Rising Groundwater Levels Research Articles

An Unsaturated Soil Mechanics-Based Numerical and Experimental Method to Assess Soil Settlement Due to Ground Water Level Rise

An Unsaturated Soil Mechanics-Based Numerical and Experimental Method to Assess Soil Settlement Due to Ground Water Level Rise

Reversibility of seawater intrusion in a coastal aquifer: Insights from long-term field observation and numerical modeling

It is essential to understand basis processes affecting the reversibility of seawater intrusion (SWI) and the related timescale after groundwater pumping stopped for coastal groundwater management. Groundwater salinity variations presented by previous studies showed a fast SWI process and the following seawater retreat (SWR) process indicated by overall salinity decrease in the coast karst aquifer in the Dalian Peninsula, northeast China. Cross-sectional variable-density flow and transport simulations using equivalent porous medium (EPM) model, dual-domain (DDM) model and the EPM with a single discrete feature representative of conduit flow (EPM-DF) are conducted to understand the SWI reversibility related to the characteristics of the flow system, including aquifer parameters and seaside boundary conditions. Large dispersity combined with a low salinity concentration at the sea boundary are necessary in the EPM and DDM models to produce a fast SWI and low salinity concentration as observed. The enhanced dispersion in the DDM model enhances the mixing in the transition zone (TZ) and produces more obvious seasonal variation but longer SWR process compared to the EPM model. The EPM-DF model produces significant salinity seasonal variation during the SWI process and a fast decrease in the SWR process. The overall fast system response but low peak concentration during the SWI might be attributed to the highly heterogeneous characteristics of the karst aquifer system, which produces a wide front edge of TZ as observed. The dispersion-dominated EPM and DDM models produced higher degree of SWI reversibility compared to the EPM-DF model, as indicated by the weaker lag effects between groundwater levels and salinity concentration. Moreover, the SWI reversibility may arise not only from the heterogeneous characteristics of the karstic aquifer system but also from the rate for rise in the inland groundwater level during the seasonal variation cycle. An overall SWR process can be divided into two stages: the first stage with rapid decrease in salinity concentration but small changes in toe associated with TZ widening and the second stage with rapid toe retreat during aquifer flushing. The flushing of the brine leakage from the solar salt field may extend the SWR process. Considering this relatively longer water quality response time than the time span in general groundwater management plans, a reasonable objective and how maintain the hydraulic head during the SWI controlling have been of a great concern to the coastal groundwater management.

Micromechanical analysis of contact erosion under cyclic loads using the coupled CFD‒DEM method

Different layers of soil often have distinct particle sizes. When exposed to the natural environment, soil is easily affected by natural rainfall, rising groundwater levels, and human activities, leading to particle contact erosion, which reduces the safety and service performance of the soil structure. In this paper, a coupled computational fluid dynamics–discrete element method (CFD–DEM) model was employed to investigate the particle migration phenomena, mechanical response of contact interfaces, variations in flow fields, and macroscopic deformation during the contact erosion process under cyclic loads at different frequencies and amplitudes. The conclusions are presented as follows: (1) Within one cycle of cyclic loading, both compression during loading and stress relaxation during unloading are the main factors triggering the migration of fine particles. (2) The migration and loss of fine particles mainly occur in the early stages of cyclic loading, where strong contact force chains are formed within the fine particle layer, leading to significant plastic deformation of the soil at the macroscopic level. (3) Under cyclic loading, changes in the soil pore structure cause an upwards hydraulic gradient in the initial quiescent water flow field. This hydraulic gradient can rupture weak contact force chains and cause particle pumping. (4) Increasing the frequency and amplitude of cyclic loading intensifies the erosion of fine particles, causing greater axial deformation of the soil. Compared to cyclic loading frequency, the amplitude of cyclic loading has a greater impact on contact erosion.

Inundation dynamics in seasonally dry floodplain forests in southeastern Brazil

AbstractFloodplains are one of the most threatened ecosystems. Even though the vegetation composition in floodplain forests is expected to reflect the variation in groundwater levels and flood duration and frequency, there is little field data on the inundation dynamics (e.g., the variability in flood duration and flood frequency), especially for the understudied seasonally dry tropics. This limits our understanding of these ecosystems and the mechanisms that cause the flooding. We, therefore, investigated six floodplain forests in the state of Minas Gerais in Brazil for 1.5 years (two wet seasons): Capivari, Jacaré, and Aiuruoca in the Rio Grande basin, and Jequitaí, Verde Grande, and Carinhanha in the São Francisco basin. These locations span a range of climates (humid subtropical to seasonal tropical) and biomes (Atlantic forest to Caatinga). At each location, we continuously measured water levels in five geomorphologically distinct eco‐units: marginal levee, lower terrace, higher terrace, lower plain, and higher plain, providing a unique hydrological dataset for these understudied regions. The levees and terraces were flooded for longer periods than the plains. Inundation of the terraces lasted around 40 days per year. The levees in the Rio Grande basin were flooded for shorter durations. In the São Francisco basin, the flooding of the levees lasted longer and the water level regime of the levees was more similar to that of the terraces. In the Rio Grande basin, flooding was most likely caused by rising groundwater levels (i.e., “flow pulse”) and flood pulses that caused overbank flooding. In the São Francisco basin, inundation was most likely caused by overbank flooding (i.e., “flood pulse”). These findings highlight the large variation in inundation dynamics across floodplain forests and are relevant to predict the impacts of changes in the flood regime due to climate change and other anthropogenic changes on floodplain forest functioning.

Natural Climate Protection through Peatland Rewetting: A Future for the Rathsbruch Peatland in Germany

Draining peatlands to create agricultural land has been the norm in Europe, but in the context of climate change and the loss of biodiversity, these rich ecosystems may reactivate their functions as greenhouse gas sinks and retreat spaces for animals and plants. Against this background, the National Moor Rewetting Strategy was put into effect in Germany in 2023, together with the Natural Climate Protection Action Plan. This article examines the methodology of peatland rewetting from scientific, administrative, social, and technical perspectives. The article focuses on an example of moor rewetting in central Germany: the Rathsbruch moor near the municipality of Zerbst, Saxony-Anhalt. To illustrate the importance of rewetting projects for degraded peatlands, five scenarios with different target soil water levels were considered, and the associated greenhouse gas emissions were calculated for a period of five years. For the planning solution, an estimate of the medium-to-long-term development of the habitat types was made based on current use and the dynamics typical of the habitat. The results for the Rathsbruch moor area showed that increasing the water level in steps of 1, 0.8, or 0.5 m has no significant influence on reducing the CO2 emissions situation, while a depth of 0.3 m has a slight influence. When the water was raised to 0.1 m below the surface (Scenario 5), a significant CO2 reduction was observed. The calculated avoided CO2 costs due to environmental damage show that the environmental benefits multiply with every decimeter of water level increase. The rising groundwater levels and extensification favor the establishment of local biotopes. This means that two of the biggest man-made problems (extinction of species and climate change) can be reduced. Therefore, this research is applicable to the development and planning of recultivation work at municipal and regional levels in Germany and beyond within the framework of EU restoration policy.

Reduction of Subsidence and Large-Scale Rebound in the Beijing Plain after Anthropogenic Water Transfer and Ecological Recharge of Groundwater: Evidence from Long Time-Series Satellites InSAR

Beijing, China’s capital city, has experienced decades of severe land subsidence due to the long-term overexploitation of groundwater. The implementation of the South-to-North Water Diversion Project (SNWDP) and artificial ecological restoration have significantly changed Beijing’s hydro-ecological and geological environment in recent years, leading to a widespread rise in groundwater levels. However, whether the related land subsidence has slowed down or reversed under these measures has not yet been effectively monitored and quantitatively analyzed in terms of time and space. Accordingly, in this study, we proposed using an improved time-series deformation method, which combines persistent scatterers and distributed scatterers, to process Sentinel-1 images from 2015 to 2022 in the Beijing Plain region. We performed a geospatial analysis to gain a better understanding of how the new hydrological conditions changed the pattern of deformation on the Beijing Plain. The results indicated that our combined PS and DS method provided more measurements both in total quantity and spatial density than conventional PSI methods. The land subsidence in the Beijing Plain area has been effectively alleviated from a subsidence region of approximately 1377 km2 in 2015 to only approximately 78 km2 in 2022. Ecological restoration areas in the northeastern part of the Plain have even rebounded over this period, at a maximum of approximately 40 mm in 2022. The overall pattern of ground deformation (subsidence and uplift) is negatively correlated with changes in the groundwater table (decline and rise). Local deformation is controlled by the thickness of the compressible layer and an active fault. The year 2015, when anthropogenic water transfers were eliminated and ecological measures to recharge groundwater were implemented, was the crucial turning point of the change in the deformation trend in the subsidence history of Beijing. Our findings carry significance, not only for China, but also for other areas where large-scale groundwater extractions are causing severe ground subsidence or rebound.

Nature-based solution enhances resilience to flooding and catalyzes multi-benefits in coastal cities in the Global South

Coastal cities are facing a rise in groundwater levels induced by sea level rise, further triggering saturation excess flooding where groundwater levels reach the topographic surface or reduce the storage capacity of the soil, thus stressing the existing infrastructure. Lowering groundwater levels is a priority for sustaining the long-term livelihood of coastal cities. In the absence of studies assessing the possibility of using tree-planting as a measure of alleviating saturation excess flooding in the context of rising groundwater levels, the multi-benefit nature of tree-planting programs as sustainable Nature-based solutions (NBSs) in coastal cities in the Global South is discussed. In environments where groundwater is shallow, trees uptake groundwater or reduce groundwater recharge, thereby contributing to lower groundwater levels and increasing the unsaturated zone thickness, further reducing the risk of saturation excess flooding. Tree-planting programs represent long-term solutions sustained by environmental factors that are complementary to conventional engineering solutions. The multi-benefit nature of such NBSs and the expected positive environmental, economic, and social outcomes make them particularly promising. Wide social acceptance was identified as crucial for the long-term success of any tree-planting program, as the social factor plays a major role in addressing most weaknesses and threats of the solution. In the case of Nouakchott City (Mauritania), where a rise in groundwater levels has led to permanent saturation excess flooding, a tree-planting program has the potential to lower the groundwater levels, thereby reducing flooding during the rainy season.

Light Intensity: A Key Ecological Factor in Determining the Growth of Pseudolarix amabilis Seedlings

The notable absence of juvenile Pseudolarix amabilis trees in forest understories suggests their vulnerability to ecological niche competition, leading to limited survival prospects. This study examines the key factors limiting the growth of P. amabilis seedlings by investigating the effects of five ecological factors: light intensity, rainfall, groundwater level, soil type, and type of fertilization, on the growth of one-year-old P. amabilis seedlings. Our results demonstrate that increasing the light intensity promotes plant growth by augmenting the leaf count, leaf biomass, plant height, stem biomass, root biomass, and total biomass. Further analysis reveals that increased light intensity influences biomass allocation, reducing the specific leaf area and leaf–stem biomass ratio, and favoring root and stem growth over leaf investment. Rainfall, groundwater level, fertilization type, and rhizosphere soil type primarily influence root growth by impacting the soil’s physicochemical properties. Specifically, rising groundwater levels lower the soil temperature and increase the soil moisture, total potassium content, and soil pH, leading to reductions in root biomass, plant height, net height increment, leaf number, and total biomass. When groundwater levels reach 21 cm and 28 cm, submerging the surface soil layer, root biomass decreases by 1.6 g/plant (−51.6%) and 2.3 g/plant (−74.2%), respectively. Further analysis reveals a gradual decrease in the root–shoot ratio above the 14 cm groundwater level, while the specific leaf area and leaf–stem biomass ratio remains unaffected, indicating stronger belowground root stress compared to aboveground stem and leaf components. The results highlight light intensity as the key ecological factor determining the growth of P. amabilis seedlings. These findings underscore the importance of considering light intensity in the management of natural stands, the cultivation of artificial forests, and the nursery cultivation of endangered P. amabilis.

Multi-Sensor Satellite Images for Detecting the Effects of Land-Use Changes on the Archaeological Area of Giza Necropolis, Egypt

The World Heritage Committee has been meeting to discuss the arrangements of existing World Heritage Sites, and, on 22–26 October, the area from Giza to the Dahshur was included in the list of World Heritage Sites. According to the Egyptian Antiquities Authority (EAA), the groundwater levels at the Pyramids Plateau are too shallow, which threatens the ancient Sphinx and Pyramids in Giza, Egypt. In addition, many geophysical studies have been carried out in the archaeological area of Giza, which prove that the area is facing the risk of a high level of groundwater, specifically threatening the Sphinx. Recent developments in Earth observation have helped in the field of land monitoring such as land use changes, risk observation, and the creation of models for protecting cultural heritage sites. This study aimed to examine the impact of land use changes on on the archaeological sites of the Giza Necropolis area by integrating various data sources including optical satellite imagery and SRTM data during the period of 1965–2019. A historical database of Corona 1965 and Landsat 2009 data was investigated along with the new acquisitions of Sentinel-2 2016 and Sentinel-1 2016 and 2019. In addition, the radar Sentinel-1 SLC data were collected and analyzed for calculating the land subsidence value in the area of interest through two periods between 6–30 July 2016 and 30 July–15 December 2016. Various methods were implemented, including cluster outliers, the Moran index, and spatial autocorrelation to examine the changes in urban masses. Additionally, the relationship between groundwater leakage and land subsidence in the region was investigated. The analysis was carried out using Envi5.3, ArcMap10.6.1, and SNAP6.0 software to extract spatial data from the raw data. The results from our investigation highlighted rapid changes in urban areas between 1965 and 2019. The data obtained and analyzed from optical and radar satellite imagery showed that changes in land use can cause changes in the topographic situation by decreasing the level of groundwater, which adversely affects Egyptian monumental pyramids and the Sphinx. Land use analysis showed that the urban area represented 7.63% of the total area of the study area in 1965, however it reached 32.72% in 2009, approximately half of the total area in 2016, and in 2019, the urban mass area increased to nearly two-thirds of the total area. The annual growth rate between 1965 and 2019 was estimated by nearly 0.642 km2/year. These land-use changes possibly affected the land subsidence value (−0.0138 m), causing the rising groundwater level close to the Sphinx. Using the information obtained from our RS- and GIS-based analysis, mitigation strategies have also been identified to support archaeological area preservation.

Using stable isotopes in deciphering climate changes from travertine deposits: the case of the Lapis Tiburtinus succession (Acque Albule Basin, Tivoli, Central Italy)

Quaternary stable isotope records of marine and lacustrine carbonate deposits as well as speleothems were extensively studied to reconstruct global and regional climatic evolution. This study demonstrates how stable isotope records of travertine provide fundamental information about climate and the consequences of its evolution on groundwater level fluctuations. The deposition of the Lapis Tiburtinus travertine succession occurred during the Late Pleistocene (150–30 ka), coeval with the last activity of the Colli Albani volcanic complex. Two boreholes (Sn1 and Sn2) were drilled into the Acque Albule Basin (23 km E of Rome), crossing the entire Lapis Tiburtinus succession. The Sn1 borehole in the central part of the basin crosscuts a travertine succession of 62.1 m in thickness, while the Sn2 borehole in the southern part of the basin is characterized by a travertine succession 36.3 m in thickness. Carbon and oxygen stable isotope ratios were analysed on 118 samples (59 samples both for Sn1 and Sn2 boreholes) representative of the entire Lapis Tiburtinus travertine succession crossed by the boreholes. Values, measured and correlated in the two drilled boreholes, permitted determination of the sensitivity of the travertine depositional system to glacial and interglacial cycles, unravelling the complex oxygen and carbon cycle dynamic recorded in such sedimentary succession. Moreover, the results obtained correlated with available pollen curves of the Mediterranean area (from the Castiglione crater, 25 km E of Rome). Regional and global oxygen isotope continental and marine curves, calibrated with the stratigraphy of the Acque Albule Basin, and available U/Th dating allow the identification of at least three phases of the last interglacial (Marine Isotope Stage 5-MIS5). The carbon isotope record, compared with CO2 flux reconstructed and associated with the volcanic activity of the Colli Albani volcanic complex, instead shows an influence from groundwater level changes. In particular, positive shifts that occurred during arid phases are associated with a lower groundwater level and increased CO2 degassing, inducing a major fractionation effect on carbon isotopes. Instead, the negative shifts occurring during more humid periods indicate the inhibition of CO2 degassing and increase in pressure, attesting to a rise in groundwater level. In this view, travertine deposits, frequently studied to define the tectonic setting and activity of the area where they develop, can thus also be used as a tool to understand climate changes and groundwater variations apparent in their stable oxygen and carbon isotope signature.

DECOMPOSITION OF RIVER HYDROGRAPHS TAKING INTO ACCOUNT DATA OF HYDROGEOLOGICAL OBSERVATIONS

In the case of absence of reliable information on fluctuations of levels and hydraulic parameters of aquifers within a large catchment, the method of river hydrograph decomposition can be used to assess groundwater component and other constituents of river water recharge. The difficulties and shortcomings of this method, which relies on specific schematizations and assumptions, are analysed and discussed. We propose to take into account the results of calculations of lateral groundwater inflow to the river accomplished using the numerical method based on observations at representative balance sites in order to improve the accuracy of the method of decomposition of the river hydrograph. A proper schematization should also be justified for river catchment (or its part), which describes the interaction of surface water, shallow groundwater, and artesian (deep) interlayer waters, which provides rationale for defining or neglecting groundwater inflow to river during the flood periods. The most disputable issue remains the allocation of the phase of “reverse water inflow to river banks” during flood periods. The groundwater level rise at the beginning of the flood results from the infiltration recharge to the aquifer and from inflow of water from the river. The contribution of inflow to river bank to groundwater level rise is dependent from the distance from the river to the observation well. To establish hydraulic head gradient from the river towards the adjacent groundwater aquifer at flood peak, at least two observation wells are needed, one of which should be located 3–4 m from the river water edge on the elevated part of the bank which is not flooded, and the other should be located 50–70 m from the bank towards the watershed. It is proposed that the phase of maximum groundwater inflow to the river should be adjusted based on the dates of the beginning and ending of the groundwater level decrease during the recession of the river flow during the flood period. The combined application of the described above methods showed that the use of only hydrograph decomposition method underestimates the share of groundwater recharge to the river by 2–5%. Based on the analysis of the Pivdennyi Buh River hydrographs during the 1980–2020 period, general tendencies of changes in the shallow groundwater and deep subsurface recharge of the Pivdennyi Buh River in its upper basin (upstream of the city of Khmilnyk) have been established: deep subsurface recharge prevailed over the shallow groundwater component (33.4 compared to 25.0% of the total). At the same time, the total subsurface runoff constituted on average 58%.

The Distribution and Evolution of Groundwater Level Depths and Groundwater Sustainability in the Hexi Corridor over the Last Five Years

Groundwater overexploitation for agricultural irrigation is prone to lead to numerous ecological concerns. This study delved into the present distribution and recent trend of groundwater levels in the plain areas of the Hexi Corridor in Northwest China according to the groundwater level depth (GWD) data from 264 monitoring wells in the Shiyang River Basin (SYB) and 107 in the Shule River Basin (SLB), recorded annually in April from 2019 to 2023. The key findings include the following: (1) Over the five-year span, the SYB’s GWD experienced change rates (CRs) ranging from −12.17 to 9.11 m/a (average: −0.13 m/a), with the number of monitoring wells showing increased and decreased GWDs accounting for 50% and 50%, respectively. By contrast, the SLB’s GWD exhibited CRs ranging from −1.87 to 2.06 m/a (average: 0.01 m/a), with the number of monitoring wells showing increased and decreased GWDs accounting for 52% and 48%, respectively; (2) the Wuwei (CR = 0.09 m/a) and Changning (0.58 m/a) basins in the SYB and the Yumen (0.06 m/a), Guazhou (0.05 m/a), and Huahai (0.03 m/a) basins in the SLB, witnessed rising groundwater levels. In contrast, the Minqin Basin (0.09 m/a) in the SYB and the southern Dunhuang Basin (0.04 m/a) in the SLB witnessed declines in the groundwater levels; (3) The groundwater sustainability assessment showed that the groundwater is still extremely unsustainable. This study’s insights are instrumental in targeted treatment, as well as the preparation and adjustment of sustainable groundwater protection strategies.

A novel approach for quantifying upper reservoir leakage

During the operational phases of the upper reservoir in a pumped storage power station, the water level, leakage area, and hydraulic gradient of the upper reservoir alter dynamically due to the cyclic pumping and draining activities. The rising groundwater level during storage introduces distinct leakage conditions within the reservoir basin, characterized by unsaturated, partially saturated, and saturated states. Consequently, reservoir basin leakage exhibits variability across these states. To address this issue, this study formulated rational assumptions corresponding to the three leakage states in a reservoir basin and derived analytical expressions for seepage calculation based on Darcy's law and the principles governing groundwater flow refraction. A case study was conducted to investigate the relationship between various factors and leakage. The results showed that leakage primarily depended on the permeability of the impermeable layer in the reservoir basin. The upper reservoir leakage was estimated, and the calculated leakage generally agreed with the measurements, offering insights into the leakage mechanism of the Liyang pumped storage power station. In addition, the reasons for disparities between measured and calculated leakage were analyzed, and the reliability of the developed method was validated. The findings of this study provide a foundation for the seepage control design of upstream reservoirs in similar projects.

Enterococci pathways to coastal waters and implications of sea level rise

Highly urban coastal communities in low lying areas and with high water tables are vulnerable to sea-level rise and to corresponding increases in coastal groundwater levels. Stormwater conveyance systems are under increased risk. Rising groundwater levels affect the hydraulics of the stormwater system thereby increasing contaminant transport, for example the fecal indicator bacteria enterococci, to coastal waters. This study offers a unique opportunity to evaluate the impacts of increased contaminant transport on marine coastal environments. Here we assessed historic and recent coastal water quality, stormwater sampling data, groundwater monitoring and tidal elevations near the coastline, in the context of altered hydraulics within the system. Two pathways of enterococci to marine waters were identified. Direct discharge of contaminated stormwater runoff via the stormwater outfalls and tidally driven contaminated groundwater discharge. As sea level continues to rise, we hypothesize that a diminished unsaturated zone coupled with altered hydraulic conditions at the coastal groundwater zone will facilitate the transport of enterococci from urban sediments to the study site (Park View Waterway in Miami Beach, FL USA). We recommend improvements to the stormwater conveyance system, and maintenance of the sanitary sewer system to mitigate these impacts and minimize transport of enterococci, and other stormwater pollutants to coastal waters. The results of this study can be useful to interpret high enterococci levels in low lying coastal areas where groundwater is influenced by rising sea water levels.

Do groundwater systems experience a ‘silent’ stress? A paradox of rising groundwater levels and stressed aquifers

Global groundwater stress poses a serious threat to both the environment and human communities. Conventionally, groundwater stress is said to occur when the demand for groundwater (both human and environmental water requirements) exceeds its recharge rate over a period of time, resulting in declining groundwater levels. Does this imply that rising groundwater levels always indicate a healthy aquifer? We hypothesize that this may not always be true as groundwater systems respond extremely slowly (often taking several years), reflecting such fluctuations as low-frequency signals, to the accumulated effects of varying climate and groundwater demands. Therefore, we suspect that “groundwater systems may be hiding stress behind apparently rising groundwater levels”. Thus, our study defines a new concept of “silent groundwater stress” and devises a new tool to detect its existence, quantify its degree and attribute the driving forces for such a silent stress. We demonstrate these in large heterogenous sub-tropical aquifer systems over the Indian subcontinent. We found that the interplay of climate and human activity has disrupted the groundwater balance, altering the resilience capacity of large aquifers, particularly in agriculturally active regions. Climate variability puts latent stress on crucial aquifers despite rising groundwater levels. A mere reduction in natural recharge by 6 % can trigger dampening of the rise of groundwater levels, thereby pushing the system closer to a tipping point beyond which one could witness a sudden breakdown of the groundwater system. In contrast, rising groundwater levels may create a temporary euphoria in areas with increased natural recharge, triggering excessive pumping and can impose a silent stress on the aquifer system. Thus, it is crucial to acknowledge and integrate this “silent” stress in groundwater management amidst climate change and water scarcity to ensure adequate supply for billions of people.

Comprehension of Seismic-Induced Groundwater Level Rise in Unsaturated Sandy Layer Based on Soil–Water–Air Coupled Finite Deformation Analysis

Immense liquefaction damage was observed in the 2011 off the Pacific coast of Tohoku Earthquake. It was reported that, in Chiba Prefecture, Japan, the main shock oozed muddy water from the sandy ground and the aftershock which occurred 29 min after the main shock intensified the water spouting; thus, the aftershock expanded the liquefaction damage in the sandy ground. For comprehending such a phenomenon, using a soil–water–air coupled elastoplastic finite deformation analysis code, a rise in groundwater level induced by main shock is demonstrated, which may increase the potential of liquefaction damage during the aftershock. The authors wish to emphasize that these results cannot be obtained without soil–water–air coupled elastoplastic finite deformation analysis. This is because the rise in groundwater level is caused by the negative dilatancy behavior (plastic volume compression) of the saturated soil layer which supplies water to the upper unsaturated soil layer, and it is necessary to precisely calculate the settlement of ground and the amount of water drainage/absorption to investigate the groundwater level rise. This study provides insight into the mechanism of ground liquefaction during a series of earthquakes.

Spatiotemporal successions of N, S, C, Fe, and As cycling genes in groundwater of a wetland ecosystem: Enhanced heterogeneity in wet season

Microorganisms in wetland groundwater play an essential role in driving global biogeochemical cycles. However, largely due to the dynamics of spatiotemporal surface water-groundwater interaction, the spatiotemporal successions of biogeochemical cycling in wetland groundwater remain poorly delineated. Herein, we investigated the seasonal coevolution of hydrogeochemical variables and microbial functional genes involved in nitrogen, carbon, sulfur, iron, and arsenic cycling in groundwater within a typical wetland, located in Poyang Lake Plain, China. During the dry season, the microbial potentials for dissimilatory nitrate reduction to ammonium and ammonification were dominant, whereas the higher potentials for nitrogen fixation, denitrification, methane metabolism, and carbon fixation were identified in the wet season. A likely biogeochemical hotspot was identified in the area located in the low permeable aquifer near the lake, characterized by reducing conditions and elevated levels of Fe2+ (6.65–17.1 mg/L), NH4+ (0.57–3.98 mg/L), total organic carbon (1.02–1.99 mg/L), and functional genes. In contrast to dry season, higher dissimilarities of functional gene distribution were observed in the wet season. Multivariable statistics further indicated that the connection between the functional gene compositions and hydrogeochemical variables becomes less pronounced as the seasons transition from dry to wet. Despite this transition, Fe2+ remained the dominant driving force on gene distribution during both seasons. Gene-based co-occurrence network displayed reduced interconnectivity among coupled C-N-Fe-S cycles from the dry to the wet season, underpinning a less complex and more destabilizing occurrence pattern. The rising groundwater level may have contributed to a reduction in the stability of functional microbial communities, consequently impacting ecological functions. Our findings shed light on microbial-driven seasonal biogeochemical cycling in wetland groundwater.

Современные экологические проблемы эксплуатации коллекторно-дренажной сети и пути их решения

Purpose: to determine the environmental issues that arose during the operation of irrigation and drainage systems, and the basic principles of managing the quality of drainage water from irrigated lands. Discussion. Analytical data on the condition of reclaimed lands, changes in groundwater levels during the operation of irrigation systems, the use of water resources, the results of theoretical and experimental studies of the collector-drainage flow quality in the irrigation system diversion collectors in the south of Russia are considered. The main problems are identified: land resources degradation, rising groundwater levels, resalinization and salt accumulation during irrigation, especially with irrigation water with increased mineralization, changes in the hydrological and hydrochemical regime of water bodies – collector-drainage runoff intakes. Legal problems associated with the classification of irrigation and drainage systems as objects of category III are highlighted. Ways to solve environmental problems, methods for managing the quality of drainage runoff, including the creation of local treatment facilities based on routing the collector-drainage network to irrigated areas suspended from the drainage system, in the range of 10–200 ha with construction of storage drainage sumps as places for metering flow and regulating the chemical composition of drainage flow. Conclusions. Pollution problems are regional in nature and are determined not only by economic activities, but also by natural factors. The set of irrigation canals, collector-drainage networks and water intakes of drainage-discharge waters participates in the inter-basin redistribution of surface and underground runoff. In the process of managing the quality of drainage water from irrigated lands and the environmentally safe operation of hydro-reclamation systems, three parties must certainly participate: reclamation departments, agricultural producers and government agencies.

The Mechanism of Rainfall-Induced Landslide Around Railway Tracks in Central Java Province, Indonesia

Landslide is one of the most disastrous natural hazards in Indonesia, causing significant fatalities and economic losses. Landslides can be triggered by several factors, such as rainfall, earthquakes, soil conditions, and others, where each landslide event has its own triggering and controlling factors. A progressive landslide occurred on the Central Java railway line which resulted in damage to the double-track railway as a transportation infrastructure. The objective of this paper is to understand the process and triggering factors of the landslide. Information was collected through field investigations and measurements based on drilling results at 3 points, geophysical surveys at 5 lines, and laboratory testing of several soil samples. Geological and geotechnical settings, topography, lithology, hydrogeology, and rainfall data of the area were analyzed. Aerial photographs and other remote sensing data were used to evaluate and discuss the information. Landslides in the study area occurred in stages, starting with the formation of a tension crack, followed by two landslides over five months. The results show that the clay material that dominates the study area is the dominant controlling factor of a landslide, triggered by long-duration, low-intensity rainfall. Rainwater entering through tension cracks increases moisture content, adding load to the slope and triggering landslides. Furthermore, the train's external load on the slope also contributes to the occurrence of landslides. The static and cyclic load of the train causes changes in the slope's pressure balance, generating a force that drives the downslope soil. Further analysis was performed using back analysis method with the limit equilibrium method to enhance understanding of slope stability parameters at the time of slope failure. The analysis was performed considering the rising groundwater level. A factor of safety (FS) value of 0.989 was obtained at the end of the simulation, indicating that the slope had failed.

Analyzing stability of protective structures as the elements of geotechnical tailing pond safety

Purpose is the assessment of soil retaining wall stability to ensure geotechnical safety during the radioactive waste tailing pond closure and further recultivation (or rehabilitation) in Kamianske town (Ukraine). Methods. Geomechanical stability of the protective structure has been assessed relying upon the analysis of geological-hydrogeological, engineering-geological, and geotechnical conditions of the certain tailing pond area using a deformation elastic-plastic model of a medium implemented on the basis of finite-element method. For the purpose, the dam slopes have been detalized taking into consideration their geometry as well as changes in vertical section of rock material characteristics in accordance with the earlier geophysical studies; exploration drilling; and engineering-geological surveys. Findings. Stability coefficients of protective tailing pond dam have been identified within the typical areas of a hydraulic structure; it provides high reliability and representativeness of the whole structure health in time as well as under various conditions of the industrial waste water saturation. It has been defined that the stability coefficients varies from ks = 1.372 to 4.758. Comparison of the indicators between 2022 and 2016 demonstrates a tendency of the slope stability coefficient decrease due to water saturation and groundwater level rise. Nevertheless, design characteristics of the structure make it possible to ensure satisfactory a stability coefficient along the whole dam length being 1.13 times higher than the standard one (i.e. ks = 1.250). Originality. The dependence of the tailing pond protective dam stability upon a water supply degree at the forecasted groundwater level rise at the expense of atmospheric and melt water ingress to the tailing pond has been defined. The danger of complete radioactive waste water saturation is a significant reduction in the stability coefficient of the protective structure, which can be supported by predictive modelling data. If strength parameters of a dam material decline for the most critical area then the strength coefficient decreases starting from 1.532 in terms of the current groundwater level down to 1.372 as for the forecasted dam water supply. The figure is more than 10% of its initial stability. Practical implications. The obtained results substantiate the necessity; moreover, they are of practical value while improving hydrological, hydrogeological, and geotechnical monitoring of the analyzed tailing pond to ensure its radiation safety under different conditions of further behaviour during closure, recultivation, or rehabilitation.