Ministry for the Environment and Stats NZ provide a national picture of the environment in regular reports produced under the Environmental Reporting Act 2015. Below is the overview of the freshwater domain from the Our fresh water 2017 report.
Freshwater domain at a glance
The condition of our lakes, rivers, streams, wetlands, and groundwater is important for a number of reasons. For Māori, fresh water is a taonga and essential to life and identity. Our economy depends on having plentiful water – agriculture, tourism, and hydroelectricity generation particularly rely on water. New Zealanders and tourists enjoy many forms of recreation that use our lakes and rivers, such as swimming, kayaking, and fishing. Our waterways also support many indigenous animals, plants, and ecosystems. Fresh water is primarily taken for hydroelectricity generation and irrigation for farms, and our fresh water quality depends mainly on the dominant land use in a catchment.
Key findings - lakes:
- Of 65 lake monitoring sites between 2009 and 2013, 24 sites had median TLI scores of very good or good, 17 monitored sites had moderate scores, and 24 monitored sites had poor or very poor scores. Lakes rated good or very good are clear (unless they have natural turbidity, eg from glacial silt) and have low concentrations of nutrients and algae (eg Lake Pukaki in Canterbury). Those rated poor or very poor tend to be turbid, with high concentrations of nutrients that promote frequent algal blooms. These lakes are rarely suitable for recreation and have habitats unsuitable for some native freshwater species (eg Lake Horowhenua in Manawatu-Wanganui).
- For monitored lake sites assessed for water quality from 2009 to 2013, the following did not meet the national bottom lines for ecosystem health: 12 of 76 sites for total phosphorus; 11 of 71 sites for total nitrogen, and 11 of 72 sites for chlorophyll-a (a measure of phytoplankton (algae) biomass in a lake). This means that these lake sites may have ecological communities that have undergone or are at high risk of a regime shift to a persistent, degraded state, due to impacts of elevated nutrients leading to excessive algal and/or plant growth, as well as from losing oxygen in bottom waters of deep lakes.
- Over the same time period, one of 48 monitored sites did not meet the national bottom line for ammonia toxicity to sensitive freshwater species.
- For total nitrogen, dissolved reactive phosphorus, total phosphorus, ammmonical nitrogen, chlorophyll-a, trophic level index, and visual clarity, more trends at monitored sites were improving than worsening over 10 years from 2004 to 2013. For bottom-water dissolved oxygen and nitrate-nitrogen, more trends at monitored sites were worsening than improving over the same 10-year period.
For more detail see: