Lake Hayes floating lifeline

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A plan has been floated to stop ugly brown algae growth choking Queenstown’s iconic Lake Hayes to death.

The newly-formed Lake Hayes Water Quality Enhancement Society is fundraising to trial a suction-pumping machine that could purify the lake in as little as two years.

Brown algae have bloomed on the lake for the past three summers, fuelled by phosphorus-rich water on the bottom.

Fish life has all but died out, and the new society’s co-founder Tom Pryde last summer report­­ed he suffered hay fever-like symptoms from swimming in it.

Engineer Bill Walker, who lives near the lake, has designed an electric-powered water en­hancer, adapted from the American-designed Solar­­Bee device that has resuscitated Wan­ganui’s Vir­­­­-ginia Lake.

Walker’s ap­pa­ratus would float on the surface above a pipe drawing phosphorus-rich water from 20m down and bring it to the top.

Bringing cooler water to the surface would knock back the algae, which only blooms at more than 18degC, and the nutrients would flush out via the Hayes Creek outlet.

Algae in only small doses would promote fish life again, Walker says.

Walker’s device would be electric-driven, using power from the Wakatipu Rowing Club shed so it could operate continuously, unlike the American solar-powered unit.

One unit, pumping 200 litres a second in a 14ha radius, would take 10 years to turn over the whole lake, Walker estimates.

One unit could be built at a cost of $60,000 to $70,000 – his company, E-Type Eng­ineering, also manufactured Skyline’s luges and AJ Hackett bungy platforms.

Pryde’s group is fundraising to buy one or ideally two units for the start of the next algae-growing season in September.

The group hopes to gain fund­­-ing from Otago Regional Council, which would also be asked to monitor the unit, Queenstown Lakes District Council and charitable trusts. It may also try to tap Lake Hayes Loop Track users, and is signing up members for $20 a head.

“Basically the problem’s getting worse and the lake is dying, and we want to try and see if we can catch it before it actually does die,” action group co-founder Jules Tapper says.

“We’re kind of men of action, not talkers – we don’t want to sit on our hands and see it deteriorate and say, I wish we had done something.”