Cleaning up our lakes

We need to reduce the amount of nitrogen and phosphorus entering Lake Rotorua, so we’ve set up an integrated framework to achieve a sustainable nitrogen limit of 435 tonnes per year.

The Rotorua Te Arawa Lakes Programme is leading the way in water quality management, because our approach is supported by science and technology.

Some of our strategies have an immediate effect on water quality, such as phosphorus locking and weed harvesting. These actions provide a short term solution, but as soon as we stop these interventions, we risk allowing water quality to decline again.

Our lakes are an important part of our culture and our identity as Kiwis. From a traditional Māori perspective, people are connected to water and to nature through whakapapa (our genealogy), mapping legend, history and knowledge from one generation to the next. Our lakes are for all to enjoy and be proud of, so cleaning them up will be a community effort.

What happens on land (from septic tanks and waste water to farming and agriculture) drastically affects our water. Nutrients, like nitrogen and phosphorus, from land activities can seep into the soil and make their way into our lakes, reducing water quality and boosting the growth of potentially toxic algae.

To ensure our lakes are left in a better state for the future, we have a tricky task ahead of us - we must prevent 320 tonnes of nutrients from entering Lake Rotorua.

Managing these issues is a key focus for the Rotorua Te Arawa Lakes Programme, but to be successful, we need to work together as a community to change the way we use the land. The programme’s first port of call? Working to reduce nutrient loss to clean up Lake Rotorua.

The Bay of Plenty Regional Council’s Water and Land Plan is also right behind us, and addresses key issues through regulatory and non-regulatory methods which include:

• Sewerage reticulation and sewerage plant upgrades - since 2007, lakeside communities have contributed to restoring water quality in several lakes

• In-lake treatment options - to help reduce the impacts of phosphorus in certain lakes, we treat incoming streams with alum. To ensure we don’t disrupt the lake’s ecosystems and environment, we’re working with the University of Waikato to monitor the project (to date there’s no indication of alum having any adverse effects)

• Land retirement and identification of land use changes and land management options

• Rule 11 to cap the existing nitrogen and phosphorus loss from land use activities in Lake Rotorua, Rotoiti, Rotoehu, Ōkaro and Ōkāreka - rule 11 sets a limit based on each property’s nutrients levels, and while it doesn’t improve water quality, it ensures no more nutrients can enter lake

• Detainment bunds and biodiversity work

• Encouraging the fencing and planting of riparian areas (the areas between land and water).

Want to help us support the sustainable and integrated management of land and water resources? Call a Bay of Plenty Regional Council Land Management officer on 07 921 3377.