Source: Environment Canterbury Regional Council
Ko Awa Ika o Wairewa is an innovative take on a conventional fish pass; an apparatus designed principally by Wayne Alexander to connect the lake to the Pacific Ocean 24/7. Effectively a long box anchored to the seabed, this highly engineered equipment represents several years of meticulous planning.
With designs now completed, the next major steps will be consenting and securing funding for construction. The apparatus can be turned off and on and could be replicated in other areas with similar problems.
“We’ve already lost 80-90 per cent of the tuna population in the northern hemisphere,” Robin said.
A tuna/eel from Te Roto o Wairewa/Lake Forsyth
“In Aotearoa, we could be facing the same situation. Losing these taonga species is not something we’re willing to accept.
“We’re extremely grateful for the commitment of Canterbury Regional Council (Environment Canterbury) and Christchurch City Council for their support and for considering unique and innovative solutions to crucial issues.”
History of success in iwi-led innovation
Civil engineering innovation is no stranger to Wairewa, with the Rūnanga already investing significantly in the development of an outlet canal, bridge and groyne as a more effective method of lake-level management and to prevent widescale flooding.
Compared to the traditional method of a direct cut opening the lake to the ocean, the infrastructure enables control over the lake levels and prevents saltwater from entering the lake when it is open, mitigating issues like algal blooms.
Since it was put in place 15 years ago, water quality continues to track in a positive direction. Cyno-toxic algal blooms have decreased by 99.6 per cent and macrophyte beds (aquatic plants) are flourishing, providing habitat, oxygen and food sources for fish, invertebrates and wildlife.
“We’re always trying to be on the front of the waka in terms of our lake knowledge,” Robin said. “We believe Te Roto o Wairewa is the only low-land lake in the country that has been able to reverse this level of decline.”
Funding support available for fish passage initiatives
The Fish Habitat Fund is an initiative to address site-specific issues that threaten native fish populations and provide financial support towards remediating these issues. Up to $100,000 per year is available for projects that support general fish passage, any threatened/at risk freshwater fish species, increasing resilience of native fish strongholds in the face of climate change.
Find out more about managing instream structures on your land.
