Landschaftsökologische Beiträge zum Flusseinzugsgebietsmanagement in der Mesta-Nestos-Region (Bulgarien-Griechenland)

The Mesta-Nestos river basin in Bulgaria and Greece is a case study for transboundary decision making support in Southeastern Europe and a show case for the development of methodologies and information gathering for integrated regional planning of water resources. Landscape ecology offers a necessary contribution to the sharing of these natural resources for integrated water resource management in compliance with the new European Water Framework Directive. Originated in the Bulgarian Mountains of Rila, Pirin and Rhodopes, the Mesta River is characterized by an abundant precipitation induced flow out of these "water towers". High mountains vegetation in the upper ranges contrast with intra-mountain basins and valleys with steppes and cultivated fields. Down river, passing the boundary with Greece, more typical Mediterranean climatic conditions regulate the runoff regime of the Nestos river. Toward its end the stream is flowing through a delta nearby Xanthi into the Aegean Sea. Land use conflicts in this water scarce region cover a wide spectrum of activities like agricultural irrigation, drinking water production, diversions for industrial water and pollution from mining as a few examples. A geographic characterisation of the catchment area is presented here as well as important actions and agreements. Surface-groundwater coupled models of watersheds need to be integrated with a wide variety of tools simulating the meteorological, soils and farming inputs, among others. Due to its progressive grid system, the MODCOU hydrological model is well suited to such schemes, especially in the Mesta-Nestos region. It is used to evaluate the annual discharge of fresh water entering Greek territory. Measures of the water quality have been done in the upper basin. Results will be illustrated by the example of the environmental situation in the alpine region of the Pirin National Park as well as in the Basin of Razlog with a stronger anthropogenic impact and pollution around a former uranium mine near the village of Elešnica. The analysis performed in the upper mountain areas indicates relatively low background pollution. Settlements, industrial areas and extens ive agricultural land use at the bottom of the mountain slopes (e.g. Valley of Razlog) induce higher matter contents in the runoff. But the self-purification process in the river network buffers this inputs as shown by bio-ecological water investigations. Although the Elešnica uranium mining plant and tailings induce radioactive traces in the runoff water with decade median concentrations which are below Bulgarian standard limits, the mine dumps and tailings are still a potential environmental hazard and the impact on neighbouring ecosystems must be monitored. The social and economic development of this transboundary region is a recently set priority for the future. It will mean an increase in water usage and more stress for the water resources if predicted global climate change regional impacts are verified. A problem focused management of the catchment area as a whole is needed for the future.