Vízügyi Közlemények, 1998 (80. évfolyam)

2. füzet - Csonki I.-Fejér V.-Klingné Ábrahám J.-Magyarics A.: A Balaton vízgazdálkodásának időszerű kérdései

282 Csonki I-Fejér V.-Klingné Ábrahám J.-Magvarics A. Tóth L.: Állóvizeink vízminősége. Szennyvíztisztítási konferencia 1/2. Budapest. 1971. VITUKI: A Balaton feliszapolódásával kapcsolatos kutatások 1961-1962-ben. Kézirat. VITUKI Budapest. 1963. VITUKI: A Balaton feliszapolódásával kapcsolatos kutatások 1963-1964-ben. Kézirat. VITUKI Budapest. 1965. VIZ-INTER.: A partvédömüvek felülvizsgálata. Tanulmány. OVF. Budapest. 1995. VIZITER V: Szabályzat a siófoki leeresztő zsilip kezelésére és a Balaton vízszintjének szabályozására. Tervszám: 19129. KDT-VÍZIG, Székesfehérvár. 1977. * * * Timely questions of water management of the Lake Balaton by Dr. István CSONKI, Vilmos FEJÉR. Judit KLINGNÉ-ÁBRAHÁM and András MAGYARICS civil engineers Intensive development activities of the vicinity of Lake Balaton, which started in the sixties, have played a significant role in the deterioration of the Lake's water quality. The plant nutrient load to the lake has been increasing and substantial quantities were accumulated, thus inducing intensive eutrophication. Blue green algae blooms became frequent. A decisive part of the counter measures was built into the Lake Balaton Water Management Development Programme (BVFP). Measures made on the watershed and the social-economic transition have slowed down and the halted the process of water quality deterioration. Modification of the roles of water level regulation and the regulation measures of the inflowing streams are the most important water management strategics. The regulation of 1

977 have confined the fluctuation of the lake water levels to the range +0.70 +1.00 m of the water level gauge of Siófok. There was a seasonally varying band of 0.15 m (Figure I.) of the upper and lower regulation limits. The proposed new system increases the 0.3 m water level fluctuation to 0.4 m and modifies the seasonally varying band from 0.15 m to 0.25 m (Figure /.). The contemplated new water regulation system would fail only in the case of an extremely dry summer half-year. The outlet and navigation gate of Siófok (Figure 2.) had been reconstructed three times, last time in 1975-78. A new reconstruction is needed for enhancing its capacities to the desired level. Another precondition of the safe regulation of water levels of the lake is the upgrading of the channel of the upper stretch of the Sió Canal. The actual flow carrying capacity of the canal is only 60 m

3/s, instead of the 80 nvVs of the original design (Figure 3.). The largest achievement of the water pollution control work is that four out of the seven regional sewer networks discharge not even treated effluents into the lake and 65% of the total sewage of the lake is being diverted to other catchment. Phase I. of the Kis (Little)-Balaton water protection system (the "Lake Hidvég") was constructed in the period 1981-85 (Figure 4.). Activities of Phase II. (the "Lake Fenéki" have commenced in 1984. A portion of this latter, the "Ingói-Marshland" of 16 km

2 area was completed in 1992 and put into operation. A part of the pollution load enters the lake via the tributary water courses. Filter zones and ponds have been constructed to retain sediment and debris. 953 km long earthen and lined stormwater ditches have been constructed in 40 settlements of the Lake Balaton catchment. About 63% of this network needs reconstruction. In order to reduce the internal load of the lake sheet-dredging of the bottom sediment of the Bay of Keszthely (Figure 5.) is needed. Investigations have shown that both phosphorus and the spores of algae are accumulating in the upper 0.1-0.2 m layer of the bottom sediment. In 1995-96 about 900,000 m

3 silt has been removed from about 4.34 km

2 bottom area. The disposal sites (Figure 6.) used for duping the dredged sediment can not receive the intended quantities and other options of disposal must be identified.