WELLINGTON, April 1 (Xinhua) -- New Zealand's river and lake water quality has shown mixed trends, with phosphorus levels improving but bacterial contamination worsening, Stats NZ reported Wednesday.
Total phosphorus concentrations decreased at 59 percent of monitored river sites between 2005 and 2024, said the statistics department.
"Phosphorus occurs naturally at low levels in rivers. Lower phosphorus levels generally mean less risk of excessive algal growth," Stats NZ environment statistics spokesperson Tehseen Islam said.
However, Escherichia coli levels, a key fecal contamination indicator raising health concerns, increased at 38 percent of monitored river sites from 2005 to 2024, while only 21 percent recorded declines, statistics showed.
Nitrogen concentrations remained mixed, with 68 percent of monitored river sites exceeding guideline limits for healthy river ecosystems between 2020 and 2024, Stats NZ said.
It noted that overall lake health in New Zealand remained poor, with 73 percent of monitored sites rated "poor" or "very poor" on the trophic level index in the four-year period, which describes lakes' ecological health based on nutrient levels and algal growth.
Trophic level index trends declined at 36 percent of monitored lake sites between 2005 and 2024, according to the statistics. ■
