Nitrate levels in subsurface waters of the Waimea Plain, -Nelson

In 1969-72, nitrate determinations were made on waters from 122 wells on the Waimea Plain, Nelson, South Island, New Zealand. Four wells showed values above 30 mg NO3-N/litre with a maximum of 50 mg/litre in one well, fifteen were in the 30-20 mg/litre range, forty-six were between 20 mg and 10 mg/litre; fifty-seven were below 10 mg/litre, and in only four wells was the nitrate concentration below 1.0 mg NO3-N/litre. Where it entered the plain, the Wairoa River usually contained about 0.07 mg NO3-N/litre, whereas the Waiiti River contained from 0.5 to 2.0 mg NO3-N/litre. Mapping of gradients of nitrate level indicated that these might contribute to aquifer definition and to sources of replenishing waters.