WELLINGTON, Nov. 20 (Xinhua) -- New Zealand's groundwater maintains good quality, but E. coli is detected in about half of the wells monitored, and a range of nitrate concentrations are observed, with a minority exceeding the country's drinking water standards.
"These findings reflect the impact of land use changes on groundwater quality," Land, Air, Water Aotearoa (LAWA) Groundwater Science Lead and Environment Canterbury Science Manager Carl Hanson said after the Groundwater National Picture 2023 was released on Monday.
E. coli detections in groundwater, which signal potential fecal contamination, are a concern for raw drinking water sources, Hanson said.
However, not all wells tested are necessarily used for drinking. Results do not reflect the quality of New Zealand's reticulated, treated drinking water supply, he said.
Nitrate levels are mostly stable at the national level but show variable trends across different areas, with higher nitrate concentrations generally in areas with intensive agricultural activities, Hanson said.
Concentrations are higher than the maximum acceptable value at 6 percent of monitored sites, meaning the water from these wells at the time of sampling was deemed a health risk if consumed, he added.
The report offers an updated glance into the state of New Zealand's groundwater resources, and underscores the importance of groundwater in New Zealand as being crucial for drinking water, irrigation, industry, and sustaining many streams and lakes.
While the 2023 summary, which analyzes data from nearly a thousand regional and unitary council monitoring sites, most sampled every three months, indicates that groundwater conditions aren't changing drastically year-to-year, it highlights persistent challenges, Hanson said.
"Like other water resources, it's at risk from contamination by pathogens and other pollutants which can affect its suitability for different uses," LAWA Project Chair Tim Davie said, adding in coastal areas, seawater intrusion can make groundwater unsuitable for drinking or irrigation. ■
