Dannevirke: Well owners urged to test

Private well owners in the district are being encouraged to protect their supply

Private well owners in the district are being encouraged to follow well protection practices and have their water tested following a recent review of groundwater quality for Horizons Regional Council.

Environmental consultancy, Pattle Delamore Partners, analysed a representative sample of 27 bores across the region for parameters including iron, manganese, ammonia, nitrate, E coli and arsenic.

Horizons groundwater scientist Abby Matthews said in most cases the region's groundwater was fine for irrigation and stock water but would require some form of treatment before human consumption.

"Based on the results and general best practice, we recommend people have their water tested by an independently-accredited laboratory if they intend to drink it," she said.

The review revealed oxidising groundwater conditions in Tararua and inland Horowhenua with reducing conditions more prominent in Manawatu, Rangitikei and coastal Horowhenua.

Ms Matthews said water in areas of oxidation is typically younger and may be more corrosive: "Oxidised groundwater is shallower and often more susceptible to the effects of land use and may include elevated levels of nutrients such as nitrate, while water in reducing conditions is usually older, deeper and slower moving and may present higher levels of iron, manganese and arsenic.

"Iron, manganese and arsenic occur naturally in earth comprising old swamp deposits which are common throughout the Manawatu basin. As groundwater moves through the strata, metals dissolve out of minerals present in soil and rocks and they can affect water supplies through discolouration, unpleasant taste or health risks."

Elevated arsenic levels were found in five bores in coastal areas and bore owners have been informed. "It's important to note these elevations occur naturally and there are no real surprises in this information. It is a reminder of the need to check before you drink," Ms Matthews said.