River Lake has been working with Bay of Plenty Regional Council to complete a report on the state and trends of water quality in Bay of Plenty rivers.
Over the ten year period 2009 to 2018 the Bay of Plenty river monitoring sites have shown overall worsening trends for total phosphorus (TP), dissolved reactive phosphorus (DRP) and nitrate (NNN); but overall improving trends for absorbance (A440), total ammonia (NH4-N) and electrical conductivity.
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.
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.
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:
Analysing water quality state and trends;
Assessing the risk of the lagoon ‘flipping’ to a dirty water state;
Contributing the the development of lagoon guidelines with quality targets for lagoon health, and management options.
Keith at River Lake coordinated an expert panel to develop possible attributes and thresholds relevant to the ecosystem health of Intermittently Closed and Open Lakes and Lagoons (ICOLLs) and brackish lakes.
The work was undertaken for Ministry for the Environment to support the National Objectives Framework (NOF) in the National Policy Statement for Freshwater Management (NPS-FM).