Water quality

Usage guide: Toggle between tabs to see different water quality data summaries. Hover over charts to see specific values. Either click and drag a chart to zoom in on a time period of interest or use the green range selector below the chart to scroll through time and expand/shrink the time window displayed. Hover over legend entries to highlight that series and click on legend entries to hide/show those series.

Integrated buoy observations

Wellington Regional Integrated Buoy Observations (WRIBO) has been monitoring Te Whanganui-a-Tara/Wellington Harbour for the period 13 July 2017 to 11 July 2022. Measurements are obtained at 1, 5, and 10 m depths below the water surface.

Key processes in Wellington Harbour include river influence and tidal flows as measured by the Acoustic Doppler Current Profiler (ADCP). Results indicate that river plumes flowing from the Hutt River are generally less than 5 m thick and persist for at least five days after peak discharge. Interestingly, sediment transport may be modified for weeks to months after an event. Data have also indicated that events occur during all seasons.

Most recent data are available at the GW live data viewer. Note that gaps in the data are due to periods of repair and maintenance where either the whole WRIBO array or instruments attached to the array were removed from the water for instrument calibration or replacement.

In the figure captions, WRIBO data refers to continuous telemetered readings from the coastal buoy. Te Awa Kairangi (Hutt River) flow, turbidity and rainfall (Taita Gorge, Melling Bridge and Shandon Golf Club) are continuously monitored using telemetered instrumentation permanently installed onsite. See the overview map for locations of sampling sites.

  • Ocean turbidity, measured in Nephelometric Turbidity Units (NTU), is produced by particles suspended in the water column which decreases sea water clarity and can impair water quality for aquatic and human life. Optical backscatter β(650nm), shown per metre-angle (/m/sr), is another measure of particles present in seawater, which can include sediment, organic matter and microorganisms.
  • Chlorophyll a biomass, presented in milligrams per cubic meter (mg/m3), indicates the amount of phytoplankton present in the water. Very high Coloured Dissolved Organic Matter (CDOM) readings, displayed in parts per billion (ppb), can reduce sea water clarity and inhibit phytoplankton growth.
  • Dissolved oxygen data are presented in micrograms per litre (μ/L) with concentrations typically decreasing with an increase in nutrients and organic matter (e.g. from urban stormwater, sewage discharges, and rural runoff from farmland). Excessive algae growth and decay in response to increasing nutrients can significantly affect the amount of dissolved oxygen available to organisms.
  • The temperature and salinity (saltiness) of marine waters are used to calculate density, which plays an important role in determining where water flows and where species are distributed.
  • Water temperature varies with depth and was measured from the surface buoy down to mid-water (10 m), which allows us to identify sharp thermoclines or uniform conditions.
  • Ocean values of salinity are typically around 35 psu. Decreases in salinity indicate the presence of river water in Te Whanganui-a-Tara/Wellington Harbour. At times salinity observations, presented in practical salinity units (psu), decrease to around 20 psu after large amounts of rainfall.
Turbidity

Note that telemetered and discrete measurements at WRIBO and those taken at the Hutt River are displayed in different units, NTU and FNU respectively, but these units are essentially the same in value (1 NTU ≈ 1 FNU). Additionally, WRIBO turbidity measurements are device constrained to less than 100 NTU while actual values could be higher.

Hutt River flow
Chlorophyll a biomass

Note that only data between zero and five mg/m3 are shown. Higher values could be observed but are typically less reliable from ocean water quality sensors.

Coloured dissolved organic matter (CDOM)

Note that only data between zero and five ppb are shown. Higher values could be observed but are typically less reliable from ocean water quality sensors.

Dissolved oxygen concentration
Salinity
Water temperature
Hutt River rainfall

Wind and currents

Wind and water currents summarised by average direction and speed from 2017 to 2022. Hover over charts to see specific values. Toggle between tabs to see averages for different seasons/depths. Hover over legend entries to highlight that series and click on legend entries to hide/show those series and focus in on particular speed brackets.

Wind speed and direction
Annual
Winter
Spring
Summer
Autumn
Water current speed and direction
1m
5m
10m
15m
20m


Waverider buoys

Three waverider buoys have been monitoring Te Whanganui-a-Tara/Wellington Harbour since 09 June 2020 with the charts below summarising key monitoring variables. Most recent data for each buoy are available through the GW live data viewer:

Water temperature
Wave height
Wave direction