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Water quality

Water quality is affected by the nutrients nitrogen and phosphorus entering the lakes from both natural and man-made activities.  When nutrient levels in lakes are too high it can cause toxic algal blooms and aquatic weed growth.

See the latest water quality results summary here.

 

Nutrient loads to the lakes have increased over time due to:

  • Sewage from lakeside communities
  • Large amounts of nutrients stored in the bottom sediments of some lakes which come from historical practices such as the discharge of treated sewage into Lake Rotorua
  • Groundwater aquifers that are being progressively enriched with nutrients from historical farming practices that will continue to feed into the lakes over coming decades.

Lake

Water Quality Target 

2016/17 

2015/16 

2014/15 

2013/14 

Stability

Rotoma 2.3 2.3 2.4 2.5 2.38 To be investigated
Tikitapu (Blue Lake) 2.7 2.6 2.9 2.9 2.82 Stable
Okataina 2.6 2.9 2.8 2.9 2.69 Stable
Tarawera 2.6 3.1 3.0 3.1 3.0 Declining
Okareka 3.0 3.4 3.2 3.3 3.30 Stable
Rerewhakaaitu   3.6 3.5 3.4 3.3 3.43 Stable
Rotoiti 3.5 3.8 3.8 3.8 3.40 To be investigated
Rotokakahi 3.1 3.8 3.7 4.0 3.63 To be investigated
Rotomahana 3.9 4.0 4.0 4.0 3.8 Stable
Rotorua 4.2 4.1 4.4 4.4 4.2 Stable
Rotoehu 3.9 4.6 4.6 4.5 3.95 Declining
Okaro 5.0 4.9 4.6 4.5 4.49 Improving
 

To find out more information on each lake go to their individual pages.