By Daniel Collins
With the sun shining and last week’s snow all but gone in Christchurch, it’s hard to imagine that the city almost ground to a halt. But not the hydrologists. While Ross was collecting snow in a saucepan, two other NIWA colleagues – Chris Appleby and Jeremy Rutherford – were out in the field doing more rigorous measurements, and far more of them. TV1 News caught them in the act.
They were making hundreds of measurements, recording how snow depth and density varied in and around Christchurch. As Jeremy put it, “snow is notoriously spatially variable”, so to get a decent picture of how much snow fell, measurements had to be made in as many locations as possible.
The one density measurement mentioned on the news clip was of some snow comprising 23% liquid water, the rest being air. Ross’s measurement from his garden was 14%.
As it turned out, many readers of The Press were also making measurements last week, at the paper’s request. A map of snow depth was printed in the paper’s Wednesday edition (17 August; alas, it’s not online). A high of 30 cm was reported in Cashmere and Huntsbury along the Port Hills, a low of 13 cm in Shirley and Burnside, while most of Christchurch were in the upper teens and low twenties. A nice example of citizen science.