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Water Quality Monitoring Reports – Q1 2023

Water Quality Monitoring Report – First Quarter 2023 (January to March)

Opuha Water Ltd publishes its quarterly water quality reports for Lake Opuha and the wider scheme catchment to share with the community the results of our extensive water quality monitoring program.

OWL takes an active role in growing community understanding of the many influences on these dynamic freshwater environments within its scheme area. The company is committed to informing and involving the community in the work OWL does to understand and protect this vital, shared asset.

Publishing quarterly water quality reports shows that Opuha is taking water quality management seriously, and demonstrates leadership in the district’s collective responsibility for protecting and improving the mauri (life force, vitality) of te taiao (the environment) in the catchment area.

Findings of interest include:

Rain events resulted in elevated turbidity in Lake Opuha with turbidity values above 200 NTU recorded.

A cyanobacteria health warning was issued for Lake Opuha in March 2023 due to scums of Woronichinia naegeliana. No cyanobacteria toxins were detected.

Turbidity within the Lake Opuha tributaries increased at times that did not correspond with rain events, the causes of which are being investigated. A slip in the catchment of Station Creek caused increased turbidity there.

An artificial fresh released by Opuha Water Limited (OWL) into the Opuha River improved water clarity. Black disc (water clarity) readings increased following the fresh, with a decrease in volatile suspended solids (typically associated with algae). The artificial fresh removed cyanobacteria and didymo from river rocks at various locations, leading to better water clarity.

‘Monitoring in the Kakahu River showed visual water clarity decreasing downstream of the discharge and suspended sediment concentration increasing immediately downstream of the discharge. It is important to note that water clarity and suspended sediment concentration are not the only values used to assess overall river health. However, OWL accepts that there is genuine concern, so it is developing workplans with NIWA, the University of Canterbury, Cawthon Institute and environmental consultants, to better understand water quality and sediment processes in Lake Opuha and its catchment, and understand additional sources contributing sediment to the Kakahu River. Download the full report here.