Estuarine water quality

Every month we are out in the Waikato region collecting water samples in estuaries to keep an eye on estuary water quality.

Our current programme started in October 2017 at Whāingaroa (Raglan) and Tairua Harbours and has expanded since then to also include Kawhia Harbour (since 2019), and the Firth of Thames (since 2020).

We collect samples from multiple locations within each estuary to look at where water from the catchment enters the estuary and how it is mixed and diluted by the oceanic water. Water samples are analysed for a range of parameters including:

• temperature
• salinity
• pH
• dissolved oxygen
• nutrients
• chlorophyll a (algal growth)
• suspended sediment
• faecal indicator bacteria

Together these parameters help us understand the estuaries’ capacity to support life such as fish, shellfish, seaweeds.

The coastal environment is dynamic, which means the water quality can change a lot over short periods of time. Water quality also changes between seasons and is affected by events such as heavy rainfall or storms. For these reasons, it is important for us to consider the water quality over several years, rather than just looking at individual sampling occasions.