Water

Continental waters

Continental waters consist of water bodies like glaciers, rivers and lakes. Differently from seawaters, they are characterized by a low salinity and they move towards the sea because they are not too deep.
See the different landscapes that we can encounter when we have a walk on the beach, on the mountains or on the hills.

• Glaciers form above the permanent snow line due to the accumulation of water at a solid state (snow that transforms into ice). The line varies according to the latitude on which continental glaciers (that uniformly cover wide areas) and mountain glaciers (that occupy mountain valleys) form. Below the permanent snow the ice melts and the water is present in a liquid state.
• watercourses, streams and rivers collect the water that flows on the Earth’s surface and that is in continuous contact with groundwater  
• the lakes are temporary deposits of water on continental depressions. They are supplied with water by watercourses called tributaries. The water flows into the out-flowing streams, streams or rivers that originate from the lake. Lake water has a low salinity, but has plenty of suspended material, and its temperature depends on local climate conditions. Also the water of big lakes can move and originate variations called seiches, due to differences in atmospheric pressure.

Not all the water that comes back to the mainland through precipitations is collected by the rivers, lakes or trapped in glaciers. A part of it filters on the soil and goes down into it due to the force of gravity until it reaches a layer of waterproof rocks that stop the passage of water: a water-bearing stratum is created. When this condition does not occur, in order to reach the water-bearing stratum artesian wells are built and the water can be extracted as it reaches the surface after being subject to a high pressure.  
The continuous exploitation of underground water determines the emptying of water-bearing stratums and lowering of soils. This occurs in Venice as a consequence of the extraction of water used for industrial aims in Marghera port area. Instead, when the exploitation occurs near coastal regions, the seawater filters underground to occupy the free spaces left by fresh water: this generates serious damages to agriculture and vegetation, as it is happening along Ravenna coast, where wide pinewood areas are dying.