HAWKE’S BAY REGIONAL
COUNCIL
Maori
Committee
Tuesday 16 August 2016
Subject: Greater Heretaunga,
Tukituki and Coastal SOE Water Quality and Ecology Reports
Reason for Report
1. Hawke’s
Bay Regional Council (HBRC) undertakes routine water quality and ecology
monitoring around the region to assess the current state of freshwater
resources, and identify whether changes in key parameters over time are
occurring. Parameters include the physical and chemical attributes of the
waterways such as nutrient levels (nitrogen and phosphorus), water clarity,
suspended sediment, and dissolved oxygen levels. Parameters also include
biological attributes such as faecal bacteria, periphyton (slime algae) and
macroinvertebrate communities.
2. State of the
Environment (SoE) monitoring and reporting is a key statutory function of the
Regional Council. The parameters we monitor help us assess whether the life
supporting capacity of the waterways is being maintained.
3. At a broad
scale, the information can be used to assess policy effectiveness. The
monitoring is of particular interest to tangata whenua, our partners and other
stakeholders, as well as interested members of the general community. SoE
information is key for policy change processes, and serves as a contextual base
to assess potential impacts of ongoing consent applications. Issues identified
during State of the Environment Monitoring may lead to targeted investigations
to explore the nature, extent and causes of suspected problems.
4. Here, water
quality and ecology information collected from SoE Monitoring programmes
between January 2004 and December 2013 is provided, covering the:
4.1. Hawke’s Bay Coastal Environment
4.2. Tutaekuri, Ahuriri, Ngaruroro and Karamu (greater
Heretaunga / TANK)
4.3. Tukituki River.
Coastal Environment Report Key Points
5. The ‘State
of the Hawke’s Bay Coastal Environment: 2008 – 2013’
report is the first report documenting the findings of the HBRC’s coastal
SoE monitoring programme.
6. Hawke’s
Bays coastal environments are subject to the combined pressures of activities
occurring both on land and in the ocean. This report describes how
Hawke’s Bay’s coastal environments are responding to these
pressures, and details the state, and trends, within our current data for six
coastal monitoring projects:
6.1. Nearshore water quality
6.2. Recreational water quality
6.3. Sediment quality
6.4. Estuarine ecology and sediment quality
6.5. Sandy beach ecology
6.6. Intertidal
reef ecology.
7. The state of
the majority of these environments is good with stable trends, with the
following key exceptions:
7.1. There was
evidence for increasing ‘muddiness’ at all estuarine monitoring
sites, with an associated reduction in sediment-sensitive taxa (i.e. a
deteriorating biological response)
7.2. 5 out of the
38 (13%) recreational water quality monitoring sites with sufficient data
showed a deteriorating trend in faecal contamination, compared with 4 (11%)
that showed an improving trend
7.3. Industrial
and urban contamination was evident around slipways in the Napier Inner Harbour
and near a stormwater outlet in the Ahuriri Harbour.
8. The most
pressing issue for Hawke’s Bay’s coastal environments are
associated with rainfall events carrying sediments and faecal matter to the
coastal environment.
TANK Water Quality and Ecology Report Key
Points
9. The report
‘Ngaruroro, Tutaekuri, Karamu and Ahuriri Estuary Catchments
– State and Trends of River Water Quality and Ecology 2004-2013’
summarises state and trends in river water quality and ecology collected during
the 2004 - 2013 river SoE monitoring period.
10. The report presents
information on water quality and ecology parameters.
10.1. Nutrients (DIN, TN and DRP, TP)
10.2. Toxicity (nitrate and ammonia)
10.3. Water clarity
10.4. Bacteriological
water quality (E. coli)
10.5. Dissolved oxygen
10.6. Temperature
10.7. Biological indicators (Algae and macroinvertebrates)
10.8. Compliance with NPS-FM attributes
10.9. Compliance with the RRMP.
11. The Ngaruroro and
Tutaekuri catchment were in excellent condition in the upper catchment and
showed some moderate nutrient enrichment and reduction in water clarity towards
the lower reaches. Ecological parameters also showed a gradient from upstream
to downstream, with increasing periphyton biomass, and declining MCI values
towards the lower reaches. All tributaries except for the Taruarau had high
nutrient concentrations, particularly phosphorus.
12. At all SOE sites in the
Karamu and Ahuriri catchments nutrient concentrations were high (particularly
phosphorus), and Macroinvertebrate Community Index (MCI) values indicated poor
ecosystem health. Excessive macrophyte growth was observed at most sites.
Karewarewa, Awanui and Taipo streams were identified as the sites most affected
by poor water quality and ecology.
Tukituki Water Quality and Ecology
Report Key Points
13. The report ‘Tukituki
River Catchment – State and Trends of River Water Quality and Ecology
2004-2013’ summarises state and trends in river water quality and
ecology collected during the 2004 - 2013 river SoE monitoring period.
14. The report presents
information on water quality and ecology parameters:
14.1. Nutrients (DIN, TN and DRP, TP)
14.2. Toxicity (nitrate and ammonia)
14.3. Water clarity
14.4. Bacteriological water quality (E. coli)
14.5. Dissolved oxygen
14.6. Temperature
14.7. Biological indicators (Algae and macroinvertebrates)
14.8. Compliance with National Policy Statement for
Freshwater Management (NPSFM) attributes
14.9. Compliance with the
Regional Resource Management Plan (RRMP).
15. The condition of sites
within the Tukituki River catchment was highly variable. Effectively pristine
conditions were observed in the upper Tukituki and Waipawa Rivers, as well as
in the Makororo River. By comparison, extremely elevated phosphorus levels were
observed in the Papanui and Mangatarata Streams, and moderately elevated
nitrogen levels were observed in the Kahahakuri Stream. Similarly, MCI was
highly variable across the catchment, with ‘excellent’ scores
consistently observed in the Makaroro River and ‘poor’ scores
consistently observed in the Papanui and Mangatarata Streams. MCI ranged from
‘poor’ to ‘fair’ at Red Bridge.
16. Notable points of concern
and/or interest were:
16.1. 6 sites showed deteriorating trends in faecal
contamination
16.2. 8 sites showed deteriorating trends in turbidity
16.3. Ammonia and DRP levels increased in association with
wastewater treatment plant discharges on the Waipawa and Tukituki Rivers
16.4. 25 out of 30 sites showed DRP concentrations in excess
(worse) than that recommended for limiting periphyton accrual
16.5. 20 out of 30 sites showed DIN levels in excess (worse)
than that recommended for limiting periphyton accrual
16.6. 7 out of 16 sites had
MCI scores in the ‘good’ to ‘excellent’ categories,
with the remaining 9 scoring in the ‘fair’ to ‘poor’
categories.
Coastal Environment Report Summary
17. Hawke’s Bay has an
extensive and varied coastal area that provides for a range of social,
cultural, economic and environmental values. Hawke’s Bay Regional Council
(HBRC) is responsible for promoting the sustainable management of the coastal
marine environment. HBRC monitors the state of the environment to provide
council with the information required to underpin decision making.
18. HBRC monitors water
quality, sediment quality and ecology in a range of coastal environments.
Nearshore coastal water quality
19. Nearshore coastal water
quality in Hawke’s Bay generally appears good. Land-based sediment
delivery to the coast is generally high and variable, highlighting periods of
fluvial sediment inputs and nearshore resuspension.
20. Nutrient levels are
similar to or lower than other sites around the country. Relatively high levels
of dissolved nutrients at Ocean Beach demonstrate that rivers are not the only
inputs of nutrients and highlight the role of oceanic contributions.
Recreational water quality
21. The susceptibility of
Hawke’s Bay’s recreational waters to faecal indicator bacteria is
variable. Marine beaches tend to have a high level of compliance with Ministry
for the Environment and Ministry of Health national guidelines and can be
considered suitable for swimming most, if not all, of the time.
22. Rivers tend to have more
variable recreational water quality, with heavy rainfall rendering some rivers
unsuitable for swimming some of the time. Lagoons, at the bottom of the
catchment, can exceed guidelines more frequently. This can be due to generally slower
flows, with higher temperatures and extensive bird-life.
23. Faecal source tracking has
highlighted the role of avian and ruminant sources when guidelines are
exceeded.
Coastal sediment quality
24. Coastal sediments form the
basis for habitats that support diverse benthic communities. The quality of
this sediment is integral to the health of the broader ecosystem. In general,
nearshore sediments away from point source discharges are well sorted, with low
levels of trace metal contaminants. However sediments adjacent to boat
maintenance and repair facilities, and stormwater outlets, have ongoing
contamination issues. Concentrations of trace metal and organic
contaminants exceed sediment quality guidelines within the Inner Harbour and
Ahuriri Estuary.
Estuaries
25. Infauna (sediment-dwelling
organisms) sensitive to muddiness indicate that Hawke’s Bay estuaries may
be experiencing moderate to high levels of sediment stress, with some sites
also showing increasing trends in mud concentrations. Increasing mud
concentrations are impacting on the benthic communities at monitoring sites
with species intolerant to higher mud fractions being largely absent from sites
where mud concentration exceeds 25%.
26. In general nutrient and
trace metal contaminant concentrations appear below guideline values for the
majority of sites with significant contamination confined to areas adjacent to
point sources and stormwater discharges.
27. A Traits Based Index (TBI)
was applied to the estuarine macroinvertebrate data, and corresponded well to
‘muddiness’. Overall scores were low, although further work needs
to verify the TBI fit to Hawke’s Bay data.
28. An overall reduction in
sediment volumes entering the estuaries would increase the health of
Hawke’s Bay estuary systems.
Sandy beaches
29. Sandy beach ecosystems include
a vast array of tiny organisms in the infauna that support coastal fisheries,
cycle nutrients and filter large volumes of seawater. In Hawke’s
Bay the infaunal community composition is highly variable, with relatively low
numbers of species and individuals. The highest abundance species are amphipod
crustaceans, which are likely to be a key food source for coastal
ecosystems. Vehicle usage of Hawke’s Bays beaches is high and
vehicles can have a deleterious effect on infaunal communities. The designation
of many beaches as roads remains a resource conflict for much of New Zealand.
Intertidal reefs
30. Similarly to sandy
beaches, intertidal reefs provide both physical protection to the land from the
effects of the sea, and areas of high biomass and diversity, supporting a range
of ecosystem services and functions. Hawke’s Bay’s reef structures
vary in character, and are largely dependent on the underlying geology.
31. The absence of the common
algae Hormosira banksii from Hardinge road reef is currently not
understood, and further work is required to explain this. Blooms of the
cyanobacteria Lyngbya sp. at Te Mahia reef may also require
investigation.
Overall
32. In general, many areas of
the Hawke’s Bay coastal environment are currently in a state that
supports the values and objectives of these systems. However some areas
are currently showing signs of stress, and further work is required to ensure
that the services and functions that underpin these values are retained.
TANK Water Quality and Ecology Report
Summary
33. For the TANK region,
Hawke’s Bay Regional Council is working through a proposed plan change.
This report informs the plan change process - and the requirement under the NPS
to set water quality limits to protect in-stream community values. This report
therefore includes more detailed information than other SOE reports, including
results from additional sites intended to fill ‘gaps’ in knowledge
and specific studies for these catchments.
34. The headwaters of the
Ngaruroro and the Tuatekuri rivers begin in the forested areas of the Kaweka
Range (north) and the Ruahine Range (south). The upper catchments are mostly in
native vegetation, and land use in the middle catchments is mainly dry stock
farming and a few dairy operations. In the lower reaches where the valley
gradient is less steep, land use becomes more varied, including vineyards and
orchards. Dry stock farming is found in the surrounding hills, and peri-urban
and commercial development is also present.
35. The Karamu catchment
extends south from Awatoto to Havelock North and west to the Raukawa Range. The
Karamu catchment is the main region in Hawke’s Bay for orchards,
cropping, and viticulture, while the southwestern half of the catchment mostly
supports dryland sheep and beef. The exception to this pattern is the Poukawa
Basin, which is a significant cropping area. Waterways in the Karamu catchment
have been extensively modified for flood protection purposes.
36. The Ahuriri is
Hawke’s Bay’s most urbanised catchment, and includes the settlement
of Napier and surrounding suburbs, north to Bay View and south to Awatoto.
37. The Tutaekuri, Ngarururo
and Karamu rivers meet the sea at the Waitangi estuary. The estuary includes a
variety of habitats, including open water, intertidal flats, salt marsh, and
two associated freshwater wetlands at Muddy Creek and The Horseshoe.
38. Due to significant
differences in the stream ‘types’ of the Ngaruroro and Tutaekuri
catchments in comparison to the Karamu and Ahuriri catchments the following SOE
Technical report presents and discusses data on the Ngaruroro and Tutaekuri
Rivers independent of the Karamu and Ahuriri.
39. The following conclusions
can be drawn from the data, analysis and information presented in this report.
Ngaruroro and Tutaekuri catchments
40. The Ngaruroro main stem
was in excellent condition in the upper to middle catchment. The lower reaches
showed some minor enrichment in nutrients and a decrease in water clarity.
Water quality parameters showed a minor upstream to downstream decline, which
was reflected in the biological indicators of periphyton biomass and
macroinvertebrate community. Overall water quality and ecology of the Ngaruroro
River main stem was healthy. The Taruarau tributary also showed excellent water
quality and ecological health.
41. The Ngaruroro tributaries
(other than the Taruarau River) were enriched in nutrients, especially
phosphorus, which was always above guideline levels. The influence of nutrient
loads coming from the tributaries into the main stem had only a minor effect on
the water quality in the main stem Ngaruroro, because large volumes of water
with high water quality from the pristine upper catchment dilutes the influence
of the tributaries.
42. The Tutaekuri main stem
showed some enrichment in nutrients from upstream to downstream, particularly
in phosphorus. Ecological parameters also showed a gradient from upstream to
downstream, with increasing periphyton biomass, and MCI values declined from
excellent to fair towards the lower reaches.
43. Tutaekuri tributaries had
water quality issues similar to the Ngaruroro tributaries, with elevated
nutrient concentrations. The high phosphorus concentrations were mostly above
guidelines. MCI was good across all tributary sites and periphyton biomass was
high in the Mangatutu Stream, and low in the upper Mangaone. The effect of
tributary nutrient loads on main stem water quality was greater in the
Tutaekuri than in the Ngaruroro, because the volume of water coming from the pristine
upper catchment is lower and the dilution effect less than in the Ngaruroro.
44. Toxicity effects on
aquatic organisms from nitrate and ammonia were not an issue anywhere in the
Ngaruroro and Tutaekuri catchments, as concentrations were always low. In the
case of ammonia levels were mostly below detection limit. Escherichia coli
(E. coli) levels were very low in both catchments and were below the
lowest guideline (‘alert’) level.
Karamu and Ahuriri catchments
45. Nitrogen concentrations
are variable across sites, with very high concentrations in the Karewarewa,
Awanui, Mangarau at Te Aute Road and Clive River. Phosphorus concentrations are
very high and always above guidelines at all sites.
46. Water clarity was low and
generally did not comply with the contact recreation guideline at most of the
sites.
47. Median E. coli
concentrations were at or below the MfE recreation guideline ‘Alert/Amber
mode’ at most of the sites except the Karewarewa, Herehere and Taipo
streams. The Herehere Stream had the highest median E. coli
concentration, which was close to the MfE ‘Action/Red mode’.
48. Toxicity risk for aquatic
organisms was generally low, with the exception of the Karewarewa, Awanui and
Taipo streams. These had elevated ammoniacal-nitrogen at times, and
nitrate-nitrogen concentrations that maintain 90% species protection but
exceeded the 99% species protection threshold.
49. Biological indicators
showed high macrophyte growth and poor MCI values that indicated the streams
were severely impacted.
50. The poor MCI values
triggered a targeted study to identify major stressors in the Karamu and
Ahuriri catchments. High water temperature, low dissolved oxygen minima and
poor habitat were identified to be major stressors in the streams where MCI was
particularly low. Excessive macrophyte growth was a contributing factor to the
severely low oxygen levels.
51. Overall, nutrient
concentrations were high (particularly phosphorus), at all SOE sites in the
Karamu and Ahuriri catchments, and MCI values indicated poor ecosystem
health. Excessive macrophyte growth was observed at most sites, but the
Karewarewa, Awanui and Taipo streams were the most affected sites.
Tukituki Water Quality and Ecology Report
Summary
52. The Tukituki catchment
extends from the Ruahine Ranges, where the Tukituki and Waipawa Rivers take
their source, to the Pacific Ocean on the East Coast of Hawke’s Bay. The
catchment covers an area of approximately 2,500 km2 and
encompasses five management zones: the Upper Tukituki/Waipawa, Ruataniwha North,
Ruataniwha South, Papanui and Lower Tukituki corridor.
53. A key feature of the
Tukituki catchment is the degree of interaction between surface and groundwater
in the Ruataniwha Aquifer, which deeply influences both the hydrology and the
water quality of streams and rivers within the Ruataniwha Plains, and of the
middle and lower reaches of the Tukituki River itself. Spatial and temporal
patterns of river flows and water quality in the Tukituki catchment cannot be
understood without an appreciation of this groundwater influence.
54. The upper parts of the
Ruataniwha Plains are identified as a groundwater recharge area, where rivers
flowing down from the Ruahine Ranges and foothill lose flow to the aquifer, to
a point where reaches of the Waipawa and Tukituki River are known to dry up in
summer. By contrast, the lower parts of the Ruataniwha Plains are characterised
by groundwater upwelling back into spring-fed streams and the main stems of the
Tukituki and Waipawa Rivers, contributing a major part of the surface flows in
these rivers during dry periods. With groundwater comes dissolved nutrients (in
particular nitrate-nitrogen), which strongly influence the spatial and temporal
patterns of water quality described in this report.
55. This report is based on
water quality and ecological data collected at 30 State of the Environment
(‘’SOE”) and compliance monitoring sites across the five
water management zones (Upper Tukituki/Waipawa, Ruataniwha North, Ruataniwha
South, Papanui and Lower Tukituki Corridor) within the Tukituki catchment.
56. Of the 30 sites, 15 are
located along the main stems of the two main rivers, the Waipawa and Tukituki
rivers, from SH50 to Black Bridge providing a detailed understanding of
longitudinal patterns, i.e. how water quality changes from upstream to
downstream. The most upstream sites on the Waipawa and Tukituki Rivers are
located at the points where the rivers cross State Highway 50 (SH50). These two
monitoring sites are considered representative of the water quality exiting the
Upper Tukituki/Waipawa Water Management Zone.
57. Many monitoring sites are
concentrated near the western end of the Ruataniwha Basin, on the main stem of
the Tukituki and Waipawa Rivers and on the main tributaries before their
confluence the Tukituki and Waipawa Rivers. A number of these sites are located
within flow gaining reaches, and both their hydrology and water quality are
strongly influenced by groundwater. This includes the lower reaches of the
Mangaonuku, Porangahau and Maharakeke Streams and the Kahahakuri Stream.
58. The Papanui Stream
catchment forms a water management zone of its own. The Papanui at Middle Road
site is located at the outflow of the catchment, before the stream descends
into the floodplain of the Tukituki River. The Papanui Stream is strongly
influenced by groundwater from the Otane/Papanui basin.
59. In this report, monitoring
data relative to a number of water quality indicators are compared with ANZECC
trigger values (as detailed in Section 2), which distinguish between ‘upland’
(elevation >150m) and ‘lowland’ elevation <150m) streams. Out
of the 30 monitoring sites considered in this report, eight are classified
‘upland’ (Makaroro River, Waipawa River at SH50, Mangaonuku Stream,
Makaretu River at SH50, Mangatewai stream at SH50, Tukipo River at SH50,
Tukituki River at SH50 and Maharakeke Stream at Limeworks Station Rd), four
sites (Maharakeke Stream U/S Makaretu River, Makaretu River U/S Maharakeke
Stream, Tukipo River U/S Makaretu River and Tukituki River at Waipukurau Ongaonga
Rd) are right on the 150m contour or just below it, while the remaining 18
sites are classified ‘lowland’.
60. Water quality and
ecological indicators monitored as part of the SOE monitoring programme may be
considered in the following groups:
60.1. Microbiological water quality indicators, such as E.coli,
which provides an indication of the level of health risk to recreational users
of the water
60.2. Basic physico-chemical indicators, such as
temperature, dissolved oxygen and pH
60.3. Indicators associated with the visual appearance of
the water, such as visual water clarity and turbidity
60.4. Toxicants, such as excessive nitrate and ammonia
60.5. Nutrients for plants and algae, such as nitrogen and
phosphorus, as controlling factors, or indicators of risk of eutrophication
(excessive plant/algae growth)
60.6. Biological indicators of
eutrophication (periphyton biomass) and ecological health (macroinvertebrate
communities).
61. The various water quality
and ecological indicators were compared with environmental guidelines and
trigger values to provide an indication of the state of water quality.
Statistical analyses of temporal trends were performed to determine whether the
water quality indicators have been improving or degrading over time. For the relevant
indicators, and where data were available, the various indicators were compared
with the Regional Plan (RRMP) Guidelines, and with the National Policy
Statement for Freshwater management (NPS-FM) (2014) Attribute States.
Monitoring data collected during the 2009-2013 period indicates the following.
Microbiological water quality
62. Data available for the
2009-2013 reporting period indicates that microbiological water quality was:
62.1. Suitable for secondary
contact recreation at all sites, with 20 out of 22 sites in the NPSFM
“A” grade and the remaining 2 sites (the Papanui and Makara
Streams) in the “B” Grade.
62.2. Suitable for primary
contact recreation (e.g. swimming) at 15 of the 22 sites where data were
available (14 sites in NPSFM “A” Grade and 1 in the “B
Grade”). The remaining seven sites (Waipawa at SH50, Makaretu at SH50,
Tukituki at SH50, Papanui Stream, Waipawa at SH2, Porangahau Stream and
Mangatarata Stream) did not meet the minimum acceptable state for full
immersion activities.
62.3. Six sites showed
significant deteriorating trends in E. coli numbers: the Mangaonuku
Stream (21% annual average increase), Tukituki River 50m U/S oxi pond (61%
annual average increase), Tukituki at SH2 (46% annual average increase),
Tukituki River at Tapairu Rd (40% annual increase), Waipawa at SH2 (50% annual
increase) and the Waipawa U/S Tukituki River (49% annual increase).
Dissolved Oxygen
63. Significant issues with
dissolved oxygen (DO) concentrations or saturation occur at only 4 of the
Tukituki catchment sites. The Mangaonuku, Kahahakuri and Papanui streams are
known to be influenced by anoxic groundwater inflows which is likely to have
influenced some of the DO readings at these sites. The Papanui and Mangatarata
Streams are slow moving streams with high macrophyte biomass. Respiration and
decomposition of the macrophyte biomass, coupled with low re-oxygenation rates
are also likely to have contributed to the low DO readings at these sites. It
is important to note that the data were limited to ‘spot’
measurements, which were unlikely to capture the daily minima.
Water clarity and turbidity
64. None of the 24 SoE
monitoring sites for which water clarity data were available met median water
clarities of 3.5m (recommended guideline for significant trout fisheries), let
alone 5m (the recommended guideline for “outstanding trout
fisheries”), although the Makaroro River, the Mangaonuku Stream and the
Tukituki River at Black Bridge did reach a water clarity of 5m or more at
times. These included all Lower Tukituki River monitoring sites (from Tamumu
Bridge to Black Bridge), and a number of tributaries including the Makaroro
River and the Mangaonuku Stream (which had the clearest water of all sites),
the Tukipo River, and the Porangahau, Maharakeke and Kahahakuri Streams.
65. No changes (improvements
or deterioration) in black disc water clarity over time were detected at any of
the Tukituki catchment sites, apart from the Mangatarata Stream (7.7% decrease
per annum). Turbidity, however showed a deterioration at eight sites across the
catchment (Mangaonuku Stream, Waipawa at SH2, Waipawa U/S Tukituki River,
Tukipo River at SH50, Tukituki at SH2, Tukituki at Tapairu Rd, Tukituki at
Tamumu Bridge and Tukituki at Red Bridge).
66. When compared with the
rest of the region’s SoE sites, the Mangaonuku Stream ranked best in the
catchment at 12 out of 98 regional sites for black disc water clarity, while
the Mangatarata Stream ranked the worst in the catchment at 90 out of 98
regional sites.
Toxicants – Ammonia
67. Elevated ammonia levels
were noticeable downstream of both the Waipawa and Waipukurau wastewater
treatment plants, and in the Papanui Stream.
68. With regards to the NPSFM
(2014) Attribute for Ammonia (Toxicity), 90% of the sites (27 out of 30) were
graded in either Band A or band B for both Median and maximum concentrations in
all individual years of record, meeting at least the 95% species protection
level. The Tukipo River and the Tukituki river upstream and downstream of the
oxidation pond discharge were graded in the “C” band for annual
maximum concentrations in one or two individual years.
69. No significant and
meaningful temporal trends in total ammoniacal nitrogen concentrations were
identified in the Tukituki catchment, except at the Makaroro River where a
deterioration of 10.3% per annum was identified.
Toxicants – Nitrate
70. All sites but 3 in the
Tukituki catchment graded in either Band A or band B for both Median and 95th
percentile concentrations in all individual years of record, and were better than
at least the 95% species protection level. The Porangahau and Mangatarata
Stream were graded in “A” or “B” bands when considering
median concentrations, but their 95th percentile concentrations fell
into “C” Band in at least one individual year. The Kahahakuri
Stream had the highest nitrate nitrogen concentrations in the catchment, and
was graded in Band C in most years for both median and 95th
percentile concentrations.
71. Improvements (decrease) in
nitrate-nitrogen concentrations over time were detected in the Porangahau
Stream, Tukituki River at Tamumu Bridge, Tukituki at Red Bridge and Tukituki at
Black Bridge (Figure 3 11).
72. Comparison with other SoE
monitoring sites in the Hawkes’s Bay region show Tukituki catchment sites
to vary across the rankings from the best in the region (Mangamahaki Stream) to
the third worst (Kahahakuri Stream), with two thirds of sites in the bottom 50%
regionally.
Nutrients – Nitrogen
73. TN and DIN concentrations
generally followed similar patterns across the catchment.
73.1. The three sites located
within (Makaroro at Burnt Bridge), or considered representative of the Upper
Tukituki water management zone (Tukituki at SH50 and Waipawa at SH50), had low
nitrogen concentrations (both TN and DIN), and were better than the upland
ANZECC trigger values and guidelines to control periphyton growth.
73.2. Within Zone 2 (Waipawa),
the Mangaonuku Stream (an upland site) is strongly influenced by groundwater,
and had elevated TN and DIN (dominated by nitrate-nitrogen) concentrations,
well in excess of both the upland and the lowland ANZECC Trigger values. The
four sites located on the Waipawa River main stem between SH2 and the
confluence with the Tukituki had moderate TN and DIN concentrations, exceeding
the lowland ANZECC trigger values, but meeting the PC6 target of 0.8 mg/L.
73.3. In Zone 3 (Tukituki),
the Makaretu at SH50 was the only upland site better than the
‘upland’ ANZECC trigger value of 0.167 mg/. The remaining 3
upland sites (Mangatewai at SH50, Tukipo at SH50 and Maharakeke at Limeworks
Station Rd) were worse than this value. The Mangatewai at SH50 and the
Maharakeke at Limeworks Station Rd were mostly worse than the PC6 target of
0.8 mg/L;
73.4. In Zone 5, the median
DIN concentration in the Papanui Stream was better than both the
‘lowland’ ANZECC trigger value and the PC6 target of 0.8 mg/L.
73.5. In the Tukituki River
main stem, the DIN concentrations were low upstream of the Waipukurao Ongaonga
Rd site, which is located upstream of the groundwater upwelling area and the
confluence with the main tributaries. Downstream of the groundwater upwelling,
DIN concentrations increased from SH2 to downstream of the Waipukurau oxidation
pond discharge.
73.6. DIN concentrations
between SH2 and Taiparu Road were mostly worse than the ANZECC trigger value
for lowland rivers and the PC6 0.8 mg/L target. At Taiparu Road, DIN
concentrations were lower and gradually decreased towards Red Bridge,
presumably as a result of dilution with the Waipawa River and in-river
attenuation of DIN by a combination of utilisation by plants and microorganisms
and de-nitrification.
73.7. DIN concentrations were
better than the PC6 target at Taiparu Road and all sites further downstream on
the lower Tukituki River. The eastern catchment tributaries (Mangatarata,
Mangamahaki and Makara Streams) were all better than both the lowland ANZECC
trigger value the Tukituki Plan Change 6 (PC6) target of 0.8 mg/L.
74. Overall, 6 out of 22
lowland sites (Makaretu River U/S Maharakeke Stream, Tukituki at Ongaonga Rd,
Papanui Stream, Mangatarata Stream, Mangamahaki Stream and the Makara Stream)
were better than the ‘lowland’ ANZECC trigger value of 0.444 mg/L
for DIN, with all remaining lowland sites (n=16) in the catchment were worse
than this value.
75. About one third of all
Tukituki catchment sites met the Biggs (2000) suggested guideline for DIN for
periphyton growth management for a 20 day accrual period, while two thirds of
the sites met the Tukituki Plan change 6 target.
76. Improvements in DIN and TN
concentrations were seen at the Porangahau Stream in the Tukituki River at
Tamumu Bridge. Improvements in DIN concentrations were also detected at the
Tukituki at Red Bridge and Black Bridge.
77. Compared with other SoE
sites in the region, Tukituki catchment sites are spread across the regional
rankings. The Mangamahaki Stream ranked 2nd of all regional sites
for DIN. The Makara Stream, Makaroro River, Mangatarata Stream and the Tukituki
River at SH50 were ranked in the top 25% regionally. At the other end of the
scale, the Kahahakuri Stream ranked in the bottom 3, and the Mangaonuku Stream,
the Maharakeke Stream (both sites) and the Tukituki River 400m d/s Oxi Ponds
are in the bottom 10 sites regionally.
Nutrients – Phosphorus
78. TP and DRP concentrations
generally followed similar patterns across the catchment:
78.1. Median DRP
concentrations were generally moderately elevated across the Tukituki catchment
(greater than 0.011 mg/L) with all but a handful of sites worse than both the
upland and lowland ANZECC trigger values. The highest DRP concentrations were
recorded in the Mangatarata and Papanui Streams (0.167 and 0.154 mg/L,
respectively).
78.2. DRP concentrations were
very low at the three sites within (Makaroro River), or considered
representative of (Waipawa at SH50 and Tukituki at SH50), Water Management Zone
4 (Upper Tukituki/Waipawa), and were considerably better than the
‘upland’ ANZECC trigger value of 0.009 mg/L, as well as the Biggs
(2000) suggested guideline for DRP for periphyton growth management.
78.3. In Zone 2, both the
Mangaonuku Stream and the Waipawa River main stem upstream of the oxidation
pond discharge had median DRP concentrations 20 to 40% worse than the ANZECC
trigger value for lowland rivers. There was an obvious increase in median DRP
concentration downstream of the oxidation pond discharge, presumably associated
with the discharge.
78.4. In Zone 3, the Tukituki
at Waipukurau Ongaonga Road and the Makaretu River u/s Maharakeke confluence
were the only two sites better than both the upland and the lowland ANZECC
trigger values. All other sites were worse than both the upland and the lowland
ANZECC trigger values. In the Tukituki River main stem, there was a distinct
increase in DRP concentrations associated with the Waipukurau oxidation pond
discharge.
78.5. The Papanui Stream (in
Zone 5) and the Mangatarata Stream had very elevated median DRP concentrations
(0.154 and 0.167 mg/L respectively), i.e. approximately 15 times the ANZECC
trigger values for lowland rivers.
78.6. In the lower Tukituki
River, median DRP concentrations decreased with distance downstream of the
oxidation ponds, and was almost as good as the ANZECC trigger value for lowland
rivers at Red Bridge.
79. Deteriorations in DRP
concentrations were seen at the Mangaonuku Stream, the Waipawa River 50m U/S
oxi pond and the Waipawa River U/S Tukituki River.
80. The Tukituki at Waipukurau
Ongaonga Rd and SH50, the Waipawa River at SH50 and the Makaroro River were
ranked in the top 25% regionally. At the other send of the scale, the
Mangatarata and Papanui Streams and the Tukituki River downstream of the
Waipukurau oxidation pond were in the bottom 10 sites regionally.
Nutrient ratios
81. With 6 exceptions, all
sites in the Tukituki catchment have nutrient ratios indicative of
phosphorus-limited conditions. The Makaroro River, the Mangatewai Stream at
SH50, and to a lesser extent the Makaretu at SH50 have nutrient ratios
indicative of co-limited conditions. The Papanui, Mangatarata, Mangamahaki and
Makara Stream have nutrient ratios indicative of predominantly N-limited
conditions.
82. It is important to note
however that nutrient ratios should be considered in parallel with the actual
nutrient concentrations, to provide an indication of the likely strength of any
nutrient limitation. For example, concentrations of both DRP and DIN are
elevated in the Mangatewai, Porangahau and Maharakeke Streams, and in the
Papanui and Mangatarata Stream, concentrations of both TN and DRP are elevated,
meaning that any nutrient limitation is likely to be very weak or absent
(unlimited conditions) in these streams. By contrast, in the Mangamahaki and
Makara Streams, DIN concentrations are very low and DRP concentrations only
moderately elevated, meaning that nutrient limitation of periphyton growth is
likely to be strong in these streams.
Biological indicators
83. MCI
(macroinvertebrate community index) scores provide an integrated indicator of
the general state of water quality and aquatic health
84. Sites on the Makaroro
River, the upper and middle Waipawa and Tukituki mainstems (SH50 and SH2), as
well as the Tukipo and Makaretu Rivers at SH50 had median MCI scores indicative
of “good” quality. The Porangahau and Kahahakuri Stream and the
lower Tukituki River had MCI scores of “fair” quality.
85. Three sites, the Papanui
and Mangatarata Streams and the Tukituki River at Black Bridge have much lower
MCI scores indicative of poor water quality. The Tukituki at Black Bridge is
known to be influenced by saline water and so the MCI scores here are not
comparable to purely freshwater sites in the catchment.
86. Periphyton is the
brown or green slime or filamentous material coating stones, wood, or other
stable surfaces in streams and rivers. It is a natural component of riverine
environments, however, excessive (‘nuisance’) growths can affect
both human use of the river and ecological values.
87. Available data indicate
that the Waipawa River at SH50, the Tukituki River at SH50 and Tapairu Rd and
the Makaretu River at SH50 have generally low median periphyton biomass, well
below both the 120 mg/m2 ‘recreational’ and 50 mg/m2
‘biodiversity’ thresholds on at least 90% of monitoring occasions.
88. Median biomasses in the
Tukipo River at SH50 and the lower Tukituki River sites (Tamumu Bridge, Red
Bridge and Black Bridge) were also better than the 50 mg/m2
‘biodiversity’ threshold, but higher biomasses, sometimes well in
excess of the 120 mg/m2 ‘recreational’ threshold
occurred at these sites at times.
89. Median biomasses in excess
of the 50 mg/m2 ‘biodiversity’ threshold but less than
the 120 mg/m2 ‘recreational’ threshold were recorded at
all other monitoring sites where data was available (Mangaonuku Stream, Waipawa
at SH2, Porangahau Stream and Mangatarata Stream). Biomasses in excess of the
120 mg/m2 ‘recreational’ threshold were recorded more
regularly in the Mangaonuku and Mangatarata Streams, and the Waipawa River at
SH2.
Decision Making Process
90. Council is required to
make every decision in accordance with Part 6 Sub-Part 1, of the Local
Government Act 2002 (the Act). Staff have assessed the requirements 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.
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Recommendations
1. That the Maori Committee receives and notes the “State of the Hawke’s Bay Coastal Environment: 2008 –
2013”, “Ngaruroro, Tutaekuri, Karamu and Ahuriri Estuary Catchments
– State and Trends of River Water Quality and Ecology 2004-2013”
and “Tukituki River Catchment – State and Trends of River Water
Quality and Ecology 2004-2013” reports.
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Authored by:
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Andy Hicks
Team Leader - Water Quality and Ecology
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Anna
Madarasz-Smith
Senior Scientist - Coastal Quality
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Oliver Wade
Environmental Scientist WQ&E
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Alexandra
Haidekker
Water Quality & Ecology Scientist
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Dr Stephen
Swabey
Manager, Science
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Approved by:
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Iain Maxwell
Group Manager Resource Management
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