A joint infiltration trial being carried out by Environment Canterbury (ECan) and Waimakariri Irrigation Ltd (WIL) at Silverstream, near Kaiapoi, is proving successful, with more than 80 litres per second reaching the aquifer via a 1.5m-deep trench.

The three-year trial has been running for four months at a site 7km east of Silverstream.

WIL environmental manager Paul Reese said initial results from the trial had provided a high level of confidence for using infiltration to augment and recharge the aquifer leading to Silverstream.

''So far it's shown us that the infiltration method can be used to add low nitrate Waimakariri River water to the aquifer, which hopefully will reduce levels of nitrates in Silverstream.''


ECan senior hydrogeologist Zeb Etheridge said no additional water was being added to the trench due to the irrigation season starting.

The team was focusing on designing a monitoring system to track where the clean water went and which part of the spring-fed stream system it ended up in.

''We plan to install the monitoring system next year prior to winter and then start a managed aquifer recharge trial.

''So far, we're really pleased with the positive results we've seen since the trial started and look forward to the next stage.''

Reese said WIL shareholders were on board with the trial and were keen to do their part to help reduce nitrate levels in Silverstream.

''We know that Silverstream is the canary in the cage and our farmers know that they have an impact on the environment, so they really want to do their bit to improve the stream.

''This is an opportunity for us to utilise our resources and infrastructure to try to get a positive outcome,'' he said.