High concern for lowland lakes

For the first time, Land, Air, Water Aotearoa (LAWA) has released a New Zealand Lake Water Quality National Picture Summary based on the comprehensive lake water quality data available on the project website.

The summary reveals the poor condition of many of New Zealand’s lowland lakes, but also the spectacular quality of some of our upland waterbodies.

Cawthron Institute Freshwater Ecologist Dr Roger Young is part of the LAWA lakes science team behind the summary and explained there is cause for concern.

“The LAWA Lake Water Quality National Picture Summary released today provides an overview of the condition of 124 monitored lakes from across New Zealand.

“We presented analysis based on the Trophic Level Index (TLI) because this index gives us an idea of how nutrient enriched a lake is. Nutrient overload leads to phytoplankton growth, reduced clarity, and toxic algae blooms.

“Looking at the TLI scores of our monitored lakes, the condition of fewer than one in five can be categorised as either very good or good, whereas more than half are nutrient enriched and categorised as either poor or very poor.

“Most of the very poor condition lakes are lowland and most of the very good lakes are found at higher altitudes. This makes sense as most human activity occurs at lower altitude, and upland lakes are often surrounded by conservation land.

“At the national level, there has not been a great deal of change over the past decade, but encouragingly there was a slight increase between 2010 and 2019 in the number of monitored lakes in very good condition,” said Dr Young.

In New Zealand, lakes are monitored for a range of water quality (chemical-physical and bacterial) and ecological indicators by regional and unitary councils. Monitored sites with the best data records in New Zealand are often located in areas that are more impacted by human activities, sites that have greatest social and cultural value, or where changes in perceived water quality have resulted in the implementation of monitoring programs.

LAWA Lake Water Quality Lead and Waikato Regional Council Freshwater Scientist Dr Deniz Ozkundakci believes it is important we support our lakes if we want to continue to enjoy them into the future.

“Regional councils and unitary authorities have a long history of lake water quality monitoring; some councils have records stretching back almost 30 years. Together, we currently monitor 163 lake sites for their condition across New Zealand and the results are all freely available on the LAWA website.

“It’s exciting to see lakes are increasingly part of the conversation about looking after our freshwater for future generations.

“From the data, we know many of our lowland lakes in developed and agricultural areas are under pressure. Nutrients from land-based activities are impacting lake health and this has consequences for our cultural, social, and economic wellbeing.

“It’s important we continue to learn and share information about the state of our lakes. The most up-to-date dataset has been used to generate the LAWA Lakes National Picture Summary 2020. With more councils building on their monitoring programmes and exciting research projects underway in New Zealand, we’re on the path to better understanding the health of Aotearoa’s precious lakes,” said Dr Ozkundakci.

Lake water quality can be improved through a combination of community-based actions, effective policies, and implementation of restoration methods.

“Across New Zealand, there’s some good work going on to support and improve our lakes, but it’s important to understand that lakes can respond very slowly to restoration and management efforts. Protection of the most pristine lakes in New Zealand is of upmost importance,” said Dr Ozkundakci.

LAWA is a collaboration between New Zealand’s 16 regional and unitary councils, Cawthron Institute, and Ministry for the Environment, with support from Department of Conservation and Statistics New Zealand.