Lets Be Clear

In 2023, a ground-breaking report detailing how and why the pristine water coming from Lake Taupo is being degraded as it passes from Taupo Gates through to Hamilton City, was released. This report (SAS202272023), commissioned by Waikato Regional Council used comprehensive water quality and flow data to define previously unknown causes of water quality change and to indicate how they then impacted river health. The data showed the river and hydro lakes as active rapid bioreactors responding biologically and physically to the influence’s nature and man applied to it. The field data was provided by 6 of DCM Process Control's monitoring stations, Hamilton City's water intake and Mercury's dam flow measurements. DCM, HCC and Mercury are significant technology or data contributors to Let’s Be Clear. 

The study extends an earlier evaluation of a 2005-2019 UV/Vis data set provided by Hamilton City Council measured at the Waikato River intake of their Peacockes’ Rd water treatment plant. Completed in 2021, this study looked at the potential of real time UV/Vis spectrophotometry to provide WRC ecologists with an increased understanding of the dynamics in Waikato River nutrient concentrations, in particular nitrate, that is not available from the historic WRC State Of the Environment grab sampling record.

The clear outcome of both reports was

• The real time data clearly indicated previously unknown repeating events linked to rain events along with patterns of change linked to controllable human activity.
• The inter-relationships between water quality parameters and between consecutive monitoring stations along the river/lake system allowed visibility of cause and effect and an understanding of the relativity of one parameter to another.
• The establishment of the ability to track events passing along the system and determine the appearance of new events between stations.
• Indications of previously theorised and other unknown hydraulic and stratified water conditions in lakes believed to not stratify.  
• An indication that the Upper Waikato is in effect a living being in a state of constant and predictable change defined by varying natural and human activity induced drivers.

WRC contributed to the work through the commissioning of the report and the through the testing of grab samples to validate the online measurements.

While outside the scope of the report, the relevance of the newly available data to comprehensive dynamic modelling and its potential role in meeting the 2010 Crown -Waikato Tainui commitment to the Waikato River Health is discussed.

The Monitoring Technology

The technology used to obtain the raw data for the report has been in use in this form since 2005. Over 200 systems have been deployed by DCM Process Control on New Zealand and Australian municipal and industrial water and wastewater treatment plants during that period.

Most installations such as at Hamilton and Tuakau Water Treatment Plants (WTP) were installed for inlet event detection, treatment process optimisation, and/or coagulant dose guidance. Whether the treatment occurs within the water treatment plant, or we take action to prevent or reduce its occurrence at source is the only change. Measurement frequencies of 2 to 10 minutes have proven beneficial in even river and hydro lake applications monitoring applications. This is not guessed at or theorised. It is defined by the rate of water quality change experienced in each application during “events”.

Despite the importance of the Waikato River to the wellbeing of a very large proportion of New Zealand’s population and the significant historic research into almost all facets of tributary and in lake processes, very little of this research has involved the collection of real time data.

These previous studies and the data collected were not intended for us in dynamic modelling of the river and due to the lack of ability to interlink these studies or their data with other work, a comprehensive understanding of the river and its systems is not available from them.

The SOE data is unable to provide sufficient contextually relevant information to build or drive a dynamic model and is intended only to provide long term quality change indications over many years. The lack of dynamic modelling for the Waikato was raised as an information gap in the 2010 edition of the book “The Waters Of The Waikato”. It is a comprehensive summary of historic technical work on the Waikato River over many years. It was the content of this book, and the knowledge gaps it defines that was the inspiration for the formation of Let’s Be Clear Charitable Trust. Professor David Hamilton – a Let’s Be Clear Trust trustee- was a co-author of this book. It is available at public libraries at no cost and well worth reading.  

The full report and the report Executive Summary is linked here with permission from Waikato Regional Council.