NIMH

National Institute of Meteorology and Hydrology

Department of Hydrology, Division of Hydroforecasts

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Overview


About the Climate

About the Climate

Bulgaria has quite specific geographic situation, being in the outheast outlying part of Europe, rather close to the Asian continent and near proximity 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 southmost 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 position of those three basins is shown by different color tones on the picture below. The precipitation is relatively well 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 January. Those are the South-most 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 North part of Bulgaria. The low flow of those rivers is higher than those at the South part.

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

Some examples of the different types of averaged annual hydrographs are give below. There one can see more or less outlined 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 river may dried up during the hot spell. Another important issue is related to the artificial regulation of the river flow. More than 60 % of the total run-off is subject of different type of seasonal and annual regulation by dams, derivation channels and other hydrotechnical structures.

Hazardous Phenomena

The winter snowfalls are considerable in Bulgaria under the combine influence of Mediterranean cyclone 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 as well. Intensive snowmelt due to the combine influence of warming and rainfall sometimes cause disastrous floods at 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 nearly not rivers drying during the hot spell (except in the karst areas), the low flow discharges are usually 50 times bigger than those of the high flow. So, droughts are among the dangerous phenomena in Bulgaria. Mostly because of the anthropogenic factors, certain regions suffer of insufficient drinking water resources.

State Principal

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