Subsurface Water Levels Research Articles

Mapping and projecting spatiotemporal trends in groundwater levels and flow direction in Pakistan's water-scarce aquifer system

Groundwater is the most vital and reliable source of fresh water globally. This study examined the variability in Depth to Water table (DTW) below ground level in agriculture-dominated Bari interfluve, Pakistan. Observing water levels empowers access and management of water resources ensuring long-term availability. Changes in the DTW were observed by preparing spatiotemporal maps using piezometric data for both pre-monsoon and post-monsoon seasons by five-year difference intervals from 2005 to 2020. Piezometric observations offer more precise real-time monitoring of subsurface water levels. The trend of the groundwater table was analyzed by non-parametric methods i.e., Mann-Kendall (MK) and Sen's slope estimator in all observation wells of districts at a significance level of 5 percent for sustainable groundwater resource management. The resulting trend of fluctuating water table showed a progressive decline in water level in all districts except a minor increase was also noticed. The seasonal fluctuation (between pre-monsoon and post-monsoon seasons) showed that the average DTW was found to be high in 46% of the total tehsils in the post-monsoon season while in 42% it was low and 12% depicted no change compared to pre-monsoon season. Piezometric observation points of DTW exhibiting a trend at a 5 percent significance level were used to project future water table depths that indicated a further alarming depleting trend for both the pre-monsoon and post-monsoon seasons in lower districts of Bari interfluve. The groundwater pattern calls for precautionary measures to see a reversal in trend or even maintain the groundwater levels for future needs.

Evaluation of meteorological drought effects on underground water level fluctuations using data mining methods (case study: semi-deep wells of Golestan province).

In most arid and semi-arid environments, groundwater is one of the precious resources threatened by water table decline and desiccation, thus it must be constantly monitored. Identifying the causes influencing the variations of the subsurface water level, such as meteorological drought, is one approach for monitoring these fluctuations. In the present study, the effect of two meteorological drought indices SPI and SPEI on the fluctuations of the underground water level was evaluated, as was their relationship with the drought index of the subsurface water level (SWI) using multivariate linear regression and M5 decision tree regression. After calculating climatic and hydrological drought indices in a 6-month time window for a long-term statistical period (1989-2018), the semi-deep aquifers of Golestan province, which is located in northern Iran, were considered as a research location for this purpose. The results demonstrated that the effect of meteorological drought does not immediately manifest in the changes of the subsurface water table and the hydrological drought index. By adding the meteorological drought index with a 6-month lag step, the average air temperature, and the total rainfall from the previous 6months as new variables, the correlation with the SWI index increases, so that in the best-case scenario, the M5 decision tree model provides the best result in predicting the SWI index. The second half of the year yielded a coefficient of determination of 0.92 and an error value of RMSE = 0.27 for the SPEI index. Among the meteorological drought indices, the SPEI index, which is based on precipitation and evapotranspiration, created a stronger link with the SWI index, which highlights the significance of potential evapotranspiration. It is a warning that, as a result of global warming, subsurface water tables in this region may fall in the future.

Observations of Decadal-Scale Brine Geochemical Change at the Bonneville Salt Flats

Over the past century, the Bonneville Salt Flats, which lies on the western edge of the Great Salt Lake watershed, has experienced changing environmental conditions and a unique history of land use, including resource extraction and recreation. The perennial halite salt crust has decreased in thickness since at least 1960. An experimental restoration project to return mined solutes began in 1997, but it has not resulted in anticipated salt crust growth. Here, primary observations of the Bonneville Salt Flats surface and subsurface brine chemistry and water levels collected from 2013 to 2023 are reported. Spatial and temporal patterns in chemistry, focused on density and water stable isotopes, are evaluated and compared with observations across seven periods of research spanning from 1925 to 2023. Declining salinity in the areas to the east of extraction ditches and south of Interstate 80 were observed. Brine extracted for potash production decreased in salinity as extraction rates increased. Between the years 1964 and 1997, the salinity of the shallow aquifer brine located beneath and to the east of the crust experienced a decrease. However, following this period, the salinity stabilized and subsequently increased. Salinity recovery was concurrent with declines in brine extraction and the salt restoration project, with the largest decrease in brine extraction being concurrent with the largest recovery in salinity. The specific impact of the restoration project on the brine salinity increase remains unclear. To the west, the shallow aquifer in the area between the Silver Island Mountains and the salt crust has increased in salinity. This increase is accompanied by a decline in groundwater levels, which enables the underground movement of solutes from east to west, following a salinity gradient away from the saline pan. Over the past 25 years, the alluvial-fan aquifer along the Silver Island Mountains has markedly declined, leading to increasingly more saline and isotopically heavier basinal waters to be extracted for industrial use. This change is concurrent with the onset of the salt restoration project, which relies on alluvial-fan aquifer waters. This compilation of changes in groundwater chemistry provides an important resource for stakeholders working to understand and manage this dynamic and ephemeral evaporite system. It also offers an example of decadal-scale change in a highly managed Great Salt Lake watershed saline system.

PENGARUH BERBAGAI LEVEL IRIGASI BAWAH PERMUKAAN DAN APLIKASI BIOCHAR TERHADAP PERTUMBUHAN DAN HASIL PADI SAWAH

This research aims to determine the effect of subsurface irrigation water level and biochar application on the growth and yield of lowland rice. The research was conducted at Experimental Garden I, Faculty of Agriculture University Halu Oleo. The study consisted of two factors of treatments laid out in an RBCD-based factorial experimental design. The first factor consisted of four levels of subsurface irrigation (S) (i.e., 0, 4, 8, and 12 cm below the soil surface). The other factor also consisted of four levels of rice husk biochar (B) (i.e., 0, 10, 20, and 30 metric tons ha–1). Each treatment combination was given three replications. The collected data were analyzed with ANOVA and the differences among treatments were tested with DMRT at P=0.05. The study showed that both factors had no interaction effect on all parameters. The subsurface irrigation treatments, however, showed significant effects on plant height (56, 70, 84 DAS), leaf area (56, 70 DAS), flag leaf area, dry weight of root and shoot, panicle length, number of grains per panicle, grain weight after harvest per hill, dry weight of 1,000 rice grains, and yield. On the other hand, the biochar treatment only showed significant effects on leaf area at 70 DAS, flag leaf area, number of grains per panicle, grain weight after harvest per hill, and dry weight of 1,000 rice grains.

Probabilistic coastal wetland mapping with integration of optical, SAR and hydro-geomorphic data through stacking ensemble machine learning model

The present study focuses on preparing the wetland map using earth observation data and applying a novel ensemble model. Eight advanced machine learning algorithms were applied to determine the probability of the occurrence of wetlands. The random forest (RF), support vector machine (SVM), and multivariate adaptive regression spline (MARS) models outperformed others. So, these models were further used to create a stacking ensemble for improving precision. The RF-SVM-MARS ensemble model was run with seven various parameters. The results show that the integrated parameter has the highest area under the curve (0.960) followed by optical-hydrogeomorphic (0.953), SAR-hydrogeomorphic (0.940), hydrogeomorphic (0.896), SAR-optical (0.892), optical (0.881), and SAR (0.702). The hydrogeomorphic variables exhibited greater influence than the optical and SAR variables. However, the integration of all selected key variables proved to be the most effective approach for probabilistic wetland mapping. The RF-SVM-MARS ensemble model can improve classification accuracy as compared to a single model. An accuracy of 96% was obtained when the ensemble model output was cross-validated with field data. The ground-penetrating radar (GPR) tool was also successfully employed to study the sub-surface strata and water level conditions in wetland and non-wetland areas. The successful application of a new ensemble approach along with the GPR technique for coastal wetland mapping in this study could encourage researchers to choose it as an appropriate methodology. Moreover, the outcomes of the work will help land-use planners and government agencies for better planning, monitoring, and promoting sustainable development of the coastal area.

ОЦІНКА РОЗВИТКУ ДЕФОРМАЦІЙ ЗЕМНОЇ ПОВЕРХНІ НА ШАХТНОМУ ПОЛІ СТЕБНИЦЬКОГО КАЛІЙНОГО РОДОВИЩА ЗА ДАНИМИ ГІДРОГЕОЛОГІЧНОГО МОНІТОРИНГУ

The paper presents the data generalization of the observations of hydrogeological monitoring of mining sites on the dynamics of groundwater level. The processing of hydro-regime studies conducted in 2009-2021 in the area of the mine bypass of the № 2 pit was carried out. Hydrogeological sections reflecting changes in water levels over time were prepared. The most important factor in the lowering of the ground surface is salt karst development. The evaluation of the intensity of karst collapse processes was based on the interpretation of the results of the dynamics of the subsurface water level. The site network consists of more than 30 observation wells drilled into suprasaline and Quaternary aquifers. The main causes of deformation of the salt rock massif and the earth's surface have been identified. These are a decrease in the geomechanical strength of the rock due to its hydration and subsequent subsidence under the geostatic load of the overlying rock, and subsidence of the clay layer covering the salt rock due to the karst process. Based on the observed data, hydrogeologically oriented spatial zoning of the mining concession was performed. As a result of the development of a complex depression in the area of influence of the karst drainage, a drop in the water level in the gypsum-clay horizons was observed over the entire area in 2009-2019. The depression funnel runs in a northwesterly direction, indicating the development of a karst channel in the salts. Significant inflow of suprasaline water in the southwestern and central parts of the mine field combined with intense karstification of the salt massif and gypsum-clay cap deposits within the depression funnel resulted in significant deformation of the earth's surface, formation of karst funnels, and technogenic and ecological threats to critical infrastructure objects. To prevent a man-made ecological catastrophe, it is urgent to develop a scientific rationale for the maximum permissible changes in the environmental parameters of the man-made geological system of the № 2 mine of the Stebnytsky potash deposit during the post-mining phase.

Development and Zones of Subsidence Dolines in Case of Shore Shiftings of Regression, Transgression and Oscillation Types

This study deals with the karstification of coastal covered karsts with the aim of looking for a relationship between sea level changes and feature development taking place on the covered parts of carbonate karsts. This relation is manifested by the fluctuation of karst water level that is controlled by the sea level. Through further studies, shore shiftings occurring during the time of various paleokarst feature assemblages can be established. The development of suffosion dolines and dropout dolines at subsurface water level is analysed. The pattern of coast zones with dolines is studied in three cases thus, on regressive coast at non-fluctuating water level (1), on transgressive coast at non-fluctuating water level (2), and at oscillating sea level at oscillating karstwater level (3). In the first case, a solution doline zone (and/or karren zone), a mixed or compound zone (with suffosion dolines and dropout dolines) and a suffosion doline zone develops landward. In the second case a suffosion doline zone develops (this may turn into a mixed zone) and during further subsidence, a filled doline zone develops which may expand at the expense of the suffosion doline zone (mixed doline zone). In the third case, close to the shore, in the glacial a dropout doline zone and a suffosion doline zone are separated. In the interglacial, a solution doline zone develops at the uncovered surface, at the outer, seaward part of the dropout doline zone dolines with lakes are formed, the development of suffosion dolines continues in the suffosion zone.

Effect of exclosure on subsurface water level and sediment yield in the tropical highlands of Ethiopia.

Grazing is a major cause of soil erosion and land degradation across many parts of Ethiopia. This study examined the effects of exclosure on subsurface water levels, soil erosion, and the relationship between daily rainfall and subsurface water levels. Piezometers were used to measure subsurface water levels in the exclosure area during 2017-2020. We found that sediment yield, runoff, and the volume of subsurface water vary greatly depending on the exclosure and temporal practices used. Exclosure of grazing land was the most effective sustainable land management practice in reducing runoff and sediment yield. In 2019 and 2020, the subsurface water level continued to rise at piezometers with exclosure, which shows that exclosure contributed to the subsurface water level rising. In addition, piezometers in grazing land and the exclosure indicate that runoff trapped by acacia decurrens trees can contribute to significant differences in subsurface water levels. Higher runoff coefficients were observed in 2017 and 2018 than in 2019 and 2020, indicating that the exclosure greatly affects runoff; therefore, its implementation is vital to reduce runoff and enhance water conservation. Sediment yields measured for 2017, 2018, 2019, and 2020 were 140.45, 133.15, 101.03, and 74.39gL-1 day-1, respectively. In 2017 and 2018, sediment yield increased, while in 2019 and 2020 sediment yield decreased because of an exclosure around the gully's cross-section and communal grazing. This study shows that erosion is reduced by exclosure, possibly due to the restoration of protective vegetation cover. This study revealed that a minimum of human and livestock intervention during the study period considerably increased groundwater levels and decreased soil erosion. Generally, the results of this study indicated that exclosure has a considerable impact on runoff and sediment. Therefore, exclosure implementation is vital to reduce runoff and sediment and enhance water conservation, thus supporting the development of effective communal grazing land management measures on the study sites and other similar environmental settings.

The Hydrologic Response to a Meteotsunami in an Isolated Wetland: Beaver Island in Lake Michigan, USA

AbstractMeteotsunamis are both a well‐known and poorly understood phenomenon. In particular, the influence of and disturbance by meteotsunamis on isolated coastal wetlands is largely unknown. This paper documents a case illustrating how water levels in an incipient foredune/swale complex in northern Lake Michigan responded to a meteotsunami event. We identified potential meteotsunami influence on wetland water levels through slope‐break and wavelet analysis, verified the presence of meteotsunami waves at surrounding lake water level gauge stations with wavelet analysis, analyzed both regional and small‐scale meteorological data to establish what source of atmospheric forcing resulted in meteotsunami formation, and used a hydrodynamic model to simulate lake surface response and meteotsunami generation. On 20 July 2019, an atmospheric bore wave propagating away from a convective storm formed a meteotsunami event in Lake Michigan that struck Sand Bay, Beaver Island and generated a 36 cm increase in subsurface wetland water levels over the course of a 1‐hr period. The potential for multiple sources of meteorological forcing and secondary wave refraction highlights several challenges with predicting generation of and effects from meteotsunami events. Additionally, while irregular, the effects of these events on isolated wetland systems have the potential to alter hydrologic and sediment budgets, vegetation growth, and dune stability; yet meteotsunami influence on isolated wetlands is an understudied phenomenon. The event presented in this study make a strong case for focused research on coastal wetland response to meteotsunamis (and meteotsunami‐like events) to address this understudied impact given its implications for coastal processes and resiliency.

CORRIGENDUM

Hydrological ProcessesVolume 36, Issue 6 e14630 CORRIGENDUMFree Access CORRIGENDUM This article corrects the following: Tidal frequencies and quasiperiodic subsurface water level variations dominate redox dynamics in a salt marsh system Emilio Grande, Bhavna Arora, Ate Visser, Maya Montalvo, Anna Braswell, Erin Seybold, Corianne Tatariw, Kathryn Beheshti, Margaret Zimmer, Volume 36Issue 5Hydrological Processes First Published online: May 25, 2022 First published: 12 June 2022 https://doi.org/10.1002/hyp.14630AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In the referenced article, Grande et al. (2022), an additional affiliation for co-author Braswell, A. has been added:-. Florida Sea Grant, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA. REFERENCE Grande, E., Arora, B., Visser, A., Montalvo, M., Braswell, A., Seybold, E., Tatariw, C., Beheshti, K., & Zimmer, M. (2022). Tidal frequencies and quasiperiodic subsurface water level variations dominate redox dynamics in a salt marsh system. Hydrological Processes, 36(5), e14587. https://doi.org/10.1002/hyp.14587Wiley Online LibraryCASWeb of Science®Google Scholar Volume36, Issue6June 2022e14630 ReferencesRelatedInformation

Tidal frequencies and quasiperiodic subsurface water level variations dominate redox dynamics in a salt marsh system

AbstractSalt marshes are hotspots of nutrient processing en route to sensitive coastal environments. Whilst our understanding of these systems has improved over the years, we still have limited knowledge of the spatiotemporal variability of critical biogeochemical drivers within salt marshes. Sea‐level rise will continue to force change on salt marsh functioning, highlighting the urgency of filling this knowledge gap. Our study was conducted in a central California estuary experiencing extensive marsh drowning and relative sea‐level rise, making it a model system for such an investigation. Here we instrumented three marsh positions subjected to different degrees of tidal inundation (6.7%, 8.9%, and 11.2% of the time for the upper, middle, and lower marsh positions, respectively), providing locations with varied biogeochemical characteristics and hydrological interactions at the site. We continuously monitored redox potential (Eh) at depths of 0.1, 0.3, and 0.5 m, subsurface water levels (WL), and temperature at 0.7 m depth at each marsh position. To understand how drivers of subsurface biogeochemical processes fluctuate across tidal cycles, we used wavelet analyses to explain the interactions between Eh and WL. We found that tidal forcing significantly affects key drivers of biogeochemical processes by imparting controls on Eh variability, likely driving subsurface hydro‐biogeochemistry of the salt marsh. Wavelet coherence showed that the Eh‐WL relationship is nonlinear, and their lead–lag relationship is variable. We found that precipitation events perturb Eh at depth over timescales of hours, even though WL shows relatively minimal change during events. This work highlights the importance of high frequency in situ measurements, such as Eh, to help explain factors that govern subsurface biogeochemistry and hydrological processes in salt marshes.

GCMs simulation-based assessment for the response of the Mediterranean Gaza coastal aquifer to climate-induced changes

AbstractIn the Eastern Mediterranean countries, groundwater contained in coastal aquifers is the predominant water source for supplying water. The Mediterranean Gaza coastal aquifer in Palestine is showing alarming signs of depletion due to climate change and human-caused influences that substantially impact the hydraulic performance of the Gaza coastal aquifer. The climate statistical modeling and the downscaling of the ensemble global climate model under the representative concentration pathway (RCP) scenarios of RCP 2.60, 4.50, and 8.50 refer to a future decreasing trend in the precipitation and an increasing trend in the temperature. The stochastic model refers to an average decrease of −5.2% in the rainfall every 20 years that coincides with the RCP scenarios that show a decrease in precipitation between 0 and −5%. The rate of temperature increase over the next 20 years is defined at +1 °C, which closely matches the RCP results. As a result of human fast-paced activities, groundwater consumption is expected to rise by nearly 55% by the end of 2040, to around 193 million cubic meters, with a substantial withdrawal trend in southern provinces of the Gaza Strip. Consequently, the aquifer model predicts that subsurface water levels might fall at a rate of −2.50% per year, reaching a level of around −27.77 m below the mean sea level (MSL) by 2040. Alternative water supplies, such as desalinated seawater and treated wastewater, with annual maximum volumes of 110 and 16.5 million cubic meters, respectively, are expected to perfectly recharge groundwater resources of the Gaza coastal aquifer at an annual rate of about +3.65% to meet a groundwater table level of around −5 m below the MSL by 2040.

Using biodiversity response for prioritizing participants and service provisions in a payment-for-water-storage program in the Everglades basin

Hydrological changes can lead to biodiversity responses that are complex and challenging to quantify. We present a framework that uses biodiversity as a criterion to address “where to buy” and “how much to buy” in a payment-for-environmental-services (PES) program focused on water storage service in the Everglades basin, USA. The PES program was designed to pay for added water storage on private cattle ranchlands by raising the spillage level in drainage control structures to reduce surface flows. We predicted that increased hydration of previously drained wetlands would benefit biodiversity, a previously unquantified but desirable co-benefit of the original program, and that a PES program offering bundled services (e.g., storage and biodiversity) can better achieve restoration goals. We quantified desirable biodiversity services (abundance of native flora and fauna such as cover of wetland and forage plants, and abundance of fishes, amphibians, and macroinvertebrates), dis-services (e.g., abundance of invasive plants and mosquitos), and hydrologic signatures (e.g., wetland water depth, inundation area and duration) at four ranches to develop eco-hydrological relationships (models) between hydrological changes and biodiversity responses. Next, a hydrologic model (MIKE-SHE/MIKE-11) was used to predict surface and subsurface water levels and flows and resulting wetland hydrologic signatures for 13 water storage alternatives on the ranches, which were used as example PES proposals. A decision-support-system (DSS) was developed to integrate (i) storage predicted by the hydrologic model, (ii) biodiversity responses predicted by eco-hydrologic models, and (iii) a user-defined preference scheme to assign importance weights to storage, biodiversity, and implementation cost. The DSS calculated a cumulative score for ranking PES proposals. By considering desirable services and dis-services, stakeholders can decide on their preferred level of services, e.g., buyer(s) may settle for less storage if there is a gain in desirable biodiversity. The DSS can identify trade-offs among services, helping stakeholders negotiate.

Development Environments and Factors of Subsidence Dolines

This study describes the development environments of subsidence dolines based on literary data (development environments create favorable conditions for the local denudation of superficial deposit and thus, for the development of depressions). Development environments are the inclination of the bearing surface, the secondary porosity of the bedrock, the characteristics of the cover, water influx into the cover, karstwater and groundwater, melting permafrost, and anthropogenic activity. These may become optimal when controlled by various geological, geomorphological, and climatic factors. Development environments may be qualitative (there is doline development in case of its presence) and quantitative (doline development occurs in case of suitable quantitative values). The development environment groups of subsidence dolines are environment groups independent of water level, environment groups dependent on water level, and anthropogenic environment groups. In the case of an environment group independent of water level, surface morphology, cover characteristics, geomorphic evolution, and water supply are determining, while in case of an environment group dependent of water level, subsurface water level and its fluctuations and the characteristics of rainfalls interrupting dry seasons are crucial. Anthropogenic impacts mainly affect doline development through water balance.

Fluctuation Characteristics of Water Level and Water Temperature of Huize Well Based on MF-DCCA

In recent decades, the network of seismic subsurface fluid observatories is developing constantly, the observation data of subsurface fluids are enriched accordingly, which provides a favorable condition for the research on the formation, occurrence, and development of earthquakes. In the observation data of subsurface fluids, water level and water temperature changes are very important observation indicators, and their fluctuation sequences are quite complicated. Therefore, this paper employed a non-linear cross-correlation method to study the relationship between the water level and water temperature of Huize Well from 2004 to 2006, and found that there’s a significant cross-correlation between the time series of water level and water temperature; then, this study adopted DCCA (detrended cross-correlation analysis) to calculate the cross-correlation coefficient under different scales and explore the continuous changes of water level and water temperature; at last, this paper used the MF-DCCA (Multifractal-DCCA) method to prove that there’s multifractal cross-correlation between the time series of water level and water temperature. Before the M5.1 earthquake in Huize area, there’s an abnormal increase in the width of the multifractal spectrum of the water level and water temperature drawn with a sliding window of 500-hour, and this is a possible earthquake precursor.

Effect of subsurface water level on gully headcut retreat in tropical highlands of Ethiopia

AbstractGully erosion is a major cause of soil loss and severe land degradation in sub‐humid Ethiopia. The objective of this study was to investigate the role and the effect of subsurface water level change on gully headcut retreat, gully formation and expansion in high rainfall tropical regions in the Ethiopian highlands. During the rainy seasons of 2017–2019, the expansion rate of 16 fixed gullies was measured and subsurface water levels were measured by piezometers installed near gully heads. During the study period, headcut retreats ranged from 0.70 to 2.35 m, with a mean value of 1.49 ± 0.56 m year−1, and average depth of the surface water level varied between 1.12 and 2.82 m, with a mean value of 2.62 m. Gully cross‐section areas ranged from 2.90 to 20.90 m2, with an average of 9.31 ± 4.80 m2. Volumetric retreat of gully headcuts ranged from 4.49 to 40.55 m3 and averaged 13.34 ± 9.10 m3. Soil loss from individual gullies ranged from 5.79 to 52.31 t year−1 and averaged 17.21 ± 11.74 t year−1. The headcut retreat rate and sediment yield were closely related over the three study seasons. Elevated subsurface water levels facilitated the slumping of gully banks and heads, causing high sediment yield. When the soil was saturated, bank collapse and headcut retreat were favoured by the combination of elevated subsurface water and high rainfall. This study indicates that area exclosures are effective in controlling subsurface water level, thus reducing gully headcut retreat and associated soil loss.

Ground Deformation of Wuhan, China, Revealed by Multi-Temporal InSAR Analysis

Wuhan, the largest city in central China, has experienced rapid urban development leading to land subsidence as well as environmental concerns in recent years. Although a few studies have analyzed the land subsidence of Wuhan based on ALOS-1, Envisat, and Sentinel-1 datasets, the research on long-term land subsidence is still lacking. In this study, we employed multi-temporal InSAR to investigate and reveal the spatiotemporal evolution of land subsidence over Wuhan with ALOS-1, Envisat, and Sentinel-1 images from 2007–2010, 2008–2010, 2015–2019, respectively. The results detected by InSAR were cross-validated by two independent SAR datasets, and leveling observations were applied to the calibration of InSAR-derived measurements. The correlation coefficient between the leveling and InSAR has reached 0.89. The study detected six main land subsidence zones during the monitoring period, with the maximum land subsidence velocity of −46 mm/a during the 2015–2019 analysis. Both the magnitude and the extent of the land subsidence have reduced since 2017. The causes of land subsidence are discussed in terms of urban construction, Yangtze river water level changes, and subsurface water level changes. Our results provide insight for understanding the causes of land subsidence in Wuhan and serve as reference for city management for reducing the land subsidence in Wuhan and mitigating the potential hazards.

Analytical Modeling of Particle Tracking for Dynamic Pumping Conditions

Movement of fluid particles about historic subsurface releases and through well fields is often governed by dynamic subsurface water levels. Motivations for tracking the movement of fluid particles include tracking the fate of subsurface contaminants and resolving the fate of water stored in subsurface aquifers. Based on superposition of the Theis solution in both space and time, this research explores an analytical solution based on the Theis equation using dynamic pumping well data to resolve how fluid particles move around wells under dynamic pumping conditions. The results provide relatively uniform capture zones for a pumping well. Further, the results show that even under continuous pumping and injection conditions, groundwater will not flow far from the well. Accordingly, groundwater positions can be evaluated based on the research for dynamic pumping. Using the assumptions proposed by the Theis solution, the analytical solution developed in this study provides a simple method to evaluate particle movement in wells used to both store and recover water.

Particle Tracking Using Dynamic Water-Level Data

The movement of fluid particles about historic subsurface releases is often governed by dynamic subsurface water levels. Motivations for tracking the movement of fluid particles include tracking the fate of subsurface contaminants and resolving the fate of water stored in subsurface aquifers. This study provides a novel method for predicting the movement of subsurface particles relying on dynamic water-level data derived from continuously recording pressure transducers. At least three wells are needed to measure water levels which are used to determine the plain of the water table. Based on Darcy’s law, particle flow pathlines at the study site are obtained using the slope of the water table. The results show that hydrologic conditions, e.g., seasonal transpiration and precipitation, influence local groundwater flow. The changes of water level in short periods caused by the hydrologic variations made the hydraulic gradient diversify considerably, thus altering the direction of groundwater flow. Although a range of groundwater flow direction and gradient with time can be observed by an initial review of water levels in rose charts, the net groundwater flow at all field sites is largely constant in one direction which is driven by the gradients with higher magnitude.

The hydrological function of a large chain-of-ponds: a wetland system with intermittent surface flows

Like many wetlands globally, the Mulwaree River chain-of-ponds system exists in two dichotomous states characterised by the presence or absence of surface flow connecting large, deep, permanently inundated ponds. We develop a conceptual model of hydrological function of this chain-of-ponds system combining surface and subsurface water levels, 2H and 18O stable isotopes and 222Rn as a groundwater tracer over a period of time that incorporated extended dry periods and large rainfall events. During high-flow or flood events, ponds are connected by flow along connecting channels and preferential flow paths. The water column is fully mixed to depths of up to 7 m. During high-flow, water level in the ponds can be greater than the water level in the surrounding floodplain aquifer, producing a hydraulic gradient away from the ponds, reflecting a losing wetland system. During no-flow periods, connecting channels and preferential flow paths are dry. A thermocline develops within the ponds and surface waters become enriched in 2H and 18O with evaporation losses. During periods of no-flow, increases in water level beyond atmospheric flux often occur during winter. Only small groundwater inflows enter the ponds from the floodplain aquifer. The hydrological function of this chain-of-ponds system is delicately balanced making it potentially sensitive to changes in climate that alter rainfall and evaporation rates, and any local-scale groundwater interference activities. Efforts to conserve and protect this system, and the aquatic ecosystems it supports, will be critical into the future.