The Otago Regional Council will test the Arrow River in
the next 10 days to ascertain if didymo is present after a
sample taken from the irrigation system at The Hills golf
course tested positive.
ORC environmental monitoring director Jeff Donaldson said
despite surrounding rivers, including the Motatapu, Shotover
and Kawarau, testing positive for the micro organism, also
known as rock snot, it had been hoped its spread into the
Arrow River could be stopped.
The positive test at The Hills indicated didymo was present
in the Arrow irrigation scheme used to irrigate Sir Michael
Hill's championship golf course, but that did not necessarily
mean it was also in the river.
The Hills superintendent Brendan Allen said the irrigation
system began blocking last summer and a sample was sent to
Niwa for testing, which found ''traces of didymo''.
The water race feeding the irrigation scheme is located just
At the golf course the freshwater algae had clung to rocks,
which had created additional work for The Hills staff who had
cleaned The Canyons water feature, near the 17th hole,
several times over summer, while the bottom of the water race
appeared to be ''slimier''.
''It's not ideal, but we have found ways of dealing with it.
''Our waterways are not used by people swimming or fishing.
It's far more significant for recreational users and river
users than for us.''
When contacted by the ODT, Mr Donaldson said the Arrow
River was last sample-tested in 2009, at which time it was
not affected by didymo.
Sample testing ceased around that time because of how
widespread the problem had become, with council staff
carrying out observation tests instead.
''It's disappointing, but we haven't confirmed it yet.
''We always knew we were in trouble with the Arrow because we
had it in the Matukituki and Motatapu.''
Mr Donaldson said while it was possible for didymo to be in
an irrigation race and not a river, the likelihood was the
Arrow was also affected, but it was unlikely to be
''The thing about the Arrow River is it carries such a high
sediment load, the sediment would act like a Steelo pad.
''The river itself is never going to develop a lot of
material because of the sediment.''
The Queenstown Trails Trust, organiser of the Motatapu
events, which include a 47km mountain bike race from Glendhu
Bay through the Motatapu, Soho and Glencoe Stations finishing
at Arrowtown, had a cleaning station at the summit to protect
Arrowtown and the Wakatipu basin from lagarosiphon, a pest
plant present in some of Otago's waterways, and didymo, Mr
''The biggest mover of the organism is the human mover.
''We've tried to ensure that people going from an affected
waterway to an unaffected waterway check, clean and dry.''
Signage was already in place around the Arrow River to
educate users on didymo and how to prevent its spread.