Water restrictions on weather team's agenda

00:00, Dec 11 2012

With no rain forecast until next week it looks certain stage one water restrictions will come into force across the Waimea Plains before Christmas.

The Tasman District Council's dry weather taskforce was to meet today to discuss the increasingly dry conditions that have seen the Waimea River's level drop since last week's rain.

Council environment and planning manager Dennis Bush-King said the 19mm of rain that fell on the plains to last Friday was enough to take the river's level to 14 cubic metres a second but its level had dropped to 3.5 cumecs by yesterday.

The trigger level for the council to consult with permitted water users about water restrictions is 2.8 cumecs. Stage one rationing (20 per cent) kicks in at 2.5 cumecs.

Meanwhile, last week's rain was not enough to flush toxin-producing algae from the Waimea River. Water testing showed high levels of toxin from blue-green algae, cyanobacteria, in the river around and below the Appleby Bridge.

Council environmental information manager Rob Smith said the development of the toxin was unusually early. Levels were usually detected in late summer and stimulated by stable water flows.


Signs have been erected at the main access points to the Waimea River advising dog owners and parents of young children to not let their charges swim in the water. Mr Smith said the signs were a precautionary measure.

He said people should look for mats of the algae on the river banks and not let dogs or small children swim there. The algae's neuro-toxin was fatal to dogs and harmful to humans.

The warnings come after a dog died a fortnight ago after swimming in the lower reaches of the Waimea River.

Mr Smith said monitoring showed the Waimea River was the only major waterway in the district with high levels of the toxin. Low levels were found in the Motueka River, near Blue Gum corner, and the Lee River. The Wai-Iti and Takaka rivers were clear, Mr Smith said.

The council was formulating a summer monitoring programme of toxin levels for the district's rivers.

The Nelson Mail