The territory of Bulgaria is 110,912 km². The country is characterized by a rich diversity in morphological, geological, geomorphological, hydro-climatic and soil-biogenic aspects.
Landscape, Climate and Water Flow
The total length of Bulgaria’s borders is 2,245 kilometres. Out of these borders, 1,181 kilometres are on land, 686 kilometres are on rivers – including the river Danube, which flows along Bulgaria's border with Romania - and 378 kilometres are on the sea. Bulgaria shares borders to the north with Romania, to the east with the Black Sea, to the south with Turkey and Greece, and to the west with Macedonia and Serbia.
The Danube River catchment basin comprises 42.5% of the territory of the Republic of Bulgaria and totals 46,930 km², which makes it the largest in Bulgaria. The main tributaries in the Bulgarian section of the river basin are the rivers Erma, Nishava, Ogosta, Iskar, Vit, Osam, Yantra, Rousenski Lom and Danube Dobroudja rivers. The Bulgarian tributaries account for 3.4% of the total runoff of the Danube River.
In terms of geography and climate, Bulgaria is very diverse with a landscape ranging from snow-capped peaks in Rila, Pirin and the Balkan Mountains to the mild and sunny Black Sea coast.
The natural landscape of Bulgaria is diverse, consisting of lowlands, plains, foothills and plateaus, as well as river valleys, basins, and mountains of varying elevations. About 70% of the country’s territory is hilly land and 30% is mountainous. The average elevation of the country’s territory is 467 metres, generally decreasing in size from south to north and from west to east.
Most of the rivers that rise in southern Bulgaria have their mouths at the Aegean Sea outside of Bulgarian territory. A notable exception is the Iskar River, which is sourced from Rila and runs through the Balkan Mountains, forming a gorge to reach the Danube. Iskar is the longest river in the country.
The climate of the country is influenced by its geographical position in the southern part of the temperate continental climatic zone, as it occupies a largely transitory position to the Mediterranean climate. The predominant vegetation is of the forest – steppe type. In the north and northeast, steppe vegetation is more common and in the south forest plants. Forests occupy approximately 30% of the country’s territory, 75% of which are deciduous forests.
Rainfall is unevenly distributed throughout the country, from 500-550 mm per year in the Danube valley and the Gornotrakiyska lowland, to 1,000-1,400 mm in the mountainous regions. The annual snow cover in Bulgaria is unstable and shows significant deviations, both with regards to elevation and geographical location.
The hydro-geographic network of the country is rather complex and in most of the regions quite dense, containing few large rivers with the exception of the River Danube.
Three national parks have been established in the country: Pirin National Park (a UNESCO natural heritage site), Rila National Park, and the Central Balkans National Park. There are also 11 nature reserves – Belasitsa, Balgarka, Vratsa Balkan, Golden Sands, Persina, Rila Monastery, Rusenski Lom, Sinite Kamani, Strandzha and the Shumen Plateau.
In 2013, the first transboundary wetlands in the country were announced. The wetland complex on the Danube "Silver - Iezerul Calarasi", "Belene Islands Complex - Suhaia" and "Ibisha Island - Bistret" were registered by the Secretariat of the Ramsar Convention on Wetlands, as a wetland border between Bulgaria and Romania.
The Bulgarian-Romanian section of the Danube represents the richest in biodiversity as part of the largest European river. It is only in this part of the river where there are no dams or other river partition facilities to prevent the natural development of ecosystems. For the same reason, it is only at this lower section of the river where four sturgeon species can still be found and (although highly endangered) they still multiply.
Sofia, the capital of Bulgaria, is situated in the western part of the country and is now the largest demographic, trade, political, cultural and educational centre. Other important cities are Plovdiv, Varna, Bourgas, Rousse, Stara Zagora, Pleven, Veliko Tarnovo.
The Danube River basin contains 126 municipalities with a population of over 3 and a half million people, which constitutes 46%of the country’s population. There are 39 populated areas in the region with a population of over 10,000, four of which have a population of over 100,000. Almost half of the population in the region is concentrated in the latter.
The Danube River basin is exceptionally rich with a large ground water supply and possesses considerable operational capacity estimated to be worth a total of 70 cubic metres per second. These waters are the most important water supply source for North-Eastern Bulgaria.
Despite the fact that there are over 300 rivers in the Bulgaria, water resources remain scarce. The Danube is the biggest river with a total length of 470 kilometres running through Bulgarian territory. Additionally, there are also 6 lakes with a total area of 87 square kilometres and water volume of 211 million cubic meters, as well as 23 dams with reservoirs of 376 square kilometres surface and water volume of 4,571 million cubic meters.
Several droughts have occurred throughout the previous century. The water demands applied for irrigation in southern Bulgaria were higher than the irrigation demands in northern Bulgaria due to less precipitation and higher air temperatures. Annual river runoff is expected to decrease as much as 14 percent in 50 years and estimated drop to 20% less at the end of the century.
The pressure on water is assessed by the ratio: freshwater abstraction/available freshwater resources. Warning threshold is set around 20%, while consumption of more than 40% indicates an unsustainable water use. Abstraction in the country after 1992 is considered to be sustainable.
Generally, Bulgaria is situated in a semi-arid zone under mixed continental and Mediterranean climate influence. Floods are generated in the Bulgarian territory due to intensive snowmelt combined with rainfall in spring. Flash floods caused by relatively isolated heavy rainfalls in summer or high flows with long duration, which might affect the stability of the levees and subsequent flooding (this is an issue only along the Danube). The flood protection practices in Bulgaria comprise range of activities, more or less intensive in different regions, depending on the flood hazard level.
In the past, Bulgaria had put a strong emphasis on heavy industry and intensive agricultural practices with limited attempts to mitigate the environmental consequences. As a result, fertilizers and pesticides polluted an estimated 60% of agricultural land, two-thirds of rivers were polluted, and two-thirds of primary forests had been leveled by the early 1990s. Since then, considerable progress has been achieved in addressing environmental pressures.
As a whole, surface waters in Bulgaria are in good condition. The transition to a market economy and the decline in production from industry and agriculture has led to a reduction in pollutants discharging into the water, as well as reducing the loads of major nutrients (nitrogen and phosphorus). As a result, nearly 75% of the river lengths in the country now meet the standards for good quality.
Surface water quality is carried out in accordance with Ordinance No 7/1986 - Criteria and standards for determining the quality of surface waters in Bulgaria until the entry into force of Regulation H-4/2013 on characterization of surface waters. There is a clear tendency of waters in good chemical status.
The Nitrates Directive was transposed into Bulgarian law by Ordinance No 2/2000 on the protection of waters against pollution caused by nitrates from agricultural sources. Based on the requirements of this Ordinance monitoring points suitable for surface and groundwater are selected. The first assessment of vulnerable areas was carried out in 2004. The first DRBMP, contains measures to reduce pollution of ground and surface waters by applying good agricultural practice, and a program of measures to mitigate and eliminate pollution, caused by nitrates from agricultural sources. The results of this program and trends on reducing nitrate pollution will be taken into account when reporting implementation of the first DRBMP.