Lake Pupuke is a 100,000-year-old volcanic lake occupying volcanic crater between the suburbs of Takapuna and Milford on the North Shore. It’s a popular recreational spot in the summer months.
In the summer of 2014, algal bloom causing brown discolouration appeared in the lake. The algal bloom is naturally occurring, non-toxic and present all year round. It isn’t dangerous to human health and poses little risk to wildlife or pets.
However, when warmer weather arrives, its growth accelerates on the surface turning the lake a dirty brown colour.
We’ve been working to understand the complex reasons behind the changing nature of the lake. Monitoring shows the water quality is relatively good; however, the lake is becoming more nutrient enriched. The increase in algal blooms is due to the higher levels of nutrients as well as pest fish and pest plants which disturb the natural ecosystem of the lake. This is not unusual for an urban lake. What is different is the depth of Lake Pupuke and that no rivers or streams feed or drain this lake, making it a “sink” for the North Shore.
Our scientists have been working on management strategies for the lake for several years. Due to the complexity of the lake, a large amount of data is needed to make informed management decisions; if the wrong measures are taken they could cause the lake to deteriorate even further.
We are working with a citizen science initiative, Project Baseline Lake Pupuke, and the Cawthron Institute on a series of studies to determine what interventions can be made to best manage the lake’s health.
North Shore Ward Councillor Richard Hills, who has met regularly with Auckland Council's Healthy Waters & RIMU teams, is proud to see that the Project Baseline Initiative is a finalist in the Mayoral Conservation Awards, to be announced Thursday 20 September.
“Swimming in the lake after school and on the weekends is a favourite memory for many of us who grew up on the Shore," he says.
"It is important to protect this for future generations. It is fantastic to see the team working so hard to ensure this takes place.”
Work to find a solution continues; an intervention investigation project begins in October 2018 and by June 2019 we will be able to make decisions on effective mitigation and restoration.