The lake is a mass of fresh, brackish or salt water, of very variable dimensions and depths, which rests for a more or less long period in a natural depression completely surrounded by emerged lands and without direct communication with the sea, whose area central is always kept free from vegetation. The ratio between the substances that contribute to its salinity is very variable, while it remains constant in the seas.
Each lake is fed by the waters of the surrounding catchment area through one or more tributaries, and the water flows into the sea through an emissary. The balance between nutrition and water loss keeps the lake alive.
The most common situation is the equilibrium between tributary and emissary, but there are cases in which the lake has only the emissary and the water derives from precipitation or from a phreatic source while it is sold not only by the emissary, but also by the ‘evaporation.
Other lakes have tributaries but no emissaries and the water is sold by evaporation or through an underground flow.
Finally, there are those without tributaries and emissaries and their existence depends on the balance between precipitation and evaporation. In this case, salt lakes can form.
If the water flows through a stream in areas at lower altitudes to the sea, you have an open lake; it is closed if there are no emissaries completely, it has no contact with the sea and is surrounded by hills or high lands.