Editing Geography of Bulgaria (section)

== Hydrography ==
[[File:Bulgaria drainage divide.svg|thumb|250px|Map of drainage systems and drainage divide in Bulgaria]]
Bulgaria has a dense network of about 540 rivers, but with the notable exception of the [[Danube]], most have short length and low water-level. The density is highest in the mountain areas and lowest in Dobrudzha, the Danubian Plain and the Upper Thracian Plain.<ref name="donchev68">{{harvnb|Donchev|Karakashev|2004|p=68}}</ref> There are two catchment basins: the [[Black Sea]] (57% of the territory and 42% of the rivers) and the [[Aegean Sea]] (43% of the territory and 58% of the rivers) basins.<ref name="donchev68"/><ref name="hydrology">{{cite web |url=http://geografia.kabinata.com/05.htm|title=Hydrology of Bulgaria|website=Topics of Geography of Bulgaria|access-date=18 October 2015}}</ref>

The [[Balkan Mountains]] divide Bulgaria into two nearly equal [[Drainage system (geomorphology)|drainage systems]]. The larger system drains northward to the Black Sea, mainly by way of the Danube. This system includes the entire Danubian Plain and a stretch of land running 48–80&nbsp;km inland from the coastline in the south. The Danube gets slightly more than 4% of its total volume from its Bulgarian tributaries. As it flows along the northern border, the Danube averages 1.6 to 2.4&nbsp;km in width. The river's highest water levels usually occur during the May floods; it is frozen over an average of 40 days per year. The longest river located entirely in Bulgarian territory, the [[Iskar (river)|Iskar]], with a length of 368&nbsp;km and a catchment area of 8,640&nbsp;km<sup>2</sup>, is the only Bulgarian Danubian tributary that does not rise in the Balkan Mountains. Instead, the Iskar has its origin in the Rila Mountains. It passes through Sofia's eastern suburbs and crosses the Balkan Mountains through a spectacular 65&nbsp;km–long gorge.<ref name="donchev68"/> Other important tributaries of the Danube include the rivers [[Lom (river)|Lom]], [[Ogosta]], [[Vit (river)|Vit]], [[Osam]] and [[Yantra (river)|Yantra]].<ref name="donchev68"/><ref name="hydrology"/> The longest river flowing directly to the Black Sea is the [[Kamchiya]] (254&nbsp;km), while other rivers include the [[Batova]], [[Provadiya River|Provadiya]], [[Aheloy (river)|Aheloy]], [[Ropotamo]], [[Veleka]] and [[Rezovo River|Rezovo]].<ref name="donchev69">{{harvnb|Donchev|Karakashev|2004|p=69}}</ref>

The Aegean Sea catchment basin drains the [[Thracian Plain]] and most of the higher lands to the south and southwest. Several major rivers flow directly to the Aegean Sea. Most of these streams fall swiftly from the mountains and have cut deep, scenic gorges. The 480&nbsp;km–long [[Maritsa]] (of them 321&nbsp;km in Bulgaria) and its tributaries drain all of the western [[Thracian Plain]], all of [[Sredna Gora]], the southern slopes of the Balkan Mountains, and the northern slopes of the eastern Rhodopes. After it leaves Bulgaria, the Maritsa forms most of the Greco-Turkish border.<ref name="donchev69"/> Maritsa's major tributaries include the [[Tundzha]], [[Arda (Maritsa)|Arda]], [[Topolnitsa (river)|Topolnitsa]], [[Vacha (river)|Vacha]], [[Stryama]], etc. The other Bulgarian rivers flowing directly to the Aegean are the [[Struma (river)|Struma]] and the [[Nestos (river)|Mesta]].<ref name="hydrology"/><ref name="donchev69"/>

Bulgaria has around 400 natural lakes with a total area of 95&nbsp;km<sup>2</sup> and volume of 278 million km<sup>3</sup>.<ref name="donchev71">{{harvnb|Donchev|Karakashev|2004|p=71}}</ref> The [[Liman (landform)|limans]] and lagoons along the Black Sea coast include from north to south [[Durankulak|Lake Durankulak]], [[Lake Shabla]], [[Lake Varna]], [[Lake Beloslav]], [[Lake Pomorie]], [[Lake Atanasovsko]], [[Lake Burgas]] and [[Lake Mandrensko]]. Of them, Lake Burgas is the most extensive with 27,6&nbsp;km<sup>2</sup> and Lake Varna has the largest volume with 165,5&nbsp;million m<sup>3</sup>.<ref name="hydrology"/><ref name="donchev71"/> The lakes along the Danube were dried to clear land for agriculture with the notable exception of the [[UNESCO]] [[World Heritage Site]] [[Lake Srebarna]].<ref name="donchev71"/> There are 170 [[glacial lake]]s in Rila and 164 in Pirin. They are an important tourist asset. The most renown lakes include the [[Seven Rila Lakes]], [[Popovo Lake]], [[Banderishki Lakes]], [[Vasilashki Lakes]], [[Vlahini Lakes]], etc.<ref name="donchev71"/> [[Swamp]]s and [[marsh]]es include [[Alepu]], [[Arkutino]], [[Aldomirovtsi Marsh]], [[Dragoman Marsh]], etc.<ref name="donchev72">{{harvnb|Donchev|Karakashev|2004|p=72}}</ref> There are around 2,200 reservoirs with a total volume of c. 7&nbsp;billion km<sup>3</sup>.<ref name="hydrology"/> The largest ones are [[Iskar Reservoir]], [[Ogosta Reservoir]], [[Dospat Reservoir]], [[Batak Reservoir]], [[Kardzhali Reservoir]], [[Ivaylovgrad Reservoir]], [[Studen Kladenets]], [[Koprinka Reservoir]], [[Ticha Reservoir]], etc.<ref name="donchev72"/>

<gallery mode="packed">
File:Veleka-river-dinev.jpg|River [[Veleka]]
File:Shabla 02.jpg|[[Lake Shabla]]
File:Dolno vasilashko ezero.jpg|[[Vasilashki Lakes|Dolno Vasilashko Lake]]
File:Vucha PAN-HDR.jpg|[[Vacha Reservoir]]
File:Arda Meanders.jpg|River [[Arda (Maritsa)|Arda]] at [[Kardzhali Reservoir]] 
</gallery>
Bulgaria is rich in [[mineral water]]s, with 225 mineral springs and a total discharge of 5000 L/s, mainly in the south-western and central parts of the country along the faults between the mountains.<ref name="donchev66">{{harvnb|Donchev|Karakashev|2004|p=66}}</ref> Most of them, 148, are situated in southern Bulgaria, while the other 77 are in the northern part of the country. The springs in the north tend to be with cool water, while those to the south are mainly warm and hot. The hottest spring in Bulgaria and the Balkans is situated in [[Sapareva Banya]] and reaches 101.4&nbsp;°C.<ref name="donchev66"/> The Bulgarian word for spa, ''баня'', transliterated as ''banya'', appears in some of the names of more than 50 [[spa town]]s and resorts. They are located in several zones: ''Balkan Mountains zone'' ([[Varshets]], [[Shipkovo]], [[Voneshta Voda]]), ''Srednogorie zone'' (Sofia, [[Ovcha kupel]], [[Bankya]], [[Pancharevo]], [[Strelcha]], [[Hisarya]], [[Banya, Plovdiv Province|Banya]], [[Pavel Banya]]), ''Maritsa zone'' ([[Kostenets (town)]], [[Kostenets (village)]], [[Dolna Banya]], [[Momin Prohod]]), ''Rilo-Rhodope zone'' ([[Devin, Bulgaria|Devin]], [[Velingrad]], [[Banite]], [[Beden, Bulgaria|Beden]], [[Mihalkovo]], Sapareva Banya), ''Struma zone'' ([[Kyustendil]], [[Sandanski]], [[Ognyanovo, Blagoevgrad Province|Ognyanovo]], [[Marikostinovo]], [[Dobrinishte]]).<ref>{{harvnb|Donchev|Karakashev|2004|p=67}}</ref>