About Waituna Lagoon
Waituna Lagoon or (Lake Waituna as locals refer to it) is a large, brackish, coastal lagoon on the southern coast of the South Island which sits at the bottom of a small, intensively farmed catchment.
Intermittently open to the sea, the Waituna Lagoon and its wetland were a major food source or food basket utilised by Maori. Waituna translates to “water of eels”. The significance of this taonga (treasure of high significance) to Ngāi Tahu was formally recognised by a Statutory Acknowledgement under the Ngāi Tahu Claims Settlement Act 1998.
Nohoanga (or settlements) were located in the vicinity of the lagoon. It had a wide variety of reliable resources (mahinga kai). The great diversity of wildlife associated with the complex includes several breeds of ducks, white heron (kōtuku), gulls, spoonbill, pukeko, oyster-catcher, dotterels, terns and fern birds.
The wetlands are an important kōhanga (spawning) ground for a number of indigenous fish species. Kai available includes giant and banded kōkopu, varieties of flatfish, tuna (eels), kanakana (lamprey), inaka (whitebait), waikākahi (freshwater mussel) and waikōura (freshwater crayfish). Harakeke, mānuka, tōtara and tōtara bark, and pingao were also regularly harvested cultural materials. Paru or black mud was available, particularly sought after as a product for making dyes.
Waituna Lagoon is almost 10 km long on its east–west axis, and up to about 3 km wide, and has a complexity of bays, peaty peninsulas, islets, and shallow gravel bars and beds. The lagoon itself is 1,350 hectares in total, and is part of the 20,000 hectare Awarua Wetland.
Fed by three creeks, the lagoon drains to the sea when a managed opening is arranged. Waituna Lagoon is a different habitat when open to the sea and tidal (estuarine) to when it is closed and ponded (freshwater).
The lagoon has high ecological habitat diversity, a unique aquatic plant community, internationally important birdlife, and large areas of relatively unmodified wetland and terrestrial vegetation, resulting in a number of nationally significant ecosystems. In addition, it is highly valued for its aesthetic appeal, its rich biodiversity, duck shooting, fishing (for brown trout primarily), boating, walking, and scientific values.
The lagoon and immediate surrounding area (a total of 3,500 hectares) was originally reserved for wetland management purposes in 1971. The unique plant and animal life lead to it being designated a Ramsar Wetland of International Importance in 1976 and classified as a scientific reserve in 1983 when it became known as the Waituna Wetland Scientific Reserve.
The extent of the Ramsar site was increased in 2008 to include nearby wetland areas and the addition of three major estuaries: Toetoes Harbour, Awarua Bay and the Invercargill (New River) Estuary. It was then renamed the Awarua Wetland.
The wetland is fed by a combination of direct rainfall, groundwater and by streams passing through the wetland to the coast. These streams drain into the Waituna Lagoon which traps sediment and nutrients. The wetland plays a general role in the recharge and discharge of groundwater, the maintenance of water quality. It is of great importance in supporting aquatic and terrestrial food chains. Environmental monitoring shows that water quality in the lagoon and the creeks that flow into it are under stress because of many years of land development in the catchment and changes in lagoon water levels.
Land development in Waituna has included the drainage of wetland areas and the clearance of indigenous vegetation In the 1950’s, the main tributaries to the lagoon were straightened and Government schemes encouraged people to clear and develop the surrounding land. These factors pose the risk of the lagoon becoming eutrophic (murky water dominated by algal slime).
The lagoon and wetland have also been a source of food and recreation for the wider community over many generations, such as fishers, hunters, trampers and bird watchers. In the past some commercial eel fishing also took place.
What are the challenges for Waituna?
The Waituna catchment has undergone many years of land development, which along with changes in lagoon water levels has put the health of the lagoon and its tributaries under stress.
As such, the catchment and lagoon require ongoing active management to improve their ecological condition. This is to reduce the risk of the lagoon changing from having clear water and an aquatic environment dominated by aquatic macrophyte plants such as ruppia, to one which has turbid and murky water dominated by algal slime and other suspended phytoplankton.
Land development has included: drainage of wetland areas; clearance of indigenous vegetation; and more recent land use intensification since the 1950's when the main tributaries to the Waituna Lagoon were straightened, and Government schemes cleared and developed land and encouraged other people to do so as well. Changing water levels in the lagoon mean that farming in the lower parts of the catchment can be challenging.