Effects of Climate Change on Hydrology and Hydropower Systems in the Italian Alps

In this study we assess the impact of climate change on the hydrological cycle of an Alpine catchment and on the management of hydropower systems. We apply the traditional climate change impact study approach, known in the literature as “scenario-based” approach, to the case study of Lake Como catchment. The “scenario-based” approach consists in employing a modelling chain, which comprises the definition of Green House Gases emission scenarios, the simulation of climate models and hydrological models, and the simulation of the impact on water resources.
We take into account an ensemble of climate scenarios, comprising two Representative Concentration Pathways (RCPs), seven General Circulation Models (GCMs) and five Regional Circulation Models (RCMs). The analysis of the climate scenarios on the domain of interest shows an increase in temperature and a seasonal shift in precipitation, causing drier summers and more rainy winters. We apply a statistical downscaling to the climate scenarios in order to match the adequate spatial resolution needed for hydrological modelling. We adopt Topkapi-ETH, a physically-based and fully distributed hydrological model, to reproduce the response of the catchment hydrology to climate change. The employment of a spatially distributed model is due to the possibility of assessing the impact of climate change on different areas of the catchment. Moreover, Topkapi-ETH allows to simulate anthropogenic infrastructures such as reservoirs and river diversions, which are widely present in the Lake Como catchment. The simulation results over the XXI century scenario show a seasonal shift in the hydrological cycle, with lower flow in summer, higher flow in winter, and an earlier snowmelt peak. This results in different patterns of storage building in the Alpine hydropower reservoirs. Finally, we analyze the uncertainty on hydro-climatic variables associated to climate modelling. Results show that the uncertainty related to the choice of the GCM is the most critical, but comparable to the one of the RCM. The choice of the RCP is generally less crucial for short lead times, but it increases in relative terms for longer lead times.

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1 I N T R O D U C T I O N 1.1 setting the context Climate change is considered to be a key factor in the availability of water resources during the XXI century [IPCC, 2014]. The rise of temperature and the shift in the distribution of precipitation at the global scale will affect the hydrological cycle and thus the water re- lated human activities. The hydrology of the Alpine regions is likely to be affected more then others since they are characterized by a high presence of snow and glaciers and are more sensitive to climate con- ditions [Zierl and Bugmann, 2005; Beniston, 2003]. The temperature increase will cause an earlier snowmelt and a shift in temporal and spatial precipitation patterns will considerably change water avail- ability. Furthermore, the impact of climate change on hydrology will be accentuated by the glaciers retreat [Haeberli and Beniston, 1998]. The hydropower plants installed in the Alps play a key role in the sup- ply of electricity and, due to their flexibility compared to other elec- tricity sources, they also provide a certain stability in the international network [Gaudard et al., 2014]. Moreover, their importance as a key resource is growing with the increase of power installed in intermit- tent renewable energy sources such as wind and solar power. Since the patterns of production of wind and solar power are very irreg- ular, and other traditional sources of electricity (e.g., nuclear power and fossil fuel) are less flexible, hydropower is a strategic source for the future. Hydropower in a mountainous country like Switzerland represents 59.7% of electricity generation [Energiebundesamt, 2012], while in Italy this value decreases to 13.2% [Terna, 2012], mantaining anyhow a considerable share of the national production. The changes currently taking place in the electricity market due to the increasing share of renewable energies and the implementation of an energy stock exchange are leading to several transformations in which hy- dropower will be one of the main players. In such a context, it is important to investigate the complex relation- ship occurring among climate, water availability, and hydropower production. When dealing with climate change, the uncertainty related to future projection can not be neglected. Climate change impact studies are the result of a complex modelling chain, which comprises the defi- nition of the Representative Concentration Pathway (RCP), the Gen- eral Circulation Model (GCM), Regional Circulation Model (RCM), the downscaling procedure, the hydrological modelling, and the mod- 1

Tesi di Laurea Magistrale

Facoltà: Ingegneria

Autore: Pietro Richelli Contatta »

Composta da 165 pagine.

 

Questa tesi ha raggiunto 50 click dal 01/12/2015.

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