Snow and water management

Snowfall and weather codes issued by the KNMI are keeping the Netherlands in their grip this week. Temperatures will rise slightly in the coming days and snow will turn to rain. The exceptional amount of snow that has already fallen is a form of precipitation and will eventually melt. Snow then becomes (melt)water. We explain what this means for our water management here.

Quantity

The amount of precipitation can be calculated using this formula: 1 cm of snow equals 1 to 1.5 mm of rain. The snow depth in our management area, from Amsterdam-Noord to Texel, varies. When it thaws, it is estimated that around 10 to 20 mm of water will end up in the ditches and canals. Our pumping stations pump away around 15 mm of water per day. The amount of snow that melts is equivalent to a very wet day. This is normal in autumn and winter. The pumping stations can pump this water away. 

Groundwater level

Snow is a water reserve that does not run off. Only when it starts to thaw does the snow gradually melt, ideally. That is when this temporary water reserve starts to move. The meltwater then slowly sinks into the ground. This is good for replenishing the groundwater.

Frozen ground

It may be that the ground is still frozen or that warmer rain is falling on a thick layer of snow. In that case, the water cannot yet penetrate the ground and will instead run off into the sewer system and ditches and canals. This will be a combination of meltwater and rainwater. We do not expect this to lead to flooding.

Saturation

When temperatures rise and snow melts quickly, meltwater can potentially drain rapidly due to soil saturation. When saturated, the soil is 'full' of water and cannot absorb any more. In that case, our pumping stations will have to process a lot of water in the water system and at our fifteen sewage treatment plants. This treated water is then discharged into surface water. Here too, we do not expect this to lead to flooding.