The Waitarakao Washdyke Lagoon Catchment is part of a threatened network along the Canterbury coast of lagoons, estuaries, swamps, wetlands, scrub, and remnant patches of native bush.
It became an official Wildlife Sanctuary Reserve in 1907 and is home – or a stop-off point – to many species of birds, including the tarāpuka/black-billed gull, ngutu pare/wrybill, taranui/Caspian tern, and poaka/pied stilt. Waitarakao is also home to native freshwater species including īnaka/whitebait and the long-fin eel (tuna) which is New Zealand’s largest native freshwater fish. Longfin eels are a taonga species for Māori and swim thousands of kilometres out to near the Tonga trench to complete their life cycle.
Many of these types of coastal wetland and lagoon environments have been lost in recent history – and those remaining are critical mahika kai environments and unique and important habitats for a range of wildlife and flora.
Waitarakao Washdyke Lagoon was historically much larger than it is today, with estimates suggesting in 1881 it was around 250 ha in size – it is now is less than 50 ha due to changing land use and development. Other parts of the catchment also contained large wetland or swamp habitats that have subsequently been drained or destroyed through historic land-use.
The lagoon’s shrinking size means that it’s becoming a challenging place for birds to nest, fish to breed, and delicate plants to grow.
There is work already underway by community groups and organisations to help control predators and improve habitat, but there is still a lot of work to do.
Caption: A rare, historic painting of Waitarakao Washdyke Lagoon in 1874
Waitarakao was once a renowned kāinga mahika kai area for mana whenua and the wider Ngāi Tahu iwi and part of a busy coastal travel route between lakes Wairewa and Waitarakao (Washdyke Lagoon) and then further south.
Waitarakao and the nearby pa was a popular stop-off point for these trips. You could travel light – as there was kai available to catch and eat all along the way.
There was a tarakihi breeding area near the lagoon – alongside other stocks of fish/kaimoana including pātiki, shark, kanakana, kina, paua, cockles and crayfish.
There were also special plants such as kōareare - the edible rhizome of raupō, patete (seven finger or umbrella tree) and karengo sea lettuce.
These are now hard to find – or not there anymore.
Despite the lagoon and surrounding parts being officially recognised as mātaitai reserves, overfishing and erosion have had an adverse effect and mahika kai resources have degraded.
Caption: Another historic painting. Handwritten caption reads: Washdyke Lagoon near Timaru NZ, Oct 1874 - Commencement of Ninety Mile beach
(Ninety Mile beach refers to a travel route used by mana whenua and wider iwi, extending from Te Roto o Wairewa/Lake Forsyth - in Banks Peninsula, to Waitarakao Lagoon)
The water quality in the Waitarakao Washdyke Lagoon and nearby streams is poor and not meeting some standards.
Polluted stormwater is contributing to poor water quality in Washdyke waterways. This impacts on the relationship of Te Rūnanga o Arowhenua with the waterway and Waitarakao Washdyke Lagoon. Stormwater can carry contaminants that impacts the safe consumption of food gathered from the waterways.
High nutrient concentrations (nitrogen and phosphorus) have been found in the waterways. This is consistent with nutrients from agricultural runoff and surrounding urban activities in the areas. Elevated nutrients can result in algae growth that can harm aquatic life.
High concentrations of metals (arsenic, zinc and lead) have been found accumulating in the waterways. These can be attributed to surrounding industrial and urban activities in the area, vehicle movements and roofs/building materials.
Environment Canterbury’s Land and Water Regional Plan and other key pieces of planning legislation require improvements to water quality in the catchment. Timaru District Council’s stormwater management plan consent, and farming land use consents, will help drive improvements - but other initiatives will also be needed.