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Norway – can water spillage be avoided?

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 hydrological balance in Norway is by the end of February estimated to be 22.5 TWh, which is close to all-time levels. During the last 20 years, we have only seen comparable situations during 2000 and 2005. Accumulated precipitation for January and February is estimated to be 45.6 TWh, which is about 22 TWh higher than normal. Inflows have been even more extreme with 170 % or 10 TWh above normal.

The hydro reservoir filling level by the end of February is estimated to be 53.2 %, which is 6.3 TWh above the normal. At the same time, the snow/groundwater level looks like it will reach 16.2 TWh above the normal.

The result of this situation means extreme reservoir levels by the end of August when the snow package has melted. We will look at present scenarios and conditions for the hydrological and power balance situation for Norway until the end of the melting season and further out.

Reservoir situation by the end of August

We assume that maximum filling in Norway by the end of August is restricted to be about 95% when taking into account skewness in filling rates between price zones. This year we see that NO4 – Tromsø has a rather low filling rate, and will most likely not reach max capacity by August.

A maximum usable reservoir filling of 95%, compared to the normal level of 82.1%, means a maximum hydrological balance of (95% - 82.1%) * 86.9 TWh = 11.2 TWh by the end of August. 86.9 TWh is the upper reservoir capacity.

  • The hydrological balance at the end of February (end of week 9) is forecasted to be 22.5 TWh (snow = 16.2, hydro reservoir = 6.3).
  • The maximum hydrological balance at the end of August (end of week 35) is estimated to be 11.2 TWh (snow = 0.0, hydro reservoir = 11.2).

A reduction of 11.3 TWh in the hydrological balance would be required to meet the maximum hydrological balance of 11.2 TWh. For this to be possible, the hydropower production must be 20% higher than the normal until the end of August. Will this be possible?

Our calculations show that the export volume from Norway must be about 4000 MW on average until the end of August to limit the reservoir filling.

See charts below for the reservoir filling and export.

The reservoir filling is based on snow-adjusted inflow and a hydropower production corresponding to the 4000 MW net export level.

For the export chart, see the comparison between our 2020-forecast to previous, wet years. The average total export these years were about 16 TWh, while the estimate for 2020 is 27 TWh (!).

4000 MW net export will, however, be very hard to obtain during offpeak-periods. 4000 MW until the end of August means a potential export of 17 TWh. We will most likely only see 75%-80% utilization, so we estimate about 3 TWh of water spillage due to export limitations.

Norway – weekly reservoir filling (percentage of max capacity).
Net export from Norway in MW/week (forecast for 2020 compared to wet years: 2012, 2015, 2016, 2017).

These calculations assume inflow levels based on normal precipitation during the whole period. As we already see, the 3 TWh water spillage could be higher, a lot higher, if we see more precipitation.

If we assume an extremely wet scenario, like the summer of 2011, we could end up with an 18 TWh water spillage during June–August. So a wet summer could cause an extreme flooding situation across Norway. Most price zones are exposed to flood risk, as we see it.

It’s about 25% probability that we will see 6-7 TWh spilt water this summer due to precipitation variations, in addition to about 3 TWh spilt water due to export limitations (mean scenario).

Closing words

The hydrological situation in Norway is extreme, and it can get even worse if we see precipitation stronger than normals during Q2 and Q3.

EQ follows the situation and updates with more blog stories when needed. Please contact us if you have any questions.

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