City drinking water safe during floods thanks to upgrade

The Oreti ‘boiling’ in flood about 100 metres downstream of the Branxholme Plant intake
just as it passed under the Nightcaps-Oporo rail bridge.

Council Water Manager Alister Murray gives an update on how our water treatment plant fared during last week’s flood:

COUNCIL’S recent $12 million dollar upgrade of its water treatment facility at Branxholme on the bank of the Oreti River proved its worth again during the February 2020 major flood event. Invercargill’s water is drawn from the Oreti River which became extremely turbid (dirty) following very high rainfall in the Oreti catchment.

Peak water level at the intake was five metres above normal on February 5, with turbidity exceeding 500 turbidity units. The river under normal conditions runs at turbidity less than five units with a typical flood ‘topping out’ at 200-250 units.

The turbidity of the water after filtration at worst, was only a little over 0.1 units which was well within what is permitted by the Drinking Water Standards.

This flood was much larger than any experienced for many years and would have resulted in considerable difficulty for the Branxholme plant to handle prior to the upgrade, probably to the extent of requiring a ‘boil water notice’.