Managed Aquifer Recharge gets close scrutiny

Two papers on aquifer recharge projects in the Poverty Bay Flats featured at the NZ Hydrological Society conference in Hamilton this week.

George Hampton, a masters student from Waikato University presented his findings on infiltration from the surface into the aquifers and Clare Houlbrooke, a consultant with Golders International, presented an update on the trial injection proposal for a Managed Aquifer Recharge (MAR).

Council’s shared services science manager, Lois Easton says the research on the aquifers in the Poverty Bay Flats and the potential tools to recharge them has undergone some close scrutiny.

Golders have presented scientific papers over the last two years to allow full scientific analysis of the methods and monitoring that is proposed for the trial.

Papers presented have been well received by the Hydrological Science and Regional Council groundwater science communities.

Ms Houlbrooke won a silver medal for a similar paper she presented to the Water New Zealand Conference in October.

“The injection trial proposal is seen as a first of its kind in New Zealand, but also that Golder’s management of the trial’s risks is being accepted by the science industry as the international standard of best practice,” says Ms Easton.

In his presentation on infiltration recharge, George Hampton says two sites were identified for a potential Managed Aquifer Recharge using infiltration basins. These two sites showed promise from desktop investigations but the infiltration rates in practice were low.

Tests at each site indicated low rates of saturated hydraulic conductivity due to the presence of sediments with low permeability – 6.12 cm/day at one site, less than one cm/day at the other site.

Mr Hampton used data from more than 30 bores in the Makauri Aquifer and used infiltrometer methods to measure the ability of water to infiltrate formations of gravel and sand.

His findings confirmed that in the main demand area of the aquifer the static water levels are declining.

There were some wells showing an increase in static water level. These were in the recharge zone where little water is extracted from the aquifer.

The infiltration trials completed last summer, showed that the potential for recharge by infiltration is limited and more work may be required looking at accessing subsurface layers to find reasonable infiltration.

ENDS

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