Frequently Asked Questions

Have you got a question on Rotorua Lakes management and restoration?

Ask Environment Bay of Plenty and we will summarise common questions and their answers on this webpage. All visitors to the website may benefit from reading the response to your questions.

Question
What is Rule 11, and how will it affect rural landowners in the Rotorua Lakes catchments? 

Answer
Rule 11 is a commonly used term for a collection of rules in the proposed Regional Water and Land Plan that will restrict landowners in some of the Rotorua Lakes catchments from increasing the amount of nitrogen and phosphorus leaving their property.  These rules have important implications for land use, development and management in certain lakes catchments.  Follow this link to a fact sheet on Rule 11.

Question
I live beside Lake Rotoiti and our household uses a septic tank system.  What new requirements are there in the revised On-Site Effluent Treatment Regional Plan, and from when do they apply? 

Answer
All septic tank systems within 200 metres of a Rotorua lake join the inspection and maintenance programme. These systems will be required to be cleaned and inspected every three years (or every six years if it is fitted with an outlet filter). If you have more than one system per four hectares in a property, or you live within 200 metres of the lake edge or within an existing urban lake edge community, by December 2010 the total nitrogen in the system discharge must not exceed 15 grams per cubic metre. 

Traditional septic tank systems will need to be upgraded to meet this target. However, Rotorua District Council is intending to reticulate the sewage in some lakeside communities before the December 2010 deadline. More information will be provided to affected residents when the reviewed On-Site Effluent Treatment Regional Plan becomes operative.  Read through the Proposed (reviewed) On-Site Effluent Treatment Regional Plan or contact Environment Bay of Plenty for more information.

Question
What is an acceptable (ideal) level of nitrogen and phosphorus leaching for various land uses?

Answer
Environment Bay of Plenty has worked from the principle of setting the acceptable level of nutrients in the lake (and the associated lake water quality) based on public consultation.  From that we can work out what the maximum nutrient load from the catchment should be. If the existing load is too high then either the land uses or the land management practices are not acceptable.

For productive land use systems, the potential for leaching nitrogen generally follows this order: forestry < sheep/beef/deer farming < arable/mixed cropping < dairy farming < vegetable cropping.  Below is a summary of researched nitrogen losses for different land uses in New Zealand.

Land Use Type	Nitrogen Leaching Loss (kg N/ha/year)
	Range	Mean
Market Gardening	80-292	177
Dairy Pasture	15-115	65
Mixed Cropping or Arable Farming	35-110	61
Orcharding (only one kiwifruit study)	50	50
Sheep	6-66	21
Forestry	3-28	3

As you can see, there is a very large variation in nitrogen losses, so it is hard to place an overall “ideal” for each land use type; especially as soil type and climate vary. But there are some management practices that can substantially reduce nutrient leaching, e.g. wintering off stock, riparian protection, appropriate fertiliser application, and erosion control. Environment Bay of Plenty’s land management officers can also assist with farm nutrient management.

Question
Is there an ideal fencing distance from the water's edge and a preferred type of plant for riparian protection? What distance from the edge of lakes and rivers and what density of planting is required?

Answer
The width and composition of a riparian (river/lake/wetland edge) protection area depends on its purpose: stream restoration, nutrient reduction, wildlife corridor, stock protection, woodlot planting. The ideal width and plants to use is also site-specific, though there are general principles for different types of riparian strips. Environment Bay of Plenty has fact sheets on this and landowners can also get free advice from Environment Bay of Plenty land management officers.

Question
Are there any proposals for extracting and using the phosphorus and nitrogen leached from land before they reach the lakes and start causing problems?

Answer
There is a proposal to trial flocculant dosing in the Puarenga and Utuhina streams, which flow into Lake Rotorua. The flocculants are chemicals that bind with dissolved phosphorus so the phophorus settles out onto the stream or lake bed and cannot be used by aquatic life. Other proposals include using geotextile socks filled with material that can absorb ammonium or phosphorus (in different cases) in streams that enter the Rotorua lakes. It may be possible to extract the nutrients for fertiliser use, but these materials may also absorb other compounds that are not desirable in fertiliser.

There are often obstacles to be overcome before these techniques can be used, including cost, environmental effects and cultural impacts. They are not a substitute for reducing nutrient loads to waterways, but can be a short-term solution in some instances.

Question
The Saving the Rotorua Lakes brochure recently arrived in my letterbox. The target Trophic Level Index (TLI) and current TLI for Lake Rotorua was not included in the Rotorua Lakes’ TLI table.

Answer
Unfortunately the TLI figures for Lake Rotorua were missed out in that table. Lake Rotorua’s target TLI in the Regional Water and Land Plan is 4.2, and its TLI at June 2003 was 4.9. The higher the TLI, the worse the water quality. For an explanation of the TLI, see Trophic Level Index.