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Update on Nordic hydro: Increased risk for flooding

Eylert Ellefsen
Archived blog post. This blog post has been transferred from our previous blogging platform. Links and images may not work as intended.

The risk for severe flooding and water spillage in the Nord Pool is on the rise. The reason is that the latest observed temperatures, and forecasted low temperatures, expectedly will further delay the melting process. Inevitably this will shift the melting to occur during periods with higher temperatures than previously expected.

The effect, in terms of inflow, is monitored and forecasted by EQ’s hydrology. Below you can see some details in this.

Be advised that, the summer the situation is rather unchanged: We still expect strong spillage from reservoirs in Norway, given normal precipitation levels through the spring and July.

Cold weather in the Nordic region increases flooding risk

The snow/groundwater reservoirs are in Norway, Sweden and Finland close to all-time high levels.

For Norway, the Norwegian water and energy authorities (NVE) are giving weekly updates of the flooding risk during the spring. In their announcement on 27 April, the conclusion was that despite very high snow levels in Norway, there is a limited risk for extreme flooding because of normal temperatures and precipitation below normal.

EQ has not observed any flooding signals from Sweden and Finland yet despite very high snow levels in some regions.

Cold weather and low inflows until end week 20 (17 May)

The latest weather forecasts (as of 6 May) show significantly lower temperatures than seen in the forecasts last week, see chart below for Norway.

Temperatures in Norway as forecasted on 6 May.

Temperatures during the upcoming weekend and start of next week will be about 5 degrees below normal. That delays the melting process, the inflow will not increase (as it usually does in early May), and the snow levels will not decline. The latest forecasts for Sweden, however, shows that inflow levels could reach normal levels at the end of week 20. See inflow forecasts for Norway and Sweden below.

For week 20 we estimate 26% of normal for Norway and 48% of normal for Sweden.

Snow levels for Norway and Sweden

The very low inflow levels and moderate precipitation means that the snow levels remain more or less unchanged until the end of week 20 (17 May).

In the charts below, you see the current snow levels for Norway/Sweden in comparison to normal and the 20 years variation band.

Notice that the snow/groundwater models are run as gross models, while the statistics are based on the net levels where the spilt water is subtracted. For Norway, we have made a preliminary net curve as we expected about 11 TWh spillage this year.

Weekly snow/groundwater for Norway (GWh). Gross (blue) and net (dashed brown).
Weekly snow/groundwater for Sweden (GWh).

We see how the 2020 snow curve is nearly flattening out weeks 18 – 20, in a period where we usually see the start of the melting season. The current situation is, in fact, extreme and the flooding risk for the spring has increased from last week.

The snow reservoir for Norway is about 190% of normal (gross) end week 20. The net number is 160%. The inflow could be 56% (gross) or 40% (net) higher than normal for the period week 21 – 33.

The Swedish snow reservoir is at a 20-year all-time high too, and we expect about 30% higher inflow than normal during the weeks 21 – 33.

Final words

EQ follows the situation and gives you updated reports during the spring and the summer.

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