Italy is a southern European state, corresponding to one of the best identified European natural regions, given the clarity of the maritime and land borders: the Alpine chain, with which it connects to central Europe (from W to E: France, Switzerland, Austria, Slovenia). As a natural region, between the Alpine watershed and the three seas (Adriatic, Ionian and Ligurian-Tyrrhenian) that surround it, the Italy (with the islands lying on its continental shelf) has an area of just over 300,000 km 2. Some continental regions (Canton Ticino, Istria), island regions (Corsica) and two autonomous states (San Marino and Vatican City) included in these limits are not part of the Italian state.
The Latin name Italia is of Oscan origin (Viteliu). The ancients derived it from that of an enotrio prince, Italo, or put it in relation with Lat. vitulus “calf”. According to modern scholars, Italy would mean “land of the Itali” and the Itali would have been an Italic population whose totem was the calf. The name initially designated (Ecateo) the southern extremity of Calabria; later (Herodotus) it extended to Metaponto and Taranto; then, in the 3rd century. BC, to Campania; shortly after, to the whole peninsula south of the Arno and Esino rivers and finally to the Alpine chain (Polybius and Cato). The official sanction of the name came with Octavian in 42 BC; the administrative union of the islands with Diocletian (Italian diocese). The geographical meaning of the name has always remained in use ever since, beyond the historical-political events.
The rich Italian hydrography involves a vast underground network, thanks to the great extension of limestone formations and coarse floods that feed mostly perennial streams.
Many lakes are scattered throughout the territory, especially in the summit areas of the Alpine mountains (circus lakes, generally small), in the pre-Alpine area (glacial excavated lakes, including Lake Garda, the largest of Italy), in the regions of recent volcanism (crater lakes), in the coastal strips characterized by dune strings (coastal lakes).
Italian rivers convey an average of 155 billion m3 into the sea every year of which 31% belongs to the Po system, 32% to the other Adriatic rivers, 26% to the Ligurian and Tyrrhenian ones, just 4% to the Ionian ones and 7% to the rivers of the islands. The glacial and nival regimes, typical of the watercourses fed by the melting of glaciers and the snowpack, have maximum flow rates in the summer months and minimum rates in winter; the fluvial regime, in the rivers that originate below the persistent snow limit, has flows conditioned by the rainfall regime. There is also a series of mixed regimes, regulated not only by rainfall but by the existence or otherwise of lakes, as well as by the possible presence of limestone rocks, which release rainwater even in periods of absence of rainfall.
The Po, the largest Italian river, is 652 km long and has a basin of about 70,000 km, collecting the waters of a large part of the internal side of the Alps and the external one of the Northern Apennines; its average flow, not far from the mouth, is estimated at 1460 m 3/ s; the amount of sediment that leads to the sea is abundant and has built a delta of considerable size. The slope of the bed, in a large part of the Po valley, is modest; 150 km from the mouth the river is only 2 m above sea level, in Pavia it already has a level higher than that of the plain, and from here it is dammed up to the mouth, where the elevation reaches 6 m. The second Italian river is the Adige, analogous to the Po for the hanging bed, the embankments, the sudden floods in autumn. The rivers of the Adriatic-Ionian side have a short course, modest extension of the basin, accentuated summer lean, conspicuous contribution of solid materials. The tributary rivers of the Tyrrhenian Sea often have longitudinal trunks, connected by intermontane basins or by cross sections, so they are characterized by a longer course and a more extensive basin. Typical are the Arno and the Tiber. The streams of Sicily, Sardinia and Calabria depend on rainfall, so they have conspicuous floods in winter and low summer temperatures; some are completely dry in summer, such as the Calabrian and Sicilian ‘rivers’, with a very wide and pebbled riverbed, due to the violent floods that occur as a result of rainfall.