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| Larch snow lysimeter site (depth = 63cm, density = 0.38, SWE = 24.0cm) |
Today's snow survey showed that the snowpack is more or less the same as in the last survey in mid-February. Snow densities have increased from about 0.3 to nearly 0.4 at the larch site, indicating that the snowpack has ripened considerably and reached a melt condition. The snow water equivalent is up slightly to 24 cm at the larch site, whereas it dropped about 2 cm to 16 cm at the cedar site.
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| 4 March: Stage = 51cm, Tw = 5C |
Downloading the stage data and plotting the hydrograph as below, we can see a very prominent flood event on 14 February. This is a typical late-winter rain-on-snow event, but the size of this event has only been exceeded once in the last 16 years of stream gauging for the months of January and February. Daily snowfalls occurred during the first 10 days of February, followed by rising levels of sunshine and rapidly warming temperatures, with a Tmax of 11.8 degrees and over 9 hours of sunshine on 12 February. This was followed by warm, cloudy and windy weather when overnight temperatures remained above freezing. On 14 February heavy precipitation of around 10mm/h and 40mm/d fell in the upstream area and Tmax reached 12.3 degrees, producing perfect conditions for rain-on-snow melt to occur throughout the basin. No sunshine was recorded, but wind speeds reached 11.3 m/s.
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| Rain-on-snow flood event on 14 February (peak Q estimated to be 18.5 m3/s) |
The three largest January/February rain-on-snow events over the past 16 years:
Date Stage (m) Q (m3/s) Daily Precipitation (mm)
2004 Feb 23 0.994 17.0 44
2009 Feb 14 1.278 32.0 52
2016 Feb 14 1.042 18.5 37
