Lake water quality trends

The LWQMN has been running for more than five years which means there is enough data to carry out trend analysis on water quality.

Twenty-five out of the 28 lakes in the network had significant trends. Improving trends were recorded in chlorophyll a (a specific form of chlorophyll), clarity, ammoniacal nitrogen, total nitrogen and trophic level index for Lake Ōmāpere which is consistent with the findings from the National Lakes Report (2010).

Positive trend results were also recorded for lakes Carrot, Kahuparere, Waiporohita and Wainui. Declining trends have been seen in lakes Kai Iwi, Morehurehu, Ngatu, Rotoroa, Rototuna and Waipara. These deteriorating trends are likely to be a result of pressures from surrounding land use such as forest harvesting, and increasing numbers of septic tanks. These trends will be further investigated. For more information, go to www.nrc.govt.nz/lakedata  

Lake Owhareiti.