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Groundwater quality monitoring 2012-13

TR 2013/01
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Report: TR 2013/01

Author: John Hadfield

About this report

This report documents the routine groundwater quality monitoring undertaken by the Waikato Regional Council, primarily for the period 2012/2013. Reporting includes summary statistics from a regional network of 111 wells sampled annually, a community network of 81 wells sampled every two years and subset of 30 regional wells sampled quarterly. The regional network is designed to represent the range of groundwater characteristics across the region rather than investigate the impacts from specific point source discharges.

Results indicate clear evidence of substantial land-use impacts on groundwater quality. The most common anthropogenic contaminant is nitrate. Nitrate exceeded the maximum acceptable value (MAV) for drinking at 5.3% of the regional network wells. A further 17.2% are over half the MAV concentration and another 40.5% of wells have concentrations above normal background (< 1 g m-3). Many of the remaining 27% have anaerobic conditions where nitrate cannot occur or may have water of an age older than farming influence. Nitrate most commonly exceeds the drinking water standards in the Pukekohe, Hamilton Basin and southern Hauraki Plains areas. Arsenic and manganese are natural determinands each exceeding the drinking water guidelines in about 5% of wells each.

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Groundwater quality monitoring 2012-13 [PDF, 2.1 MB]