Table 7.11: Nitrate nitrogen concentrations in some New Zealand groundwaters.

Location	Type of aquifer	Concentration (g/m3 nitrate-N)	Exceeds MAV1	Land use above aquifer	Data sources
South Island
Waimea Plain,	Confined	-		Crops,	Thomas (1995)
Tasman	Unconfined			Effluent disposal
Christchurch	Unconfined	4-8 g/m3	-	Pasture, Crops,	Bowden (1986)
	Confined	<1 g/m3		Point sources
Lincoln	Unconfined	-		Pasture, Crops	Adams et al. (1979)
Ashley Catchment	Unconfined	-		Pasture, Crops	Bowden et al. (1982)
Ashburton	Unconfined	4-8 g/m3	-	Pasture, Crops	Burden (1984)
Clutha Valley (1988)	-	0.2-5.3 g/m3	-	Pasture	Close and McCallion
North Island
Northland	-	<0.01-3.5 g/m3	-	Pasture	Smith et al.(1993)
Bay of Plenty (48 wells sampled)	-	<4.3 g/m3	-	Pasture	O'Shaughnessy and Hodges (1992)
Pukekohe, Onewhero (129 wells sampled)	Confined & unconfined	<0.1-23.5	(7 wells)	Pasture, Market gardening	Ringham et al., (1990)
Hamilton Lowlands	Unconfined	-		Pasture, Dairy	Hoare (1986)
Hauraki Lowlands	-	-	(5 wells)	Pasture	Environment Waikato (1993)
Takapau Plains	-	about 10 g/m3		Pasture, Effluent disposal	Willoughby and Dravid (1992)
Heretaunga Plains	Unconfined	10-20		Pasture	Burden (1980)
Tokoroa	Confined	-		Pasture, Effluent disposal	Bird (1987)
	Unconfined
Taranaki	-	<10 g/m3	-	Pasture, Effluent disposal	Smith et al. (1993)
Manawatu	<30 m	313 g/m3		Pasture	Brougham et al. (1985)
	>30 m	<2 g/m3
Wairarapa	Confined	<7.5 g/m3	-	Pasture	O'Dea (1980)

Adapted from Roberts et al. (1995)

¹ A tick in this column means that at least one of the wells in each sample exceeded the Maximum Acceptable Value (MAV) for nitrate-nitrogen stipulated by the New Zealand Drinking Water Standards (Ministry of Health, 1995c).

The MAV is much lower for groundwaters discharging into nitrogen-limited lakes in the central North Island.