The outbreak of gastroenteritis at Havelock North last year has the Clutha District Council assessing its own water supply treatment plants for risk.

It's a requirement for the council to have a water safety plan and identify ways to minimise potential risks at treatment plants.

The Evans Flat and Glenkenich plants pose the greatest health risk as they are sourced from a stream within rural catchments.

There are plans to upgrade the plants to reduce risk.

The upgrade projects are expected to be completed in the next 12 months.