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Comparison of the results after 80 yr obtained from transient simulation showing (a) recent groundwater table configuration in relation to the topography, and the quasi-steady-state hydraulic head distribution and flow pattern in case (b) of pure gravity-driven case, (c) combined driving forces with gravity and lower overpressure, (d) combined driving forces with gravity and moderate overpressure and (e) combined driving forces with gravity and higher overpressure. Hydraulic head values are colour-shaded; groundwater flow directions are indicated by black arrows; dark blue numbers represent the surface water levels (m asl); dark blue bold number in rectangle represents the maximum hydraulic head along the water table (m asl); red bold number in rectangle showing hydraulic head maximum within the flow field (m asl); and dashed lines show the boundaries of different flow systems: L1, L2, L3, L4 are local, I1 is intermediate, R1, R1′, R2, R2′ are regional flow systems. OP represents overpressured upward flow domain. Purple arrows with numbers in rectangle showing the maximum penetration depth of the upper gravity-driven flow system. "qin(bot-
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Our recent knowledge about the role of different fluid driving forces in the response of groundwater flow systems to climate change is still limited. This current study aimed to evaluate possible spatial and temporal changes in complex, gravity- and overpressure-driven groundwater flow systems induced by climate change and look for general trends a...
Contexts in source publication
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... the results showed, the degree of overpressure at the bottom of the system clearly determines the penetration depth of the upper, topography-driven flow system, which represents, at the same time, the boundary between gravity-and overpressure-driven flow domains. As the degree of overpressure (and consequent hydraulic head increment at the bottom) increases, the penetration depth of the topography-driven local flow systems decreases (e.g., from 600 m without overpressure to 200 m with high overpressure in the case of the L2 system, Figure 5). In parallel, the drop of groundwater level was obviously affected by the magnitude of upward overpressured flow. ...
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... parallel, the drop of groundwater level was obviously affected by the magnitude of upward overpressured flow. Recharge reduction led to a 3.6 m decline in the pure gravity case, while to a 3.1 m water level drop involving medium overpressure (represents characteristics similar to the sample area), and even to a smaller, 1.0 m decrease in the case of the highest overpressure ( Figure 5), showing that the higher the overpressure, the lower the groundwater level decrease over time. As a consequence, changes in surface water levels are also affected, as proven by the opposite change in the case of lake 2 with the highest overpressure case (0.4 m water level rise, Figure 5b) compared to the pure gravity simulation (2.1 m water level drop, Figure 5e). ...
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... reduction led to a 3.6 m decline in the pure gravity case, while to a 3.1 m water level drop involving medium overpressure (represents characteristics similar to the sample area), and even to a smaller, 1.0 m decrease in the case of the highest overpressure ( Figure 5), showing that the higher the overpressure, the lower the groundwater level decrease over time. As a consequence, changes in surface water levels are also affected, as proven by the opposite change in the case of lake 2 with the highest overpressure case (0.4 m water level rise, Figure 5b) compared to the pure gravity simulation (2.1 m water level drop, Figure 5e). ...
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... reduction led to a 3.6 m decline in the pure gravity case, while to a 3.1 m water level drop involving medium overpressure (represents characteristics similar to the sample area), and even to a smaller, 1.0 m decrease in the case of the highest overpressure ( Figure 5), showing that the higher the overpressure, the lower the groundwater level decrease over time. As a consequence, changes in surface water levels are also affected, as proven by the opposite change in the case of lake 2 with the highest overpressure case (0.4 m water level rise, Figure 5b) compared to the pure gravity simulation (2.1 m water level drop, Figure 5e). ...
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... level decrease was highest (d hmax = −3.6 m, Figure 5) in the case of the pure gravity-driven simulation, which was moderated by the involving overpressured flow. As the results of the numerical investigation highlighted, the higher the degree of overpressure at the bottom of the system, the lower the decrease in groundwater level after 80 yr. ...
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... the results of the numerical investigation highlighted, the higher the degree of overpressure at the bottom of the system, the lower the decrease in groundwater level after 80 yr. In parallel, the magnitude of upward overpressured flow clearly determines the penetration depth of near-surface local flow systems, which is the deepest in the pure gravity-driven case and gradually decreases with the increase in overpressure (from 600 m to 200 m, Figure 5). It was also revealed that as the flow intensity of a shallow gravity-driven flow system decreased, the relative role of overpressure started to increase, and could buffer the effects of recharge reduction on groundwater levels depending on the degree of overpressure. ...
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... groundwater level changes suggest differences between lake 1 and lake 2 in terms of their response to recharge reduction. In the case of lake 1, taking place at the lower flank of the ridge, a slight increase in water level is expected, while lake 2, being closer to the watershed at a higher elevation, will likely become dry in the future ( Figure 5). The diverse behaviour of the lakes can be originated from their different hydraulic position, i.e., fluctuation in water level is the greatest at the recharge area, while more stable in the main discharge area, described also by Zhao et al. [57]. ...
Citations
... Inorganic carbonates are found in medium amounts (3.5-4.5%). Soil fertility and the choice of agricultural crops are first of all limited by the low soil moisture content, as well as its extreme seasonal distribution and the low water retention capacity of the topsoil [35][36][37]. Frequent desiccation exposes the soil to sandstorms, which carry away large amounts of low-density humus particles. ...
Soil moisture reserves are a key factor in maintaining soil fertility and all other related ecosystem services (including carbon sequestration, soil biodiversity, and soil erosion control). In semiarid blown-sand areas under aridification, water preservation is a particularly crucial task for agriculture. The international Diverfarming project (2017–2022), within the EU Horizon 2020 Program, focused on the impacts of crop diversification and low-input practices in all pedoclimatic regions of Europe. In this three-year experiment conducted in the Pannonian region, the impact of intercropping asparagus with different herbs on some provisioning and regulating ecosystem services was evaluated in the Kiskunság sand regions. Relying on findings based on a range of measured physical and chemical soil parameters and on crop yields and qualitative properties, advice was formulated for farmers. The message drawn from the experiment is somewhat ambiguous. The local farmers agree that crop diversification improves soil quality, but deny that it would directly influence farm competitiveness, which primarily depends on cultivation costs (such as fertilization, plant protection, and labour). Further analyses are needed to prove the long-term benefits of diversification through enriching soil microbial life and through the possible reduction of fertilizer use, while water demand is kept at a low level and the same crop-quality is ensured.
... On the one hand, groundwater acts as a buffer against the negative effects of climate change [16] due to the long residence times. In the case of local flow systems, however, especially in recharge areas, climate change is reflected in declining water tables and simplifying flow systems due to the decreasing recharge [17][18][19]. Consequently, connected, vulnerable wetlands and GDEs may face water shortages [20][21][22], especially in recharge and flow-through regions of gravitational flow systems, where the dominant groundwater flow direction is downward or horizontal, causing a negative water balance. As a result, wetlands may dry up, or shrink in area. ...
Climate change and increasing human impacts are more emphasised in recharge regions, where the main flow direction is downward, resulting in negative water balance. Two wetlands located in the recharge position of regional groundwater flow systems were investigated in the Nyírség region, Hungary, as pilot areas for representing wetlands in similar hydraulic positions. Hydraulic data processes, chemical data evaluations, and numerical simulations revealed that the wetlands are fed via local flow systems, superimposing regional-scale recharge conditions in the area. The wetlands are discharge and flow-through types in connection with local flow systems. Nevertheless, in the case of significant regional water table decline—due to the high vulnerability of recharge areas to climate change—local flows are degraded, so they are not able to sustain the wetlands. To preserve the groundwater-dependent ecosystems in the areas, water retention at the local recharge areas of the wetlands may help in the mitigation of water level decline under present-day conditions. If the regional water table continues to decline, comprehensive water retention solutions are needed in the whole region. The results highlight that understanding the natural wetland–groundwater interactions at different scales is crucial for the preservation of wetlands and for successful water retention planning.
... Groundwater depletion is believed to be a localized issue; hence, the flow models usually provide an accurate understanding of local groundwater recharge. Researchers have used groundwater flow models to analyze local depletion issues [23,24]. However, most of the studies are limited to the estimation of the reduction in groundwater extraction for maintaining balance in the system [25][26][27]. ...
... Groundwater depletion is believed to be a localized issue; hence, the flow models usually provide an accurate understanding of local groundwater recharge. Researchers have used groundwater flow models to analyze local depletion issues [23,24]. However, most of the studies are limited to the estimation of the reduction in groundwater extraction for maintaining balance in the system [25][26][27]. ...
Groundwater is an essential water resource in the current era, and studying its sustainability and management is highly necessary nowadays. In the current area of research interest, the reduced mean annual Sutlej River flow, the increase in the population/built-up areas, and enhanced groundwater abstractions have reduced groundwater recharge. To address this issue, groundwater recharge modeling through ponding of the Sutlej River was carried out using a modular three-dimensional finite-difference groundwater flow model (MODFLOW) in a 400 km2 area adjacent to Sutlej River. The mean historical water table decline rate in the study area is 139 mm/year. The population and urbanization rates have increased by 2.23 and 1.62% per year in the last 8 years. Domestic and agricultural groundwater abstraction are increasing by 1.15–1.30% per year. Abstraction from wells and recharge from the river, the Fordwah Canal, and rainfall were modeled in MODFLOW, which was calibrated and validated using observed data for 3 years. The model results show that the study area’s average water table depletion rate will be 201 mm/year for 20 years. The model was re-run for this scenario, providing river ponding levels of 148–151 m. The model results depict that the water table adjacent to the river will rise by 3–5 m, and average water table depletion is expected to be reduced to 151 to 95 mm/year. The model results reveal that for ponding levels of 148–151 m, storage capacity varies from 26.5–153 Mm3, contributing a recharge of 7.91–12.50 million gallons per day (MGD), and benefiting a 27,650–32,100-acre area; this means that for areas benefitted by dam recharge, the groundwater abstraction rate will remain sustainable for more than 50 years, and for the overall study area, it will remain sustainable for 7–12.3 years. Considering the current water balance, a recharging mechanism, i.e., ponding in the river through the dam, is recommended for sustainable groundwater abstraction.
Groundwater overexploitation is a serious problem in the Turpan Basin, Xinjiang Uygur Autonomous Region of China, causing groundwater level declines and ecological and environmental problems such as the desiccation of karez wells and the shrinkage of lakes. Based on historical groundwater data and field survey data from 1959 to 2021, we comprehensively studied the evolution of groundwater recharge and discharge terms in the Turpan Basin using the groundwater equilibrium method, mathematical statistics, and GIS spatial analysis. The reasons for groundwater overexploitation were also discussed. The results indicated that groundwater recharge increased from 14.58×108 m3 in 1959 to 15.69×108 m3 in 1980, then continued to decrease to 6.77×108 m3 in 2021. Groundwater discharge increased from 14.49×108 m3 in 1959 to 16.02×108 m3 in 1989, while continued to decrease to 9.97×108 m3 in 2021. Since 1980, groundwater recharge-discharge balance has been broken, the decrease rate of groundwater recharge exceeded that of groundwater discharge and groundwater recharge was always lower than groundwater discharge, showing in a negative equilibrium, which caused the continuous decrease in groundwater level in the Turpan Basin. From 1980 to 2002, groundwater overexploitation increased rapidly, peaking from 2003 to 2011 with an average overexploitation rate of 4.79×108 m3/a; then, it slowed slightly from 2012 to 2021, and the cumulative groundwater overexploitation was 99.21×108 m3 during 1980–2021. This research can provide a scientific foundation for the restoration and sustainable use of groundwater in the overexploited areas of the Turpan Basin.
Managed aquifer recharge (MAR) is an increasingly popular technique; however, the significance of groundwater flow dynamics is rarely examined in detail regarding MAR systems. In general, a high hydraulic gradient is not favoured for MAR implementation, as it causes higher water loss and mixing of recharge water with native groundwater. However, during groundwater-dependent ecosystem (GDE) rehabilitation, these hydraulic gradient-driven flow processes can be taken advantage of. The aim of this research is to test this hypothesis by evaluating the effect of groundwater table inclination, topography, and other local characteristics on MAR efficiency from the perspective of GDE restoration. MAR efficiency was examined from recharge to discharge area in a simple half-basin based on theoretical flow simulations, using GeoStudio SEEP/W software. Different scenarios were compared to analyse the groundwater level increase and the infiltrated water volumes and to assess the efficiency of MAR based on these parameters in each scenario. The theoretical results were applied to a close-to-real situation of Lake Kondor, a GDE of the Danube-Tisza Interfluve (Hungary), which dried up in the past decades due to groundwater decline in the area. Based on the results, initial hydraulic head difference, model length, and hydraulic conductivity are the most critical parameters regarding water level increase at the discharge area. The water amount needed for increasing the water table is mainly influenced by the thickness of the unsaturated zone and the material properties of the aquifer. The findings can help better understand MAR efficiency in light of local groundwater flow processes and contribute to optimising MAR systems. The results of the study suggest that, if water is infiltrated at the local recharge area, the water table will also increase at the corresponding discharge area, which positively effects the connected GDEs. This approach can serve as a nature-based solution (NBS) to sustain sensitive ecosystems in changing climatic conditions.
This review paper briefly summarizes the research results of the majority (∼70%) women team of the Hydrogeology Research Group of Eötvös Loránd University, Hungary, led by Judit Mádl-Szőnyi. The group had originally focused on basin-scale groundwater flow systems and the related processes and phenomena but extended its research activity to other geofluids in answer to global challenges such as the water crisis, climate change, and energy transition. However, the core concept of these studies remained the basin-scale system approach of groundwater flow, as these flow systems interact with the rock framework and all other geofluids resulting in a systematic distribution of the related environmental and geological processes and phenomena. The presented methodological developments and mostly general results have been and can be utilized in the future in any sedimentary basins. These cover the following fields of hydrogeology and geofluid research: carbonate and karst hydrogeology, asymmetric basin and flow pattern, geothermal and petroleum hydrogeology, radioactivity of groundwater, groundwater and surface water interaction, groundwater-dependent ecosystems, effects of climate change on groundwater flow systems, managed aquifer recharge.
