Impacts of climate change scenarios on runoff regimes in the southern Alps

Abstract

Abstract. The potential impact of climate change scenarios on the runoff regime in the Italian Alpine area was investigated. A preliminary analysis of the output of three Global Circulation Models (PCM, HADCM, ECHAM) was needed to select IPCC-based scenarios for the 2000–2099 period. Two basins, 1840 and 236 km2 in size, respectively, and with different glaciated areas and storage capacity of reservoirs were selected as case studies. The PCM model, the one capable to better reproduce the observed rainfall regime in the investigated area, with the IPCC SRES A2 scenario was adopted for the meteorological forcing. On average for the two basins, an increase of annual precipitation of about 3% is expected for the 2050 scenario and should not significantly vary at the end of this century compared to present conditions. At the same time temperature should increase of 1.1°C in 2050 and 2.4°C for 2090. Because of the coarse resolution of the climate models' output, the statistics of the simulated rainy days and daily precipitation were adapted to the scale of the two selected basins using a modified version of the multiplicative cascade β-model, proposed in the literature to explain the statistics of intermittent fully developed turbulence. As regards to land cover, glaciated areas are decreased, in the future scenarios, according to the Kuhn's concept of equilibrium line adaptation to climate fluctuations. The tree-line altitude is increased, according to the observed trend since the end of the Little Ice Age: thus boundary conditions for evapotranspiration changed. The resulting meteorological variables and hydrological parameters were used to run the WATFLOOD hydrological model in order to assess the changes of runoff regimes in the two watersheds. A decrease of about 7% of annual runoff volume for the 2050 scenario and of 13% for the 2090 scenario was estimated, on average, at the outlet of the Oglio river basin, the largest one. In the smaller Lys basin, where the glaciated area is 8% of the total area, the annual runoff is foreseen to decrease by about 3% (for the 2050 scenario) and 14% at the end of this century. Also the runoff regime changes are significant, with an increase of spring melt and a decrease of summer and autumn runoff. No clear evidence is found for changes in the precipitation extremes and in the fraction of rainy days.

Hydrologic vulnerability to climate change of the Mandrone glacier (Adamello-Presanella group, Italian Alps)

“…Discrepancies between the model and the observations are comparable with those reported by [9] and [30], who analyzed the signals of three Global Climate Models in an area including the Adamello glacier. Also the temperature regime is fairly in agreement with observations, at least in the summer period, as will be discussed in the fourth section.…”

“…As different climate models and socio-economic scenarios result in highly variable meteorological predictions, we also compared the average mass balance obtained by applying the multiple-linear regression equation (7) using temperature and precipitation predictions by three global climate models (GCMs), already investigated for the Adamello glacier area in [9]. In this way we obtained in Table 4 ranges of inter-model and inter-scenario mass balance simulation, which are an estimate of the degree of 'uncertainty' of mass balance projections depending on the climate forcing adopted: even if B2 and A2 scenarios were not used to simulate the mass balance with PDSLIM, they indicate a high range of temperature predictions for the same scenario.…”

Evaluation of future hydrological cycle under climate change scenarios in a mesoscale Alpine watershed of Italy

“…Citterio et al, 2007;Maragno et al, 2009; and in turn a modified hydrological cycle (e.g. Barontini et al, 2009). …”

Water yield responses to climate change and variability across the North–South Transect of Eastern China (NSTEC)

“…WY represents the maximum water availability for natural ecosystems and human society. Due to the interactions between P and ET and their high spatiotemporal variability, WY is highly variable and likely the most uncertain component in water balance (Barontini et al, 2009). Since P can be measured relatively easily, recent hydrologic studies have focused on ET, a flux that is more difficult/costly to quantify at local, regional and global scales (Fernandes et al, 2007;Gao et al, 2007;Jung et al, 2010;Sun et al, 2011;Bing et al, 2012).…”

“…The sign and magnitude of changes in the climatic variables vary by location and time as predicted by IPCC and empirical findings from historical studies (IPCC, 2007;Dang et al, 2007;Lu et al, 2009). Therefore, hydrologic change in response to climate change and variability is expected to be highly variable in space and time, and large uncertainty exists (Davi et al, 2006;Vicuna and Dracup, 2007;Barontini et al, 2009;Zhang et al, 2009). Understanding the spatial and temporal ecohydrological responses to global change is especially critical to China given the large challenges of water shortage facing this rapidly developing country (Liu and Xia, 2004;Piao et al, 2010).…”