Case Study

The analysis is addressed to four sub-catchments of the Upper Tiber River basin. The basin is located in Central Italy and its topography varies from 200 m above sea level in the south and 1,080 m in the east. The region is characterized by a Mediterranean semi-humid climate with precipitations occurring mostly in the autumn-spring period. Based on the period 1951-1999, the average annual precipitation is about 890 mm. The maximum mean monthly precipitation occurs in November (130 mm) and the minimum in July (40 mm). The minimum and maximum temperature are, on average, 16.9°C and 26.7°C in summer, respectively and 3.2°C and 9.7°C in the winter, respectively. The four sub-catchments, Niccone (137 km2), Caina(206 km2), Genna (91 km2) and Cerfone (284 km2), are shown in Fig. 11.1a.

Raingauges Gauging stations Thermometers Study catchments Trasimeno Lake stream network

20 30km

Legend

Raingauges Gauging stations Thermometers Study catchments Trasimeno Lake stream network

SCENARIO A2

Jii Feb teb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec i 2020- 2050 2080

SCENARIO B2

Jan Feb Mar AprMayJun Jul AugSept Oct NovDec

Jan Feb Mar AprMay Jun Jul AugSept Oct NovDec

2020 2050 2080

20 30km

Fig. 11.1 (a) Morphology of the Upper Tiber River Basin and location of the hydro-meteorological monitoring network. The shaded regions refer to the four catchments selected for this study. (b, c) Monthly changing of rainfall and temperature derived by the emission scenarios A2 and B2, provided by GCM-HadCM3 models for Central Italy

The methodology has been applied considering both the actual climate conditions such us defined by time series of rainfall and temperature observed in the period 1989-2007 and the ones derived by the emission scenarios A2 and B2 provided by GCM-HadCM3 models of Hadley Centre (UK) and underlined in the "Special Report on Emission Scenarios" (SRES). These two scenarios are of reference for two opposite hypothesis of social development [9, 10]. In particular, the analysis has been addressed considering the scenarios for rainfall and temperature at 2020, 2050, 2080 that are representative of the average monthly changing at short term (2010-2039), medium term (2040-2069) and long term (2070-2099), respectively. Based on A2 and B2 scenarios, for the central Italy, it is expected that in 2080 the total annual rainfall decrease of -0.5 mm/day and 0.14 mm/day, respectively, while the mean annual temperature increase 5.3°C and 3.9°C for A2 and B2 scenario, respectively (see Fig. 11.1b, c). The rainfall, overall, tends to decrease in the summer for all scenarios; whereas in October and April the rainfall fluctuations go from -30% to 50%, for both the scenarios. These monthly changes were applied to time series observed in the four sub-catchments of Upper Tiber basin to obtain perturbed series of temperature and rainfall. In this way, three perturbed series of temperature and rainfall were generated, each one representative for the period 2020, 2050 and 2080.

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