Landscape, Climate and Water Flow
The total length of Bulgaria’s borders is 2245 kilometres. Of these borders, 1181 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 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 percent of the territory of the Republic of Bulgaria and totals 46,930 square kilometres, 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 percent of the total runoff of the Danube River.
Geographically and in terms of climate, Bulgaria is very diverse with the landscape ranging from the 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, river valleys, basins, and mountains of varying elevations. About 70 percent of the country’s territory is hilly land and 30 percent is mountainous. The average elevation of the country’s territory is 467 metres, generally decreasing from south to north and from west to east.
Most of the rivers that rise in southern Bulgaria have their mouths in the Aegean Sea outside Bulgarian territory. A notable exception is the Iskar river that takes its source 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 mostly defined by its geographical position in the southern part of the temperate continental climatic zone and occupies a transitory position to the Mediterranean climate. The predominant vegetation is of the forest – steppe type. In the north and northeast, more common is steppe vegetation and in the south forest plants. Forests occupy approximately 30 percent of the country’s territory, 75 percent of these are deciduous forests.
Rainfall is unevenly distributed throughout the country, from 500-550 millimetres per year in the Danube valley and the Gornotrakiyska lowland, to 1000-1400 millimetres 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, without very big rivers except for 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 were announced the first transboundary wetlands in the country. Wetland complex on the Danube "Silver - Iezerul Calarasi", "Belene Islands Complex - Suhaia" and "Ibisha Island - Bistret" 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 is the richest in biodiversity part of the largest European river. It is only in this part of the river that there are no dams and 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 though highly endangered they still multiply.
The capital of Bulgaria Sofia is situated in the west part of the country and now is the largest demographic, trade, political, cultural and educational centre. 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 percent 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 in ground waters and possesses considerable operational capacity assessed to be worth a total of 70 cubic metres per second. These waters are the most important water supply source for North-Eastern Bulgaria.
Bulgaria is scarce in water resources, despite that over 300 rivers in the country. The Danube is the biggest one with total length of 470 km on Bulgarian territory. There are also 6 lakes with a total area of 87 square kilometres and water volume of 211 million cubic meters, and 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 up to 14 percent in 50 years and to be 20 percent 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 percent, while consumption of more than 40 percent indicates an unsustainable water use. Abstraction in the country after 1992 is considered to be sustainable.
Generally Bulgaria is situated in the semi-arid zone under the mixed continental and Mediterranean climate influence. Floods are generated on the Bulgarian territory under
intensive snowmelt mixed with rainfall in spring. Flush 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 level of flood hazard.
In the past Bulgaria had put strong emphasis on heavy industry and intensive agriculture with limited attempts to mitigate the environmental consequences. As a result, by the early 1990s an estimated 60 percent of agricultural land was polluted by fertilizers and pesticides, two-thirds of rivers were polluted, and two-thirds of primary forests had been levelled. Since then, considerable progress has been achieved in addressing environmental pressures.
Surface waters in Bulgaria as a whole are in good condition. Transition to market economy and the decline in production from industry and agriculture has led to a reduction in pollutants discharged into water, including reducing the loads of major nutrients (nitrogen and phosphorus). As a result, nearly 75 percent of the length of rivers in the country 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.
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, and 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 .