How much nitrogen is too much nitrogen to avoid prolific periphyton growth in the Manawatu River?
We ran an experiment in 2019 to help answer this question for Palmerston North City Council. Here is our 2019 experimental setup.
River Lake has been working with Palmerston North City Council for many years to help understand and reduce the effects of the Tōtara Road wastewater treatment plant (WWTP).
We have undertaken monitoring of aquatic macroinvertebrates, periphyton, water quality, and diurnal fluctuation in dissolved oxygen. We have also undertaken investigations and experiments to understand river processes.
Learn about the role of nutrients in driving excessive periphyton growth in the Manawatu River, and how periphyton mine phosphorus from fine sediment captured within their mats. Click the link below:
In 2017 PNCC initiated a Best Practical Option (BPO) review of how to improve the treatment and disposal of wastewater in the future. River Lake is part of a team assisting with this process.
Here is our 2019 experimental setup to assess what concentrations of nitrogen are required to control periphyton growth in the Manawatu River.
A newly made stream diversion on the Huntly Bypass Project, in November 2016, and two years later in 2019 after plants have grown.
What is the phosphorus load to Lake Rotorua and how much comes from human activity?
River Lake revised estimates of P loads to Lake Rotorua to account for groundwater catchment areas, geothermal inputs and long-term average loads.
This work contributed to the Science Review required by Plan Change 10 of the Bay of Plenty Regional Water and Land Plan (RWLP).
Read the report here:
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.
View River Lakes Assessment of Effects for the Project here: Kaituna Maketu current state aquatic
River Lake contributed to the Lagoon Technical Group (LTG) and Catchment Technical Group (CTG) advising Southland Regional Council on interventions to protect and restore Waituna Lagoon.
Waituna Lagoon is a highly valued, large brackish coastal lagoon and a wetland of international importance (Ramsar site). Ruppia (seagrass) is a key stone species central to the ecological functioning, of the lagoon. It is threatened by nuisance filamentous algae, sedimentation, an an opening regime that can increase salinity when the seagrass is germinating.
Our work included:
Find the report here: Waituna lagoon Guidelines
Pristine kahikatea swamp forest on the Mimi River in Taranaki. Home to giant kōkopu, banded kōkopu, redfin bully and longfin eel.
Setting nutrient limits for complex ecosystems is challenging. We used multiple lines of evidence to set robust nutrient limits to safeguard the macrophyte community in Waituna Lagoon.
Read more in our paper on setting nutrient limits for lakes (click the link below).
Large longfin eel caught when sampling in Donald Creek near Featherston Wastewater Treatment Plant.
