

The Ahuriri Estuary has different physical characteristics to the Tukituki and Waitangi Estuaries. There are no large riverine inputs, and the estuary itself is relatively shallow and meandering with extensive wetlands. The lack of riverine inputs is reflected in the salinity regime, with tide height the significant variable affecting salinity at all sites (Table 5-1). Unlike the Tukituki and Waitangi Estuaries, conductivity remains high in the estuary throughout the tidal cycle (Figure 5-4) (Figure 3-5, Figure 4-5, Figure 4-7). The limited freshwater inflow, generally shallow water and meandering nature of the channel, combined with wind mixing, limit the stratification of the water in the estuary. This lower degree of stratification means that the extent of saltwater influence is more likely to have an impact on the bankside vegetation than in the Waitangi or Tukituki Estuaries.

It is possible that the extent of saltwater influence recorded in the Ahuriri Estuary was unusual as large diebacks of the saltwater intolerant plant raupo were observed upstream of Site 2 during the summer of 2013. The presence of raupo suggests that under typical conditions, saline or brackish water does not travel this far toward the head of the estuary. Another factor that could have caused some of the dieback of the Raupo was input of heavily brackish water (measured at 35 mS/cm) from a pump station 500m up-stream from site 3. The reason for this pump station to be discharging heavily brackish water is unknown but could be due to the disturbance of previously static marine silts or an increased level of seawater ingress into the groundwater due to the drought conditions.

Data collected in the Tukituki and Waitangi Estuaries suggest that Council-managed activities are unlikely to influence the maximum extent of saltwater influence in these estuaries appreciably, because of the dominant effect of the physical barrier caused by the riverbed rising above sea level, regardless of flow. This has the potential to affect the distribution of species that do not have a high degree of salt tolerance. Further monitoring over longer time periods and through different flow conditions is required to verify this. The limited inflow of freshwater into the Ahuriri Estuary means that while it is likely to be less susceptible to changes in low flows than other estuaries, the relatively low gradient makes it more susceptible to issues such as sea level rise caused by global warming.

Initial surveys of the estuaries prior to logger deployment showed that bankside vegetation was of little use as an indicator of the extent of saltwater influence, primarily because these estuaries are generally highly modified (channelised and denuded of native vegetation). An exception was the upper reaches of the Ahuriri Estuary. Secondly, the water in the estuaries (especially the Tukituki and Waitangi Estuaries) is highly stratified, generally confining the saltwater to the deepest parts of the channel (the thalweg), limiting contact with and therefore effect on the bankside vegetation. The best broadscale indicator of the saltwater wedge appeared to be water clarity. Under low flow conditions the river waters appeared less turbid than the associated marine waters. This resulted in a visually identifiable change in the waters that was verified using a field conductivity meter.

The initial surveys of the estuaries, carried out on spring tides (>1.7m), led to under-estimation of the extent of the saltwater influence because of the unexpectedly large delay in the tidal wave reaching the upper parts of the estuaries. Previously the tidal delay in the Ahuriri estuary was believed to be +2.5 hours (Madarasz-Smith, pers. comm.). The data collected during this investigation shows the tidal delay to vary between 3 hrs at Site 0 at the mouth of the Taipo Stream, to as much as 9 hrs at the at the head of the estuary (the maximum extent of saltwater influence). It was only by deploying static continuous recording devices such as those used in this investigation that it was possible to determine the extent of this tidal wave delay.

The interface between saline and freshwater is highly productive, characterised by effects such as phytoplankton blooms (J. Lobry 2003). During these surveys, extensive phytoplankton blooms were observed in the Clive (24/01/13) and Ngarururo (15/04/13) rivers, and small localised blooms were observed in the Tukituki (27/02/13) and Tutaekuri (27/02/13) Rivers. Samples collected from both the Ngarururo and Tukituki Rivers were dominated by Cryptomonas sp. For blooms to persist in estuaries, warm temperatures and stable flow conditions are required. A similar bloom of Cryptomonas sp. was observed by Robertson and Stevens (Stevens 2008) in the upper areas of the Motupipi Estuary (Tasman) which was caused by a combination of excessive nutrient concentrations, a stable salt wedge, warm water temperatures, stable base-flows and limited turbulent mixing. The conditions in the Hawke’s Bay estuaries where blooms occurred generally mirrored the conditions observed in the Motupipi estuary: Water temperatures were high, flows were extremely low and stable, causing little turbulence and a stable salt wedge. These conditions may be regarded as atypical because the region was in the middle of a prolonged drought, with uncharacteristically low flows that persisted over a longer period of time than usual. Under normal conditions when flows are generally higher and more varied, it is unlikely that blooms would have a chance to form. Further study of the extent and frequency of bloom formation in the regions estuaries will be required to understand the dynamics involved, or whether Council-managed activities influence the extent or persistence of these blooms.

HAWKE’S BAY REGIONAL COUNCIL

Maori Committee

Tuesday 24 June 2014

SUBJECT: RMA Section 35a Requirements

Reason for Report

1. The purpose of the paper is twofold. Firstly, it is to provide an overview of the requirements in section 35A of the Resource Management Act 1991 to keep and maintain records of iwi and hapu in the region. Secondly, it is to update the Committee on how the region’s local authorities led by the Regional Council, are working together to build a GIS-based application for improved s35A RMA record-keeping.

Background

2. Section 35A of the RMA requires councils to keep and maintain records about iwi authorities and any groups that represent hapu for RMA purposes. Similar requirements are also placed on the Crown. Such records may include statutory areas defined by legislation (RMA or others such as the Fisheries Act 1996); organisations recognised in statutes; and Post Settlement Entities recognised by the Crown for RMA purposes.

3. Specifically, councils must keep and maintain:

3.1. the contact details of each iwi authority and any groups that represent hapu for RMA purposes;

3.2. planning documents recognised by each iwi authority and lodged with the council; and

3.3. any area where iwi or hapu exercise kaitiakitanga.

4. The local authority must include in its records all the information provided to it by the Crown, but may seek and hold other information from other sources. The duty to keep and maintain records in relation to hapu is only applicable if that hapu requests the Crown or local authority to include the relevant information. Any such records of iwi and hapu groups must only be used for RMA purposes.

5. Other RMA requirements associated with records of iwi authorities and hapu groups include:

5.1. Schedule 1 Clause 3(1)(d) - councils shall consult “with tangata whenua of the area who may be so affected, through iwi authorities” during preparation of policy statements and plans [emphasis added]

5.2. Schedule 1 Clause 3(1)(e) - councils may consult with anyone else during preparation of policy statements and plans [emphasis added]

5.3. S36A – explicitly states that an applicant and council do not have any duty to consult any person regarding the preparation, processing or decision-making in relation to a resource consent.

6. Hawke's Bay Regional Council already keeps records of iwi authorities and marae/hapu groups. Those records are currently in spread sheet form. From time to time, additional references may be made to online resources from other organisations such as:

6.1. Te Kahui Mangai provided by Te Puni Kokiri on behalf of the Crown (www.tkm.govt.nz)

6.2. Maori Maps provided by Te Potiki National Trust (www.maorimaps.com) and

6.3. Tuhono iwi info provided by the Tūhono Trust (formerly known as the Tautoko Māori Trust) (www.tuhono.net).

7. Currently, each of the main city and district councils in Hawke's Bay holds variable information about iwi authorities and hapu groups in their respective Districts.

Development of a GIS-based application

8. In May 2014, planning and GIS staff from each of the four TLAs and Hawke's Bay Regional Council met and discussed development of a digital repository of information regarding iwi and hapu groups in the Hawke's Bay region. Those present agreed that a regional GIS-based application that spatially records location of marae and contact details would complement improvements to how councils meet the requirements of s35A RMA. Improvements can be made collectively and made available through a GIS/web-based application covering the whole Hawke's Bay region, rather than each council continuing to hold individual sets of records for s35A RMA purposes.

9. In addition to data required to fulfil councils’ obligations under s35A RMA, the following was considered to be additional useful capability to potentially build into a regional data repository over time:

Information	Details
Areas of interest/significance relating to kaitiakitanga	Hapu ‘precincts’ Buffer zones
Filtered public information	‘Swiss Bank’ of site/area information e.g. sensitive waahi tapu information.
Hapu/marae contact details	Websites, postal, phone, contact personnel
Marae locations	Maps and photos
Publicly available cultural/heritage sites Waahi Tapu sites	Heritage New Zealand NZ Archaeological Association District Plans Regional Plans
Related hapu/iwi planning documents	Hapu Management Plans MOUs; Protocols; Agreements, etc.
Website links	Hapu/iwi websites Hapu Management Plans

Next Steps

10. In relation to iwi authorities, data already exists and has been obtained from Te Kahui Mangai – the Crown’s dataset of iwi authorities and groups representing hapu for RMA purposes.

11. In relation to marae locations and associated hapu contacts, the Regional Council, Hastings District Council and Wairoa District Council have various existing GIS datasets. Central Hawke's Bay District Council and Napier City Council would require further resources to develop datasets for marae location and contact information. At the May meeting of council staff representatives, it was agreed that the collation of additional information should start with the engagement of marae/hapu. Details of any such engagement are yet to be planned.

12. As the majority of spatial and contact information is already readily available online, the council staff representatives considered that it was appropriate to publish information in a regional GIS-based application. The development of a ‘pilot’ application can be undertaken by the Regional Council in the short-term using existing datasets supplied by the TLAs. Further discussion will be required regarding on-going maintenance of the datasets.

13. Planning and GIS staff will have further discussions about development of the GIS-based application to keep and maintain records for s35A RMA purposes; and medium-term, keep and maintain records of marae and hapu for broader local government engagement and decision-making purposes.

Decision Making Process

14. Council is required to make a decision in accordance with Part 6 Sub-Part 1, of the Local Government Act 2002 (the Act). Staff have assessed the requirements contained within this section of the Act in relation to this item and have concluded that, as this report is for information only and no decision is to be made, the decision making provisions of the Local Government Act 2002 do not apply.

Recommendation

1. That the Maori Committee receives the report.

Esther-Amy Bate

Planner

Gavin Ide

Manager, Strategy and Policy

Helen Codlin

Group Manager Strategic Development

Attachment/s

There are no attachments for this report.

cfu	Coliform Forming Units
*E. coli*	Esherichia coli
HAB	Harmful Algal Bloom
HBRC	Hawke’s Bay Regional Council
MfE	Ministry for the Environment
MoH	Ministry of Health
MPI	Ministry of Primary Industries
MPN	Most Probably Number
NTU	Nephelometric Turbidity Units
SFRG	Suitability for Recreation Grade

Received	TLA	Map Ref	Activity	Applicant/ Agency	Status	Current Situation
21 January 2014	NA	1	Application under Coastal and Marine (Takutai Moana) Act 2011 Nga whanau o Moeangiangi Pt 42N has made an application for a Protected Customary Rights Order and a Customary Marine Title Order for an area lying between Waipatiki and Mohaka. This application is made under section 100 of the Marine and Coastal Area (Takutai Moana) Act 2011.	Nga whanau o Moeangiangi Pt 42N (Wayne T Taylor)	Notified	1 April 2014 · Not considered necessary for HBRC to join High Court proceedings. No further response required.
5 December 2013	NCC	2	Plan Change 10 to the Operative City of Napier District Plan. A community driven Plan Change to harmonise district wide provisions between the Napier District Plan with the Hastings District Plan, incorporate the Ahuriri Subdistrict Plan and update provisions as a result of recent Napier City Council policy changes and decisions into the Napier District Plan.	NCC	Notified	1 April 2014 · HBRC lodged submission on Change 10 in February 2014. · Napier CC are currently summarising submissions. Further submissions yet to be invited.
8 November 2013	HDC	3	Proposed Hastings District Plan Review of the Hastings District Plan in its entirety. Includes the harmonisation of district wide provisions between the Napier District Plan with the Hastings District Plan where relevant..	HDC	Notified	1 April 2014 · HBRC lodged submission on proposed Hastings District Plan in February 2014. · Hastings DC are currently summarising submissions. Further submissions yet to be invited.
1 August 2013	NA	4	Application under Coastal and Marine (Takutai Moana) Act 2011 Rongomaiwahine has made an application for a Protected Customary Rights Order and a Customary Marine Title Order in the general Mahia Peninsular area under section 100 of the Marine and Coastal Area (Takutai Moana) Act 2011.	Rongomaiwahine (Pauline Tangiora)	Notified	1 April 2014 · Council has opposed the grant of the orders unless the nature and geographical extent of the orders is specified with sufficient detail to enable the Council to appropriately understand the effect of the orders sought. · High Court has been assessing validity of other parties joining these proceedings. No additional actions or responses have been required from HBRC since joining proceedings in late 2013.

1	Ahuriri Estuary Contact Recreation and Food Gathering Report
2	The Tukituki, Waitangi and Ahuriri Assessment of the Extent of Saltwater Influence in Hawke's Bay Estuaries

Year	Median concentration (MPN /100mL)	Proportion of samples >43 MPN/100 mL (%)	Compliant with guideline values?
2006/07	9	20	No
2007/08	14	10	Yes
2008/09	10	5	Yes
2009/10	14	20	No
2010/11	39	40	No
2011/12	5	20	No
2012/13	3	0	Yes

Item	Topic	Councillor/Committee member / Staff
1.
2.
3.
4.
5.

Please Note - Pre Meeting for Māori Members of the Committee begins at 9 am