The latest water quality report for rivers and lakes across Otago from the Otago Regional Council (ORC) paints a poor picture for some tributaries in the Lower Clutha Rohe.

The 2023 report submitted to the Environmental Science and Policy Committee last week, from water quality scientist Markus Dengg, showed that the state of river and lake water quality is

spatially variable across Otago.

The quality of river and streams at high elevations under predominantly native cover or conservation land such as Lake Hāwea, Wānaka and Wakatipu, and some tributaries of the Clutha

Mata-Au such as the Lindis, Nevis and Dart rivers, rated higher than those lower down the catchment.

Sites at the bottom of catchments tended to have higher concentrations of E. coli than upper catchment sites, and testing over the past summer (2023-24) at the Shaky Bridge in Alexandra on

the Manuherekia River, found it was only recommended for swimming half of the time.

The ORC currently monitors 105 river sites and eight lakes throughout the region, and E.coli is naturally present in animal faeces and in freshwater and can reach high concentrations by the

addition of wastewater or runoff from agricultural pastures to streams.

High densities of E. coli indicate that the water has been contaminated with faecal matter and may therefore contain pathogens (such as cryptosporidium) that can cause illness.

The lower Manuherekia River is classified as at the lowest end of the water quality, where ecological communities have undergone or are at high risk of a regime shift to a persistent,

degraded state, the report said.

There was also potential for acute toxicity impacts and significant, persistent stress on a range of aquatic organisms.