Autumn dry spell continues in the Bay: last week’s rain welcome
The extended spell of dry weather is necessitating conservation measures by many domestic and commercial users in Golden Bay. Last week’s rain was welcome and in some cases prevented more serious measures being taken.
“We had 70 mm in the Anatoki, 44.5mm in the Waingaro, 58mm at Upper Takaka and 28mm at Kotinga closer to town,” said TDC water resource engineer Joseph Thomas. “There was a pretty useful 25mm up the Aorere as well.”
Mr Thomas said that the major water-takers would certainly have been worried about restrictions before the rain.
“The three main irrigators in the Takaka Valley are on controls that are determined by the river flow. That is influenced quite a lot by what the Cobb Dam does. If there’s no generating going on, there are low flows and so the irrigating will cease. We have electronic monitoring at Upper Takaka so we can easily keep tabs on what’s happening. The Cobb is not low at the moment. Ten days ago the lake was 45.2 per cent full; that’s a reasonable amount of water in storage. In 2008 and 2009 it got as low as two per cent full.”
The two other big water-takers are Golden Bay’s salmon farms at Anatoki and Te Waikoropupu. Until the last rain, they were both operating under some restrictions and, if the river flows had continued to decrease, further restrictions would have been imminent, said Mr Thomas.
“They’d both have been getting worried until the rain came, I’d say. The period from the end of March until the end of April is an important one, especially for the salmon farm at Te Waikoropupu. They’re a breeding farm now so their job is to produce fish for the sea-cages. That makes them a bit more flexible than they used to be, but they’ve been lucky to get that bit of rain.”
Mr Thomas also described the lower Takaka Valley as “a very interesting place, hydrologically speaking.”
“It’s a fantastic water resource. It’s the end of the system so that’s where a lot of water comes out,’ he said. “That’s why the alluvial gravels stay pretty wet unless we have an extreme drought.”
On the subject of water quality, Mr Thomas was equally enthusiastic. “I’ve been sampling water there every three months for 20 years,” he said, “and the quality has remained remarkably stable. The underground karst caverns store provide so much water storage that things don’t change much.”
Neil Wilson
