National Institute of Meteorology and Hydrology

Hydrological Information and Forecast

The Weather






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About the Climate

About the Climate

Bulgaria has quite specific geographic situation, being in the easternmost part of Europe, rather close to the Asian continent and near to the subtropical Mediterranean region. It gives grounds for rapid change of the climate from north to south. In climatic aspect the major part of the country belongs to the European moderate-continental zone. The southernmost and southeastern regions are under the strong influence of the Mediterranean continental-subtropical zone.

Hydrological Regime

Map of Bulgaria The Bulgarian river watersheds belong to three major basins: the Danube river basin (most of the rivers in North Bulgaria); the Black Sea basin (most of the rivers in East Bulgaria); Aegean Sea basin (most of the rivers in Central and South-West Bulgaria. The positions of these three basins are shown by different color tones on the figure below. The precipitation is annually distributed, the high and low flow periods are quite well outlined, mostly because of the evaporation conditions.

Generally the high flow of the rivers under the Mediterranean influence is in December and January. Those are the Southernmost parts of the Aegean Sea basin. The low flow period of those rivers is quite dry because of the corresponding distribution of the rainfall and better evaporation conditions.

The high flow period of the rivers under the Continental influence is at April—June. These are rivers of the Danube river basin, at the Northern part of Bulgaria. The low flow of those rivers is higher than that of the southern rivers.

Significant influence on the annual distribution of discharges causes the permanent snow cover, which is formed in the high mountains during winter seasons. The snow pack is accumulating the winter precipitation thus transferring water from winter to late spring and early autumn.

Some examples of the different types of averaged annual hydrographs are given below, showing the types of the distributions described above, or some mixture of them.

The lowland areas are usually used for agriculture, while the mountain areas are covered by different types of forests. About 30 % of the Bulgarian territory is covered by well karstified carbonate rocks. Only in the karstic areas the rivers may dry up during hot spells. Another important issue is related to the artificial regulation of the river flow. More than 60 % of the total run-off is subject to different types of seasonal and annual regulations by dams, derivation channels and other hydrotechnical structures.

Hazardous Phenomena

Winter snowfalls are considerable in Bulgaria under the combined influence of Mediterranean cyclones and anticyclone or ridge from North. Combined with strong winds, the snowfalls often cause dangerous situations on the Northeast part of the country and in the high mountains. Intensive snowmelt due to the combined influence of warming and rainfall sometimes causes disastrous floods on certain Bulgarian rivers. Hailstorms quite often create dangerous conditions and significant economic losses. According to the climatic conditions certain parts of the country might be classified as semi-arid. Nevertheless there are almost no rivers drying during the hot spells (except in the karst areas), the low flow discharges are usually 50 times smaller than those of the high flow. So, droughts are among the dangerous phenomena in Bulgaria. Mostly due to the anthropogenic factors, certain regions suffer of insufficient drinking water resources.

State Principal

The Principal for all the issues related to water is the Ministry of Environment and Water. Water in Bulgaria is state property. In this respect The Ministry is actually the owner of this national resource, it is giving permits to water users, it is dealing with the short and long term planning in the field and keep the national balance of the resource. There are several organizations in the field ensuring the rolling mechanism of water affairs, which are given in the principle scheme below.