The Eurotas or Evrotas (Greek: Ευρώτας) is the main river of Laconia and one of the major rivers of the Peloponnese, in Greece. The river's springs are located just northwest of the border between Laconia and Arcadia, at Skortsinos. The river is also fed by underwater springs at Pellana and by tributaries coursing down from Mt. Taygetos and Mt. Parnon, which flank the Eurotas valley to the west and east, respectively. The river is 82 kilometres (51 mi) long, flowing in a north-south direction and emptying into the Laconian Gulf.
The classical Eurotas was changed to Iri in the Middle Ages and only changed back to Eurotas in recent times. Eurotas, however, is not the most ancient name of the river. It does not appear in the works of Homer, which purport to recount the stories and geography of Mycenaean Greece. In that legendary time, the Dorians are not known to have been present in the Eurotas Valley. At some time prior to being called Eurotas, the river was the Bomycas and the Himeras.
One etymology derives the word Eurōtas from the ancient Greek eurōs, "mold." The adjective, eurōeis, "moldy," is genuinely ancient, used as an epithet of Hades in Homer. It is, however in the Ionic dialect.
The source of the Eurotas River is a surface spring called Piges Evrota (Πηγές Ευρώτα, "Eurotas Springs") located near the village of Skortsinos, Arcadia, by the side of the road ascending from Kyparissi. The spring is an outlet of an aquifer located in the adjacent limestone ridge at a locale called Kephalari. The ridge, a karst, is not part of the Taygetus Massif, but, like the other mountains of Arcadia, is a nappe raised by the compressional forces on the Hellenic Plate by the subduction of Africa. The spring is also called Logaras Spring.
Logaras Spring supplies an anciently constructed catchment basin about the size of a pond, sometimes called a lake, which exits both to irrigation channels and to the Alpheios stream (not to be confused with the Alpheios river in the northwestern Peloponnese). The flow is copious except in times of drought. A recent study measured the outflow through the catchment exit every 15 days for 540 days in 2006-2007. It recorded a maximum of 1748 cubic m per hour and a minimum of 310.5 cubic m per hour. From the catchment at an altitude of 430 m (1,410 ft) part of the water flows into the Alpheios stream, which enters the upper Eurotas.
The Laconian Alpheios stream is unconnected with the Alpheios river in Arcadia. The identity of their names comes from an ancient geologic misunderstanding that the Eurotas and the Apheios were connected underground, which deceived even Pausanias, one of the best ancient geographers. He believed they had the same source but that the outflow stream disappeared into a chasm only to emerge at different locations as different streams. In the most exaggerated form of the myth, the Alpheios continues under the Mediterranean to Sicily or elsewhere.
Today, the river is hydromorphologically far from its natural state. The main problem is anthropogenic abstraction of water, by many methods, from the shallow aquifer through which it flows. The valley contains about 7000 wells. Water is directly removed by irrigation ditches, weirs, and pumping stations. Consequently, the river is intermittent; large sections are typically dry of surface water, even though water still flows in the aquifers. Flash flooding is a problem. Through flood control, the riverbed has been widened in places and straightened, and the vegetation has been removed from its sides. The lower river runs between dikes in a long, straight course.
Most of the numerous tributaries of the Eurotas are right-bank, feeding the shallow aquifer. They are, however, intermittent and ephemeral. The major ones have cut deep ravines into the Taygetus Massif. The few left-bank tributaries, receiving waters from the deep aquifer, are more substantial, but still intermittent.
The classical Oineus was changed to Kelefina in the Middle Ages and not restored to its ancient name until recent times. The current Magoulitsa was formerly the Trypiotiko.
The rich alluvial soil through which the final 10 km of the Eurotas flows was not there in antiquity. The Eurotas has aggraded the innermost bay of the gulf. The old coastline can be approximated by a line on the periphery of the plain of Elos marking the border within which prehistoric archaeological sites are not found. The line on the west follows the Skala-Gytheion road to Skala, the Skala-Molaoi road to Vlachiotis, southeast along the edge of the rising terrain to Asteri and south from there to the coast. Due to changes in sea level, some land on the flanks of the gulf has been drowned.
The current communities of Elos, Leimonas and Agioi Taxiarches have been constructed on aggraded land. As Pausanias mentions that Elos was a port city, the current Elos cannot be identified with it. Skala, on the other hand, means "place of embarkation." The location of the ancient port, however, is not yet known for certain.