Vízügyi Közlemények, 1988 (70. évfolyam)

4. füzet - Major Pál-Neppel Ferenc: A Duna-Tisza közi talajvízszint süllyedések

A Duna- Tisza közi talajvízszint süllyedések 625 - Lower groundwater levels started to appear around the beginning of the 70's; the phenomenon has slowed down somewhat between 1971 and 1975 but gained a new impetus today (Fig. 3 and 4). - It could be observed that the annual average values of precipitation decreased first by a lower rate - from the period of 1971-1975 - but later the process accelerated (Fig. 7). Over the 15 year-long period of 1971 1985 the deficit in precipitation was greater by 1000 mm as compared to the 15 year-long averages of the previous 70 years (Table III). It is apparent that the period of reduced precipitation and lower groundwater tables are in coincidence. - Extended forested areas (Table I) contributed heavily to actual évapotranspiration. It is striking that the area of forests and of dropping groundwater levels were in coverage in 1985 (Fig. 5). - Exploitation of drinking water (Fig. 6. Table II) from deep groundwater reserves caused significant pressure-drop in these resources ( Fig. 3). The area of depression was in coincidence with the layout of water-conducting layers with considerable thickness but also with the area affected by dropping groundwater tables (Fig. 2). On the flatland of Solt - where only meteorological factors acted on the groundwater from among the three usual factors causing level dropping - no lower groundwater levels were experienced (Fig. 4). Consequently, drought was not the reason of dropping groundwater tables. - The authors speculated that combined meteorological and sylvicultural influences cannot be responsible for lower groundwater levels. They arrived to the conclusion that serious and enduring drops are induced by at least three simultaneous factors: meteorology, forests and large-scale exploitation of water from deep groundwater reverves. - Without any proof it was guessed that lower groundwater tables could have been developed - although in a more moderate way - if favourable, say almost average meteorological conditions prevailed. This guess will enhance the opinion that improved meteorogical conditions cannot automatically restore the groundwater aquifer existed before 1970. When recommendations are contemplated it should be borne in mind that water supply and agricultural productions are equally in danger in the area. Water balance investigations (Tables IV and V) have led to the conclusion that the problems of water supply and agriculture can be solved by letting the water to move from shallow aquifers toward deeper layers, if the exploitation of drinking water from the deeper layers is reduced, and the growth of newly forested areas os slowed down in the area between Danube and Tisza. Diversion of surface water from the Danube and distributed over the area may increase drinking water resources and shallow water reserves alike - along with some seepage toward the deeper layers - but also the amount of water ready for irrigations. All these aspects will contribute to the safety and productivity of agricultural productions in the area between The Danube and Tisza. * * * Les abaissements du niveau de la nappe phréatique entre le Danube et la Tisza par MAJOR P.. ingénieur de génie civil et NEPPEL F.. professeur de géologie et de géographie Les auteurs représentent les abaissements du niveau de la nappe phréatique observés dans la région située entre le Danube et la Tisza. A partir des éludes réalisées au Centre de Recherches des Ressources Hydrauliques (VITUKI). les auteurs constatent que: Dans certaines régions situées entre le Danube et la Tisza on observe des importants abaissements du niveau de la nappe phréatique qui sont unique dans le pays (Fig. 1.) La période initiale de ces abaissements est le début des années de 1970. Au cours de la période de 1971 à 1975 on a observé une faible intensité d'abaissement, et après on a démontré une intensité accrue (Fig. 3. et 4.) qui dure même à nos jours. - A partir de la période des années de 1971 à 1975 la pluviométrie moyenne annuelle est