Hydropower, snow and ice

Hydropower, snow and ice

Change in glacial runoff is one of the most important consequences of future climate change in Iceland, Greenland and some glaciated watersheds in Scandinavia. Such changes will have a strong impact on the hydropower industry as flow volumes, seasonalities and extreme values change. The rapid retreat of glaciers also has other implications; for example changes in fluvial erosion from currently glaciated areas, changes in the courses of glacial rivers, which may affect roads and other communication lines, and changes that affect travellers in highland areas and the tourist industry.

Glaciers cover about 11% of the area of Iceland and they receive about 20% of the precipitation that falls on the country. They store the equivalent of 15-20 years of annual average precipitation over the whole country as ice. Substantial changes in the volume of glacier ice may, therefore, lead to large changes in the hydrology of glacial rivers, with important implications for the hydropower industry and other water users. Glacial runoff affects most of the larger watersheds in Greenland, which have been investigated with regard to hydropower potential, and it constitutes a relatively large component in the water budget of several hydropower plants in Norway. As an example, the Svartisen ice cap and smaller ice caps and glaciers in the same watershed cover about 50% of the drainage area used by the Svartisen hydropower plant in northern Norway.

Glaciers significantly modify streamflow in quantity, variability and timing by temporarily storing water as snow and ice and in liquid form on different time-scales. Annual basin runoff is enhanced or decreased in years of high or low melting, respectively. Glacial discharge shows pronounced melt-induced diurnal and seasonal cyclicity, the latter beneficial in many cases since glacial meltwater is typically released during periods of otherwise low flow conditions in many areas of the world. The effect of climate warming on glacial runoff includes an initial increase in total glacial runoff and peak flows, and a considerable amplification in the diurnal runoff oscillation, followed by significantly reduced runoff totals and diurnal amplitudes as the glaciers retreat.

In addition to the direct effect on runoff caused by glacier mass balance changes due to changes in climate, feedback effects caused by glacier dynamics may lead to migration of ice divides and subglacial watersheds and change subglacial water courses. This can in some cases cause locally very large relative changes in the discharge of rivers that issue from glacier margins, with implications for bridges, roads and other infrastructure.

During historical times, glaciers and ice caps in the Nordic countries have retreated and advanced in response to climate changes that are believed to have been much smaller than the greenhouse-induced climate changes that are expected during the next decades to century. The "Hydropower, snow and ice" work group of CES will analyse the effects of future climate change on glaciers and ice caps in the Nordic countries and their implications for the hydrology of glacial rivers.

For further information, contact
Tómas Jóhannesson tj@vedur.is

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