River algae lap up heavy rain

By ELIZABETH BINNING

Continuing heavy rain could boost the Waikato River algae growth, say scientists.

Environment Waikato water quality scientist Bill Vant said a heavy downpour in the past 48 hours was more likely to encourage algal growth than to flush it out of the Waikato River.

The naturally occurring algae, which reproduce rapidly in warm, humid conditions, have been found in high concentrations throughout the Waikato River.

Scientists will not know if the bloom is toxic until Monday.

Yesterday, officials put up signs from Orakei-Korako at Taupo to Port Waikato warning people that contact with the water could be harmful.

Mr Vant said the rain of the past few days would not have been enough to destroy the algae, which have been recorded at more than double the safe limit in several hydro lakes along the Waikato River.

"We would need a very large amount of flushing to get rid of the algae that are already stored in the hydro lakes."

If anything, Mr Vant said rain probably helped the algae because it provided a valuable food source.

"What the rain will have done is carry more material from the land, in particular nitrogen phosphorus, into the hydro lakes.

"The algae should be very pleased with that because that's what they grow on."

Mr Vant said more tests were taken from six points along the river yesterday to establish how much algae remained in the water and what impact the rain had had.

Medical officer of health Dr Felicity Dumble said the testing would continue and warning signs would remain in place until scientists found out if the algae were toxic.

Dr Dumble said most people were taking notice of the health warnings.

She had been contacted by dozens of groups wanting more information about the risk of entering potentially toxic water.

The potential risk proved more than enough to keep some groups out of the Waikato altogether.

A water-skiing competition, to be held at Lake Karapiro this weekend, was relocated to Taupo at the last minute.

Organisers spent most of yesterday trying to contact up to 150 people to tell them the competition had changed locations and they would need to find new accommodation in Taupo.

A rowing event at the Lake Whakamaru Christian Youth Camp, just south of Tokoroa, was also cancelled following the health warning.

But not everyone chose to adhere to the warning.

Marathon swimmer Paul Percy, who is swimming the Waikato River to raise awareness about diabetes, has decided to continue with his campaign.

He said he had been in the water for the past 10 days and not had any health problems.

He did, however, cancel a Dip for Diabetes event at Lake Karapiro because he did not want to encourage other people into the water, while there was a potential for health problems.

Herald feature: Environment