Auckland Council regularly monitors four of the most recreationally used 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 region's freshwater bodies.
The quality and overall health of the region's lakes is strongly dependent on a variety of biotic and anthropogenic factors. These include the type and depth of the lake as well as the associated land use within their respective catchment areas. Most of the region's lakes are considered to have good water quality and 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.
Auckland Council has two separate methods of monitoring the health and ecological state of the lakes within the region. The first of these monitoring programs is the water quality 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 samples. 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 lakes.