Detection of E. coli bacteria
A key indicator of groundwater contamination by microorganisms, some of which can cause diseases. Faecal bacteria from livestock, onsite wastewater discharges, stormwater and other sources can contaminate groundwater. See the LAWA factsheet for more information.
The Drinking Water Standard New Zealand (DWSNZ) uses E. coli as an indicator of faecal contamination in drinking water. For drinking water supplies, E. coli counts should be below the Maximum Acceptable Value (MAV) of <1 cfu/100 ml.
Groundwater within Connectivity Category A (direct) that has maximum counts above the guideline is the highest risk to drinking water safety in the surface water system. See groundwater connectivity for more information on surface water connectivity categories.
Usage guide: switch tabs to look at different variables – drag and scroll on the map to move and zoom in on areas of interest – click on a site circle to see more information and subset the table below to that specific site – use the selection box on the map ( ) to subset table data to sites in that area.
All calculations use E. coli (cfu/100ml). Click on the +/- button at the end of a row to see the raw sample data and highlight that site on the map above. Click on a table header or the arrows ( ↓↑ ) next to it to sort the data by that column.
