The contribution of József Tóth to modernization of Hungarian hydrogeology

Abstract The paper describes the influence of József Tóth and his groundwater flow theory on the evolution of paradigms in Hungarian hydrogeology. The artesian mechanism has been the basic framework for hydrogeologists for the last two centuries. The evolution from the artesian paradigm to basin hydraulics took place in four stages in Hungary. The first stage was represented by the activity of Szebényi (1955), Urbancsek (1963) and Rónai (1963). Their studies were limited to shallow depths, recognizing the correlation between downward and upward flow with high and low topography, but did not produce a model for the observed pattern. In the second stage Erdélyi (1976) enhanced the gravity-driven flow-pattern for shallow depths but avoided the question of deep overpressures. In the third stage Tóth and Almási (2001) concluded that the groundwater flow pattern is made up of an overpressured regime driven by tectonic compression and a topography-driven meteoric regime above it. In the fourth stage Tóth and Almási (2001)'s conclusions were confirmed by studies for the Danube-Tisza Interfluve (DTI) by Mádl-Szőnyi and Tóth (2009). It was found that the gravity-flow systems are perched on ubiquitously ascending waters and that vertical flow occurs through conductive faults and between rock grains

Soil and wetland salinization in the framework of the Danube-Tisza Interfluve hydrogeologic type section

Abstract The Danube-Tisza Interfluve has an agricultural economy but is plagued by severe problems of soil and wetland salinization. The objective of the study was to determine the source of the salts and the controls and mechanism of their distribution. For the Danube-Tisza Interfluve two different groundwater flow regimes, namely a gravity-driven meteoric fresh water regime and an overpressured saline water one, were identified within the framework of the Danube-Tisza Hydrogeologic Type Section (Mádl-Szőnyi and Tóth 2009). It was also recognized that the salts originate partly from the basin sediments and partly from the basin basement. The latter contains NaCl-type water with 10000–38000 mgL−1 total dissolved solid content. The vertical flow through conductive faults and the cross-formational ascent of the deep waters, combined with the gravitational systems’ geometry and the flow-channeling effect of the near-surface rocks, explain the pattern of soil salinization and the contrasting chemistry between the wetlands of Danube Valley and the Ridge Region

Potential maps for the hydrogeologic prerequisites of the installation of deep geothermal doublets and groundwater source heat pump systems in Budapest, Hungary

Budapest is famous for its thermal springs and spas and outstanding thermal water resources. In the 21st century renewable energy utilization — including the use of geothermal energy — became the focus of interest. Improving the use of the different forms of geothermal energy requires the assessment of their possibilities. The potential for deep geothermal doublet systems for direct heating in Budapest was evaluated based on the temperature conditions, the depth and reconnaissance of the carbonate reservoir. NW Buda is not appropriate for thermal water exploration. SW and SE Budapest have better temperature conditions but the lithology of the reservoir is uncertain. Beneath Pest the thermal water is well exploitable. It is obvious from the map of the region that the area is promising; however, due to the hydraulic continuity of the system, reinjection is desirable. Considering the reliability of the employed data the geothermal potential map is suitable only for general orientation and guidance. The geothermal potential map for Groundwater-sourced Heat Pump Systems (GHPS; scale = 1:40,000) was assembled by evaluating the thickness and appearance of the gravel strata and water table, complemented by the sulfate content as an aggressive component of groundwater. The original geothermal potential map series can be used for the evaluation of potential sites in Budapest. It can be concluded that the Buda side of the Danube River is almost entirely unsuitable for shallow groundwater-based heat pump installations. The only areas under consideration are Óbuda and the riverbanks. On the Pest side, there is no gravel in the central part; the largest areas close to the river and in the immediate surroundings are uncertain, with patches of suitable and possible categories. The southern and eastern area of Pest is the most prospective for GHPS installation. The potential maps only consider natural parameters; however, installation may be strongly influenced by the urbanization and the city environment

Identification of near-surface saline water in the Lake Kelemenszék area, Danube-Tisza Interfluve, Hungary

Abstract In the Danube Valley, a chain of saline lakes and a salinized area are situated in the discharge zone of two different waters. The two watertype were followed till the near surface by regional chemical and hydraulic investigations (Mádlné Szőnyi and Tóth 2009). The goals of this study were to prove the presence of these different waters in the near surface zone around the Lake Kelemenszék, and allocate their connection to the lake and to the salinized ground surface. Near-surface geophysical measurements (VES, RMT) supported the regional hydraulic and chemical results. The sediments are saturated by saline water down to 110 m beneath the lake, and to the east the fresh water is prevalent. The local chemical investigations strengthened this distribution. Highly saline water with Na-HCO3-Cl-type discharges into and around the lake. To the east there is a continuous change towards a (Ca,Mg)-(HCO3)2-type fresh water discharge. The interface between the two water types is a 2–3 km wide transition zone. The results of the investigations proved that the saline water of the deep flow system rises to the surface and provide salt for the salinization of the area

Injection related issues of a doublet system in a sandstone aquifer - A generalized concept to understand and avoid problem sources in geothermal systems

This study proposes a concept and presents a workflow to examine potential reasons for low injectivity of sandstone aquifers. Injection related problems are a major challenge for the sustainable utilization of geothermal waters. In order to completely understand and avoid the geothermal reinjection problems, potential problem sources acting on different scales should be taken into consideration. Thus, in the workflow, possible problem sources are considered on regional, reservoir and local scale and categorized into 1) effect of regional hydraulics (potential presence of overpressure and upward flow) 2) inadequate reservoir performance (limited extent, low permeability and performance) and 3) local clogging processes (particle migration, mineral precipitation, microbial activity). Hydraulic conditions are characterized by defining the pressure regime and the direction of vertical driving forces. The reservoir properties are given by determining the grain size and the size of the reservoir layers, as well as the permeability and the transmissivity of the reservoir and the capacity of the injector. Physical, chemical, and biological clogging processes are investigated by specifying the rock properties and determining particle content of the fluid; by analysing the type, probability and amount of the scaling and estimating the potential for corrosion; and by evaluating the possibility of biofilm formation. The concept and the workflow were first tested on a geothermal site (Mezőberény, SE Hungary, installed in 2012) that had to stop operation because of unsuccessful reinjection. The low injectivity of the well is a consequence of several separate problems and their interaction: Reservoir properties are insufficient due to low permeability and transmissivity of the reservoir and the limited vertical and horizontal extension of the sandstone bodies. Precipitation of carbonates, iron and manganese minerals is predicted in hydrogeochemical models and observed in solid phase analysis. Microbial material is produced from the particularly high organic content of the produced thermal water. Injection problems due to hydraulic effects are not expected since the regional pressure regime is slightly subhydrostatic. In summary, reservoir properties determine a low injectivity, which is further decreased to a critical level by the clogging processes. The proposed generalized concept guides a detailed reservoir and geothermal system analysis which is essential for a sustainable geothermal operation.Petroleum Engineerin

Characteristics of discharge at Rose and Gellért Hills, Budapest, Hungary

Abstract This study focuses on the discharge characteristics of the Buda Thermal Karst (Budapest, Hungary) found at the Rose and Gellért Hills. The Buda Thermal Karst is a recently active hydrothermal karst system in the heart of Budapest. Studying this unique hydrogeologic system is thus a challenge because of the human impact effects. The research approach is based on the concept of hydrological system analysis (Engelen and Kloosterman 1996), which means that the flow system geometry and recharge-discharge features must correlate when the influence of man on the flow regimes of an area is negligible. Therefore the flow system geometry could be deduced from the evaluation of manifestations of flowing groundwater. To achieve this archival hydrogeologic data and recent observations were used. Based on the localization of springs, collections of archival temperature and chemical data, as well as recent observations, conceptual models were established for the discharge in the Rose Hill and Gellért Hill areas. The observations indicate different discharge characteristics for the two study areas

Numerical investigation of the combined effect of forced and free thermal convection in synthetic groundwater basins

The theoretical examination of the combined effect of water table configuration and heat transfer is relevant to improve understanding of deep groundwater systems, not only in siliciclastic sedimentary basins, but also in fractured rocks or karstified carbonates. Numerical model calculations have been carried out to investigate the interaction of topography-driven forced and buoyancy-driven free thermal convection in a synthetic, two-dimensional model. Effects of numerous model parameters were systematically studied in order to examine their influence on the Darcy flux, the temperature and the hydraulic head field. It was established that higher geothermal gradients and greater model depths facilitate the evolution of time-dependent free thermal convection in agreement with changes of the thermal Rayleigh number and the modified Péclet number. However, increasing water table slope and anisotropy coefficient favor the formation of stationary forced thermal convection. Free thermal convection mainly affects the deeper part of the midline and the discharge zone of the synthetic model. In the examined model basins, the position of the maximum hydraulic head is located within the bottom thermal boundary layer near the recharge zone. This divergent stagnation point underlies a local downwelling zone characterized by underpressure. These simulations draw attention to the importance of understanding the combined effect of forced and free thermal convection in sedimentary basins regarding regional groundwater flow patterns, and temperature distributions

Hidraulic potential anomaly indicating thermal water reservoir and gas pool near Berekfürdő, Trans-Tisza Region, Hungary

Abstract In the surroundings of Berekfürdő (Trans-Tisza Region) a significant positive anomaly was observed in the fluid potential field, in the course of a regional-scale hydrogeologic study of the Great Hungarian Plain (Tóth and Almási 2001). It was assumed that the cause of this phenomenon could be the presence of structural elements in an overpressured fluid potential field. The seismic, hydraulic and hydrogeochemical evaluation of the anomaly proved the presence of a complex structure. The results furnish an example for the theoretical model of Matthäi and Roberts (1996). The identified faults, which define the basement high and rise close to the surface, represent direction-dependent control over the fluid flow systems of the Study Area. The detected horizontal barrier fault zones may act as lateral seals of the Tatárülés-Kunmadaras gas field and might ensure the active water pressure of the reservoir system. The junction of the vertically conducting and horizontally sealing fault zones near Berekfürdő represent the southern limit of the prolific hydrocarbon-bearing Szolnok and the identified “extra“ aquifer. The junction of these faults causes intensive water upwelling which was drilled by Pávai-Vajna in 1928. This exploration initiated the development of the Berekfürdő Spa

Mapping vegetational and salinization phenomena to evaluate the extent of Lake Kelemenszék, Hungary

Abstract Lake Kelemenszék (Danube-Tisza Interfluve, Hungary) is a shallow saline lake which is fed, beside by precipitation, partly by meteoric and also by rising saline groundwater. The aim of the present study was to map the seasonally variable extent of the lake. The developed method is based on mapping of vegetational and soil salinization phenomena around the lake caused by discharging groundwater. It was found that an outer salty berm determines the maximum extent of the lake. Therefore, from the mapped maximum possible extent of the lake, from the lake-bed morphology and from the recorded lake water level, the actual lake extent and water amount can be deduced. Military and cadastral maps from the past 220 years and a satellite image were used to characterize the historical time variability of the lake extent. Additionally, an actual groundwater level map was compiled based on shallow well data. RMT sounding was carried out to evaluate the TDS content of the saturated near-surface sediments to examine the interaction between the lake and the canals around it