IONUT MINEA ^1* Daniel Boicu ² Abdelazim Negm ³ Martina Zelenakova ⁴ Mustafa Demirci ⁵

• ¹ Department of Geography, Faculty of Geography and Geology, Alexandru Ioan Cuza University, Iași, Romania
• ² Research Center with Integrated Techniques for Atmospheric Aerosol Investigation in Romania, RECENT AIR, Laboratory of Interdisciplinary Research in Geo-Chemistry of Rural Areas, Environmental Quality Monitoring Station for Geographic Research, Alexandru Ioan Cuza University, Iași, Romania
• ³ Department of Water and Water Structures Engineering, Faculty of Engineering, Zagazig University, Zagazig, Al Sharqia, Egypt
• ⁴ Technical University of Košice, Košice, KoSice, Slovakia
• ⁵ Iskenderun Technical University, Hatay, Türkiye

In today's society, groundwater reserves are an essential resource for different communities globally from regions where problems associated with the depletion of groundwater resources are critical (the Mediterranean area, the Sahel area or the central part of India) to areas that have only come into the sights of researchers in the field in recent decades (the Arctic or Antarctic area) [1].The excessive and unsustainable exploitation of these resources generates negative effects that are observable globally, with a greater incidence in developing countries and third-world regions [2].One of the main causes of pressure on groundwater is the rapid growth of the global population, which has quadrupled in the last century and continues to grow. In addition, this demographic expansion implies an increased demand for food, which causes the expansion of agricultural areas and increasing demand for irrigation resources [3,4] and achievement of climate neutrality targets in sustainable water resources management [5].The significant decline in groundwater resources cannot be explained solely by the increase in global population and water demand. Multiple studies have highlighted a link between climate variations and fluctuations in the level of underground water, especially in surface aquifers [6,7,8,9]. The effects of rapid population growth, surface water pollution and increasing climate uncertainties will lead to increased dependence on groundwater in the future. At the same time, the impact of climate change and climate variability is a growing challenge for the current generation. It may become more severe in the future due to human interventions in nature [10,11].Groundwater plays a crucial role in the global climate balance. However, the effects of climate change on these resources remain unclear due to the complex interactions and feedback processes specific to the atmosphere-hydrosphere system. Climate change influences groundwater resources in various ways. Within the hydrological cycle, they can affect soil infiltration rates, percolation at greater depths and, implicitly, groundwater recharge. In addition, rising temperatures increase evaporation at ground level, which reduces the amount of water available to recharge aquifers. In contrast, anthropogenic impacts on groundwater resources are mainly driven by water extraction through pumping and indirect impacts of irrigation and land use changes [12,13].Looking into the future, according to the data presented by the Intergovernmental Panel on Climate Change (IPCC), the average global temperature tends to increase between 2-4°C, an aspect that becomes even more plausible if you take into account that the average global surface temperature has already recorded since 1861 an increase of 0.6°C [14]. As a result of the increase in temperature, the hydrological processes can suffer profoundly, and the intensification of the water evaporation from the topographic surface and the transpiration of the plants takes shape even more.Consequently, climate change will influence the distribution, timing, and intensity of rainfall, indirectly affecting the distribution and storage of water.Researchers use both specific hydrological models to assess the potential impact of climate change on surface and groundwater resources to determine groundwater recharge, including in the analysis data such as hydrological dynamics, soil, and surface structure, as well as methods that involve monitoring and evaluation of groundwater resources in situ or based on satellite data sets, developing index sets [15]. These methods provide valuable and cost-effective information, contributing to developing, evaluating and optimizing groundwater management strategies, policies, and projects.The complexity of the components of the hydrological system and how climate change acts on groundwater resources induce the realization of analyzes that must take into account aspects related to the past, historical data, current problems, and future projections. Studies show that in addition to the anthropogenic impact, climate change, by increasing temperatures, changes in the precipitation regime, and the intensification of evaporation processes, governs the availability of water resources. Thus, it was found on the basis of the studies that a better understanding of the impact induced by climate change on groundwater resources is obtained through a large-scale analysis, both from a spatial and a temporal point of view. The analysis of the impact of climate change on underground water resources in various areas of the globe offers a complementary perspective in understanding the phenomenon through the lens of different analysis methodologies.Innovative methodologies such as the Time-Lapse Electrical Resistivity Imaging (TL-ERI) method and machine learning-based time series clustering [16] allow the monitoring of groundwater levels and the estimation of storage capacities, obtaining precise information about the seasonal changes of the underground level, allowing identifying critical areas where an aquifer is under pressure induced by climate variations. In situ observations are a tool that provides a clear perspective on the impact of climate change. An analysis of historical data on temperature and precipitation variations can provide valuable information on the vulnerability of surface water resources with subsequent effects on groundwater. The fluctuations of a lake in response to the temporal variation of climatic parameters can also be relevant for the study of underground reserves, reserves that can change in terms of recharge and discharge of neighboring aquifers [17]. Anticipating the future impact of climate change on water availability for a given region, starting from reporting historical data to long-term simulations provides relevant information from the perspective of achieving an efficient management of groundwater and avoiding the induction of water stress through overloading of water resources in underground in periods of prolonged drought [18,19]. At the same time, technical solutions, based on three-dimensional numerical models on computational fluid dynamics must be identified to reduce the anthropogenic impact on groundwater quality [20].Recent studies highlight climate change's significant and complex impact on groundwater, reducing aquifer recharge and storage capacity. The increase in the unpredictability of precipitation and its manifestation through seasonal changes, frequency variability, and intensity variation superimposed on the increase in temperatures and the intensification of evaporation generate the irregular recharge of the surface and deep aquifers. The adaptation and effective management of the groundwater resource, both globally, regionally and locally, is becoming a priority area in the context of current and future climate change.