West Coast rain gauge can't deal with heavy rain

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The Metservice says it will have to change its rain gauge at Haast because it is "not responding well to periods of heavy rain".

If the figures are to believed, Haast has recorded far less rain than Greymouth or Hokitika this year.

Lake Moeraki Wilderness Lodge owner Gerry McSweeney said he had noticed a major anomaly in the figures for the past six months between the rainfall figures the Metservice provided for Haast and the data he collected at Lake Moeraki, 30km north.

Lake Moeraki has been consistently recording 60 to 75 per cent more rain than Haast.
Dr McSweeney has run a Metservice weather station for 26 years and believed his current data was reliable. Historically, Lake Moeraki received about 10 per cent more rain than Haast.

He also operated the fully automated rain gauge there for the National Institute of Water and Atmospheric Research (Niwa).

He noted the Metservice records published daily in the Greymouth Star were, for the first time, showing Haast has been recording less rain than Hokitika and Greymouth. "I simply don't believe this," Dr McSweeney said.

From April 24 to April 29, he recorded 265mm of rain at Lake Moeraki, whereas Haast had just 163.4mm. From May 6 to 10, Lake Moeraki recorded 202.5mm of rain, and Haast 114mm.

Dr McSweeney contacted the Metservice, which replied: "We are planning on changing the type of rain gauge used at Haast. The feeling is that the type currently used is not responding well to periods of heavy rain fall."

Metservice meteorologist John Law told the Greymouth Star today it looked as if the Haast rain gauge was under-reporting rainfall in the area.

"This may be due to a fault with the instrument and the observation team are currently investigating the device and hope to have it operational again very soon.

We are grateful to the observer at Lake Moeraki for sharing his observations."