IAEA-SM-361/8P XA9950102

THE DYNAMIC OF ENVIRONMENTAL ISOTOPES AND UNDERGROUND CONNECTION OF PRESPA AND OKRSD LAKES.

J. ZOTO Institute of Nuclear Physics { TNP ), Tirana, R.EFITVH Consultant hydrogeologist, Tirana, Albania S. AMATAJ Institute of Nuclear Physics ( ESP ), Tirana, Albania The Small Prespa lake, Big Prespa lake and Ohrid lake there are three lakes in the southeaster part of Albania and in border with and ex - Yugoslavian Republic of . The altitude above sea level { asl) for Big Prespa and Ohrid lakes are respectively, 850 m and 695 m. ; between Small and Big Prespa lakes exist a surface natural communication and the water flows from Small tu Big Prespa lakes. Between these lakes are situated Dry and Galichitsa mountains with the highest peak 22S7 m ( asl ); these mountains are composed from carbonatic karstic rocks. la the western and southern part of the Dry Mountain in albanian territory there are some karstic springs as Tushemishti, Mancarishti, Progeri ect. By the artificial chanai, in the albanian part, the water of Devolii river flows in the Small Prespa lake {!]. Method of environmental isotopes is used on problems related to the engine of water systems. The local precipitations and Prespa lakes water were examined as a potencial sources of recharge to Dry Mountain groundwater. The mean elevation of infiltration area ( groundwaier recharge area ) were expected to be higher th&n Prespa lake elevation. The altitude effect of the isotopic composition of the meteoric water is used for the identification of waters coming from different potential groimdwater recharge sources of Dry Mountain During three years is sampling the water in the system of sampling points of the region, including some points of karstic springs, some points in the lakes, some local springs and Devolii river; die frequency of sampling every two months. Also, during the sampling are measured temperature and conductivity of the water [3]. The 5O-18 and 5H-2 of the water of Small Prespa lake are different for the sampling points ( respectively - 9.55 %© and - 65.2%o for the entry point of Devolii river in the lake , to - 6.17 %o and - 38.7 %© for the sampling point near the border with Greece). The "5" values for the sampling points in the Big Prespa lake are almost the same and concretely - 0.74 %o for O-1S and - 17.5 %c for H-2, but for the karstic springs in the Ohrid lakeside these values are respectively - 5.18 %o and - 4G.9 %*. Refering the hydrochemical, geological and isctopicai data of the samples , the paper will present more information and some conclusions concerning: - the hydrologies! balance of the system ( Dry Mountain, three lakes, Devoii! river and karstic springs };

116 - the dynamic of the environmental isotopes in the lakes and the intensity of the evaporation of the water; - the intensity of the hydrological relationship between Prespa and Ohrid lakes and underground communication between lakes [2]; - some ideas about the other possible way of outflowing water from Prespa lakes. REFERENCES [1] - Hidrologjia e Shqiperise, Instituti Hidrometeorologjik, Tirane 1984. [2] - T. Anovski, B. Andonovski, B. Minceva : Study on hydrologic relationship between Ohrid and Prespa lake, IAEA, Vienna, 1988. [3] - R. Eftimi, P. Skende, J. Zoto : Nje studim isotopik i lidhjes hidraulike te hqeneve te Ohrit dhe te , Konferenca kcmbetare u Uji - pasuri e madhe ", Tirane, 1996.

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