Marlborough groundwater is generally of very high quality, and can normally be used without treatment. However, groundwater in some areas contain substances that can affect human health or aesthetics.
Aesthetics mean non life-threatening problems such as staining whiteware or causing unacceptable tastes or odours.
These substances can occur either as a result of naturally occurring processes, such as the weathering of rocks, or due to man-made inputs such as fertilisers or pesticides.
Most contaminants found in Marlborough's groundwater, with the exception of nutrients, are from natural sources.
Focus areas for Marlborough District Council surveys include Rarangi, Riverlands and the Wairau Valley.
Higher levels of arsenic, manganese, iron, chloride, and boron have been measured in some wells.
Pesticides have not been found in high concentrations in Marlborough groundwaters with the exception of isolated cases involving well head contamination.
Likewise, microbe contamination doesn't appear to be a significant issue, even in relatively densely settled rural residential type settlements.
Potability is the word used to describe whether water is suitable for human consumption and meets the New Zealand Ministry of Health Drinking-water Standards 2005.
Marlborough District Council has produced fact sheets for information on these subjects:
Marlborough groundwater is used for a variety of purposes including crop irrigation, drinking, stock, wine or food processing, industrial and municipal water supply.
Arsenic has been found in some Marlborough groundwaters at levels above the human health limit specified in the NZ Drinking Water Standards.
Groundwater naturally flows towards the coast, where it discharges to the sea. The freshwater and seawater meet each other at a position called the saltwater interface.