What is being done for Lake Rotorua
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Lake Rotorua
"Lake in a basin". A number of the Rotorua lakes were named by Ihenga, a grandson of the captain of the Arawa canoe Tamatekapua.
He named the largest lake, Rotorua nui ā Kahu-matamomoe, in honour of his father-in-law and uncle, Kahumatamomoe. "Rotorua nui" refers to the large basin-like lake.
Lake Rotorua is the largest lake in the district and the most productive trout fishery in New Zealand. With the city of Rotorua on its shores, it is much valued and used by locals and tourists alike.
It is probably New Zealand's best-known lake island, and is closely associated with one of the best-known Māori legends, that of Hinemoa and Tutanekai. It is said that Hinemoa swam across the lake to her lover Tutanekai who lived on Mokoia Island.
The lake was formed from the crater of a large volcano in the Taupo Volcanic Zone. The quality of the water in Lake Rotorua also affects Lake Rotoiti as the two lakes are linked by the Ohau Channel.
Water quality status
Great achievements have been made for Lake Rotorua and the water quality continues to be the best it has been in decades. The lake remains at or around its target Trophic Level Index (TLI) of 4.2depending on the climatic conditions. Regional Council doses aluminium sulphate into two streams which flow to the lake, the Puarenga and Utuhina, the aluminium sulphate locks the phosphorous into the sediment removing it from the water column. This intervention is a key reason why the lake is achieving its water quality target but this is not a long term solution for the lake.
The key to long term sustainable water quality will be reducing nutrients from land-use. A Stakeholder Advisory Group was formed with representatives from the pastoral, water quality, forestry and iwi sectors. This collaborative forum was integral to the development of an integrated framework made up of solutions for reducing nitrogen that enters the lake, including the development of Plan Change 10.
Solution for long term water quality
An integrated framework of solutions aims to achieve long term water quality. It includes:
- Proposed Plan Change 10 – a set of rules to remove 140 tonne of nitrogen from entering Lake Rotorua from pastoral farming.
- Gorse Conversion Programme - $2.5 million fund to remove 30 tonnes of nitrogen from entering Lake Rotorua
- Lake Rotorua Incentives Programme - $40 million incentive fund to remove 100 tonnes of nitrogen from entering Lake Rotorua through voluntary land use/management change
- Engineering solutions – Bay of Plenty Regional Council will use engineering initiatives to remove 50 tonnes of nitrogen from entering Lake Rotorua
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At a glance |
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Lake size: |
8060 ha |
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Catchment area |
50060 ha |
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Elevation |
280 m |
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Average depth: |
11 m |
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Deepest point: |
45 m |
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Formed: |
140,000 years ago |
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Has geothermal input |
Catchment Map
Click here to view image of map.
Groundwater Information
| Area (ha) | |
| Groundwater catchment | 53,789 |
| Groundwater catchment (not including Lake Rotorua) | 45,704 |
Land Slope
| Slope (degrees) | Area (ha) |
| 0-7.9 | 18,109 |
| 8-15.9 | 9,672 |
| 16-25.9 | 7,652 |
| 26+ | 6,178 |
| No slope information | 398 |
Rainfall
| 100mm rainfall bands (mean precipitation 1981-2010) | |
| 1300-1400mm | 692 |
| 1400-1500mm | 2,231 |
| 1500-1600mm | 9,567 |
| 1600-1700mm | 5,271 |
| 1700-1800mm | 5,908 |
| 1800-1900mm | 4,710 |
| 1900-2000mm | 2,830 |
| 2000-2100mm | 2,761 |
| 2100-2200mm | 2,946 |
| 2200-2300mm | 2,267 |
| 2300-2400mm | 2,826 |
Land Use Capability Class (LUC)
| Land Use Class | Area (ha) |
| 2 | 534 |
| 3 | 5,227 |
| 4 | 13,148 |
| 6 | 17,421 |
| 7 | 4,363 |
| 8 | 843 |
| Town or Lake | 473 |
Target and Results
To meet community expectations Lake Rotorua needs to reach a sustainable load of 435 tonnes of nitrogen and managephosphorous entering the lake. We also need to reduce the impact of nutrients already in the lake.
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Water Quality target |
4.2 |
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2017 result |
4.1 |
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2016 Result |
4.4. |
Nutrient research
| Report title | Author/s | Summary | Date |
| Management of Phosphorous and nitrogen inputs to Lake Rotorua, New Zealand | J.C. Rutherford, R.D. Pridmore and E. White | This is the original report that informed that a sustainable load of 435 tonnes of N and a reduction of 10 tonnes of phosphorus is required to meet water quality targets (pre-1960s) | 1989 |
Actions and achievements
|
Action |
Achieved as at June 2016 |
Status |
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Land use and land management change (not Incentives Scheme) |
3.94T N .08 T P |
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9.74 T N 2.5.86 T P |
Lakeside communities in Brunswick, Hinemoa Point, Tarawera Road and Paradise Valley have connected to sewerage reticulation. |
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0 |
Plant scheduled for construction 2018-2019. |
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0.07 T N |
Floating wetland established. |
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0.02 T P |
8 detainment bunds have been installed |
Action Plan
Lake Action Plans direct what steps need to be taken to improve lake water quality to meet the communitys' expectations
