Councils must act on water quality
It’s good to see Ed Taylor raising the issue of Lake Wanaka water quality in the July 13 Mirror.
Things seem to be changing in Lake Wanaka. Each year there are more concerns expressed by fishermen about lake snow (or lake snot) clogging fishing lines and impacting fishing success.
Filters in boat cooling systems become blocked, and both commercial and domestic users of town supply water are expressing concern about filters clogging more frequently.
In early June this year a large algal bloom about 6 hectares in size was seen in Stevensons Arm. When water was sampled there in mid June, even after a strong northerly, there were high numbers of the diatom (a kind of planktonic algae) associated with lake snot present. Such large algal blooms are normally associated with nutrient availability.
Our pristine deepwater alpine lakes are at risk. Councils do not appear to have the resources to meet their statutory responsibilities for lake water quality management or the catchments feeding into them.
Our alpine lakes have been recipients of build-up of multiple decades of urban, agricultural and recreational run-off of nutrients, toxins, pathogens, parasites, and decades of build-up of invasive aquatic plants and animals.
The Guardians of Lakes Wanaka and Hawea are concerned that the risks faced by the lakes are not being managed. Ed Taylor mentioned a monitoring buoy for Lake Wanaka. The Guardians place priority on the development of a lakes management plan which incorporates and builds on the values and wishes of local communities. Such a document would then provide a framework for the planning of appropriate research and monitoring leading to effective management actions.
Our deepwater lakes are complex ecosystems and while multiple monitoring buoys will be a part of the solution in water less than 80 metres deep, most (around 85%) of Lakes Wanaka, Hawea and Wakatipu are much deeper than that. Preventing the decline of water quality and protecting our alpine lakes ecosystems is vital for the ongoing viability of the communities that depend on these lakes continuing to attract people to the region.
Reducing the risks of increasing nutrients, of increasing pollutants and spread of invasive species will require much greater investment by councils, businesses depending on (or impacting) lakes water quality, and community groups.
There are also roles for the Ministry for the Environment and Department of Conservation. The current level of activity by Otago Regional Council and
Queenstown Lakes District Council will result in the lakes continuing to face increasing risk of declining water quality.
Dr Don Robertson is retired. He has 38 years of experience in aquatic resource management and research. He is also involved with the Guardians of Lake Hawea.
Don Robertson was chief scientist for biodiversity and biosecurity for NIWA.