Long-term water balance investigations in the Danube-Tisza Interfluve of Hungary, Europe

Increasing aridity of the Danube-Tisza Interfluve of Hungary has led to shallow ground-water decline threatening traditional farming practices, making wetlands disappear and saline lakes dry up. The long-term (1950-2024) water balance of the region is estimated with the help of 0.1˚ resolution monthly evapotranspiration estimates of the complementary relationship method, as well as spatially interpolated well-measurements of unconfined groundwater levels from 1950-2017. Recharge to the groundwater, obtained as the difference in annual precipitation and evapotranspiration, gradually decreased from around 130 mm in the early 1950s to 20 mm by 1978 then increased slowly to about 47 mm by 2008 and finally dropped again afterwards to its lowest, 14 mm level in 2024. The area is estimated to lose around 55 ± 18 mm of water annually. Previous studies indicate that 80% - 90% of it may occur as discharge to the Danube and Tisza River as well as deep seepage to the underlying regional aquifer, and about 10% - 20% as baseflow contribution to the scattered streams of the interfluve. The loss is 10 mm above the mean annual recharge rate of 1950-2017 (13 mm for 1950-2024), producing the observed overall 2 - 2.5 m drop in unconfined groundwater levels. As long as recharge rates stay predominantly under 55 mm/yr, there remains little hope that the unconfined groundwater of the interfluve could return to the 1950s’ level.