Environment Southland will use its emergency powers under the Resource Management Act to mechanically open the Waituna Lagoon to the sea starting from tomorrow (24 Sep).

The lagoon is part of the Awarua-Waituna wetland complex and is recognised as a wetland of international significance. It is home to many species of native birds, plants, fish and insects, as well as trout, and is a culturally important site for Ngāi Tahu

General manager integrated catchment management Lucy Hicks said the lagoon had been very high for several weeks, sitting above 2.5m and this was impacting our communities, the roads, paddocks and farming activities in the area.

“Our scientists have been working with DOC scientists and other experts to assess the impacts consistently high water levels will be having on ecological health, and what that might look like leading into summer.”

“To prevent ecological harm, we have made the decision to open the lagoon, which will also support the community.”

The lagoon will be opened by diggers removing gravel from the bar until a channel is formed and water from the lagoon can flow through to the sea.

Work is expected to take several days to complete.

The opening needs to be carefully coordinated to occur when conditions allow it to be done safely and effectively, Hicks said.

“Opening the lagoon at this time of year has its pros and cons.”

“We’ve considered the timing, the need to flush nutrient-laden waters to prevent sustained algal growth, while considering the needs of Ruppia and other macrophytes which germinate and grow in spring/summer.”

“The goal is by flushing nutrients and sediment, this opening will help ‘reset’ the lagoon so that we can reduce the frequency of openings for ecological health.”

“We will be doing all we can to increase the odds of the lagoon closing prior to summer."

"Historically, it has required the right combination of wind and sea conditions to push gravel back into the channel that we will be creating with the digger.”