Lake Okaro

Lake Okaro

Lake Okaro

The meaning and origin of the name has been lost over time, but Lake Okaro is considered to be of significant taonga to Ngati Whaoa / Ngati Tahu.

Lake Okaro/Ngakaro is the smallest of the Rotorua lakes under public management. Appreciated for its quiet rural setting, it is surrounded by farms and is also a popular water-skiing spot. The lake has had a significant algae problem due to the levels of nitrogen and phosphorus nutrients which have increased over several decades. The nutrient-rich deposits over the catchment from the 1886 Tarawera eruption also have an ongoing effect on the lake's water quality.

At a glance  
Lake size: 31 ha
Catchment area:  367 ha
Elevation: 419 m
Average depth: 12.5 m
Deepest point: 18 m
Formed: 800 years ago
Drains to Lake Rotomahana via Haumi Stream  








Water Quality Status

Water quality in Lake Okaro has fluctuated over the last 10 years.  Historically the lake has suffered from regular seasonal algal blooms. Over the 2014 and 2015 years the lake has complied with its TLI target of 5.0. This has been largely as a result of actions to reduce nutrients coming from the mainly agricultural catchment and targeted alum dosing to lock up phosphorus in the sediments. All actions in the action plan have been completed.

Catchment Map

Click here to view image of map.

Target and Results

To meet community expectations for Lake Okaro's water quality nitrogen inputs need to reduce by a total of 910 kilograms and phosphorus to reduce by 20 kilograms per year.

Water Quality target 


2017 result


2016 result






Nutrient information




Total load 

2.4 Tonnes 

380 Kilograms 


1.5 Tonnes

360 Kilograms

Action and achievements

All actions have been completed for Lake Ōkaro and it has met its target TLI.  Additional science and modelling work will be undertaken to understand the long-term changes that may occur in the lake and help to inform any further review of the Action Plan.



Achieved as at June 2016


In-lake phosphorus treatment

240 kg N  380 kg P

90 kg P


Constructed wetland

348 kg N  16 kg P

149-597 kg N 31-303 kg P


Riparian management

423 kg N  37 kg P



Best management practices

139 kg N

124 kg N 65 kg P


Read Lake Okaro Action Plan