How deep is the snow at your place?
Snowfall is not routinely measured in New Zealand, but is an important part both of our natural hazards and our water resources.
Snow which falls at high elevations will generally melt slowly in spring; it will be absorbed by soil (for use by vegetation) or become runoff, which adds to stream flow. Snow which falls at low elevations will generally melt quickly after the snowfall, and be absorbed by soil and added to groundwater.
Measurements of snowfall at low elevations around New Zealand are few and far between, and yet the data would be really helpful in understanding how snowfall occurs, and quantifying snow-related risks to infrastructure (e.g. buildings, power lines, etc.) and impact on water resources. After all, the large majority of New Zealand's population and infrastructure reside closer to the coast than the mountains.
And so we'd like your help to measure snowfall. You can measure the snow depth after it snows and, if you're extra keen, measure the snow water equivalent (snow density) too.
Your measurements will help us to characterise the complex patterns of snow depth and water content which are important for monitoring New Zealand's water resources and snow-related risks.
- Safety first. Do not make any measurements if it puts you or anyone else at risk. Data is valuable, but not that valuable. See the Civil Defence page on storms
- Measure the snow depth (in mm, please).
- Choose a location (for example, your lawn, or local park, etc). Choose somewhere typical; don’t just focus on deep snow or snow drifts.
- Put a ruler vertically into the snow right down to ground level and record the snow depth in mm. Do this 10 times, each time at a different place in that location.
- Estimate how far apart these points are from one another: it could be just 10 metres or 100 metres. Don't make them further apart than that.
- Try to repeat measurements at the same places in your location, throughout the day during fine spells (not when it is snowing). Ideally, measurements should be repeated in the morning and the afternoon.
- If there are several days of snow, repeat these measurements at the same general location each day during fine spells, not when it’s snowing.
- Repeat these measurements at as many locations as you like, but keep your measurement records separated.
- Measure the snow water equivalent
- This measurement tells us how heavy the snow is, or its density. This is a very important parameter used to estimate snow loadings for buildings.
- Choose a location and measure the snow depth following the above instructions.
- Find an old saucepan (or similar cylinder) with straight sides, and measure its (inside) diameter
- Press the upside-down saucepan vertically down into the snow until you reach the ground (snow may need to be compressed into the pan – that’s ok)
- Pick up the saucepan and most of the snow should come with it. Pick up any snow that falls out and put it in the pan.
- Slowly melt all the snow in the pan, and measure the volume of water (e.g. with a measuring jug). Take care not to boil off the water.
- Repeat this exercise as many times as you’d like, being sure to keep the results distinct.
- Record the time of measurement, depth of snow, the diameter of the container, and the volume of melted water. Also record the location (e.g., in my garden or in a park, post code 9999 or street address).
- Send us your measurements. See 'Send us your measurements' below for more details
What will happen to the data?
The data will be given to any scientific study that asks for it. No personal information such as personal details and address will be made available.
If we have enough data, we'll develop a Google Map, shortly following the event, to share – it will be posted on this page.
We look forward to your wonderful, citizen-powered data!
If you'd like to know what the snow density is, the equations are shown below. Please note that they only work for cylindrical containers.
Snow volume (in mL*) = pi x ([Diameter in mm]/2)2 x [Depth in mm] / 1000
* mL = millilitres, or 1/1000 litres.
Snow density (in %) = 100 x [Volume of melted water in mL] / [Volume of snow in mL]
If snow depth = 180 mm, pan diameter = 200 mm, and the volume of melted water = 1620 mL,
then snow volume (mL) = 3.1416 x (200 / 2)2 x 180 / 1000 = 5655 mL.
Thus, snow density = 100 x 1620 / 5655 = 29%.
Last year, when we started this, we got a number of responses!
For each location, send us your 10 snow depth measurements (in mm) and whatever snow water equivalent (snow density) measurements you made. Be sure to include a description of this location (e.g., in my garden, in a park) as well as a post code (address is optional and will be kept confidential).
Also, make sure you include the location of the measurements and the date and time of observation.