Rising Groundwater Levels Research Articles

Analyzing trends and change points in hydro-meteorological parameters and groundwater level in the Barak river basin in India

Climate change has a substantial influence on a range of meteorological factors and the global hydrological cycle. This paper presents an analysis of the annual rainfall (P), temperature (including maximum temperature: Tmax, minimum temperature: Tmin, and average temperature: Tavg), stream flow (Q) data from 6 gauging sites, and groundwater level (GL) data from 7 groundwater stations in and around the Barak River Basin in India from 1986 to 2020. To identify patterns in the time series, the simple linear regression (SLR) approach, the Mann-Kendall (MK) test, the Hamid Mann-Kendall (HMK) test and the Spearman's Rho (SRO) tests have been employed. Pettit test has been used to identify the change points in the time series. The results indicated an increase in the Tmax and the Tmin across the study area, while no clear patterns were found in the Tavg time series. Except for the ‘Hailakhandi’ station, the annual total rainfall series showed an increasing trend. Tmax and Tmin showed a directional change point between 1999 and 2005, and between 2001 and 2007, respectively, according to change point analysis. Except for two stations, overall declining trends in the annual stream flow were found. Moreover, a total of five out of seven groundwater stations indicated a rise in groundwater levels. The findings presented here offer valuable insights into the current condition of the Barak basin and emphasize the importance of implementing sustainable water management practices.

PRINCIPLES OF CALCULATIONS AND ARRANGEMENT OF LOCAL DRAINAGE SYSTEMS IN PRIVATE BUILDING TERRITORIES

Abnormally heavy rains in the first two spring months of 2023 revealed the unpreparedness and lack of protection of many settlements in the Kyiv region from excessive moisture and inundation. Among them, is Novi Petrivtsi village, where the natural conditions for surface runoff and precipitation infiltration (lack of visible surface slopes and poorly permeable cover sediments) are unfavourable and significantly complicated by buildings, and a network of highways. The long-term retention of water on the surface, the rise of groundwater levels, and the layered structure of the upper part of the geological section provide grounds for the use of combined local drainage systems with compliance with drainage standards of at least 3,0 m. Since the high density of buildings often does not allow for contour drainage around residential buildings, it is necessary to lay single-line horizontal drainage to a greater depth than for a conventional contour drainage of 3,5 meters or more. However, the lack of roadside ditches and other water intakes and means of orderly drainage do not allow homestead drainage systems to work as efficiently as possible. This requires the creation of an orderly system of water intakes (trenches and closed collectors) on the scale of the village. Foreign experience convinces that the rational planning of such systems is possible under the conditions of establishing the character of rainfall distribution with a resolution of 1–5 minutes in time and a step of 500 m across the area. Meteorological radar is used to record radar images of rain and study its intensity. An effective solution to the water drainage problem is impossible without detailed engineering and geological investigations. Due to them, litho-facies inhomogeneities in the aeration zone and water-saturated stratum, which lead to the retention and support of groundwater, were discovered in the local area. Taking into account the spatial boundaries of these engineering and geological elements allow drainage more efficiently. Drainage capacity is substantiated by forecasts of changes in the maximum amount of precipitation per day and two days in a row. Due calculating the drainage capacity, it should be taken into account that the maximum amount of precipitation in the future period will have a guarantee of 0,5-2,0% less than the actual maximum values. In the calculation part, the main attention is paid to the selection of equations for determining the width of influence of a single horizontal drain. Five formulas have been selected that can be used to solve similar problems. The time of onset of the established mode of operation of a single drain was calculated. Future research should focus on the collection of high-resolution rainfall and local urban runoff data, as well as the implementation of urban drainage models.

Short‐term dynamics of drainage density based on a combination of channel flow state surveys and water level measurements

AbstractHeadwater streams often experience intermittent flow. Consequently, the flowing drainage network expands and contracts and the flowing drainage density (DD) varies over time. Monitoring the DD dynamics is essential to understand the processes controlling it. However, our knowledge of the event‐scale DD dynamics is limited because high spatial and temporal resolution data on the DD remain sparse. Therefore, our team monitored the DD dynamics and hydrologic variables in two 5‐ha headwater catchments in the Swiss pre‐Alps in the summer of 2021, through mapping surveys of the flow state and a wireless streamwater level sensor network. We combined the two data sources to calculate the DD at the event‐time scale. Our so‐called CEASE method assumes that flow in a channel reach occurs above a set of water level thresholds, and it determined the DDs with accuracies >94%. DD responses to events differed for the two catchments, despite their proximity and similar size. DD ranged from 2.7 to 32.2 km km−2 in the flatter catchment (average slope: 15°). For this catchment, the discharge‐DD relationship became steeper when DD exceeded 20 km km−2 and DD increased substantially with relatively small increases in discharge. For rainfall events during dry conditions, the discharge‐DD relationship showed counterclockwise hysteresis, likely due to initially high groundwater discharge from the area near the catchment outlet; once rainfall stopped, DD remained high during the streamflow recession due to rising groundwater levels throughout the catchment. For events during wet conditions, the discharge and DD responded synchronously. In the steeper catchment (average slope: 24°), the DD varied only from 7.8 to 14.6 km km−2 and there was no hysteresis or threshold behaviour in the discharge‐DD relationship, likely because multiple groundwater springs maintained streamflow throughout the network during the monitoring period. These results highlight the high variability in DD and its dynamics across small headwater catchments.

Arizona Groundwater Explorer: interactive maps for evaluating the historical and current groundwater conditions in wells in Arizona, USA

Groundwater is an important water source in Arizona, accounting for about 41% of water use in this mostly arid-to-semiarid state in the southwestern United States, and the availability of groundwater resources in the state is a concern. To provide accessible information from depth-to-groundwater data, a series of web-based interactive maps were developed, called the Arizona Groundwater Explorer (AGEx). Scripts were written to harmonize and synthesize groundwater datasets from the two largest publicly available sources, subset these data to address different groundwater availability questions, and display the results in online, interactive maps. The combined dataset contained 1,820,122 depth-to-groundwater measurements from 1891 through 2022 from 41,918 wells in Arizona. Data views are provided for 20 topics, including recent (2020 or later) depth to groundwater (4,569 wells), historical (pre-1950) depth to groundwater (4,287 wells), wells with long-term (≥50 years) records (1,183 wells), wells with recent groundwater level decline (277 wells), wells with recent groundwater level rise (120 wells), and linear trends in groundwater levels over ten 10-year periods (number of wells ranging from 341 in 1978–1987 to 1,208 in 2003–2012), among others. With ongoing drought in the region resulting in declining surface-water supplies in Arizona, groundwater may play an even larger role in satisfying water needs in the state. The AGEx series of maps provides a nonspecialist audience with an improved understanding of historical, current, and changes in groundwater levels in Arizona.

Effect of Groundwater Level Rise on the Critical Velocity of High-Speed Railway

The increasing frequency of extreme rainfall is leading to a rise in groundwater levels in coastal areas, significantly affecting high-speed railway operations. To address this concern, this study developed a 2.5-dimensional finite element model of a coupled track-embankment-ground system based on Biot’s porous media theory to analyze the effect of groundwater level rise on the critical velocity of high-speed railways and vibration responses. The findings reveal a consistent decrease in the critical velocity of high-speed railways with rising groundwater levels. Particularly, the increase in groundwater levels within the embankment significantly influences the critical velocity compared to a similar rise in the foundation’s groundwater level. Furthermore, deformations induced by passing trains significantly increase as groundwater levels rise. Specifically, when the groundwater level rises from the foundation bottom to the subgrade surface, subgrade surface deformation increases by approximately 55%. As trains approach the critical velocity, significant vibration phenomena, known as the “Mach effect,” occur at the foundation surface. Importantly, as groundwater levels rise, the “Mach effect” intensifies. Analyzing the vibrating frequency spectrum of the displacement response demonstrates a substantial increase in vibration amplitude, particularly in the high-frequency region, as groundwater levels rise. This study highlights that the rise in groundwater level not only amplifies vibrations but also extends the propagation of high-frequency vibrations, underscoring the importance of effective embankment waterproofing in controlling track vibrations.

Effects of Irrigation Projects on the Classification of Yellow River Terrace Landslides and their Failure Modes: A Case Study of Heitai Terrace

The study of the classification and failure modes of Yellow River terrace landslides under the influence of irrigation projects is of key importance to alleviate the paradox between the rapid evolution of terrace landscapes caused by landslides and the survival of local residents. However, such studies remain controversial, despite it being widely recognized that a rise in groundwater level caused by irrigation is a key factor associated with landslide failure modes. In this paper, we take the Heitai terrace as a case study. Using aerial images and field investigations, we classify landslides in the Heitai loess layer into type A landslides (not related to groundwater) and type B1 and B2 landslides (related to groundwater). We analyze the failure modes and disaster-causing characteristics of each type of landslide, and our results indicate that the attenuation in soil strength is a key factor common to both type A and type B landslides, based on which type A landslides with small volume and short sliding distance are able to block the previous spring discharge, causing a rise in localized groundwater, which further contributes to type B landslides; the location of previous type B1 landslides with a large volume and long sliding distance and type A landslides may be more susceptible to type B2 landslides with a small volume and short sliding distance, where there are low confining pressures during the lower soil shear process. Therefore, we believe that the inevitable interaction effects between the failure modes of landslides during landslide evolution, which govern the geomorphological evolution of the Heitai terrace, are unavoidable. Combining these data with numerical analyses, we further demonstrate that a rise in groundwater level and discontinuous attenuation of soil strength caused by changes in soil properties during irrigation together control terrace landslides and their failure modes. From the results of interferometric synthetic aperture radar time-series monitoring of Yellow River terrace activity with and without irrigation projects, and electrical resistivity tomography groundwater detection, we conclude that in the future, Heitai terrace will continue to experience a high intensity of landslide activity, and conditions for the most catastrophic type of landslide (type B1) will remain, including the high localized groundwater caused by previous landslides, and the discontinuous attenuation of soil strength caused by the deterioration in soil properties. In this context, we believe that slope-cutting engineering will be one of the most economical means to achieve future landslide-type transformation on the Heitai terrace; this will mitigate the process of geomorphological evolution and improve the human living environment.

Developing a multi-objective simulation-optimization model for ecological water conveyance in arid inland river basins

Study regionMiddle and lower reaches of Tarim River, southwestern of Xinjiang Province, China. Study focusEcological water conveyance is an important measure to protect the fragile ecosystem of inland rivers in arid areas. This paper attempted to present a integrated model for optimal ecological water conveyance scheme (EWCS). In this model, the impact of the duration of water conveyance and the water allocation of each channel on the groundwater level was considered. The optimized ecological water conveyance scheme can simultaneously maximize groundwater level rise value (GLRV) and minimize ecological water conveyance volume (EWCV). New hydrological insights for the regionAn simulation-optimization model was proposed based on MODFLOW model, Kriging surrogate model and NSGA-II. The study obtained the Pareto frontiers of EWCS in three typical years (dry, normal and wet), and made decisions using the TOPISIS-Entropy method. The scenario comparison results indicated that the optimized EWCS requires less EWCV than the existing one when achieving the same GLRV, proving that the optimized EWCS has higher water resource utilization efficiency. This simulation-optimization model fills the research gap of EWCS in arid inland river basins and provides scientific guidance for government management.

Spatiotemporal analysis of groundwater level trends and recharge rate estimation in the unconfined aquifer of Yogyakarta-Sleman Groundwater Basin, Indonesia

Groundwater is the primary water resource used for domestic, industrial, and agricultural needs for the community in the Yogyakarta-Sleman Groundwater Basin area. The urbanization rate has increased since the 1970s and has made massive use of groundwater, causing environmental problems, including the quality and quantity of groundwater. Therefore, this study aimed to investigate the spatiotemporal groundwater fluctuation trends based on the non-parametric Mann-Kendall test and recharge rate estimation using the water table fluctuation (WTF) method. The groundwater level data were collected from monitoring wells across the study area during 2018-2022, particularly emphasizing 8 wells representing recharge, transition, and discharge areas. The results showed that the groundwater fluctuation pattern generally followed the season. During the rainy season from January to April, groundwater reached the shallowest level and began to decline gradually when it entered the dry season from May to October. Groundwater recharge rate was estimated to vary from 171.49 to 1,505.56 mm/year. Meanwhile, the Mann-Kendall test showed that most of the Yogyakarta-Sleman Groundwater Basin area did not experience significant fluctuation trends, except for two monitoring wells in the center of Yogyakarta City which had increasing groundwater level trends. The rising groundwater levels were expected to be caused by urban wastewater recharge. This study has provided a new description and insights into spatiotemporal changes in the groundwater table and the quantification of groundwater recharge.

Transport and Retention of Fecal Indicator Bacteria in Unsaturated Porous Media: Effect of Transient Water Flow.

For production of clean drinking water, the processes governing bacterial remobilization in the unsaturated zone at transient water flow are critical. Although managed aquifer recharge is an effective way to dispose of pathogens, there are concerns about recontamination after heavy precipitation. To better understand how bacteria that were initially retained in porous media can be released to groundwater due to transient water content, transport experiments and modeling for Escherichia coli and Enterococcus moraviensis were conducted at the soil column scale. After inoculating dune sand columns with a bacteria suspension for 4 h, three rainfall events were performed at 24-h intervals. The effluent from sand columns was collected to analyze bacteria breakthrough curves (BTCs). After the rainfall experiments, the bacteria distribution in the sand column was determined. The collected BTCs and profile retentions were modeled with HYDRUS-1D, using different model concepts, including one-site kinetic attachment/detachment (M1), Langmuirian (M2), Langmuirian and blocking (M3), and two-site attachment/detachment (M4). After inoculation, almost 99% of the bacteria remained in the soil. The M1 and M2 bacteria models had a high agreement between observed and modeled concentrations, and attachment and detachment were two significant mechanisms for regulating bacteria movement in a porous medium with fluctuations in water flow. At the end of the experiment, the majority of bacteria were still found within the depth range of 5 cm to 15 cm. Our experiments show that E. coli is more mobile in sandy soils than E. moraviensis. The results of this study also suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Follow-up studies are needed to completely understand the variables that regulate bacteria remobilization in the unsaturated zone of dune sands. IMPORTANCE At managed artificial recharge sites in the Netherlands, recontamination of infiltrated water with fecal indicator bacteria has been observed. The results of this study suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Bacteria that accumulate in the unsaturated zone, on the other hand, can multiply to such an extent that they can be released into the saturated zone when saturation increases due to major rain events or a rise in groundwater level.

Nitrate attenuation with rising groundwater levels: An integrated assessment using isotope tracers and microbial signatures

Nitrate contamination of groundwater has long been a source of concern. Most field studies conducted in areas with rising groundwater levels have found an increase in nitrate concentration owing to nitrate leaching, but they have not investigated the possible biogeochemical processes. In this study, dual nitrate isotopes and microbial signatures were combined to assess and quantify nitrate attenuation in the North China Plain with an apparent groundwater-level recovery trend over the past decade. Significant denitrification was revealed using the dual nitrate isotopes on the temporal scale. High-throughput sequencing provided microbial functional and taxonomic evidence, showing the relative abundances of denitrification-related functional genes negatively related to the nitrate concentration. Nitrate attenuation was strengthened in the aquifer as the groundwater levels rose, with a larger temporal enrichment factor (ε) value of −25‰ compared with the spatial ε value of −5‰. This study is the first to reveal the mechanisms of nitrate attenuation in aquifers undergoing groundwater-level recovery with an integrated assessment using nitrate isotope tracers and microbial signatures. In identifying the main nitrate attenuation processes, it is important to consider the scale and domain of interest and to conduct sufficient spatial and temporal monitoring to capture transient conditions.

Review of artificial recharge prospects for augmentation of groundwater in Egypt: A case study of El Bustan extension area

Artificial recharge (AR) is the process whereby surface water is directed purposely underground to augment natural replenishment of groundwater reserves. During the period 1996–1998, the Research Institute for Groundwater started artificial recharge using infiltration basins in El Bustan experimental station in the western Nile Delta region. Recently, during the period 2020–2021, artificial recharge activities have been resumed in the experimental station. In this work, changes in hydrological conditions affecting the experimental station since its inception are reviewed and assessed. Artificial recharge using the infiltration basin are then applied, where results of these experiments are evaluated and compared to the previous ones. This is achieved with the objective of making an updated evaluation of the prospects of artificial recharge considering the changes in hydrological conditions. The study revealed that rise of groundwater levels is the major change affecting aquifer conditions in the study area. Such progressive rise of groundwater levels resulted in reducing the vadose zone thickness by more than 50% of its original thickness in 1996. This rise is attributed to uncontrolled recharge due seepage from nearby canals and irrigation return flow in the western Nile Delta region for the past 25 years. In view of the impacts of uncontrolled recharge, it is concluded that future work should shift from AR to managed aquifer recharge (MAR) to store water in the aquifer for subsequent recovery. It is recommended that further studies should use numerical modeling for exploring MAR schemes that can sustain the aquifer hydrologic equilibrium. Such MAR schemes should facilitate conjunctive use of surface and groundwater for improved water use management in the western Nile Delta region.

Investigation on overburden thickness considering face and anti-floating stability of shallow shield tunnel

Ensuring the safety of water-rich shield tunnels requires a reasonable design of overburden thickness. However, few studies have comprehensively investigated the design of overburden thickness for shield tunnels in terms of both face and anti-floating stability. In this study, the traditional wedge-prism model was optimized, and formulas for active and passive limit support pressure of tunnel faces were derived for various excavation inclination angle and seepage conditions. The analytical solution for two limit support pressures, with special attention on the proposed passive failure model were verified using finite element numerical simulations. Design procedures for a reasonable range of overburden thickness were provided based on the analytical solution of the uplift resistance and limit support pressure. The passive limit support pressure was found to increase with the cohesion and internal friction angle of soil stratum and decrease with the excavation inclination angle, while the active limit support pressure exhibited the opposite trend. The two limit support pressures increased with rising groundwater levels.

Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh‐Tidal Channel Interface

AbstractTidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C‐bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform‐tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24‐hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+ and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C‐bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p < 0.05) more terrestrial‐like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p < 0.05) more marine‐like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform‐tidal channel interface.

Mitigation of urban waterlogging from flash floods hazards in vulnerable watersheds

Study regionThe Aswan region is a vast plateau in the South of Egypt located 150 m above mean sea level (AMSL). Within this region, the tourist city of Aswan is Egypt’s southernmost city, located on the east bank of the Nile River. Study focusThe occurrence of flash floods can severely impact low-lying and densely populated areas. Therefore, highly vulnerable areas require effective mitigation measures to guarantee public safety and preserve archeological sites of great importance. This study investigates the interaction between the soil, surface water, and groundwater in the Aswan region of Egypt. Based on the rainfall analysis and the watershed hydrology, six different scenarios were run using the MODFLOW and Watershed Modeling System (WMS) software, which simulated rainfall recurrence intervals of 2, 5, 10, 25, 50 and 100 years. New hydrological insights for the regionThe model's results indicated that an increase in the recurrence interval produced a rise in the groundwater level (GWL) up to 8.82 m (AMSL). Therefore, constructing three dams was proposed as a solution at the three basins of Al- Haytah, Al-Kimab, and Umm-Buwayrat. The proposed solution allows the storage of large volumes of water upstream. It mitigates GWL's rise within and near Aswan City. The presented study can be applied to vulnerable watersheds in arid and semi-arid regions. It can help policymakers to integrate additional sustainable solutions into construction dams and their implementation in development plans.

The Disastrous Effects of Soil Salinity and pH on Environmental Systems

Soil salinity is a natural element of arid and semi-arid climates and it is becoming a growing concern in the soils across the world. When water-soluble salts build in a soil, it gets salinized. These salts contain chloride, sulphate, carbonate, bicarbonate and sodium in addition to potassium and magnesium. Due to shortage of oxygen, soil with a high salt level becomes incapable of supporting plant and animal life. This review discusses the causes of salinity, its impact on plant growth, their limits/standard in the environment systems and case studies of saline land. Besides this, salinity levels in streams and lands are generally rising as a result of rising groundwater levels. Most of the rural and urban communities have lost productive cropland and water supplies due to natural instability to these environments and human induced interferences. Crop productivity, seed germination soil and water quality are adversely affected by soil salinity. A coastal region is also particularly vulnerable to climate change. There is a need to study soil salinization and its measures in detail for sustainable environmental systems.

Slope Failure Risk Assessment Considering Both the Randomness of Groundwater Level and Soil Shear Strength Parameters

Conducting research on slope failure risk assessment is beneficial for the sustainable development of slopes. There will be various failure modes considering both the randomness of the groundwater level and soil shear strength parameters. Based on the integrated failure probability (IFP), the traditional failure risk analysis needs to count all failure modes, including the failure probability (Pf) and failure risk coefficient (C), one-by-one. A new slope failure risk assessment method that uses the sum of the element failure risk to calculate the overall failure risk is proposed in this paper and considers both the randomness of the groundwater level and soil shear strength parameters. The element failure probability is determined by their location information and failure situation; the element failure risk coefficient is determined by their area. It transforms the complex overall failure risk problem into a simple element failure risk problem, which simplifies the calculation process and improves the calculation efficiency greatly. The correctness is verified with the systematic analysis of a classical case. The results show that the slope failure probability and failure risk are greatly increased from 1.40% to 3.30% and 0.829 m2 to 2.094 m2 with rising groundwater level, respectively.

Influence of precipitation event magnitude on baseflow and coastal nitrate export for Prince Edward Island, Canada

AbstractThe export of anthropogenic nitrate to coastal waters, which depends on the interplay between many factors such as land use and meteorological forcing, is a rising concern in many regions of the world. The present study investigates the effect of precipitation event magnitude on baseflow and associated groundwater‐driven nitrate export in Prince Edward Island, Canada. Twenty‐year time‐series of precipitation, stream flow, and groundwater levels across the island were analysed to establish a three‐way relationship between precipitation, groundwater level rise, and baseflow increase along a hydrological response pathway in this island setting. The analysis was performed by extracting hydrological responses for groundwater level and baseflow for a selected subset of relatively isolated precipitation events. The results reveal a non‐linear relationship between precipitation event magnitude and baseflow change that is also observed for precipitation events associated with hurricanes and post tropical storms. A time‐series of streamflow nitrate concentrations during Hurricane Dorian's passage (September 2019) was used to evaluate the relevance of these findings for nitrate export. The data show that baseflow increases after a heavy precipitation event have limited impact on streamflow concentrations, but result in substantial and sustained increase of nitrate export (calculated by multiplying concentration by flow). These observations are consistent with a recharge‐induced water table rise leading to increased hydraulic gradients that drive discharge of shallow nitrate‐containing groundwater. Due to the similarity of the processes governing groundwater flow to the sea and to streams, the results can be used to gain insights into the impacts of precipitation event magnitude on direct groundwater discharge to coastal waters. On Prince Edward Island, this applies to at least the 13% of the island's surface area that is closer to the ocean than to any stream and likely feeds submarine groundwater discharge pathways.

FEATURES OF THE STRUCTURE, FUNCTIONING AND RECONSTRUCTION OF THE LANDFILL NIZHNEKAMSKNEFTEKHIM PUBLIC JOINT STOCK Co.

PJSC Nizhnekamskneftekhim is one of the largest petrochemical companies in Europe. Industrial production was launched there in 1967. Production waste is stored in a sludge reservoir and waste landfill. The landfill has been operating since 1982. It is equipped with systems of surface and underground drainage, impervious curtains, and two belts of observation wells. More than 0.5 million m3 of mostly solid waste III-V classes of hazard has been accumulated there. The landfill capacity is depleted by more than 80%. Its operation has led to a significant groundwater level rise (4.0–4.5 m) and groundwater pollution, the water salinity reaching 12.75 g/l, and hardness, 73.9 mmol/l. These negative hydrogeoecological effects are primarily due to increased atmospheric recharge of groundwater and the active interaction of atmospheric precipitation with the waste substance. There is plan to reconstruct the landfill. It involves encapsulating the waste in a watertight reservoir confined by artificial geosynthetic materials with extremely low filtration properties. Hydrodynamic and balance methods were used to determine the infiltration supply of groundwater in natural and disturbed conditions, productivity of underground drainage; the continuously formed flow rate of polluted groundwater, which is not intercepted by drainage system (with the flow discharge equal to 116.7 m3/day); as well as modern and predicted (postreconstruction) water balances. The effectiveness of the existing engineering protective structures of the landfill was assessed. It is shown that the planned reconstruction should lead to a decrease in the groundwater level and its pollution degree. In this case, the concentrations of organic substances, which are the priority pollutants, will decrease most intensely. The geological environment of the landfill site is characterized by significant buffer (protective) properties. They control just local spreading of contaminated groundwater. According to the data of numerous different-time sampling at a distance of 1.0–1.5 km from the landfill in the direction of groundwater current spreading, no signs of pollution caused by the landfill operation are registered. The main processes determining the self-purification of groundwater are as follows: dilution of polluted water by pure infiltration nutrition, the minimum layer of which is 67.6 mm/year; chemo- and biodestruction of pollutants, their sorption, diffusion-dispersion scattering and precipitation as pH–Eh conditions change.

Groundwater level and temperature changes following the great Tangshan earthquake of 1976 near the epicenter

Several meters of rise in groundwater level with significant changes in groundwater temperature were observed near the epicenter of the 1976 Tangshan earthquake—an intraplate earthquake with a magnitude of M S=7.8 that occurred in northern China. The origin of the groundwater level rise, however, remains a mystery. Studying the groundwater level rise can provide insight into the faulting process and has implications for water resources. In this study, we analyze the indications of the groundwater temperature data on the characteristics of the rising groundwater. The results show that the upward flow was maintained for approximately 5 days, and the depth of the rising groundwater was about 1–2 km. We then examine the groundwater level and temperature data with several reported models in order to explain the cause of the groundwater level rise. The results indicate that the groundwater level rise is attributable to the earthquake-induced enhancement of vertical hydraulic connection between the shallow and deep aquifers, leading to the upwelling of deep fluids that causes the groundwater levels to rise.

Inferences of Groundwater Response to Projected Hydroclimatic Changes in North Florida

Discerning anthropogenic stressors on groundwater is critical for climate change adaptation to reduce risks and increase resiliency. Long-term groundwater level trends are forecasted and examined at three sites in North Florida using a large ensemble of Global Climate Model (GCM) projections under low and medium emission scenarios. The forecasts indicate groundwater levels are likely to decline from 2020 to 2099. However, the declines are expected to accelerate after 2040s, reaching critical levels by the end of this century. Pumping impact constitutes 10% to 45% of future declines but is amplified by enhanced drought. Examination of distinct influence of rainfall, evapotranspiration (ET), and groundwater pumping on future trends shows highly divergent groundwater response to projected hydroclimatic changes. The future long-term rainfall trend may lead to rising groundwater levels, which may be overshadowed by heightened ET loss driven by climate change and increased groundwater pumping, causing steep declines. This study also reveals poor performance of predictions driven by GCM projections in replicating the timing of high and low levels at the sites influenced by Florida’s peninsular climate due to the limitation of downscaling and bias-correction to capture oscillations in climate cycles driving hydrologic memory. However, groundwater levels are predicted well by a few GCMs at one site influenced primarily by continental climate. Additionally, a multidecadal harmonic analysis exposes presence of centennial periodicity in groundwater levels, which opens a new perspective in the understanding of climate change impacts on groundwater resources. Further investigation is needed to better understand the effect of centennial cycles on future groundwater levels and how these cycles can be incorporated into the downscaling methods. Hence, GCM-based forecasts are recommended to be cautiously utilized for groundwater resource planning when they significantly depart from historical long-term cyclic patterns.