Climatic driven variability of surface water energy potential and implications for future hydroelectricity

Abstract:

An average year the production in Norway and Sweden is around 190 TWh and these two countries stand for about 70% of the hydropower energy stored in the available reservoirs of Europe. There are large challenges for the future use of this regulatory capacity with regard to balancing the electricity production in Europe under climate variability, compliance to water management plans under the Water Framework Directive and to the shifts to more renewable, but intermittent, energy sources required by the Renewable Energy Directive. A main aim of this project is to describe the variation over time of hydrological fluxes across Scandinavia in terms of their energy properties and to link that information to climatic factors and the regulation of hydroelectricty. Along these lines we explored daily data of digitalized hydro-climatological data from 1961, which were used to calibrate the HBV-model for 1001 watersheds in Sweden and the energy potential has been estimated as an average for that period (Figure below). These tentative results show that the surface water energy potential constitutes about one per mille of the latent heat flux due to evapotranspiration and it is, therefore, very sensitive to any fluctuation in the energy quantities of the hydrometeorological system. Tentative analysis suggests that the energy availability of surface water in Sweden exhibits significant decadal long fluctuations from 115 TWh/year up to 180 TWh/year, which follow several different time scales and periodicities, ranging from century-long trends to fluctuations occurring on time scales of a decade and shorter. In addition, 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.