Lake’s future hangs in the balance
Waterfowl are stinking up the city’s ancient lake and faecal bacteria is putting recreational users at risk.
Ducks, geese, Australianbanded coots and pigeons make up a large chunk of the avian species dropping faeces into and around Hamilton’s 17,000 year old Lake Rotoroa. And its future hangs in the balance.
Pigeons have been an especially prevalent in recent years, according to Hamilton City Council’s 2017 Lake Domain Management Plan.
Bacteria levels in the lake are too high, said water resources engineer and scientist Tim Cox. Monitoring at sites around the lake, over several years, show elevated levels of bacteria from birds.
‘‘The number one issue with the lake is bacteria... faecal bacteria that makes you sick.’’
Add to that the amount of nutrients entering the water from stormwater run-off and nutrients already settled into the lake sediment and you have a recipe for toxic algal blooms with no easy fix.
‘‘We still see the lake go green at times and produce an algae that’s toxic - this blue-green algae that prevents swimability at certain times of year.’’
There is a willingness to restore Lake Rotoroa to a swimmable standard. But there are also gaps in knowledge and the potential for conflict over what’s most important.
Hamilton City Council parks and recreation manager Maria Barrie said water quality is a key theme in the Lake Domain Man- agement Plan and three steps are in place to achieve it: clarify the state of the lake; identify water quality measures for recreational use and develop a strat- egy to improve water quality.
But University of Waikato biological scientist Professor Brendan Hicks said the lake has, since 1992, slowly improved in terms of the nitrogen and phosphorus levels, algal blooms and water clarity.
Rotoroa is finding its way on its own - albeit slowly.