Transboundary Water Resources Management NATO ASI Series 1994: Transboundary Water Issues Between Greece-Bulgaria and Turkey: The Case of the Meriç / Evros River

Not: Figürlerin, Tabloların ve Formüllerin daha yüksek çözünürlüklü görüntüleri için görsele sağ tıklayıp “resmi yeni sekmede aç” seçeneğini seçiniz

Transboundary Water Issues Between Greece-Bulgaria and Turkey: The Case of the Meriç / Evros River

Pages 439 – 451

Ahmet Samsunlu, Derya Maktav

Sedat Kabdaşlı

Istanbul Tech. Univ., Environmental Eng. Department

Remote Sensing Department, Hydraulic Department, Istanbul Turkey

The UN Convention on the Protection and Use of Transboundary Water Courses and International Lakes

An international convention was held on March 17, 1992 in Helsinki under the auspices of the United Nations. According to this convention; the parties involved shall, in particular, take all appropriate measures to prevent, control and reduce any transboundary impact to reduce pollution of waters causing or likely to cause transboundary impact; and to ensure that transboundary waters are used with the aim of ecologically sound and rational water management, conservation of water resources and environmental protection.

They should also ensure that transboundary waters are used in a reasonable and equitable way, taking into particular account their transboundary character, in case of activities which cause or are likely to cause transboundary impact.

Measures for prevention, control and reduction of water pollution, shall be taken, where possible, at the source. These measures shall not directly or indirectly result in a transfer of pollution to other parts of the environment. The parties should be guided by general principles such as the precautionary principle and polluter-pays in a way that needs of the present generation are met without compromising the ability of future generations to meet their own needs. They may cooperate in order to develop harmonized policies, programs and strategies covering relevant catchment areas. The application of this Convention shall not lead to the deterioration of environmental conditions nor lead to increased transboundary impact.

Water Resources and Water Quality

The concept of “Water Quality” defined as the combination of physical, chemical and biological features and the technical dimensions of which is determined by selecting appropriate parameters, is an important factor in the evaluation of water resources.

If multipurpose usage of transboundary waters is in question, it is necessary to consider the purpose needing the highest “water quality”. But the priorities may be different for every country and this is quite a difficult problem to be solved by international authorities.

For each type of use there must be a quality dimension to be protected in the water resource (receiving water). This dimension named as “quality criteria” is defined as standards or legislation which change in different countries depending on their level of technical and scientific developments.

These differences between the quality criteria and water quality demands depending on the main goal of the usage in different countries can cause some dispute that can be finished by making an intemational management organization. This kind of organization is difficult to be made. Therefore, a communication should be constituted first in order to the discuss problems and to transfer the data obtained in national base and to exchange the knowledge.

The River Meriç is an example of transboundary waters due to the water quality problems resulting from the usage of river water for different purposes in Turkey, Greece and Bulgaria. Meetings between the relevant countries continue, but scientists must take part in these meetings, too.

The Meriç Basin

Meriç Basin which was coded as ()l in basin planning by General Directorate of State Water Works (DS) in Turkey, is located in Trakya. The boundaries of the basin, as shown in Figure l, extend to Bulgaria and the water line of Istranca mountains in the north; Viz.e, Saray and Erkezky in the east, and Saroz Bay passing Orlu and Tekirda in the south.

Meriç River, with its five tributaries, including Arda, Tunca, Ergene and Doanca, Eskenderky streams is the most important river in the basin Ergene River and its branches are the main water dicharging river of the basin. Although the Arda and the Tunca Rivers join the Meriç River in Turkey, resources of these rivers are in different countries: Arda in Greece, and Tunca in Bulgaria.

Food and textile industries are mostly widespread in the basin. Ergene River and its branches are most polluted in the basin. Most of the industries have designed or constructed their tæatment systems in recent years. The present treatment systems mostly were designed and operated by using physical and chemical tæatment.

Water Quality of the Meriç River

In the basin, experimental measurements have been made and conducted at 27 stations located on the Meriç, Arda, Tunca and Ergene Rivers by General Directorate of State Water Works since 1979. [D.S.I. 1985] [Karpuzcu, et al. 1992]. The location and codes of these stations are shown in Figure l. At these stations the parameters given in the Water Pollution and Control Regulations have been measured panicularly. In this paper, instead of the detailed evaluation of the whole stations, the stations placed on the main changes and on the joint points were selected and the water quality was investigated. For this purpose, 001, 007, 008, 009, 010 (Meriç River), 002 (Tunca River), 003 (Arda River) and 0.17 (Ergene River) coded stations were selected. For evaluation purposes, parameters important from water pollution and control points of view, BOD5, dissolved oxygen, N02-N, total dissolved solid matter parameters were considered.

Figure 1: Meriç Basin

The results obtained by using yearly averaged values of 1980, 1985 and 1990 are shown in Figs. 2, 3, 4, and 5. On the same figures the values used for the classification of water are also shown. If the BOD5 parameter is taken into account, no change is seen in water quality except 002 station in Fig. 2.

The river can be classified as second class at the 001-002 stations but for the year 1990, 002 station is in the third class and 003 cooled stations is in the first class. Water quality of 007-010 cooled stations were dropped to second class in 1985 and 1990 while being first class in 1980. During the monitoring period, the dissolved oxygen values which represent the first class water quality along the river, do not change significantly (Fig.3).

Fig. 4 shows the changes in nitrite concentration in the basin for the years 1980-1990. At the 003 station, in 1980 and 1985 third class and in 1990 second class water quality were Observed while it was fourth class at 001 and 002 for all years. At 007-010 stations generally third  water quality was determined. Water quality class of ()09 station increased to third class in 1990. Evaluating the TDS values, it can be concluded that water quality of the river is between first and second class except the measurement at 010 stations at which third water quality was detemined in 1980. Also Turkish Ministry of Environment stated that water quality of the Meriç Basin represents the first and second class water quality except few measurements of pH, NH3-N, N02-N, BOD5, O-P04, Fe. Pb and Cu at some stations. Annual mean values of chosen parameters, nitrite, TDS, DO, BOD5 were calculated and the graphic representing the yearly changes in between 1980 and 1990 are seen in Figs. 6 to 9.

As it can be seen from these Figures;

The average BOD5 value is around 6 mg/l and refers to 2nd class water quality.

The average DO value is around 10 mg/l and refers to 1st class water quality.

The average nitrite value is around 0.04 mg/l and refers to 2nd class water quality. The average TDS value is around 0,9 mg/l and refers to 2nd class water quality.

The Meriç River can be classsified into second class according to the results mentioned above. In order to improve the water quality of the Basin, the pollution loads carried by Tunca River from Bulgaria and Ergene River from Turkey should be controlled and pollution level should be decreased. To sustain the pollution of Meriç River at its present level, Bulgaria, Turkey and Greece should take necessary precautions by being in communication as closely as possible.

Water Quality Problems in the Meriç Delta

In the Meriç Delta, the saltwater intrusion into the river through the river mouth at the coast consitutes an important water quality problem. The Meriç River arrives at the Aegean Sea at the Saroz Bay after flowing 187 km along the borderline between the countries of Turkey and Greece. Just before arriving at the sea, it forms a large delta with very interesting properties, such as lagoons and their channels. This delta with its lagoons is seen on the satellite image in Fig. 10. This image is formed using Landsat Thematic Mapper data [Maktav, D., 1994].

Figure 2: BOD5 values for 1980, 1985 and 1990

Figure 3: DO values for 1980, 1985 and 1990

Figure 4: NO2-N values for 1980, 1985 and 1990

Figure 5: TDS values for 1980, 1985 and 1990

Figure 6: BOD5 values from 1980 and 1990 from Meriç River

Figure 7: DO values from 1980 and 1990 from Meriç River

Figure 8: NO2-N values from 1980 and 1990 from Meriç River

Figure 9: TDS values from 1980 and 1990 from Meriç River

Figure 10: Landsat image of the Meriç Delta in the year 1992

Generally. hydraulic processes in a river delta are mostly dominated by water discharge, water level, mean elevation of the bottom, water surface slope, mean flow velocity, cross section area, mean depth, sediment discharge, mean sediment concentration and hydrodynamic conditions of the coast in the vicinity of the mouth (Mikhailov, V.N., 1969). Also, the offing is a component of the river mouth area, and delta front is the most dynamic type of the shore as a result of interaction between river and sea (Skriptunav, N.A., 1969). In light of these considerations, it is obvious that Meriç Delta is under effect of highly dynamic conditions, and the saltwater intrusion occurs when the water discharge is less than 30 m3/sec. Because, the mean elevation of the river bottom is -2.50 m and inverse hydraulic slope can be seen when the mean sea level is higher than the still water level due to the wave motion. Additionally, the river bed slope is also inverse in the delta and tidal range is about 0.6 m in the Saroz Bay. As a result of all these, the saltwater can reach approximately 35 kms upstream the Meriç River.

In recent years, many large dams with large storage capacities in Bulgaria were constructed and water discharge in Meriç River has been reduced. Especially in summer periods, water discharge dropped to 4.9 m3/sec. On the other hand, in the delta, at both sides of the river rise farming were made. The rise farming covers an area of about 65000 ha in Turkey. For irrigation purposes Turkey purchases about 14 000 000 m3 of water from Bulgaria in the months of August and September. But, this still does not solve the saltwater intrusion problem in the delta.

The decrease of water discharge is also important for the river mouth, delta morphology and ecology. The Meriç Delta between Turkey and Grece has quite important ecologic properties because of the lagoons and their channels. In natural conditions, the river changes its route due to the yearly change of hydraulic conditions. Some erosion and accumulation can be seen at both sides of the river, even some small islands are formed. But, for the very low water discharge, quite a large sedimentation problem arises around the river mouth. The reason for this is, that the coast of Saroz Bay consists of very fine sandy beaches at which very strong

this is, that the coast of Saroz Bay consists of very fine sandy beaches at which very strong alongshore sediment transport occurs. That is why at the Meriç River mouth the sand accumulation is a very big problem due to the significant waves in direction of SE. This problem will be chronic unless the river water discharges are high enough.


Turkey has great potential from water resources and quality points of view compared to other countries. But in order to prevent water resources and quality, the required precautions should be taken as much as possible. If the domestic wastewater caused by rapid population growth rate, and unsound urbanization, industrial and agricultural wastewaters are discharged to receiving media without any treatment and control, the water resources will be polluted or the present pollution level will reach a dangerous level.

Therefore, to prevent and increase the water resources potential a new study has been started.

In the first stage, it was decided to construct the treatment plants of whole big settlements for their domestic wastewaters. In addition, required regulations to force the industries to construct their treatment plants were established. And in order to support them financially, a fund wms established.

Furthermore, the construction of the treatment plant of the erkezky Organized Industry Region, which is discharging its wastewaters to Orlu stream, tributary of Ergene River, was started.

It can be concluded that the water quality of the Meriç River, and morphologic and ecologic properties of its delta strongly depend on the regulation of water discharge by the Bulgarian dams. Therefore, cooperation between Turkey, Greece and Bulgaria is needed. It is also necessary, according to the Helsinki Convention, that all related countries have to take appropriate measures for conservation of ecological structures of transboundary waters. At that point, the difficulty is to evaluate the problems related to the changes in natural environment. Generally, in order to obtain a sufficient solution, an extensive monitoring through field measurements is necessary.

The application of remote sensing technology in addition to the field measurements can give a spatial view for transboundary waters. Besides, the integration of remote sensing technology and field measurements is essential for transboundary waters because of the following reasons:

a.         A transboundary coastal zone covers generally large coastal areas. It is difficult to obtain spatial views for large areas.

b.         In transboundary coasts, in-situ measuremenLs should be can-ied out by transboundary states. This can raise some problems in obtaining global results as a whole.

If an integrated monitoring program may be applied with a scheme given in Fig. I l, all the results obtained by field measurements in national bases can be gathered in a central station, in

Figure 11: Integration of monitoring measurements in a transboundary framework.


DS, State Water Works, Water Quality. Data( 1979-1982). Ankara. 1985.

DS, State Water Works. Water Quality. Data( 1983-1984). Ankara. 1985.

Karpuzcu, M.. Ministery of Environment of Turkey: An Investigation Project on Pollution Levels and Water Qualities of Water Catchment Areas, Meris- Basin. Bosphorus University. Environmental Sciences Institute. 1992.

Maktav, D.. Kabdaşlı, S.. Landsat Thematic Mapper Monitoring of Lake Salda Turkey. 1994 ACSW/ASPRS Annual Convention. Reno. USA. 1994.

Mikhailov, V.N. Hydrologic-morphometric characteristics of (klta H-anches. Hydrology of deltas, Proceedings of the Bucharest Symp. May 1969. pp. 146-158.

Skriptunov, N.A., Hydrological processes in offings and their role in fomation of a front. Hydrology of deltas, Proceedings of the Bucharest Symp. May 1969. pp. 164-172

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