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Hydrology of Prespa Lakes

Hydrology of Prespa Lakes. Molnar Kolaneci Hydrometeorological Institute Tirana, ALBANIA. Introduction.

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Hydrology of Prespa Lakes

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  1. Hydrology of Prespa Lakes Molnar Kolaneci Hydrometeorological Institute Tirana, ALBANIA

  2. Introduction • Prespa Lakes (Big and Small) and Ohrid Lake constitute the biggest water system in Balkan. The total watershed area of this complex water system amounts to 2970 km2. The surface area of Big Prespa is about 253 km2 and Small Prespa about 47 km2 . • The fact that three countries, Macedonia, Greece and Albania, share this complex water system, make more difficult a real hydrologic analysis.

  3. Water level regime • The critical situation of water level in Big Prespa Lake. • After 1988 it is observed a continuing and fast decrease of water level in Big Prespa Lake. The historical minimum of water level was decreased for more than 4 meter. • In last years the communication of Big and Small Prespa is interrupted.

  4. Waterlevel regimeContinue • Until now, three would be the main hypothesis about this spectacular phenomenon: • Tectonic falling of the lake bottom • Widening of underground channels connecting Prespa and Ohrid lakes. • Influence of meteorological parameters(climatic changes)

  5. Water level regimeContinue • In the last field campaign (2002) was observed a very interesting fact near Zaveri: the discovery of an underground path constructed by stones. • A similar path exists also in Liqenas (Pusteci) connecting Small Island.

  6. Water level regimeContinue • These facts serve as indicator that we can formulate the fourth hypothesis: the cycle of water level variation may be longer than our observation period (50 years).

  7. Water Balance • The only possible way to define a real water balance of Prespa Lake is the exchanging of the hydrometeorological data between the three neighbouring countries and cooperation between professional institutions.

  8. Water BalanceSmall Prespa LakeLake area surface 47.4 km2 Catchment area 189 km2 • Inflow: • Contribution of precipitation (direct on water mirror) b) runoff from catchment area c) underground inflow d) artificial inflow from Devolli River (Albania) • Outflow: • surface or groundwater outflow b)evaporation c)irrigation Evaporation: (Equation of Penman Combined approach) s RN + cpa (ea – ed)/ra Eo = C/L *  s + 

  9. Elements Inflow 106 m3 Outflow 106 m3 Precipitation 30 Runoff, catch. area 22.8 Surface flow 55 –60 41 Groundwater - - Evaporation 53.5 Irrigation 15 TOTAL  110  110 Water BalanceSmall Prespa Lake  Tab. 1 Summary results

  10. Elements Inflow 106 m3 Outflow 106 m3 Precipitation 186 Runoff (catchment area) 299 Surface inflow 41 Groundwater 129 Evaporation (open water surface) 279 Irrigation 10 TOTAL 526 418 Water BalanceLake area 253.6 km2Big Prespa Lake Catchment area1058 km2  Tab. 2 Summary results

  11. Water BalanceBig Prespa Lake The differences between inflow and outflow may be explained by sublacustrine springs that are not possible to measure. With more reliable data is possible to evaluate better the elements of water balance of Big Prespa Lake in order to determine more accurately the contribution of sublacustrine springs.

  12. Hydrology of Prespa LakesConclusions The location of Prespa lakes between three countries inhibits intensive integrated studies. 2.Relatively little climatological or hydrological data in the region 3. Total absence of data for the mountains areas-hazardous computation. Human activity in the area is not well evidenced in all three countries. 5. Water level of Big Prespa Lake is in continuing decreasing up to date and none of hypothesis has priority. Hydrometeorological monitoring program is required in Prespa region.

  13. Thank you for attention

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