There were dozens of natural and artificial lakes in Greece, as well as many lagoons. Most lakes are freshwater and have formed mainly far from the coastlines as a result of tectonic or volcanic forces, or from the melting of glaciers. Lagoons -which are shallow coastal water reservoirs connected to the sea via a wider or a narrower opening- can be converted to freshwater lakes when the inflow of saltwater from the sea is for some reason interrupted and an adequate inflow of freshwater occurs from flowing drainage basins.
There are also lakes with salt or brackish water, when the substratum contains many soluble salts or it receives an inflow of saltwater. Artificial lakes, which are created by the construction of dams in brooks, streams or rivers in order to store water for various objectives (irrigation, farming, drinking water, etc), is the most important category of artificial (man-made) wetlands in Greece. They cover a considerable area and have contributed to the creation of significant ecosystems in the Greek wetland chapter.
Greece has internationally significant protected wetlands that are included in the International Convention of Ramsar (1971), signed by Greece and ratified by virtue of Legislative Decree 191/74. There are 10 wetlands listed below:
- Amvrakiko Bay: Etoloakarnania, Preveza, Arta
- Axiou Delta - Loudia – Aliakmona: Thessaloniki, Imathia, Pieria
- Evros Delta: Evros
- Kotychiou Lagoon: Ileia
- Mikri Prespa Lake: Florina
- Vistonis Lake, Porto Lagos, Ismaris Lake (Mitrikou) and Mesis Lagoons: Rodopi, Xanthi
- Koroneia and Volvi Lakes: Thessaloniki
- Mesolongi Lagoon : Etoloakarnania
- Nestou Delta and adjacent Lagoons: Xanthi
- Kerkine Lake: Serres