Future perspectives of run-of-the-river hydropower and the impact of glaciers' shrinkage: The case of Italian Alps

We assess the impacts of nine climate-change scenarios on the hydrological regime and on hydropower production of forty-two glacierized basins across the Italian Alps, assumed exemplary of similar systems in other glacierized contexts. Each of these basins includes one (or more) hydropower plant, here treated as a run-of-the river system. We implemented a semi-distributed hydrologic model that divides each basin in elevation bands and reconstructs orographic effects on both precipitation and temperature. The nine climate-change scenarios quantify the individual and combined effects of an increase in temperature and a change in liquid-solid phase partition. The simulation horizon is 2016-2065. Thus, we avoided long-term scenarios and worked at short medium range to maximize the relevance of this work for decision makers. Our results predict a decline of about -30% in average summer runoff across all basins compared to present. Because most of this decrease in runoff occurs during high-flow periods when the run-of-the-river capacity of these plants is exceeded, this result translates into a median decrease of about -3% in hydropower production for run-of-the-river systems through 2065, across all the basins and all scenarios. The predominant cause of this decline is glacier shrinkage, whereas different temperature or precipitation trends plays a marginal role. Run-of-the-river hydropower production in basins where the current glacier coverage is less than 10% of total area is particularly robust to climate change.