Water resources in Iceland - Impacts of climate variability and climate change

University dissertation from Department of Water Resources Engineering, Lund Institute of Technology, Lund University, Sweden

Abstract: Hydropower is the main source of electricity production in Iceland. In 2005, 80.8% of all electricity was generated by hydropower (7015 GWh). Hydropower production is affected both by variations and changes in discharge. This thesis focuses on studies of the trends and the variability found in records of discharge and climatic variables, combined with watershed modelling and an analysis of a projection of future runoff in Iceland. The variability in the atmospheric circulation strongly affects precipitation and runoff in Iceland. A study of the relationship between sea level pressure, sea surface temperature, precipitation, temperature and discharge showed that the regional climate in Iceland cannot be directly related to one or two clear patterns of atmospheric variability, despite, or perhaps because of, the proximity to the northern center of action in the North Atlantic Oscillation, i.e., the Icelandic Low. The large decadal variability in climate and runoff in Iceland complicates the detection of a climate change signal in past record. The trend analysis showed that during the period 1961-2000, a significant increase in non-glacial discharge cannot be determined, despite an increase in measured precipitation. Meanwhile, spring temperatures have a negative trend, and spring floods therefore increase and tend to occur later in the year. These trends in past climate and runoff are not fully consistent with projections of future climate and runoff changes, where temperature in Iceland are expected to increase in all seasons and precipitation should also increase. A runoff map was calculated with the WASIM watershed model for all of Iceland for the period 1961-1990 and compared with a runoff projection for the period 2071-2100 according to a HIRHAM climate projection with boundary conditions from the HadAM3H model and A2 and B2 emissions scenarios. The evaluation of future runoff shows that runoff may become substantially higher in 2071-2100 than 1961-1990, mainly because predicted higher temperatures will increase the glacier melt. In addition, the seasonal changes in runoff are likely to be significant since higher temperatures cause less snow accumulation during winter. This projection of future runoff therefore implies great changes in the hydropower production potential in Iceland associated with climate change.

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