In recent years water-related issues are increasing globally, some researchers even argue that the global hydrological cycle is accelerating, while the number of meteorological extremities is growing. With the help of large number of available measured data, these changes can be examined with advanced mathematical methods. In the outlined research we were able to collect long precipitation datasets from two different climatical regions, one sample area being Ecuador, the other one being Kenya. Using the methodology of spectral analysis based on the discrete Fourier-transformation, several deterministic components were calculated locally in the otherwise stochastic time series, while by the comparison of the results, also with previous calculations from Hungary, several global precipitation cycles were defined in the time interval between 1980 and 2019. The results of these calculations, the described local, regional, and global precipitation cycles can be a helpful tool for groundwater management, as precipitation is the major resource of groundwater recharge, as well as with the help of these deterministic cycles, precipitation forecasts can be delivered for the areas.

A number of climatic cycles and teleconnections are known on the Earth. By definition, the cycles can have a periodic effect on the global climate, while teleconnections can influence the weather at large distances. At the same time, it is overwhelmingly assumed that the hydrological cycle is permanently intensifying all over the world. In this study, we determine and quantify some connections among these climatic cycles and precipitation data from across Hungary. By using cross-correlation and cross-spectral analysis, the connections of the climatic patterns and oscillations with the precipitation of different Hungarian areas have been defined. We used the 1950–2010 timeframe in order to be able to detect effects of several climatic patterns, such as the El Niño-Southern Oscillation (ENSO), the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Pacific/North American teleconnection pattern (PNA) and the Atlantic Multidecadal Oscillation (AMO) on the rainfall events of the Carpathian Basin. Data from four different precipitation measurement sites and oscillation indexes from several databases were used. The results help to understand the patterns and regularities of the precipitation, which is the major source of natural groundwater recharge, and a handy tool for future groundwater management measures. Because of the defined connections, any changes in these teleconnections will probably influence the future utilization of the Hungarian groundwater resources.

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In Hungary, both the supply for drinking water, irrigation water and balneological water demand are satisfied mostly from groundwater. In our study, we present four areas where lawmakers will have to answer questions urgently in the future. The re-injection of thermal water used for energy purposes, the obligation to notify and authorize wells drilled into groundwater aquifers, and the growing need for irrigation water from the agricultural sector, as well as the regulations of cross-border water bodies, are all urgently need a solution to ensure sustainability. In this complex work, legislation can effectively help professionals to meet our goals.

An innovative methodology is introduced to study abandoned oil exploration drillings for possible geothermal energy production at a test area in northeast Hungary. An evaluation method supported by robust statistical analysis was elaborated to provide the possible future investors with adequate technical and earth-science related information for their decision-making processes. All the available data of 161 abandoned hydrocarbon wells, with different physical conditions, were examined based on the proposed evaluation system to provide information about the geothermal energy potential for each well, as well as over a bigger area. The abandoned wells and their environments, the quantity of stored heat, and the fluid temperature and geothermal heat were the key parameters determined, which are critical when considering geothermal energy utilization or thermal water production. The maximum amount of stored energy was determined as the sum of the amount of energy extractable from the rock and the fluid. The heat stored in the rock was determined by basin modelling. The evaluation process, using one-dimensional (1D) basin modelling and 3D lithological-stratigraphic modelling, was successfully applied in the pilot area. The maximum amount of heat stored in the fluid can be determined by subtracting the heat stored in the rock from the total heat. Drilling and completing geothermal wells are rather expensive in Hungary, depending on the depth and the types of geological formations. The application of this research could greatly reduce the cost and risk of creating new geothermal energy systems based on production wells or abandoned wells in Hungary or elsewhere.