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Large differences in Alpine hydro balances

Eylert Ellefsen - 3 August 2019 12:05

EQ's new hydrology models indicate that we enter August with large differences in hydrological balance across the Alpine area. Switzerland and Austria now have reservoir fillings of, respectively, 12% and 8% above their seasonal normal, whereas France and Italy are on their seasonal normal. High snow reservoirs and delayed melting during the spring, was followed by a heatwave end of June and start of July. This sparked melting, led to high inflow levels and ultimately rapidly increasing hydro reservoir levels in Switzerland and Austria. The graph illustrates the status in Alpine hydrological balances at the beginning of August.

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How did we end up here?

The difference in reservoir status may be explained by diverse development in many of the factors that contribute to the reservoir levels. The table shows net precipitation, inflow and net production, for the Central Western European (CWE) area and Italy in July.

Italy, as a whole, showed higher precipitation than normal, while the central part was rather dry. The temperatures averaged 2 °C higher than normal. However, notice that by mid-July temperatures were close to normal.

Italy and Switzerland came out with relatively high production, while the other countries produced slightly less than their seasonal normal. The total net hydro production (pumping plants not included) of about 19 TWh, represents about 20% of total consumption in the region.If we exclude Germany, which has low hydropower generation, the coverage is about 25%.

These numbers indicate the importance of hydropower in the spot markets during the summer period.

Delayed melting and a heatwave 

The hydropower situation in the Alpine region (CWE+IT markets) was influenced by the heatwave we saw at the end of June and during July. The seasonal snow levels melted very quickly during the last weeks in June/start of July, and hydro reservoir levels increased rapidly in Switzerland and Austria in particular due to the high inflows.


During July the inflows levels declined towards normal levels despite a rather dry period. This indicates that melting from glaciers contributed to higher reservoir levels in the central parts of the Alps.

Development in snowpack

The energy content in the snowpack varied across the Alps this year. For France, the snowpack was lower than normal, while for the Central Alps – Switzerland and Austria – the levels were far higher than normal. Due to precipitation and delayed melting during May, the Swiss snowpack was at an all-time high by end of May. The main melting process started as late as week 23, and we see from the charts the declining snowpack during weeks 24–30.

Temperatures by end of June increased towards 6 °C above normal (week 26), which means about 15 °C at 2000 meters above sea level.

We saw more or less the same development for Austria.

For France, the inflows did not exceed the normal due to moderate snow levels, while we for Italy saw inflows somewhat above normal in June/July as an average.

All-time high seasonal reservoir levels

The Swiss reservoir level end of July reached an all-time high and hydro production has increased due to continued high inflows. For Austria, the production has softened the last weeks as Austria is not so exposed to the high mountain areas as Switzerland. French hydropower production has been moderate during July and reservoir filling now close to normal.


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Topics: precipitation energy- inflow- hydrological balance- melting- hydro production

Eylert Ellefsen

Eylert Ellefsen

Senior market analyst and hydrology expert by Energy Quantified. He has held various leading positions within power market analysis for Markedskraft and now in Energy Quantified. Eylert is the go-to person for questions related to power price formation and hydrology.

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