Coastal Wairau Plain Aquifers
The coastal aquifers occur at depths of greater than 30 metres below the surface and are located within several kilometres of the Te Koko-o-Kupe/Cloudy Bay coastline.
Due to their proximity to the coast, abstraction of water from these aquifers creates the potential for seawater intrusion. This is the process whereby the boundary between freshwater and seawater moves inland, although to date it has not occurred.
Due to the growth in demand and the need for special management, the aquifers at the coast have been defined recently as a separate groundwater system to the Wairau Aquifer.
The northern boundary has been defined further inland for management purposes due to a lesser groundwater flow, and a higher risk of seawater intrusion.
Interestingly, well water levels vary with the nearby tide. Levels rise with the incoming tide, and fall on the outgoing cycle.
This area is intensively monitored by Marlborough District Council which operate a sentinel well network to provide early warning of an unacceptable inland migration of the seawater interface.