Initial results follow Mangawhai water testing

A preliminary water testing programme has been undertaken in Mangawhai over the past six months.

Water sampling was undertaken at six sites to identify issues affecting harbour water quality and to assist in identifying remedial actions to improve water quality in the harbour.

Sondes (buoys) were also placed in the estuary by Northland Regional Council (NRC) to monitor turbidity, salinity, pH, rain levels and temperature.

Results from both water testing and the sondes have been analysed but are still to be fully interpreted.

Preliminary findings, however, show that there are trends which will help guide further more targeted testing and recommended actions.

As the sampling programme is still underway no detailed analysis of the data has been undertaken, however, it is clear there is a major contrast in nutrient loadings between the pasture catchments and the forest stream, and that major rainfall events cause sharp increases in nutrients and suspended solids from all catchments.

Once full scientific interpretation has taken place, the next step will be to determine remedial actions at a catchment level to help improve water quality, such as fencing streams and riparian planting.

The study aims to compare water quality from the two major catchments emptying into the harbour by sampling at the Insley Street bridge and the Molesworth Drive causeway.

Two smaller sub-catchments were also sampled at Devich Road and Cove Road bridges.

Data from these largely pastoral catchments will be compared with samples from the Tanekaha Stream where it emerges from its fully forested Brynderwyn catchment.

It is hoped the results will not only show how water quality from developed catchments differs from that of a fully forested catchment, but also identify the priority areas for remedial action.

This initiative has been made possible with the efforts of the Community Advisory Group (who undertook the water sampling as well as advising the Project Team), Te Uri o Hau, Northland Regional Council and Kaipara District Council.

This initiative has acted as a catalyst to a new monthly water testing programme which is being undertaken by Northland Regional Council.

The more-intensive new monthly testing programme will provide significantly more information than NRC’s current regime and supports the work undertaken in the preliminary programme.

TESTING: Members of the Council water sampling team at the Devich Road sampling location during a weather event.