Managed Aquifer Recharge In Poverty Bay
Annual Conference
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The Gisborne District Council (GDC) has identified long term water availability in the Poverty Bay area as being a potentially limiting factor in future regional development. A substantial proportion of the water used for irrigation across the Poverty Bay Flats is derived from groundwater, with most of the abstraction being from the confined Makauri Aquifer. Reviews of groundwater levels in the Poverty Bay Flats area have identified declining groundwater pressure trends in this aquifer as an environmental and water supply reliability issue. These trends are linked to increasing groundwater abstraction for irrigation purposes. Current groundwater abstraction rates are however substantially less than the consented allocations.
The GDC is investigating water management options to stabilize and restore groundwater trends and improve future water supply reliability in the Poverty Bay area. One option under investigation is the use of Managed Aquifer Recharge (MAR) to replenish and sustain groundwater yields from aquifers beneath the Poverty Bay Flats. Golder Associates (NZ) Limited (Golder) was commissioned by GDC to undertake a pre-feasibility assessment for a MAR program.
The MAR pre-feasibility assessment carried out by Golder included an evaluation of the challenges and needs for Poverty Bay water management, source water options, direct injection and surface infiltration options and water quality management requirements. The pre-feasibility analysis indicated a groundwater replenishment scheme (GRS) focused on the Makauri Aquifer has the potential to:
A full feasibility study has now been initiated by GDC, including construction of a pilot injection bore to be drilled into the Makauri Aquifer and an injection trial to be undertaken during 2015-2016. Pumping and flow control equipment together with monitoring systems are to be installed in the injection bore. Monitoring systems will also be installed in selected nearby bores to track aquifer pressure and water storage responses to the trial. Changes in groundwater quality in response to the injection program will also be monitored.
In summary, Managed Aquifer Recharge (MAR) has the potential to replenish and support sustainable groundwater yields from aquifers beneath the Poverty Bay Flats. The next step in establishing a GRS for Poverty Bay is the construction and testing of a pilot trial injection bore.