About the issue

In 1968 the Electricity Commission of New Zealand constructed the Otahuhu Power Station.  A weir was placed across the waterway forming the Ōtara Lake to provide a reservoir of cooling water for the plant.  The tidal function of the waterway was disrupted and sediment and contaminants from the 3,500 hectare stormwater catchment began to accumulate in the 50 hectare lake. Contaminants including significant quantities of zinc, copper and lead are trapped within the 50 hectare estuarine lake, along with an estimated 230,000 m3 of sediment and a thriving mangrove infestation.

In the order of 45 billion litres of rainfall lands within the catchment each year and the displacement of rainfall is undermined by the rapid loss of permeable surfaces due to industry and housing development.   The waterways are impacted by extreme water flow events causing erosion and flushing away habitat and ecosystems. Where waterways have been channelized, increased water temperature is also contributing to an unsustainable environment and the accumulation of a range of contaminants make it unsafe for secondary and primary water contact.   Within one generation the community and mana whenua have lost the ability to fish, swim, recreate and enjoy the lake and waterway system. 

The main issues that the Placemaking: Otara Waterways and Lake Strategic Plan is addressing are:

  • Sedimentation
  • Contaminants
  • Poor urban design (historic)
  • Waste water treatment
  • Litter
  • Pest plants and Animals
  • Poor connection and interaction with waterways
  • Lack of pride in and knowledge about the waterways

Capture