The Rotorua Lakes Protection and Restoration Action Programme
Rotorua’s twelve stunningly beautiful lakes have been under pressure from human activities for many decades. The problem is too much nitrogen and phosphorus, nutrients that feed algal growth, which in turn degrades water quality.
No one element of the community is responsible for the problem: septic tank leachate, runoff from pastoral land, urban runoff, geothermal inputs, and rainfall all contribute to the nutrient load.
In October 2000, Environment Bay of Plenty, Rotorua District Council, and the Te Arawa Maori Trust Board released 'Strategy for the Lakes of the Rotorua District', a document that identified long-term management goals for the lakes. The two priority issues were the establishment of the relationship between the three parties and the urgency to address declining water quality. At the same time Environment Bay of Plenty released its proposed Water and Land Plan that set water quality targets for each lake as a Trophic Level Index (TLI). Five lakes did not meet their target TLI, and therefore an action plan will be prepared to identify the actions necessary to protect and restore lake water quality.
The Action Plan for Lakes Rotorua and Rotoiti was launched at a public meeting on 26 January 2004. Over 200 people attended, reinforcing public concern over the closure of Lake Rotoiti in the summers of 2003 and 2004 due to toxic algal blooms.
Scientific work has shown that the total input of nutrients from Lake Rotorua’s total catchment needs to be reduced by over 30%. It has also highlighted that the flow through the Ohau Channel into Lake Rotoiti is the main source of nutrient input to that lake. Scientists have measured increases in nitrogen load to Lake Rotorua from old age groundwater. A complicating issue in many of the Rotorua lakes is the release of nutrients, particularly phosphorus, from bottom sediments during periods when oxygen is depleted in the bottom waters.
Thus options to bring about improved water quality will include not only possible land-use change and land-use management, but also sewage reticulation, engineered structures, oxygenation, and the use of flocculants.
A technical advisory group, including scientists from NIWA, the University of Waikato, and Environment Bay of Plenty, has been established to oversee the scientific investigations and associated outcomes.
Paul Dell Group Manager Regulation & Resource Management Environment Bay of Plenty