LWAG hosting John Gifford, Lake Water Quality Soc Chair, (Rotorua) at April 20 meeting
LWQS has a long and proud history. The society was originally formed in 1961 as the Lakeweed Control Society and in 2000 shifted to its current name taking on the greater responsibility of advocacy for the restoration of the lakes across the Rotorua District. We work with the Te Arawa Lakes Trust and IWI to achieve our goal. In additional we foster research and education on lakes; work with local, regional and central government and community groups in our quest to restore the lakes to health. The Rotorua Lakes comprise a dozen major lakes and some smaller ones, in the central volcanic region of the North Island of New Zealand. They are set in a glorious landscape of native bush, conifer forests, farmland, and scattered clusters of homes. Each is different, but human activities have damaged them all. We seek to fix those that have deteriorated and prevent the best from further degradation.
We want present and future generations of locals, other New Zealanders and tourists to be able to enjoy them, as thousands already do every year. We welcome your interest, wherever in the world you may live.
Water quality for the Rotorua lakes has been an important issue over the last 50 years, with the deterioration of water quality being attributed to both natural and man-made influences. The main attributes influencing lake water quality have included, change in water clarity due to turbidity, change in oxygen concentrations, nutrients such as nitrogen and phosphorus, temperature and pH.
As lake water quality deteriorates (reducing oxygen levels, increased nutrients, increased turbidity and high daily variation in temperatures and pH) then toxic alge blooms may occur and amenity values become limited. Some of the factors that have influenced the addition of nutrients to the Rotorua Lakes have included sewerage from lake side communities, nutrients stored in bottom sediments arising from historic land use practices and urban development and the contamination of groundwater arising from farming practices over many years.
One of the key parameters used to measure the water quality of the Rotorua Lakes is the "Trophic Level Index (TLI). The trophic level index is based on the total nitrogen, total phosphorus, algae and water clarity. A TLI of less than 2 indicates very good water quality wheras a TLI of greater than 5 indicates poor water quality. The risk of environmental problems such as algal blooms and the loss of water clarity increase with a higher the TLI.
The TLI for each lake is monitored annually and compared to targets. From Lakes Water Quality/Te Kahui Kounga Wai website: https://lakeswaterquality.co.nz/water-quality/