Waitaki stream 'not neglected'

Discoloured water in a stream feeding the Waitaki River is likely to be a byproduct of irrigation, but the history of the stream is not one of neglect, Environment Canterbury says.

Glenavy man Merv Cochrane contacted the Herald this week, concerned about the greeny-brown water coming from the Waikakahi Stream, feeding a northern braid of the river.

Yesterday, ECan director regulation Kim Drummond said the area Mr Cochrane had been concerned about had been visited three times, though only on the third visit – on Wednesday – did ECan staff find the stream cloudy. "A water quality scientist will be sampling the tributary to determine the cause of the discoloration.

"At this stage, staff think the discoloration is likely to be a byproduct of catchment-wide border dyke or flood irrigation, largely on dairying properties."

Mr Drummond said past regular water sampling showed the brown discoloration was caused by dissolved organic carbon that had leached from the soil.

"The problem is generally worse during the summer months when there is more irrigation occurring and more leaching potential."

It had become more noticeable after the Waitaki's main flow was diverted during January's flooding. Since then the tributary had emptied into a very small braid.

"This issue has some history to it and it is not one of neglect. Fourteen years ago, Environment Canterbury's resource care team and local farmers formed the Waikakahi Stream Resource Care Group. Together they have made significant progress – the stream is nearly entirely fenced and much of its length has also been planted to improve riparian habitat and shading for aquatic and bird life.

"This has led to a significant reduction in sediment loads in the stream."

Mr Drummond said many of the border-dyke irrigators have had extensive re-bordering and re-levelling works to improve irrigation performance and in more recent years the stream had fallen within the Clean Streams Accord.

It is one of five national dairy industry research streams.

Mr Drummond said organisations were working together to improve water quality of waterways, like the Waikakahi Stream.

- © Fairfax NZ News