Environment Southland to use emergency powers to open Waituna Lagoon

Environment Southland will use emergency powers under the Resource Management Act to mechanically open Waituna Lagoon to the sea.

General Manager Integrated Catchment Management Lucy Hicks said the lagoon level had remained high for several weeks, sitting above 2.3 metres for the past five days and above 2.2 metres since late July. The sustained high water level is affecting nearby communities, roads, paddocks, and farming activities.

“We’ve been working to understand what these prolonged high-water levels as well as high levels of nutrients and sediment mean for the lagoon’s ecological health, particularly as we head into the warmer months,” Lucy Hicks said.

“Opening the lagoon now will help reduce the risk of ecological harm, while also easing some of the pressure being felt by the local 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.

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

“There are trade-offs in opening the lagoon at this time of year,” Lucy Hicks said. “We need to reduce the risk of nutrient-rich water sitting in the lagoon and fuelling algal growth, while also considering spring and summer growth for Ruppia and other aquatic plants.”

Closing the lagoon cannot be done mechanically, it requires the right combination of wind and sea conditions to push gravel back into the channel that we will be creating with the digger.

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