Waituna
The Waituna Lagoon is one of the best remaining examples of a natural coastal lagoon in New Zealand and is unique in Southland and New Zealand.
It is a highly valued, large, brackish coastal lagoon that is fed by three creeks, and drains to the sea through a managed opening. Historically the lagoon was surrounded by peat bog wetland, the drainage from which gave the lagoon its characteristic clear brown stain, low nutrient status, and low pH. It had high ecological habitat diversity, a unique seagrass community (Ruppia dominated), internationally important birdlife, and large areas of relatively unmodified wetland and terrestrial vegetation. In addition it is highly valued for its aesthetic appeal, its rich biodiversity, duck shooting, fishing (for brown trout primarily), boating, walking, and scientific appeal. The Waituna Lagoon is part of the internationally recognised Awarua Wetlands, which became a Ramsar site in 1976. The cultural significance to the local Ngai Tahu people was recognised under a Statutory Acknowledgement with the Ngai Tahu Claims Settlement Act 1998.
What is the "Waituna Catchment"?
In the Waituna catchment, the Waituna Lagoon is the lowest point. There are three creeks that flow into the lagoon. They are;
- Moffat Creek
- Carran Creek
- Waituna Creek
These three large creeks, and other small waterways and drains that are on farms (either open or under the ground) make up the drainage network. This network transports water, sediment or soil particles, nutrients and other material from the land within the catchment to the lagoon. Groundwater also transports nutrients to the lagoon.
Partnership
Environment Southland is leading a multi-agency response to stop the lagoon flipping. We are working with the Department of Conservation, DairyNZ, Fonterra, Federated Farmers, Beef and Lamb, Southland District and Invercargill City Councils, Fish and Game Southland, several community groups involved in the catchment, Iwi, local farmers and residents.
What's the problem?
The Waituna Lagoon sits at the bottom of a small, intensively farmed catchment. Because of many years of land development in the catchment, including drainage of wetland areas and clearance of indigenous vegetation, the lagoon is now experiencing a number of problems. These are exacerbated by the lagoon's extreme susceptibility to water quality problems because it does not have a permanent opening to the sea, and hence is poorly flushed. Therefore, nutrient inputs tend to stay within the Lagoon. In an agricultural catchment like Waituna, the primary concerns are excessive nutrients and sediment leading to eutrophication.
Environmental monitoring shows that the water quality in the lagoon and the creeks that flow into it has deteriorated meaning the lagoon has high levels of nutrients. Nutrients, particularly nitrogen and phosphorus, are needed by plants and animals for growth. Nutrients are essential, but high levels are harmful. The rate of deterioration of the lagoon has increased markedly since 2009 and the results confirm the lagoon is sick. Ruppia, a critical species that the lagoon ecosystem depends on is being stressed, and the lagoon is at imminent risk of flipping.
Flipping would mean we would see the lagoon change from having clear water and an aquatic environment dominated by seagrass (Ruppia) to turbid, murky water dominated by algal slime – this would be devastating for the lagoon, the plants and animals that live in it – and for hunting and fishing!
The catchment at a glance:
- Waituna Lagoon is located 40 km south east from Invercargill
- The lagoon is 1350 hectares (ha), the catchment is approx 20,000 hectares (ha)
- More than 80 different species of bird have been recorded in the wetland complex
- Hunting and fishing camps have been in the area for over 100 years
- Waituna receives over 2000 'angler days' per year
- From small dwellings to large farms there are approximately 130 properties in the catchment
- There are at least 5 types of farming in the catchment (arable, forestry, sheep, beef and dairy)
- Consented dairy cow numbers have more than doubled since 2000
- There are 40 dairy effluent discharge consents, up from 28 in 2000
- Environment Southland has monitored water quality at 4 sites in the lagoon since 2003
News
Read the latest information about what is going on at the lagoon.
Updates
Regular updates are being provided to stakeholders regarding progress made on the Waituna response. These will be publicly available here as they are issued.
Environment Southland is the brand name of Southland Regional Council.