The Auckland Council traditionally monitored the water quality of the 7 largest lakes within the region, since June 2013 two of these lakes were dropped and now the Council regularly monitors 5 of the most important lakes.
These lakes were chosen based on their size, location, catchment land use, water quality and their ability to serve as a reliable representation of the regions freshwater bodies. Aside from the 5 regularly monitored lakes there have been 33 lakes assessed by the Auckland Council & NIWA using the LakeSPI (Submerged Plant Indicators) assessment criteria.
The quality and overall health of the regions lakes is strongly dependant on a variety of biotic and anthropogenic factors. These include the type and depth of the lake as well as the associated land usage within their respective catchment areas. Most of the regions lakes are considered to have good water quality however majority of them have a moderate ecological rating. This is partially due to the establishment of invasive aquatic flora and fauna. The biggest threat to lake water quality appears to be nutrient enrichment which is commonly associated with agricultural practices within the catchments.
The Auckland Council has two separate methods of monitoring the health and ecological state of the 5 biggest lakes within the region. The first of these monitoring programs is the Regional lakes water quality & ecology program which is a routine monitoring program that measures a suite of water quality variables as well as a trophic state assessment. These variables are measured by taking regular physical water samples, in situ water quality readings as well as phytoplankton and rotifer samples. Furthermore a permanent water quality buoy has been deployed in Lake Pupuke with a similar one being scheduled for deployment in Lake Ototoa. The second monitoring program is used to assess lake trophic state by means of aquatic macrophytes (LakeSPI).
The above mentioned monitoring programs coupled with a variety of natural resource management policies are used as a tool to both monitor and manage the ecological state of the region’s biggest lakes.