Mesta/ Nestos River basin

The basin of the river Mesta/Nestos is shared by Bulgaria and Greece.

Hydrology and hydrogeology

The river has its source in the Rila Mountains in the vicinity of Sofia (Bulgaria), and, flowing through Greece, ends in the North Aegean Sea. The basin has a pronounced mountainous character in its upper part, and a lowland character further downstream. The Dospat/Despatis is a major transboundary tributary; the river has its source in the Rodopy Mountains in the vicinity of Sarnitsa (Bulgaria), and flows into the Mesta/Nestos River in the territory of Greece.

Large parts of the basin in Bulgaria and Greece have been designated as Natura 2000 sites. The Nestos delta, in Greece, is of great ecological importance, and has been designated as a Ramsar Site.

In Bulgaria, surface water resources are estimated to be 958 × 106 cu m/year (average for 1961 – 2002), and groundwater resources are 91.8 × 106 cu m/year (average for 1980 – 2008).

Total water resources per capita are estimated to be 8,188 cu m/year (average 1980 –2008). Bulgaria reported that global climate change over the last 20 years has resulted in an approximately 30% decrease in precipitation, and a subsequent decrease in water resources in the basin; provisions to address the decrease of water resources will be included in the programme of measures of the RBMP. Bulgaria reports that a reduction of flow has been observed in the Mesta from the late 1930s to the early 2000s.

Major dams for hydropower generation and irrigation include those of Thisavros (built in 1997) and Platanovrisi (built in 1999) in Greece, and the Dospat Dam (on Dospat River – built in 1967) in Bulgaria.

Orvilos-Agistros/Gotze Delchev karstic aquifer (No. 142), shared by Bulgaria and Greece (presented in the assessment of the Struma/ Strymonas River), extends to and is hydraulically linked with the surface water system of both Mesta/Nestos and Struma/Strymonas Rivers basins (as reported by Bulgaria). According to Greece, the shared aquifer is not hydraulically linked to the surface waters of either basin.

Pressures, status and responses

When last reported in the First Assessment, the water quality was “suitable for irrigation and water supply for other uses”. In the few years preceding the First Assessment, the quality of the Mesta had improved, as a result of reduced economic activities (including industrial), and the construction of small local wastewater treatment plants in Bulgaria. Values for a few water-quality determinands in the Mesta River downstream from the city of Hadzhidimovo are shown in Figure 2.

figure 2

Hydro-technical constructions such as dams (serving hydropower generation, irrigation and drinking water supply purposes) and small hydropower stations in the Bulgarian part have caused hydromorphological alterations, and exert pressure on the environment. The diversion of watercourses towards reservoirs used for drinking water supply was reported by Bulgaria. There are water losses due to degraded water distribution infrastructure. Drinking water quality is of concern in some areas, but action to address related issues has been taken.

Total water withdrawal in Bulgaria, in 2006, was 9.473 ×106 cu m/year. 21% of total water withdrawal is used for agriculture, 49% for domestic, 14% for industry, and 17% for other uses. In addition, 133.909 ×106 cu m/year is used for hydropower production.

The increase of tourism in the area is followed results in increased water consumption needs.

Uncontrolled solid waste disposal in the Bulgarian part had resulted in water pollution, causing potential environmental problems, especially in times of heavy precipitation. Measures to address this issue are being taken: wastes from all eight municipalities in the river basin are now being collected; about 25 uncontrolled disposal sites were closed; most of them have already been rehabilitated.

Sand extraction is an issue of concern.

With regard to institutional arrangements for water management in the basin, the part extending through Bulgaria has been assigned to the West Aegean Basin District, while the part extending through Greece has been assigned to the Eastern Macedonia and Thrace Basin District. The RBMP for the West Aegean Basin District, in Bulgaria, covers the part of the basin falling within the country’s territory.

With regard to monitoring in Bulgaria, new monitoring programmes are established in accordance to the WFD. An automatic station on the Mesta/Nestos River was established in Bulgaria near the Bulgarian-Greek border to measure both water quality and quantity parameters.

Transboundary cooperation

Information on cooperation between Bulgaria and Greece is available in the assessment of the Struma/Strymonas River Basin.

According to the agreement that was concluded between Bulgaria and Greece in 1995 referring specifically to the Mesta/ Nestos, Bulgaria is obliged to deliver to Greece 29% of the average run-off of the river generated in the Bulgarian territory. According to Bulgaria — concerned by the observed reduction of run-off — the actualization of the basis for the calculation is overdue.