What's polluting our streams?

18:28, Dec 02 2012

The Marlborough District Council environment committee wants funding for a study to find the source of pollution in four rural streams.

The problem streams are Are Are Creek, which flows from near Okaramio into the Wairau River; Doctors Creek, which flows from Benmorven Hills through Fairhall and into the Taylor in Blenheim; Mill Stream, which flows from above Wairau Valley township into the Wairau River; and the Opawa River catchment.

Council environmental scientist Fleur Tiernan said water quality was very poor at a quarter of the 34 sites monitored each month, poor at a quarter of the sites and good or excellent at the remainder.

Nitrate levels had fallen during five years of monitoring, but phosphorus and E coli bacteria contamination at many sites had increased and water clarity had fallen.

"The reason is not known," she told the environment committee meeting in Blenheim on Friday.

Catchment management studies were the best way of discovering what was behind the deteriorating water quality, Ms Tiernan said.


In the Rai catchment, three years of intensive monitoring led to the council supporting an environmental farm plans programme which this year extended into north Marlborough.

The problem streams would benefit from fencing and planting, Ms Tiernan said.

The more pastoral farming in a catchment, the poorer the water quality.

Nitrate levels were highest in Doctors Creek, Mill Stream and Murphys Creek, spring-fed with Wairau groundwater which met drinking water but not ecological toxicity standards, Ms Tiernan said.

Her report described water quality as very poor at testing sites including the Taylor River in central Blenheim and as poor at sites including the Opawa River at Swamp and Hammerichs roads.

Councillor David Dew said rural water quality problems were being dealt with but attention was just starting to fall on sources of urban pollution.

He suggested that catchments of the Opawa River running across the Wairau Plains through Blenheim should also be studied.

Environmental science and monitoring manager Alan Johnson later told the Marlborough Express that water quality in the Taylor River was regularly tested through the council environment and bathing water monitoring programmes.

A stormwater strategy was being developed that would include monitoring stormwater outlets into the Taylor River.

The Marlborough Express