Category Archives: Maketū Estuary

Kaituna River Mixing Study

River Lake studied the mixing of diagonal drain pump station with the lower Kaituna River. We used Rhotomine dye WT to understand how well the pump station discharge mixed across the Kaituna River before the intake for the new diversion to Maketū Estuary.

The work was done for Bay of Plenty Regional Council rivers and drainage team.

Rhodamine WT dye entering the Kaituna River from the Diagonal Drain pump station, 2.3 km upstream from the river mouth (9 Nov 2017). Photo by Andy Belcher.
Lower Kaituna River facing towards Maketū Estuary. The borrow pits are visible on the true right of the river. At this location discharges from Diagonal Drain had mixed across 50% to 70% of the river, depending on the tide (9 November 2017). Photo by Andy Belcher.

Kaituna River re-diversion

The Ongatoro/Maketū estuary is a shallow, inter-tidal estuary located north of Te Puke. In 1957 the Kaituna River was diverted directly to sea and the influence of the river on the estuary was dramatically reduced. This resulted in accelerated in-filling from the
flood tide delta, loss of mussel beds, loss of wetlands and sea grass, algal accumulations and changes in the benthic fauna. The project sought to re-divert more of the river back into the estuary to improve the ecology and mauri.

River Lake provided science and planning input for the application to re-divert the Kaituna River back to the Ongatoro/Maketū Estuary. Keith co-ordinated and led the science input related to water quality and ecology. He jointly prepared a gap analysis,  undertook investigations, prepared AEE reports relating to water quality and ecology and presented at the Consent Hearing and the the Environment Court.

Water quality and biota are strongly influenced by internal nutrient loads (e.g. sediments). An important part of the investigations was to quantify the likely internal loads compared to external loading predicted by the hydro-dynamic model. This involved measuring oxygen regimes and mapping algal accumulations.

View River Lakes Assessment of Effects for the Project here:  Kaituna Maketu current state aquatic