A comprehensive analysis of the climate change and structural uncertainty on a complex water system. Case study in Como-Muzza, lake-agricultural district

Climate change models uncertainty analysis are quite addressed in the literature, especially after each IPCC report. In fact they o er comprehensive statistical information about the uncertainty of each GCM or RCM. In addition, the CC impact on the water resources is also well elaborated by numerous of studies and even governmental reports that o er guidelines for CC mitigation and adaptation. Anyway, after the AR5 was published, introducing the new concentration pathways and the new regional down-scaling framework EUROCORDEX, there are still no strong assessments and case studies that will asses the new approach and the uncertainty that follows. Over the decades, using Global Circulation Models to simulate future climate scenarios have been proved applicable and useful for depicting plausible future conditions and for climate change impact studies. However, given multiple GCMs simulations that are tuned to run under di erent assumptions (or initial conditions), a comprehensive uncertainty analysis is necessary in order to better understand those projected future conditions and its implications, as was done by IPCC in its Assessment Report. On the other hand, many studies on the climate change impact tend to use only a few projections within the impact assessment model, without justifying their choice of the scenarios. Moreover, small number of projections may also overlook the consequence due to the uncertainty in the GCM outputs. In this study we o er a broad vision by investigating many up-to-date GCMs outputs available from latest IPCC project, and evaluate their impact on a complex water system within a decision-analytic modeling framework. The studies starts with a detailed statistical analysis of the projected temperature and precipitation. Followed by assessment of their impact on the water related activities in Lake Como basin as well as the downstream irrigation districts represented by Muzza. The specfi c features of our approach, applied trough complicated multiple model simulations are: i.)Inflow generation, ii.) impact quanti fication based on a set of performance indicators, considering both upstream and downstream stakeholders; ii.)designing management polices, by meanings of optimal control techniques; iii.) preserving the multi-objective nature by Pareto Frontiers generation, evaluating the indicators and the uncertainty produced by diff erent GCM/RCM combinations. After the application of suggested framework, the three confliicting objectives are discussed under baseline, CC and co adaptive simulation. The water de ficit and the farmers pro t are more likely to be highly impacted of the CC, while the flooding stands more inert for some projected results. While the analysis run, we discuss the "inner" uncertainty of the CC scenarios, and prove that is rather significant . However the structural, modeling uncertainty is the most significant, despite the natural variability contribution is important and over cross with other sources of uncertainty. Notwithstanding the robustness of this analysis we o er a simple planning measure for successful mitigation and adaptation strategies facing the CC impacts.