Mauri Compass Wananga: Hinepare Marae, Rangitukia - November 2024
Trends and Observations
We have collated and summarised water quality trends from data collected in the Waiapu Catchment at the following sites:
Poroporo River at Rangitukia and Mata River at Aorangi Makarika Road.
<We recommend using a Laptop, PC or installing the Google Earth App on your Phone>
Click here to explore our map: MAURI COMPASS: LAWA, DATA, TRENDS AND LOCATIONS
Poroporo River at Rangitukia and Mata River at Aorangi Makarika Road.
<We recommend using a Laptop, PC or installing the Google Earth App on your Phone>
Click here to explore our map: MAURI COMPASS: LAWA, DATA, TRENDS AND LOCATIONS
Biodiversity in the Waiapu River Catchment
The Waiapu River Catchment boasts a diverse range of habitats that play essential roles in supporting the region's biodiversity. Riparian zones, located alongside rivers and streams, are critical for stabilising riverbanks, filtering runoff, and providing vital habitats for both aquatic and terrestrial wildlife. These zones are crucial in maintaining water quality and species diversity within the catchment. Wetlands are another important habitat, known for their water filtration capabilities, flood regulation, and their ability to support rare and endangered plant and animal species. In addition, the native forests of the Waiapu catchment provide shelter for a variety of birds, insects, and other wildlife, while also contributing to soil stability and water regulation. Grasslands, both native and introduced, further contribute to the region’s ecological diversity by supporting unique species.
The flora of the Waiapu River Catchment is equally diverse. Native trees like kahikatea, totara, and rimu are prominent in the forested areas and play a vital role in shaping the ecosystem. Wetland plants such as carex and flax support the region's wetlands by providing habitat and contributing to essential ecological functions. The understory in these forests, consisting of plants like mānuka and kānuka, enriches the biodiversity of the forest floor, supporting smaller fauna and maintaining a healthy ecosystem.
The catchment also supports a range of fauna, including birds like the North Island kākā, tui, and bellbird. These bird species are important for the pollination of native plants, helping to sustain the region's flora. The long-tailed bat, an endangered species, depends on the forested areas for roosting and feeding. The region's streams are home to native fish species such as whitebait and giant kokopu, which thrive in clean, cool waters, making them indicators of the catchment's healthy aquatic ecosystems.
Pest Control in the Waiapu River Catchment
Pest control is a critical ongoing effort in the Waiapu River Catchment. Local councils, such as the Gisborne District Council, have implemented pest management programs aimed at controlling invasive species like stoats, rats, and possums, which threaten the survival of native wildlife. These programs often involve a combination of trapping, poisoning, and habitat restoration. Community groups, such as the Waiapu Catchment Community Trust, are also heavily involved in pest control efforts, working on the ground with initiatives like trapping, restoration projects, and species monitoring.
However, pest control in the Waiapu catchment faces several challenges. The rugged terrain and remote areas make access difficult, limiting the effectiveness of control measures. Additionally, pest control efforts require ongoing funding, which can be a challenge to secure. Collaboration between government agencies, local communities, and environmental organisations is also crucial, as coordinating efforts is essential for a unified and successful approach to pest management.
Woolly Nightshade and Invasive Species in the Maraehara River Region
In the Maraehara River region, woolly nightshade (Solanum mauritianum) poses a significant ecological threat. This invasive species spreads quickly, forming dense thickets that overshadow native plants and reduce biodiversity. Woolly nightshade not only competes for resources with native species but is also toxic to local wildlife and livestock, further threatening the ecological balance. The plant’s presence has prompted local efforts to control its spread, often involving manual removal for smaller infestations. In larger areas, carefully managed herbicide applications are used to prevent the plant from overtaking native vegetation.
Local communities play a critical role in managing woolly nightshade. Many control efforts are community-led, focusing on raising awareness, educating the public, and increasing recognition of the plant’s detrimental effects. By engaging in manual removal and herbicide use, these initiatives are working to curb the spread of woolly nightshade and protect the region’s biodiversity.
Other invasive plants, such as pampas grass and blackberry, also pose challenges to the region. Pampas grass forms dense stands that outcompete native species and are difficult to manage, requiring methods such as cutting, burning, and herbicide treatment. Similarly, blackberry thickets spread rapidly and dominate areas, displacing native flora. Mechanical removal and herbicide applications are often necessary to control these infestations and restore native plant communities.
The Waiapu River Catchment boasts a diverse range of habitats that play essential roles in supporting the region's biodiversity. Riparian zones, located alongside rivers and streams, are critical for stabilising riverbanks, filtering runoff, and providing vital habitats for both aquatic and terrestrial wildlife. These zones are crucial in maintaining water quality and species diversity within the catchment. Wetlands are another important habitat, known for their water filtration capabilities, flood regulation, and their ability to support rare and endangered plant and animal species. In addition, the native forests of the Waiapu catchment provide shelter for a variety of birds, insects, and other wildlife, while also contributing to soil stability and water regulation. Grasslands, both native and introduced, further contribute to the region’s ecological diversity by supporting unique species.
The flora of the Waiapu River Catchment is equally diverse. Native trees like kahikatea, totara, and rimu are prominent in the forested areas and play a vital role in shaping the ecosystem. Wetland plants such as carex and flax support the region's wetlands by providing habitat and contributing to essential ecological functions. The understory in these forests, consisting of plants like mānuka and kānuka, enriches the biodiversity of the forest floor, supporting smaller fauna and maintaining a healthy ecosystem.
The catchment also supports a range of fauna, including birds like the North Island kākā, tui, and bellbird. These bird species are important for the pollination of native plants, helping to sustain the region's flora. The long-tailed bat, an endangered species, depends on the forested areas for roosting and feeding. The region's streams are home to native fish species such as whitebait and giant kokopu, which thrive in clean, cool waters, making them indicators of the catchment's healthy aquatic ecosystems.
Pest Control in the Waiapu River Catchment
Pest control is a critical ongoing effort in the Waiapu River Catchment. Local councils, such as the Gisborne District Council, have implemented pest management programs aimed at controlling invasive species like stoats, rats, and possums, which threaten the survival of native wildlife. These programs often involve a combination of trapping, poisoning, and habitat restoration. Community groups, such as the Waiapu Catchment Community Trust, are also heavily involved in pest control efforts, working on the ground with initiatives like trapping, restoration projects, and species monitoring.
However, pest control in the Waiapu catchment faces several challenges. The rugged terrain and remote areas make access difficult, limiting the effectiveness of control measures. Additionally, pest control efforts require ongoing funding, which can be a challenge to secure. Collaboration between government agencies, local communities, and environmental organisations is also crucial, as coordinating efforts is essential for a unified and successful approach to pest management.
Woolly Nightshade and Invasive Species in the Maraehara River Region
In the Maraehara River region, woolly nightshade (Solanum mauritianum) poses a significant ecological threat. This invasive species spreads quickly, forming dense thickets that overshadow native plants and reduce biodiversity. Woolly nightshade not only competes for resources with native species but is also toxic to local wildlife and livestock, further threatening the ecological balance. The plant’s presence has prompted local efforts to control its spread, often involving manual removal for smaller infestations. In larger areas, carefully managed herbicide applications are used to prevent the plant from overtaking native vegetation.
Local communities play a critical role in managing woolly nightshade. Many control efforts are community-led, focusing on raising awareness, educating the public, and increasing recognition of the plant’s detrimental effects. By engaging in manual removal and herbicide use, these initiatives are working to curb the spread of woolly nightshade and protect the region’s biodiversity.
Other invasive plants, such as pampas grass and blackberry, also pose challenges to the region. Pampas grass forms dense stands that outcompete native species and are difficult to manage, requiring methods such as cutting, burning, and herbicide treatment. Similarly, blackberry thickets spread rapidly and dominate areas, displacing native flora. Mechanical removal and herbicide applications are often necessary to control these infestations and restore native plant communities.
Learn At Your Own Pace
INSTRUCTIONS
- Watch each episode of the awe-insiping Why Apu? series.
- Answer a 5 question Kahoot to test your understanding of the key aspects of episode.
- Kia kaha!
"Embark on an awe-inspiring journey into the heart of Raukūmara, a forest teetering on the edge of ecological disaster. In episode one, we delve into the profound spiritual bond shared by Ngāti Porou and Te Whānau-ā-Apanui with their beloved ngahere (forest). Witness their unwavering commitment to rejuvenate this vital ecosystem as the survival of all life downstream hangs in the balance. Don't miss this powerful exploration of nature, culture, and resilience - the ultimate call to action! -
Why Apu? is a six-part series by Te Amokura Productions. Ngā mihi Te Māngai Pāho and NZ On Air."
Why Apu Episode 1: Watch the Youtube Video then answer the 5 Questions below it:
Why Apu? is a six-part series by Te Amokura Productions. Ngā mihi Te Māngai Pāho and NZ On Air."
Why Apu Episode 1: Watch the Youtube Video then answer the 5 Questions below it:
EPISODE 1 https://www.youtube.com/watch?v=fLoDRZ6T0y0&t=1325s
The video explores the environmental challenges faced by the Raukūmara region due to climate change, extreme weather, and human impact, leading to ecological collapse. It highlights the efforts of local communities and the Department of Conservation to restore and protect the area, including the controversial use of 1080 to control pests. The narrative emphasises the importance of reconnecting people with their land and the need for collective action to preserve the ecosystem.
Highlights
Key Insights
The video explores the environmental challenges faced by the Raukūmara region due to climate change, extreme weather, and human impact, leading to ecological collapse. It highlights the efforts of local communities and the Department of Conservation to restore and protect the area, including the controversial use of 1080 to control pests. The narrative emphasises the importance of reconnecting people with their land and the need for collective action to preserve the ecosystem.
Highlights
- Climate Change: Extreme weather and human impact are reshaping our environment.
- Invasive Species: Pests like deer and possums threaten the ecosystem’s balance.
- Erosion: Riverbanks are eroding, leading to sediment issues in waterways.
- Restoration Efforts: Communities are stepping up to restore the land and its biodiversity.
- Wildlife Decline: Bird populations are suffering due to habitat destruction.
- Community Involvement: Local groups are actively engaged in conservation and education.
- Hopeful Future: Efforts to combat ecological damage show promise for recovery.
Key Insights
- Climate Impact: The landscape is increasingly affected by climate change, leading to a new environmental norm which compels urgent action.
- Biodiversity Crisis: The introduction of pests has led to ecological collapse, highlighting the interdependence of species and the need for effective management.
- Erosion Challenges: Riverbanks are collapsing, affecting water quality and ecosystem health, making restoration crucial for future stability.
- Community-Led Restoration: Local initiatives are essential in driving change, showcasing the importance of indigenous knowledge in conservation efforts.
- Wildlife Recovery: Despite current challenges, there are signs of wildlife resilience, indicating that restoration efforts may yield positive results.
- Education & Awareness: Addressing community fears about pest control methods like 1080 is critical for gaining support for conservation initiatives.
- Sustainable Practices: The emphasis on giving back to the land reflects a shift towards sustainable management practices for future generations.
Questions
- What is one of the primary effects of climate change on the environment?
a) Decrease in biodiversity
b) Extreme weather reshaping the landscape
c) Reduction of invasive species
d) Decreased community involvement - Which invasive species are mentioned as a threat to the ecosystem's balance?
a) Rats and stoats
b) Deer and possums
c) Wild pigs and goats
d) Rabbits and feral cats - What is a significant issue caused by erosion?
a) Loss of native plants
b) Sediment build-up in waterways
c) Increased population of birds
d) Decline in rainfall patterns - What is the role of local communities in environmental restoration?
a) They fund government conservation projects
b) They lead restoration efforts and utilise indigenous knowledge
c) They create wildlife reserves
d) They remove all pests without using chemicals - What is crucial for gaining public support for pest control methods like 1080?
a) Lowering costs of pest control
b) Raising awareness and education on its importance
c) Increasing the number of pest species
d) Reducing community involvement in decision-making
Water Quality
Poroporo River at Rangitukia
1. E. coli:
Water Quality Statistics for Maraehara River Testing Locations
1. Maraehara River at Te Araroa
Indicator
Average Value
Peak Value
Threshold/Standard
Trend (Last 5 Years)
E. coli (cfu/100mL)
175
450 (after rainfall)
< 260 for safe recreational use
Fluctuating
Total Nitrogen (mg/L)
1.2
1.8
Ideal: < 0.5
Slight decline (by 15%)
Dissolved Reactive Phosphorus (mg/L)
0.03
0.05
Ideal: < 0.03
Stable with minor fluctuation
Water Clarity (Turbidity) (NTU)
6.5 NTU
20 NTU (after heavy rains)
Ideal: < 5 NTU
Improvement (by 20%)
Key Observations:
Maraehara River at Te Araroa - Trends in Water Quality
1. E. coli Levels
Trend: Fluctuating with occasional spikes.
Details: Over the last five years, the levels of E. coli have shown major fluctuations, sometimes after rainfall. Generally, spikes are associated with runoff from areas surrounding the Maraehara River used for agriculture where animal waste and fertilisers runoff to the river. Although efforts have been made to try and reduce contamination by the implementation of more-comprehensive land-use practices, including fencing-off of stock from waterways, the bacteria levels still frequently exceed safe recreational limits (>260 cfu/100mL). During dry weather, E. coli levels in the creek are generally within acceptable limits; heavy rainfall events cause exceedances, which sometimes reach as high as 450 cfu/100mL.
Recommendation: Further riparian buffer zone development and runoff control should continue, especially above the impairment site.
2. Total Nitrogen (TN)
Trend: Lightly decreasing in the last 5-year period, with an overall 15% improvement.
Details: The water at this location has been experiencing a slow, steady increase in nitrogen levels. The mean concentration of total nitrogen in water decreased from the average in 2015 to approximately 1.2 mg/L by 2020. This may indicate that nutrient management, such as reduced fertiliser use and improved pasture management, is taking effect. Even with this improvement, nitrogen levels remain above the ideal ecological limit (<0.5 mg/L); thus, more needs to be done.
Recommendation: Given these findings, emphasis should continue to be placed on agricultural runoff reduction through best farm management practices, judicious use of fertilisers, and planting native vegetation along the river.
3. Dissolved Reactive Phosphorus (DRP)
Trend: Stable with minor fluctuation.
Details: The concentrations of DRP-a major nutrient contributing to algal blooms-have been fairly stable, about 0.03 mg/L. There are occasional peaks after heavy rain due to erosion and sediment runoff from agricultural lands. While it is just at the edge of the threshold, any increase may shift the balance in favour of unwanted algal growth. Maintenance of this stability indicates that the phosphorus management factor, such as reductions in fertiliser application near the river, has prevented further deterioration.
Recommendation: Continued phosphorus monitoring, coupled with erosion control to limit sediment and nutrient transport into the river.
4. Water Clarity (Turbidity)
Trend: Improvement - 20% better clarity
Details: There is some great improvement in water clarity at Te Araroa, especially during dry months. This indeed has come down from an average of about 8 NTU in 2010 to an average of around 6.5 NTU in recent years. Such improvement could be brought about by ongoing reforestation and erosion control measures, planting of native vegetation along riverbanks to reduce sediment runoff. However, during high rainfall events, turbidity still spikes as high as up to 20 NTU, which suggests that disturbance of land from forestry or agriculture upstream remains an issue.
Recommendation: Further effective sediment management up-stream, along with the maintenance of forest cover will be crucial in the future to sustain and, where possible, improve water clarity.
Maraehara River at Waikura Valley
Indicator
Average Value
Peak Value
Threshold/Standard
Trend (Last 5 Years)
E. coli (cfu/100mL)
130
320 (after rainfall)
< 260 for safe recreational use
Stable with occasional spikes
Total Nitrogen (mg/L)
0.9
1.3
Ideal: < 0.5
Slight improvement
Dissolved Reactive Phosphorus (mg/L)
0.02
0.04
Ideal: < 0.03
Improvement (by 10%)
Water Clarity (Turbidity) (NTU)
5.8 NTU
18 NTU (after heavy rains)
Ideal: < 5 NTU
Improvement (by 15%)
Key Observations:
Maraehara River at Waikura Valley - Water Quality Trends
1. E. coli Levels
Trend: Stable with spikes
Details: E. coli levels at Waikura Valley have remained largely stable; however, there are bacterial contamination spikes following rainfall, as was also the case in Te Araroa. While averages sit around 130 cfu/100mL, peak levels during storm events can go as high as 320 cfu/100mL. This would seem to indicate that runoff from agriculture is still a major contributor, particularly from grazing livestock. By contrast to the Te Araroa site, where minor improvements have taken place over time, this would appear more consistently impacted by land-use activities.
Recommendation: As it has in the past been for Te Araroa, the only means by which bacterial contamination can be reduced will be through a very strong riparian planting program and by keeping stock well away from waterways.
2. Total Nitrogen (TN)
Trend : Slight improvement (5 - 10% reduction in the last 5 years).
Details: Nitrogen levels in Waikura Valley are not as high as in Te Araroa, averaging about 0.9 mg/L but still above the ecological threshold of 0.5 mg/L. The lower values for this area probably indicate more stringent nutrient management practices upstream in the countryside catchment, including reduced applications of fertilisers. However, the gains have been minor, thus showing that additional measures in nutrient management will be needed to realise significant cuts.
This positive trend should be further supported through recommending precision agriculture techniques that minimise the use of fertilisers, as well as the promotion of sustainable land-use practices.
3. Dissolved Reactive Phosphorus (DRP)
Trend: Improving: 10% reduction
Description: DRP at Waikura Valley have been trending downwards at a constant rate of 10% over the previous five years. This trend is most likely the result of erosion control and reductions in phosphorus-based fertilisers on surrounding farmland. DRP levels have decreased from 0.03 mg/L to an average of 0.02 mg/L nearer to the optimum below which undue nutrient accumulation in the river is avoided. This trend is indicative that the local actions, including fencing from waterways and riparian planting are having a discernible effect.
Recommendation: The continued management of phosphorus, along with causing the prevention of soil erosion will be crucial for maintaining this trend
4. Water Clarity Turbidity
Trend: Improvement 15% better clarity.
Information: Waikura Valley has also been experiencing improvement in its water clarity within the last ten years. Its average turbidity decreases from 7 NTU to approximately 5.8 NTU, which is an improvement of about 15%. This may be attributed to sediment management involving strategies on reforestation and punging of forestry operations in sensitive areas. However, it goes high after heavy rain outfalls that bring sediments from upstream sites upward, indicating more functions of erosion control are needed.
Recommendation: Continued erosion control and sustainable forestry practices in the upstream catchments will help continue this trend and provide further reductions in turbidity.
Trend Analysis:
Maraehara River at Te Araroa: E. coli median value demonstrates variability between 2009 and 2013; however, improvements in nitrogen and clarity present good improvement toward an improved water quality state. Phosphorus does not indicate a significant trend but continues to demonstrate a stable state and thus requires continued monitoring.
Maraehara River at Waikura Valley: Although there are slight improvements in nitrogen and phosphorus, along with clarity, land management practices seem to be effective; E. coli still remains a problem after rainfall. Improvements in both sites can be seen, but further improvements in practice will be required to maintain nutrient runoff and bacterial contamination during wet periods. For long-term improvement in water quality, active monitoring and continued conservation are required.
External References:
Nga Wai o Waiapu Waiapu Catchment Plan
Water data for lakes, rivers and swimming spots from LAWA
Poroporo River at Rangitukia
1. E. coli:
- State: Classified within the best 50% of all sites indicates a relatively good water quality concerning E. coli contamination when compared to other sites nationwide.
- Trend: The 'very likely improving' trend suggests effective management practices or natural recovery processes that have resulted in lower E. coli counts over the past five years.
- 5-year median: The median concentration of 130 cfu/100ml over the past five years provides a baseline against which recent improvements are measured.
- Clarity:
- State: Ranking in the worst 25% of all sites implies significant issues with water clarity, possibly due to land use activities such as agriculture or deforestation upstream.
- Trend: The lack of assessment on the trend suggests insufficient data or inconsistent monitoring intervals that make it challenging to establish a clear trend.
- 5-year median: A median clarity measure of 0.61 metres indicates fairly turbid conditions.
- Turbidity:
- State: Similar to clarity, being in the worst 25% for turbidity highlights ongoing challenges with suspended particles in the water.
- Trend: The 'likely improving' trend is a positive sign, indicating some recovery or successful mitigation efforts affecting turbidity levels.
- 5-year median: A median turbidity of 24 NTU (Nephelometric Turbidity Units) is relatively high, which supports the poor ranking but also pairs with an improving trend.
- Total Nitrogen & Related Compounds:
- States: Generally, the site performs well (in the best 25% for most nitrogen measures), suggesting low levels of nitrogen pollution, which is favourable for maintaining aquatic health.
- Trends: Not assessed for most nitrogen parameters, indicating either a lack of consistent data over the period or that changes have not been significant enough to establish clear trends.
- Median Values: Low median values across nitrogen indicators reflect a site with traditionally low nitrogen contamination, which is beneficial for aquatic ecosystems and correlates with less agricultural runoff or effective nitrogen management.
- Ammoniacal Nitrogen:
- State: Being in the worst 50% indicates higher levels of ammoniacal nitrogen, which could be due to localised pollution sources such as wastewater discharge.
- Trend: The 'very likely improving' trend is encouraging, suggesting interventions or natural processes are reducing this pollutant over time.
- Dissolved Reactive Phosphorus & Total Phosphorus:
- State: Placed in the best 50%, these measures suggest moderate levels of phosphorus, which could stem from both natural sources and human activity.
- Trend: The 'very likely degrading' trend for dissolved reactive phosphorus is a concern, indicating increasing levels that could lead to eutrophication and harmful algal blooms if not addressed.
- Median Values: The median levels are low but rising phosphorus levels could disrupt the aquatic ecosystem balance, prompting the need for monitoring and potential intervention.
Water Quality Statistics for Maraehara River Testing Locations
1. Maraehara River at Te Araroa
Indicator
Average Value
Peak Value
Threshold/Standard
Trend (Last 5 Years)
E. coli (cfu/100mL)
175
450 (after rainfall)
< 260 for safe recreational use
Fluctuating
Total Nitrogen (mg/L)
1.2
1.8
Ideal: < 0.5
Slight decline (by 15%)
Dissolved Reactive Phosphorus (mg/L)
0.03
0.05
Ideal: < 0.03
Stable with minor fluctuation
Water Clarity (Turbidity) (NTU)
6.5 NTU
20 NTU (after heavy rains)
Ideal: < 5 NTU
Improvement (by 20%)
Key Observations:
- E. coli levels remain a concern, with spikes following rainfall events indicating runoff contamination from nearby agricultural areas.
- Total Nitrogen levels have shown some improvement due to better land management practices, though they remain above ideal ecological thresholds.
- Water Clarity has improved significantly, particularly in dry months, thanks to increased riparian planting and erosion control efforts.
Maraehara River at Te Araroa - Trends in Water Quality
1. E. coli Levels
Trend: Fluctuating with occasional spikes.
Details: Over the last five years, the levels of E. coli have shown major fluctuations, sometimes after rainfall. Generally, spikes are associated with runoff from areas surrounding the Maraehara River used for agriculture where animal waste and fertilisers runoff to the river. Although efforts have been made to try and reduce contamination by the implementation of more-comprehensive land-use practices, including fencing-off of stock from waterways, the bacteria levels still frequently exceed safe recreational limits (>260 cfu/100mL). During dry weather, E. coli levels in the creek are generally within acceptable limits; heavy rainfall events cause exceedances, which sometimes reach as high as 450 cfu/100mL.
Recommendation: Further riparian buffer zone development and runoff control should continue, especially above the impairment site.
2. Total Nitrogen (TN)
Trend: Lightly decreasing in the last 5-year period, with an overall 15% improvement.
Details: The water at this location has been experiencing a slow, steady increase in nitrogen levels. The mean concentration of total nitrogen in water decreased from the average in 2015 to approximately 1.2 mg/L by 2020. This may indicate that nutrient management, such as reduced fertiliser use and improved pasture management, is taking effect. Even with this improvement, nitrogen levels remain above the ideal ecological limit (<0.5 mg/L); thus, more needs to be done.
Recommendation: Given these findings, emphasis should continue to be placed on agricultural runoff reduction through best farm management practices, judicious use of fertilisers, and planting native vegetation along the river.
3. Dissolved Reactive Phosphorus (DRP)
Trend: Stable with minor fluctuation.
Details: The concentrations of DRP-a major nutrient contributing to algal blooms-have been fairly stable, about 0.03 mg/L. There are occasional peaks after heavy rain due to erosion and sediment runoff from agricultural lands. While it is just at the edge of the threshold, any increase may shift the balance in favour of unwanted algal growth. Maintenance of this stability indicates that the phosphorus management factor, such as reductions in fertiliser application near the river, has prevented further deterioration.
Recommendation: Continued phosphorus monitoring, coupled with erosion control to limit sediment and nutrient transport into the river.
4. Water Clarity (Turbidity)
Trend: Improvement - 20% better clarity
Details: There is some great improvement in water clarity at Te Araroa, especially during dry months. This indeed has come down from an average of about 8 NTU in 2010 to an average of around 6.5 NTU in recent years. Such improvement could be brought about by ongoing reforestation and erosion control measures, planting of native vegetation along riverbanks to reduce sediment runoff. However, during high rainfall events, turbidity still spikes as high as up to 20 NTU, which suggests that disturbance of land from forestry or agriculture upstream remains an issue.
Recommendation: Further effective sediment management up-stream, along with the maintenance of forest cover will be crucial in the future to sustain and, where possible, improve water clarity.
Maraehara River at Waikura Valley
Indicator
Average Value
Peak Value
Threshold/Standard
Trend (Last 5 Years)
E. coli (cfu/100mL)
130
320 (after rainfall)
< 260 for safe recreational use
Stable with occasional spikes
Total Nitrogen (mg/L)
0.9
1.3
Ideal: < 0.5
Slight improvement
Dissolved Reactive Phosphorus (mg/L)
0.02
0.04
Ideal: < 0.03
Improvement (by 10%)
Water Clarity (Turbidity) (NTU)
5.8 NTU
18 NTU (after heavy rains)
Ideal: < 5 NTU
Improvement (by 15%)
Key Observations:
- Phosphorus levels have shown a noticeable improvement, likely due to successful buffer planting and nutrient control measures in the area.
- Nitrogen and clarity both reflect minor improvements over the past five years, although further efforts are needed to sustain these gains.
Maraehara River at Waikura Valley - Water Quality Trends
1. E. coli Levels
Trend: Stable with spikes
Details: E. coli levels at Waikura Valley have remained largely stable; however, there are bacterial contamination spikes following rainfall, as was also the case in Te Araroa. While averages sit around 130 cfu/100mL, peak levels during storm events can go as high as 320 cfu/100mL. This would seem to indicate that runoff from agriculture is still a major contributor, particularly from grazing livestock. By contrast to the Te Araroa site, where minor improvements have taken place over time, this would appear more consistently impacted by land-use activities.
Recommendation: As it has in the past been for Te Araroa, the only means by which bacterial contamination can be reduced will be through a very strong riparian planting program and by keeping stock well away from waterways.
2. Total Nitrogen (TN)
Trend : Slight improvement (5 - 10% reduction in the last 5 years).
Details: Nitrogen levels in Waikura Valley are not as high as in Te Araroa, averaging about 0.9 mg/L but still above the ecological threshold of 0.5 mg/L. The lower values for this area probably indicate more stringent nutrient management practices upstream in the countryside catchment, including reduced applications of fertilisers. However, the gains have been minor, thus showing that additional measures in nutrient management will be needed to realise significant cuts.
This positive trend should be further supported through recommending precision agriculture techniques that minimise the use of fertilisers, as well as the promotion of sustainable land-use practices.
3. Dissolved Reactive Phosphorus (DRP)
Trend: Improving: 10% reduction
Description: DRP at Waikura Valley have been trending downwards at a constant rate of 10% over the previous five years. This trend is most likely the result of erosion control and reductions in phosphorus-based fertilisers on surrounding farmland. DRP levels have decreased from 0.03 mg/L to an average of 0.02 mg/L nearer to the optimum below which undue nutrient accumulation in the river is avoided. This trend is indicative that the local actions, including fencing from waterways and riparian planting are having a discernible effect.
Recommendation: The continued management of phosphorus, along with causing the prevention of soil erosion will be crucial for maintaining this trend
4. Water Clarity Turbidity
Trend: Improvement 15% better clarity.
Information: Waikura Valley has also been experiencing improvement in its water clarity within the last ten years. Its average turbidity decreases from 7 NTU to approximately 5.8 NTU, which is an improvement of about 15%. This may be attributed to sediment management involving strategies on reforestation and punging of forestry operations in sensitive areas. However, it goes high after heavy rain outfalls that bring sediments from upstream sites upward, indicating more functions of erosion control are needed.
Recommendation: Continued erosion control and sustainable forestry practices in the upstream catchments will help continue this trend and provide further reductions in turbidity.
Trend Analysis:
Maraehara River at Te Araroa: E. coli median value demonstrates variability between 2009 and 2013; however, improvements in nitrogen and clarity present good improvement toward an improved water quality state. Phosphorus does not indicate a significant trend but continues to demonstrate a stable state and thus requires continued monitoring.
Maraehara River at Waikura Valley: Although there are slight improvements in nitrogen and phosphorus, along with clarity, land management practices seem to be effective; E. coli still remains a problem after rainfall. Improvements in both sites can be seen, but further improvements in practice will be required to maintain nutrient runoff and bacterial contamination during wet periods. For long-term improvement in water quality, active monitoring and continued conservation are required.
External References:
Nga Wai o Waiapu Waiapu Catchment Plan
Water data for lakes, rivers and swimming spots from LAWA