Snow lysimeter troubles

Cover removed from lysimeter bucket to allow cleaning

Another day of sub-zero field work and snow survey difficulties, but we did at least have blue skies and sunshine! First up I had to dig out the lysimeter bucket at the larch site as looking at the logger data it had not moved at all. This is a sure sign of trouble as even during the coldest periods the bucket will tip several times a day due to ground heat melt at the base of the snowpack. I found the trouble - larch needles clogging the bucket intake - and cleaned it all up nicely. Mind you, I had to remove about 70cm of snowpack and get down on my knees to reach it, as it is set well below ground level.

Compared to two weeks ago, barely any new snow had accumulated. This is most rare for January, which along with December generally has the heaviest and most frequent snowfall. The weather can change dramatically over short distances in Japan. While we basked in sunshine all day in Murakami (albeit -3 degrees), the area from Niigata City to the south was getting hit by the biggest snow storm so far this year.

Snow survey can be tough

Snow lysimeter at the tributary site (elev. 140m)

Now sometimes snow survey can be a piece of cake. If the snowpack is not frozen hard, if the air temperature is just above freezing, if the sun is even shining, then for sure it can be one of the most pleasant things to be doing on a winter's day. Especially if the snow is quite deep, say around 2 metres, then it can be immensely satisfying taking your sample core of snow and weighing up the amount of water that will be released in the coming spring to irrigate the paddy fields and put your dinner on the table so to speak.

But the trouble with days like today is that with the sub-zero temperatures, your snow core freezes inside the sample tube, and no matter how hard you scrape, shake and prod, you just can't get the sampler clean for the next sample. It's immensely frustrating and can leave you in quite a bad temper. Maritime snowpacks will often contain a little moisture, especially at the base where you have ground heat slowly melting the snow, and it will instantly freeze to the aluminium sampler when you extract your snow core.

Still, my two students persevered and completed the survey as best they could at the tributary site, while I serviced the snow lysimeter and zipped up into the mountains a bit further to change the battery on the logger measuring spring water temperature. We also charged the winter storage gauge at the site, before brewing up hot coffee for lunch using the local stream water - delicious!

Snow survey (larch site): depth 69cm, SWE 20cm, density 0.29.