Maritsa

Maritsa ( ), also known as Meriç ( ) or Evros ( ), is a river that runs through the Balkans in Southeast Europe. With a length of , it is the longest river that runs solely in the interior of the Balkan peninsula, and one of the largest in Europe by discharge. It originates in the Rila mountains and flows through Bulgaria in its upper and middle reaches, while its lower course forms much of the border between Greece and Turkey. Its drainage area is about , of which 66.2% is in Bulgaria, 27.5% in Turkey and 6.3% in Greece. It is the main river of the historical region of Thrace, most of which lies in its drainage basin.
It has its origin in the Rila Mountains in Western Bulgaria, flowing southeast between the Balkan and Rhodope Mountains, past Plovdiv and Parvomay (where the Mechka and the Kayaliyka join it) to Edirne, Turkey. East of Svilengrad, Bulgaria, the river flows eastwards, forming the border between Bulgaria (on the north bank) and Greece (on the south bank), and then between Turkey and Greece. At Edirne, the river flows through Turkish territory on both banks, then turns towards the south and forms the border between Greece on the west bank and Turkey on the east bank to the Aegean Sea. Turkey was given a small sector on the west bank opposite the city of Edirne. Maritsa then flows past Kastanies, Pythio, Didymoteicho and Lavara in Greece. It enters the Aegean near Enez, where it forms a river delta. The Tundzha is its chief tributary; the Arda is another one. The lower course of the Maritsa/Evros forms part of the Bulgarian–Greek border and most of the Greek–Turkish border. The upper Maritsa valley is a principal east–west route in Bulgaria. The unnavigable river is used for power production and irrigation.
Etymology.
The earliest known name of the river is "Euros" ("Εύρος", Alcman, 7th–6th century BC). Indo-European "*ewru" and Ancient Greek "εύρύs" meant "wide". The Indo-European "wr" sound shifted in Thracian to "br", creating the Thracian name "Ebros". Thereafter, the river began to be known as "Hébros" () in Greek and "Hebrus" in Latin. Rather than an origin as "wide river", an alternative hypothesis is that Hebros meant "goat" in Thracian. 
Since, when first attested, Europe referred only to Thrace proper, the name of the continent is possibly derived from this river. 
While the name "Έβρος" (Hebros) was used in Ancient Greek, the name "Μαρίτσα" (Maritsa) had become standard before the ancient form "Έβρος" (now: Évros) was artificially restituted in Modern Greek. The name "Maritsa" may derive from a mountain near the mouth of the river known in antiquity as "Μηρισός" or "Μήριζος", Latinized as Merit(h)us.
History.
In 1371, the river was the site of the Battle of Maritsa, also known as the battle of Chernomen, an Ottoman victory over the Serbs. Vukašin Mrnjavčević and Jovan Uglješa died in the battle.
Illegal transborder migration.
The Maritsa/Evros river as a natural barrier on the border between Turkey and Greece has become a major route for migrants from a variety of countries attempting to enter the EU illegally. At the height of the 2010s migrant crisis, in 2012, a border barrier was erected on the Greek side in order to prevent illegal crossings into Greece and thus into the EU.
Following the heavy losses Turkish armed forces incurred at the hands of the Russian-backed Syrian government in northern Syria at the end of February 2020, a drastic change in Turkey's policy towards irregular migrants on its territory led to escalation of the situation at the Evros border crossings as well as exacerbation of tension between Turkey on one hand and Greece and the EU as a whole on the other hand.
In May 2020, news emerged that Turkish forces occupied a of Greek territory, Melissokomeio, as shown on maps of 1923, following a change in the flow of the Maritsa/Evros river.
Tributaries.
Starting from the river's source, significant tributaries of Maritsa include:
Floods.
The lower course of the river Maritsa/Evros, where it forms the border of Greece and Turkey, is very vulnerable to flooding. For about 4 months every year, the low lands around the river are flooded. This causes significant economic damage (loss of agricultural production and damage to infrastructure), which is estimated at several hundreds million Euro.
Recent large floods took place in 2006 and 2007. Several causes have been proposed: more rainfall due to climate change, deforestation in the Bulgarian part of the catchment area, increased land use in the flood plains and difficult communication between the three countries.
Honours.
Maritsa Peak on Livingston Island in the South Shetland Islands, Antarctica is named after Maritsa River.
"La Maritza" is also a 1968 song written by and Pierre Delanoë and interpreted by Sylvie Vartan.
Hebrus Valles on Mars is named after this river.
The Bulgarian Maritsa motorway, which roughly follows the course of the river from Chirpan (where it branches out of the Trakia motorway) to the Turkish border at Kapitan Andreevo, is also named in honour of the river.