Management of Lake Fertő H idrology and water management University of Debrecen Centre for Environmental Management and Policy 7. Lakepromo Meeting & Seminar April 11-13, Aalborg, Denmark

Main hydrological characteristics (1) - the surface area is 315 km 2 - the lake is years old steppe lake (western steppe lake of Eurasia) - largest salt lake of Europe - shallow lake: average depth is under 1 m, deepest point is 180 cm - high water level fluctuation, last date of drying out was between main characteristic of the lake is reed covered areas and marshes - residence time of water: 3,5 years - total P loading: 144 t/year - siltation, eutrophication Catchment area (km 2 ) Lake area (km 2 ) Length (km) Average width (km) Depth (m) Cubic capacity (million m 3 ) Length of shoreline (km) Reed (km 2 ) Lake Fertő (Hungarian part)1120 (175)315 (75)36 (7)8,2 (10)1 (0,8)39 (26)92 (25)180 (63) University of Debrecen Centre for Environmental Management and Policy

Main hydrological characteristics (2) Lake Fertő/Neusiedlersee is characterized by: -high concentration of salt, about 2000 mg/l, but the total salt concentration may exceed 2500 mg/l in the summer - alkaline pH, - natural, high dissolved organic substance. - Regarding poorly polluted point and diffuse sources, from the point of view of bacteriology, the situation is not exceptionable; so it’s outstandingly suitable for recreational tasks. -The state of the Lake Fertő in accordance with the determination of both Hungarian and Austrian side is meso-eutrophic. University of Debrecen Centre for Environmental Management and Policy

Main hydrological characteristics (3) Water regime of Lake Fertő - factors affecting water regime: precipitation, evaporation, surface inflow and ground water, outflow through Hanság Channel - according to latest research, ground water sources are not significant. - most important factor decreasing water regime is evaporation - average inflow of the lake is 0,22 m 3 /s -features of the water regime based on past 39 years:Precipitation = 566 mm Evaporation = 872 mm Inflow = 168 mm -evaporation and precipitation are the 2 significant factors University of Debrecen Centre for Environmental Management and Policy

Main hydrological characteristics (4) Evaporation Precipitation Several years’ average University of Debrecen Centre for Environmental Management and Policy months

Main hydrological characteristics (5) The following table indicates the fluctuation of water level from 1966 to University of Debrecen Centre for Environmental Management and Policy

Water level regulation 1955: after the II World War Austria and Hungary started discussions on cross border water management 1956: contract signed on Regulation of the Cross-border Water Management 1992: sluice in Mexikopuszta that caused significant changes concerning water regime. Water level fluctuation decreased by 1 m as a result of the construction, and average water level increased by 0,5 m. The wind has an effect on water level, therefore, several sampling places can be found around the lake. Past dry years caused water level decrease at Lake Fertő. University of Debrecen Centre for Environmental Management and Policy

Water supply (1) 2002: Austrian-Hungarian Water Committee decided to develop a general ecodynamic strategy for Lake Fertő. 2005: Hungarian-Austrian Water Management Committee assessed the possibilities of water supply with a focus on water quality and ecology. Main findings of the Committee: - water supply of Lake Fertő is not reasonable concerning ecological reasons - important is the maintenance of the lake as part of the landscape University of Debrecen Centre for Environmental Management and Policy

Water supply (2) Water supply demand of Lake Fertő is 30 million m 3 /year Irrigation demand for Fertő-zug 10 million m 3 /year Such water supply should happen during winter Solutions for water supply: 1. Rába-Répce-Hanság Channels 2. Rába-Répce-Kardos-ér-Ikva -Hanság Channel Direct water supply is not possible: Rába/Fertő conditions - nutrient 10x -salinity 1/10 University of Debrecen Centre for Environmental Management and Policy

Water supply alternatives (1) Ecological effects 1. Long-term levelled water balance Objective of the supply: use of the Lake for recreation (larger size of boats); but this is a demand of a small part of society Such objective is harmful for the Lake’s natural states that is totally adverse to development objectives Concerning ecological and nature protection points of view, such supply is not to be supported! University of Debrecen Centre for Environmental Management and Policy

Water supply alternatives (2) Ecological effects 2. Long-term negative water balance Objective of the supply: prevention measure against the drying out of the Lake Long-term negative water balance can change the landscape and the region itself, and may lead to drying out. The objective of water supply to compensate water loss and to preserve landscape is acceptable! SOLUTIONS? University of Debrecen Centre for Environmental Management and Policy