Nitrate levels on Waimakariri zone committee agenda

Andrew Arps

Nitrate leaching in parts of the district, as well as salt water entering the Kaiapoi River, will be on the agenda as the Waimakariri zone committee works towards its sub-regional plan.

Waimakariri zone manager Andrew Arps said research was ongoing. The challenge was to remain focused on determining where the biggest impact could be achieved and delivering recommendations that could be clearly understood.

''We don't want things to get overly complicated,'' Mr Arps said.

The committee held a closed workshop last month and is due to hold its first official meeting for the year on March 12 as it considers ongoing research by Environment Canterbury (ECan) scientists into groundwater flows under the Waimakariri River and nitrate and salination levels in the Kaiapoi River, as well as three years of reports.

The draft sub-regional plan, which would be a series of recommendations, was due out for public consultation in June and was expected to be signed off in September.

The process was delayed last year while ECan studied groundwater flows under the Waimakariri River. Chief scientist Dr Tim Davie announced in December that low levels of nitrates were getting into drinking water supplies in Kaiapoi, Belfast and north Christchurch.

''The pre-Christmas announcement was just the first stage and is part of ongoing work,'' Mr Arps said.

A bigger challenge for the zone committee was nitrate levels at the Silverstream end of Kaiapoi River, which was much higher than the accepted national standard.

Groundwater from the Eyre catchment was the most likely source of the nitrates, but the issue was complex, Mr Arps said.

''There is no doubt the alluvial soils in that whole Eyre catchment area is sensitive.

''But those nitrates showing up now are not from the last few decades, they are from up to the last 150 years . . .''

This meant the full impact of the present land use in the catchment may not be known for decades, meaning it ''will get worse before it gets better'', Mr Arps said.

''The good thing is there is work being done and people don't have their heads in the sand.''

-By David Hill
Central Rural Life