Vízügyi Közlemények, 1994 (76. évfolyam)

1. füzet - Hankó Z.-Alföldi L.-Starosolszky Ö.: A Felső-Duna és a Szigetközi hdirológiai jellemzőinek megváltozása a dunacsúni vízlépcső üzembehelyezése nyomán

52 Ilankó 7..-Alföldi L.Starosohzky Ö. mean river discharge in the Rujka-Gönyű reach is appr. 2000 nr'/sec with an average slope of 0.3 m per kilometre. This however covers high variability. The mean groundwater level is practically the same as that of the water level corresponding to the mean discharge of the river. The water table slopes from the Danube towards S-SE at a rate of 0.6 - 0.7 m/km (Figure 11). 'Die groundwater is being fed by the River Danube at a rale of 8.6 nr'/sec, while recharge from precipitation water amounts to 0.8 m

3/seconly. (Figure 12). Consequently if one wanted to abstract 1 million m'/d (or 11.6 nrVsec) flow from a series of wells located outside the flood levee of the River Danube (as was proposed for drinking water supply in Central-Europe), then this would cause a substantial regional depression of the water table (Figure 13). With the Cunovó River Barrage in operation the river flow of the main channel was decreased to 300 nvVsec and the rest of the flow is diverted to the power canal of the Gabcíkovó Hydroelectric Power Plant. This How rejoins the main channel of Danube at Palkovicovo (at rkm 1811). Due to this diversion the water level of the main channel was decreased to 121 m B.S. at Rajka and to 114 m B.S) at Dunaremete, while the water level corresponding to the actual discharge is regained at Palkovicovo. The groundwater table along the Danube follows the water levels of the main channel, with the exception of the reach upstream of Dunakiliti, where groundwater levels are rising due to increased seepage How from the Cunovó reservoir. The groundwater table is inclined towards S-SE with a relatively unchanged slope of CI.6-0.7 m/km (although at a lower elevation). Between Dunakiliti and Rajka the groundwater table is higher than the water level of the main channel and its slope is also steeper. In the lower reach, downstream of Dunaremete the slope decreases, along with the similar decrease of the slope of the open channel water surface. Results of calculations indicate that in this altered situation the recharge of the aquifers under the Szigetköz area was decreased to 6-7 nr'/sec. This means losses of recharge from the River Danube as well as from the flow that originated from the Csallóköz. (Figures 16 and 17). Along with the sinking groundwater table the extent of the area where the groundwater level reaches the base of the topsoil layer is also dramatically decreasing (this is the area where agricultural water demand, the moisture need of the crop, can be partially met from the groundwater via capillary rise, (Figure 14). Investigation of groundwater dynamics due to the unsteady flow in the boundary rivers repealed two important facts: First; the changes of the groundwater table follow, in a band of 1 - 2 km width, the water level changes of the River Danube vary rapidly (within one day). The second conclusion is that development of steady state conditions of the groundwater regime would require steady state conditions of 3 months duration in the water courses that define the position of the groundwater table (rivers Danube, Mosoni-Danube, Rábca, Lajta, and the Hanság Canal). Since no steady conditions lasting for 3 months are expectable with reasonable probability the groundwater regime remains dynamic at all times (Figures 17-20). Veränderung der hydrologischen Charakteristiken der Oberen Ungarischen Donau und der kleinen Scliiitteninsel infolge der Indiensstcllung der Wasserstufe Dunacsün von Dr. Zoltán HANKÓ, Dij'l.-Ing.-Dr. László ALFÖLDI, DipL-Cleoi, Dr. der WissDr. Ödön STAROSOLSZKY, Dipl.-Wasserbau Ing., Kand. der Wiss. Diese Studie ist eine Zusammenfassung derjenige VTIJKI Sfudia, Forschungsberichten und Gutachten welche sich mit der zur Auslösung der Aufgaben der Wasserstufe Dunakiliti im oberen