Why monitor snow
Snow is a vital source of water for ecosystems and people. Snowpack is one of the most important resources in mountain regions, both economically and ecologically. Mountains act as natural reservoirs: they store snow in winter and release it in spring as temperatures rise. Knowing how much water snow will provide each year is essential for short- and long-term planning.
Snow Water Equivalent (SWE) is the amount of water contained in the snowpack. It helps water managers and hydrologists plan water use.
Key figures
| Indicator | Value |
|---|---|
| Water supply coming from snowmelt | 60–70% (higher in high-mountain regions) |
| Snow produced by 1 cm of rain | from 2 cm (wet snow) to over 50 cm (dry, powdery snow) |
| Main SWE monitoring metrics | 3: percent of normal, rain/snow charts, 30-year trends |
| Historical comparison period | 30 years |
| SWE measurement range with a CRNS sensor | 0 – 10,000 mm water equivalent |
| Sites in the ARPA Veneto SWE network | 25, Italy’s first continuous remote monitoring network |
| CRNS measurement features | Contactless · continuous · autonomous · no snow depth limit · maintenance-free |
Measuring SWE
Measuring the water in snow is not easy. Monitoring sites are often hard to reach, and the snowpack changes constantly, sometimes suddenly. Air temperature controls how much water a centimetre of snow holds: 1 cm of rain can produce anywhere from 2 cm of wet snow to over 50 cm of dry, powdery snow. This is why snow depth does not directly show how much water the snow contains, and why SWE is the more reliable reference.
The three main metrics
- Percent of normal: compares current snow conditions with the typical historical conditions for the same basin on the same day.
- Rain/snow charts: with climate change, more precipitation falls as rain instead of snow. Water-year charts compare the two forms of precipitation and help identify snow drought.
- 30-year trends: show annual observations over the last 30 years, so the current year can be compared with past ones.
Snow and climate change
Rising temperatures may shrink the snowpack, with a strong impact on water resources.
- Water availability: snow melts earlier, so water reaches rivers sooner and is less available in summer. Flow becomes more variable, both from year to year (floods one year, low flow the next) and within the same year (higher flow in winter, lower in summer).
- Agriculture and livestock: lower summer flow reduces water for irrigation and food availability, as well as the quality and quantity of forage.
- Infrastructure: more rain and less snow change the timing and size of peak flows. This means more erosion, more stress on dams, canals, roads and bridges, and the need to release water from reservoirs earlier.
- Ecosystems: lower summer flows warm the water and put freshwater fish under stress. Earlier snowmelt also disrupts riverside vegetation and can favour invasive species.
State of the art: CRNS sensors
The most innovative way to measure SWE is the cosmic-ray sensor (CRNS, Cosmic Ray Neutron Sensing). It monitors SWE at the installation site without contact, continuously and fully autonomously, with no snow depth limit and no maintenance.
ARPAV (ARPA Veneto) has installed CRNS SWE sensors at 25 sites, creating Italy’s first network for continuous, remote snow monitoring.
Applications of SWE monitoring
- Basin-scale water resource management
- Hydropower generation
- Avalanche risk monitoring
- Structural monitoring of large buildings (snow load)
- Snow and weather research
The Finapp impact
- Contactless measurement of water content in soil and snow
- Precise, digital water management
- Less waste, lower energy costs, higher productivity