The spreadsheet below contains the source data to this indicator's graph and any additional data.
The upper graph shows how many of a group of 12 shallow lakes are currently found in each nutrient enrichment category. For five of these lakes there is enough information to measure any changes in water quality over time. The middle graph shows the proportion of the lakes that have improved (nutrient levels have decreased), have not changed or have deteriorated (nutrient levels have increased) in their level of nutrient enrichment. The bottom graph shows the proportion of samples collected from five lakes during 2010-18 contained levels of potentially toxic cyanobacteria that exceed guideline values. Note that these five lakes are sampled because cyanobacteria blooms are known to have occurred in them in the past.
No changes in water quality were found in Lake Hakanoa and Lake Whangape between 2002 and 2018. Water quality in Lake Rotomanuka showed improvements in chlorophyll a and total phosphorus concentrations but deterioration for Secchi depth and total nitrgoen concentration. While total phosphorus concentrations and Secchi depth in Lake Waikare improved between 1998 and 2018, total nitrogen concentrations showed deterioration. Lake Serpentine North showed deterioration for Secchi depth and total nitrogen concentrations.