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Lake Rotokawau (Pouto) at centre

Water Quality
Water quality data for this site
Can I trust this data?

This dashboard shows information on the data collected by the regional councils and unitary authorities for water quality indicators, analysed as state and trend. Select an indicator to see the historical monitoring data.

  • State

    The state is represented by attribute bands in the National Policy Statement for Freshwater Management 2020 for most indicators.

  • Trend

    Trend shows how the quality of water is changing over time. Depending on the sampling history duration, five, ten and fifteen year timescales are available:

Can I trust this data?

The Cawthron Institute has worked alongside regional councils to verify the processes and methods used for data collection, laboratory analysis of samples collected, quality assurance and the statistical analysis and interpretation of the results presented.

For more details on each tick, see our 'Can I Trust This Data?' Factsheet.

Can I trust the data for this site?
Data Collection

Lake water quality is being monitored in this region. Davies-Colley et al. (2012) suggest that all councils should monitor lake water quality as part of their State of the Environment Monitoring Programmes, if lakes occur in the region.

State - Sampling

All samples were collected using approved field protocols and have been analysed in accredited laboratories.

State - Quality Assurance - Data Processing

Data at this site has had some form of data processing measures applied. Therefore, the data shown here are more robust than data with no data processing applied.

State - Quality Assurance - Quality Coding

Data shown here hasn’t had any kind of quality coding applied. Therefore, the data shown here is less robust than quality coded data.

Trend - Sampling Frequency

Samples are collected quarterly at this site. Proposed national guidelines suggest monthly sampling is required for robust trend analysis. Therefore, any trends shown here are less robust than those calculated from data collected monthly.

Phosphorus

Total Phosphorus
{{medianHeading('TP')}} {{medianValue('TP')}}
State
{{TP.StateScore | uppercase}}
{{stateMsg('TP', TP.StateScore)}}
N/A
{{stateMsg('TP', TP.StateScore)}}
Trend
{{trendMsg('TP', TP)}}

Total Phosphorus sample history at this site

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Total Phosphorus samples for Lake Rotokawau (Pouto) at centre
mg/m³
Date

What is this graph showing me?

This graph is displaying Total Phosphorus concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for Total Phosphorus are as outlined in the National Policy Statement for Freshwater Management 2020:

A
Lake ecological communities are healthy and resilient similar to natural reference conditions
B
Lake ecological communities are slightly impacted by additional algal and plant growth arising from nutrients levels that are elevated above natural conditions
C
Lake ecological communities are moderately impacted by additional algal and plant growth arising from nutrients levels that are elevated well above natural reference conditions
National bottom line: Annual median 50 mg/m³
D
Lake ecological communities have undergone or are at high risk of a regime shift to a persistent, degraded state, due to impacts of elevated nutrients leading to excessive algal growth and/or plant growth, as well as from losing oxygen in bottom waters of deep lakes
 Download data

Nitrogen

Nitrogen

Total Nitrogen
{{medianHeading('TN')}} {{medianValue('TN')}}
State
{{TN.StateScore | uppercase}}
{{stateMsg('TN', TN.StateScore)}}
N/A
{{stateMsg('TN', TN.StateScore)}}
Trend
{{trendMsg('TN', TN)}}

Total Nitrogen sample history at this site

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Total Nitrogen samples for Lake Rotokawau (Pouto) at centre
mg/m³
Date

What is this graph showing me?

This graph is displaying Total Nitrogen concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for Total Nitrogen are as outlined in the National Policy Statement for Freshwater Management 2020:

A
Lake ecological communities are healthy and resilient similar to natural reference conditions
B
Lake ecological communities are slightly impacted by additional algal and plant growth arising from nutrients levels that are elevated above natural conditions
C
Lake ecological communities are moderately impacted by additional algal and plant growth arising from nutrients levels that are elevated well above natural reference conditions
National bottom line: 750 mg/m³ for seasonally stratified and brackish lakes. 800 mg/m³ for polymictic lakes.
D
Lake ecological communities have undergone or are at high risk of a regime shift to a persistent, degraded state, due to impacts of elevated nutrients leading to excessive algal growth and/or plant growth, as well as from losing oxygen in bottom waters of deep lakes
 Download data

Nitrogen

Ammoniacal Nitrogen
{{medianHeading('NH4N')}} {{medianValue('NH4N')}}
State
{{NH4N.StateScore | uppercase}}
{{stateMsg('NH4N', NH4N.StateScore)}}
N/A
{{stateMsg('NH4N', NH4N.StateScore)}}
Trend
{{trendMsg('NH4N', NH4N)}}

Ammoniacal Nitrogen sample history at this site

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Ammoniacal Nitrogen samples for Lake Rotokawau (Pouto) at centre
mg NH4-N/l
Date

What is this graph showing me?

This graph is displaying Ammoniacal Nitrogen concentrations over the selected time period.  These monitoring data have not been pH adjusted.  You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for Ammonia (toxicity) are as outlined in the National Policy Statement for Freshwater Management 2020:

A
99% species protection level: No observed effect on any species tested
B
95% species protection level: Starts impacting occasionally on the 5% most sensitive species
National bottom line: Annual median 0.24 mg NH4-N/L. Annual 95th percentile 0.40 mg NH4-N/L (milligrams ammoniacal-nitrogen per litre).
C
80% species protection level: Starts impacting regularly on the 20% most sensitive species (reduced survival of most sensitive species)
D
Starts approaching acute impact level (ie risk of death) for sensitive species
 Download data

Algae

Algae

Chlorophyll a
{{medianHeading('CHLA')}} {{medianValue('CHLA')}}
State
{{CHLA.StateScore | uppercase}}
{{stateMsg('CHLA', CHLA.StateScore)}}
N/A
{{stateMsg('CHLA', CHLA.StateScore)}}
Trend
{{trendMsg('CHLA', CHLA)}}

Chlorophyll a sample history at this site

Showing:
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Chlorophyll a samples for Lake Rotokawau (Pouto) at centre
mg/m³
Date

What is this graph showing me?

This graph is displaying Chlorophyll a concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for Chlorophyll a are as outlined in the National Policy Statement for Freshwater Management 2020:

A
Lake ecological communities are healthy and resilient, similar to natural reference conditions
B
Lake ecological communities are slightly impacted by additional algal and/or plant growth arising from nutrient levels that are elevated above natural conditions
C
Lake ecological communities are moderately impacted by additional algal and plant growth arising from nutrient levels that are elevated well above natural reference conditions. Reduced water clarity is likely to affect habitat available for native macrophytes
National bottom line: Annual median 12 mg/m³. Annual maximum 60 mg/m³.
D
Lake ecological communities have undergone or are at high risk of a regime shift to a persistent, degraded state (without native macrophyte/seagrass cover), due to impacts of elevated nutrients leading to excessive algal and/or plant growth, as well as from losing oxygen in bottom waters of deep lakes
 Download data

Algae

Cyanobacteria
{{medianHeading('CYANOTOT')}} {{medianValue('CYANOTOT')}}
State
{{CYANOTOT.StateScore | uppercase}}
{{stateMsg('CYANOTOT', CYANOTOT.StateScore)}}
N/A
{{stateMsg('CYANOTOT', CYANOTOT.StateScore)}}
Trend
{{trendMsg('CYANOTOT', CYANOTOT)}}

Cyanobacteria sample history at this site

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Cyanobacteria samples for Lake Rotokawau (Pouto) at centre
mm³/l
Date

What is this graph showing me?

This graph is displaying Cyanobacteria concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for Cyanobacteria are as outlined in the National Policy Statement for Freshwater Management 2020:

A
Risk exposure from cyanobacteria is no different to that in natural conditions (from any contact with fresh water)
B
Low risk of health effects from exposure to cyanobacteria (from any contact with fresh water)
C
Moderate risk of health effects from exposure to cyanobacteria (from any contact with fresh water)
National bottom line: 80th percentile = 1.8 mm³/L biovolume equivalent of potentially toxic cyanobacteria OR 10 mm³/L total biovolume of all cyanobacteria.
D
High health risks (eg, respiratory, irritation and allergy symptoms) exist from exposure to cyanobacteria (from any contact with fresh water)
 Download data

Clarity

Secchi disc depth
{{medianHeading('SECCHI')}} {{medianValue('SECCHI')}}
State
{{SECCHI.StateScore | uppercase}}
{{stateMsg('SECCHI', SECCHI.StateScore)}}
N/A
{{stateMsg('SECCHI', SECCHI.StateScore)}}
Trend
{{trendMsg('SECCHI', SECCHI)}}

Secchi disc depth sample history at this site

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Secchi disc depth samples for Lake Rotokawau (Pouto) at centre
metres
Date

What is this graph showing me?

This graph is displaying Secchi disc depth measurements over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The grades for Secchi disc depth are defined as follows:

A
Water clarity is greater than 7 metres in depth
B
Water clarity is greater than 3 metres and less than 7 metres in depth
C
Water clarity is greater than 1 metre and less than 3 metres in depth
D
Water clarity is less than 1 metre in depth
 Download data

Bacteria

E. coli
{{medianHeading('ECOLI')}} {{medianValue('ECOLI')}}
State
{{ECOLI.StateScore | uppercase}}
{{stateMsg('ECOLI', ECOLI.StateScore)}}
N/A
{{stateMsg('ECOLI', ECOLI.StateScore)}}
Trend
{{trendMsg('ECOLI', ECOLI)}}

E. coli sample history at this site

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E. coli samples for Lake Rotokawau (Pouto) at centre
n/100ml
Date

What is this graph showing me?

This graph is displaying E. coli concentrations over the selected time period. You can adjust this period by changing the dropdowns. These records form the basis for the state and trend indicators displayed on the dashboard. 

Find out about how State and Trend are calculated.

What do the attribute band icons mean?

The bands for E. coli are as outlined in the National Policy Statement for Freshwater Management 2020:

A
For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 1%*.
B
For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 2%*.
C
For at least half the time, the estimated risk is <1 in 1000 (0.1% risk). The predicted average infection risk is 3%*.
D
20-30% of the time, the estimated risk is >=50 in 1000 (>5% risk). The predicted average infection risk is >3%*.
E
For more than 30% of the time, the estimated risk is >=50 in 1000 (>5% risk). The predicted average infection risk is >7%*.
* The predicted average infection risk is the overall average infection to swimmers based on a random exposure on a random day, ignoring any possibility of not swimming during high flows or when a surveillance advisory is in place (assuming that the E. coli concentration follows a lognormal distribution). Actual risk will generally be less if a person does not swim during high flows.
 Download data
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