NRC established the Lakes Water Quality Monitoring Network (LWQMN) in 2005. Water quality samples are taken from 31 lakes around Northland every three months and are analysed for a range of parameters, such as nutrients and bacteria. Each lake is given a Trophic Level Index (TLI) according to the amount of nutrients present in the water. In addition, 82 lakes around the region are surveyed annually to assess their ecological value. Each lake is given a ranking according to its ecological significance.
In 2007-08, of the 32 lakes surveyed as part of the LWQMN, 53% were classified as mesotrophic or oligotrophic and 47% were classified as eutrophic or worse. Of the 82 lakes surveyed for ecological value, 51% were found to have moderate to low value, while 28% were found to have moderate to high value. 21% were found to have outstanding ecological value. No new infestations of the pest plant ‘oxygen weed' were found during survey work in 2007-08 however, the pest plant ‘bladderwort' was found for the first time at Kai Iwi Lakes.