Jason and Joey were up early this morning to shuttle the last remaining gear from the glacier, which was mostly related to a sonic distance ranger to be suspended over the stream to measure the water height over time. A week earlier we had suspended a cable across the stream at a location where the high banks would hopefully protect it from being washed away. Today we hung the sonic ranger on that cable, with the help of some metal conduit we salvaged from the glacier from previous campaigns. The idea is that once a minute, the unit beams down high frequency sound waves downwards onto whatever surface is beneath it. The waves then bounce off that surface and the unit receives them, counting the time it takes for this to happen. The speed of sound is a pretty straightforward function of air temperature, so the unit can then convert the travel time of the waves into a distance measurement. We use these instruments primarily to measure snow accumulation and ice melt on the glacier. But as the stream rises and falls, whether due to rain or to differences in ice melt throughout the day, the unit will also record this in the same way. To convert this height measurement into a discharge measurement, Jason manually makes discharge measurements at different stream heights to determine the relationship between height and discharge. We then use this relationship to convert all of the height measurements from the sonic ranger into discharge. Fortunately for Jason, it was not snowing or hailing today, so the conditions for wading across the stream and making measurements were substantially more pleasant than the last time he did it last week, though the higher water did overtop his hip-waders, leading to chillier feet.
Jason surveys while Joey writes down the numbers.
The water moves faster than the glacier.
It moves fast enough to move big rocks.
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Friday, 27 June 2008 04:37
Day 66: Final stream equipment installedWritten by Matt Nolan
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