Hidrológiai Közlöny 1978 (58. évfolyam)

3. szám - Dr. Sebestyén Olga: A Balatonnal kapcsolatos megjegyzések

142 Hidrológiai Közlöny 1978. 4. sz. Oláh J.—Tóth L.—O. Tóth E.: Szokatlanul nagy tápanyag terhelés Comments on the problems of Lake Balaton Dr Olga Sebestyén Lake Balaton is a very pleasant summer resort for both our contrymen as well as for the visiting tourists. It could be easily reached. Both in calm and in stormy weather the extensive lake fits beautifully to the charming landscape. Besides being a national treasure tourism provides a considerable income for the country. To keep the lake in a healthy condition the limnological features of the lake have to be considered. Natural properties of Lake Balaton The natural properties of the lake came especially to the foreground as soon as pollution occured through various reasons, such as: 1. increase of tourism, 2. growth of population around the lake, 3. establishment of industrial plants. All these resulted in various problems of pollution. The sewage problems are the most crucial ones. Lake Balaton is a shallow waterbody (mean depth 3 m, at a short channel of the Tihany narrows, 11m) long shoreline due to the shape of the basin extensive surface (610 km

2) cachment area 5200 km

2 water-content of the basin 2 km

3 renewal of the water-content 2.2 years (calculation) there are more than 40 tributaries among them the river Zala is the largest outlet at Siófok: the Sió channel (sluices) A ) The water quality of the lake is determined by the geology hydrology meteorology (precipitation; wind etc.) and the climate of the catchment area. B

) As to the water content of the basin, being the environment for Balaton biota, the followings should be emphasised beside the chemical, physical, and hydrological parameters of the water quality: a

) geographic situation of the basin b ) shape and size of the basin c ) long shoreline d

) proportionally extensive surface and limited water content — possibilities for pollution. e

) Direction of the most frequent wind being perpendicular to the longitudinal axis of the elongated basin (Zách A., 1952): the water-dynamics caused by this western (NW) wind resulting in the erosional nature at the southern (SE) shore; this wind drives the smoke-laden clouds from the industrial plants located west of the lake-lakeward, and the precipitation may effect the chemical parameters of the water. It carries dust also which increases the sediments. This wind-through the water dynamics-discourages the growth of the rooted submersed macrovegetationresulting in the eprofundal nature (Lenz) at a considerable part of the bottom. This situation — in turn

—gives a like character to the bottom of the shallow waterbody (,Sebestyén 1943, 1949, 1973). According to Ullyott and Knigth (1938) the light condition at the bottom could provide enough light for the growth of rooted submersed vegetation even in stormy weather. The water-dynamics is the factor which hinders the establishment of rooted vegetation there. For the effects of an unusual meteorological conditions (prolonged wind-still and drought) in the environmental features of this shallow water-body at the end of the warm water season, see Sebestyén—Entz — Felföldy, 1951. The present problems of Lake Balaton Natural features of Lake Balaton Determining factors of water quality The water-content of the basin, as the environment of the Lake biota. Problems: The limited volume of the water in the shallow basin in proportion to the extensive surface and long shore-line. Maintenance of the eprofundal nature at parts of the bottom and the „lake like" appearance of the extensive but shallow water-body. Sources of pollution: Long shorelines for the limited volume of water in the lake increase of tourism growth of the population at the neighbourhood resulting in the growing sewage problem and the growth of solid wastes non satisfactory hygienic conditions Summary I) The lake as the environment of its biota 1. The water quality is determined by: geology hydrology meteorology (precipitation, wind etc.) climate in the catchment area. 2. the lake proper I shoreline I surface extensive [ cachment area pollution limited f depth (shallowes) •j water-content in the I basin the basin shape: elongated NE/SW geographical position water-dynamics unproportional long shoreline pollution extensive surface extreme shallowness pollution limited water content Along with all these problems the ageing of the lake has to be considered. II. The ageing of the lake Ageing is a natural phenomenon. (The deepest part of the lake territory is the oldest one: North-West from the Tihany-peninsula) Signes of ageing: regression of the shoreline (Keszthely-öböl-bay) culmination of sediments increases of the trophic conditions (Bay of Keszthely-öböl etc.) (Sebestyén 1964) III. What are needed a

) satisfactory sanitary condition (canalisation) around the lake, sewage deposit b ) moderation of tourism settlement (population) around the lake c

) rational using of lake water for drinking and household purposes d ) stopping of

: the inflow of sewage effluents the water use for I irrigation industrial I plants e

) provisions for healthy drinkwater f

) to develope immediate territories around the lake: parks for protection against the effect of the washing at the erosional shores g ) education for the lake's protection [ in schols I general I public I visitors