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.
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.
Floating mats of the cyanobacteria Lyngbya sp. in an isolated section of the Maketu-Ongatoro Estuary. Reducing this cover of algae is one reason for the Kaituna River Re-Diversion Project (Bay of Plenty Regional Council).