Spatial and temporal patterns in the energy potential of surface water in Sweden
Abstract
Recent investigations show that land-use changes and hydropower regulation has caused significant changes in the annual runoff periodicity in Swedish rivers during the 20th century. Those changes in the annual periodicities are caused by structural alterations in river basins affected by intense agriculture and hydropower regulation. In addition, we found significant long-term (decadal) fluctuation in the available energy potential of surface runoff of Sweden, which has a significant impact on the planning of hydropower regulation and watershed management plans. Based on daily precipitation data in the period 1961 - 2005 we simulated using the HBV model the surface water runoff and the associated energy potential in 1001 watersheds covering the entire surface of Sweden. Comparisons were made with individual time-series of river discharge dating as far back as to the 1850s. As an average for the entire surface of Sweden, the five-year running mean of the energy potential of surface water varies between 115 TWh / year up to nearly 180 TWh / year with significant fluctuations on different periods extending up to at least 10 years. The 30-year running mean of the discharge of River Dalälven shows a decrease from 360 m3/s in the mid 19th century to 290 m3/s in 1965 and, thereafter, a significant increase. The more than century-long discharge time-series also shows decadal fluctuations that are well correlated with the fluctuations noted over the entire surface of Sweden. The fluctuations of energy potential show coherence up to 30 - 40% with the North Atlantic Oscillation index. The handling of these significant temporal variations in energy levels for hydropower purposes depends on the spatial coherence of river discharges. Consequently, we analysed the coherence spectrum of major rivers and found for the most separated rivers in Sweden that the coherence approaches asymptotically about 20 - 25 % for long-term variations. Neighbouring river basins could have coherence spectra starting at just few percents for weekly periods and increasing to over 90% for annual periods. The low coherences in river discharge on the national spatial scale is an important 'asset' for dealing with the significant temporal fluctuations in energy potential within hydropower production.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.H23J..05W
- Keywords:
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- 1807 HYDROLOGY Climate impacts;
- 1804 HYDROLOGY Catchment;
- 1878 HYDROLOGY Water/energy interactions;
- 1880 HYDROLOGY Water management