The Kāpiti Coast District Council (KCDC) has decided to apply to the Regional Council for a resource consent for the Waikanae River recharge scheme.
Next month the KCDC will ask the Greater Wellington Regional Council if it can take up to 30,700 cubic metres a day of water from the Waikanae River — and at times of low river flows replace it with ground water.
I understand it’s the first time such a scheme has been used in NZ for such a large population.
Reports presented to Councillors said there is enough water in the borefield to cover a high population growth and the threat of a major drought (called a 50-year event, meaning once in 50 years) up to 2060.
This is based on research by the Council over the past three years.
But Council reports show two risks in the project:
- There is a risk of saline (salt) intrusion, though the KCDC says this risk is low and will be restricted to the coastal fringe. But it will mean the closing of K13, a very productive bore close to the coast.
- Recent investigations show the aquifer systems are inter-connected. This means the KCDC scheme could impact on private shallow bores in the area during “drawdown” in times of drought. Councillors have been told the impact would be local and would reduce with distance from the Council bore.
Project manager Phil Stroud says modelling shows that 30 to 50 private wells could be affected in the shallow aquifers — and 10 to 15 deeper wells in the Waimea and Pleistocene aquifer.
Private owners told
He says the KCDC has already been in touch with the bulk of the private bore owners in the area.
“Given the information we have gathered, we believe the numbers of bores that could be affected will be less,” he says.
Extensive research has been undertaken on the impact of pumping groundwater into the Waikanae River in times of drought. A recent study suggests there could be some increase in algae growth with some types of algae, but this is considered to have only a minor effect on the river.
The reports presented to Council also contain feedback and recommendations from the Technical Advisory Group (TAG) chaired by Don Hunn.
The Advisory Group concludes that the work undertaken for Council had been ‘painstaking and well done’ and members think Council has been put in a position to make the final decision about whether and when to proceed with staged river recharge.
River monitoring with Maori
Councillors have been told stakeholders, two independent scientists, and the Te Āti Awa Water Working Group (WWG) have agreed that the Council should bring in a river monitoring programme which would address any effects as they arose.
Talks were now underway with Te Āti Awa on a plan to monitor future river conditions and on projects to improve the upper river catchment.
Deputy Mayor Roger Booth, who chaired the Council meeting, says:
“This is a significant step in our goal of providing a dependable ,high quality supply of treated river water to residents in Waikanae, Paraparaumu and Raumati for the next 50 years.”