L'acqua nei fiumi e nei laghi

The rainwater on the lands above sea-level is approximately 108400 km3 year-1, and of this about one third reaches the oceans by way of rivers. The remaining two-thirds return to the atmosphere by evaporation and transpiration from plants. To satisfy the current demotechnic needs for fresh water, we must refer to the approximately 40000 km3 year-1 which make up the rivers, lakes and artificial reservoirs. In this chapter, the principal rivers and lakes on the various continents are described, listing their geographic location, flow rate, volumes, etc.; Italian rivers and lakes are treated in greater detail. Artificial reservoirs are also mentioned.