Changes In Water Table Research Articles

Prediction of the dynamic changes of water table based on the quantitative theory type I in the Piedmont Plain of the Taihang Mountains

Statistical analysis was conducted on groundwater table data in the Ji Yuan Basin from 2006 to 2018, revealing a continuous downward trend in the groundwater table with imminent depletion of shallow groundwater resources. To ensure the sustainable development of groundwater resources in the area, a quantitative model of groundwater table was successfully constructed using the principles of the Quantitative Theory Type I. This model included seven benchmark variables: rainfall, evaporation, exploitation, hydraulic conductivity, specific yield, lithology of the vadose zone, and land-use type. These factors are key contributors to the decline in groundwater levels in the study area. The model yielded an average residual value of 0.35 m and an adjusted R2 of 0.789, indicating that it can explain 78.9% of the benchmark variables with acceptable accuracy. Additionally, the model successfully simulated four types of groundwater dynamics, with the best results obtained for the rainfall infiltration-exploitation-evaporation type. This study’s findings suggest that the model can be utilized to predict the dynamic characteristics of the groundwater table and guide groundwater extraction activities.

Numerical modelling of pore water pressure response beneath a raft foundation during real river floods

Tall buildings with basement levels are increasingly being built due to need for space in large cities. Frequently, such structures are built involving a raft foundation and diaphragm walls below the water table. In addition, sometimes such buildings are located on floodplains. Therefore, if a river flood event occurs, the building can be exposed to pore water pressure (due to the fluctuation of water table) acting beneath its raft foundation. The generated subpressures will depend on the water table changes with time, and on the way such pressures are transmitted through the ground. Previous works have studied this behavior through laboratory and small-scale tests or numerically; however, many of them have used a constant hydraulic gradient and the water table fluctuations with time have been ignored. In this work, the evolution of pore water pressures with time mobilized beneath a raft foundation of a building built in a floodplain is studied. To do that, full-scale numerical models capable of simulate a river flooding and its corresponding overflow are developed. Such models incorporate data from water table change–time curves recorded during real river floods associated with a set of river regimes. Additionally, the effect of factors such as the soil permeability, the diaphragm wall length, and the soil thicknesses on water pore pressures beneath a raft foundation are also analyzed. Results suggest numerical models developed herein are capable of reproducing pore pressures induced beneath a raft foundation during river flooding. Furthermore, it was found that the above-mentioned factors could impact the percentage of pore water pressure mobilized beneath the raft foundation with respect to the maximum pore water pressure that could be induced during river flooding, and that the principal risk arises in buildings near large catchments where the flow increases over an extended period. Finally, practical implications and recommendations to practitioners are provided.

Diatom cell-size composition as a novel tool for quantitative estimates of the water table in peatlands.

Diatom cell-size composition is an indicator of aquatic environmental changes but has been rarely investigated, especially in semi-terrestrial peatlands. In this study, both taxonomic composition and cell-size composition of diatoms were analysed in 41 samples from two montane peatlands, northeastern China. Redundancy analyses revealed that diatom taxonomic composition was significantly related to the depth to the water table (DWT) and Ca2+, while cell-size composition was significantly associated with DWT and Si. DWT was the most important factor and its sole effect explained 26.2% and 17.9% of the total variance in taxonomic composition and cell-size composition, respectively. Accordingly, diatom-based water-table transfer functions were developed based on taxonomic composition and cell-size composition, respectively. The maximum-likelihood (ML) model based on diatom taxonomic composition had the best performance, with a correlation coefficient value (R2) of 0.78 and the root mean squared error of prediction (RMSEP) of 6.66 cm. The ML model based on cell-size composition had similar performance, with an R2 of 0.78 and the RMSEP of 6.87 cm, suggesting that diatom cell-size composition can be a new quantitative means to track past water-table changes. This method requires further appraisal with palaeoecological data but offers a new option that deserves exploration.

Small-scale hydrological patterns in a Siberian permafrost ecosystem affected by drainage

Abstract. Climate warming and associated accelerated permafrost thaw in the Arctic lead to a shift in landscape patterns, hydrologic conditions, and release of carbon. In this context, the lateral transport of carbon and shifts therein following thaw remain poorly understood. Crucial hydrologic factors affecting the lateral distribution of carbon include the depth of the saturated zone above the permafrost table with respect to changes in water table and thaw depth and the connectivity of water-saturated zones. Landscape conditions are expected to change in the future due to rising temperatures and polygonal or flat floodplain Arctic tundra areas in various states of degradation; hydrologic conditions will also change. This study is focused on an experimental site near Chersky, northeast Siberia, where a drainage ditch was constructed in 2004 to simulate landscape degradation features that result in drier soil conditions and channeled water flow. We compared water levels and thaw depths in the drained area (dry soil conditions) with those in an adjacent control area (wet soil conditions). We also identified the sources of water at the site via stable water isotope analysis. We found substantial spatiotemporal changes in the water conditions at the drained site: (i) lower water tables resulting in drier soil conditions, (ii) quicker water flow through drier areas, (iii) larger saturation zones in wetter areas, and (iv) a higher proportion of permafrost meltwater in the liquid phase towards the end of the growing season. These findings suggest decreased lateral connectivity throughout the drained area. Shifts in hydraulic connectivity in combination with a shift in vegetation abundance and water sources may impact carbon sources and sinks as well as transport pathways. Identifying lateral transport patterns in areas with degrading permafrost is therefore crucial.

Late Holocene changes in the water table at an alkaline fen in Central Latvia: Their impacts on CaCO3 deposition at the fen and relation to the hydroclimate patterns of the Eastern Baltic Region

Sediments of CaCO3-precipitating alkaline fens, comprising biotic and abiotic indicators of water table changes, are among the most reliable archives for obtaining palaeohydrological data. The study uses a semiquantitative method based on a combination of selected indicators (plant macrofossils, mollusc shells, degree of peat decomposition) to estimate the relative changes in the water table position at Lustūžkalns alkaline fen, Latvia, Eastern Baltic Region. The study also aims to determine the time frames of CaCO3 deposition at the fen using loss on ignition and carbon and oxygen stable isotope records. The chronology of the three sediment sequences studied is based on the AMS radiocarbon dating of terrestrial plant macrofossils. Although the reconstructed water table positions revealed differences between the cores, the major shift from the low water tables persisting since ca. 5000 cal yr BP to the prevailing high water stands at ca. 3000 cal yr BP was common to all the sequences. The major shift observed is consistent with a change from low to high water tables in peatlands in Latvia and at numerous fens and bogs across the Eastern Baltic Region, Fennoscandia and NW Europe. Concurrent with the increase in the water tables was the onset of CaCO3 precipitation on the Lustūžkalns fen surface, which began at ca. 3000 cal yr BP and accelerated from ca. 2500 cal yr BP. The Late Holocene CaCO3 precipitation at Lustūžkalns can be attributed to the change from warm and dry conditions during the Holocene Thermal Maximum (HTM) to cooler but humid during the Late Holocene. In contrast, in Central and Western Europe, the main period of freshwater carbonate precipitation occurred during the warm and humid HTM.

Effects of water-table changes following rainfall events on arsenic fate and transport in groundwater–surface water mixing zones

This study investigated the effects of groundwater–surface water (GW–SW) interactions on the fate and transport of arsenic (As) following rainfall events and subsequent water-table changes in GW–SW mixing zones, comprising the riparian and hyporheic zones, near an abandoned gold mine. During the dry and wet periods, stream conditions changed from flow-through to gaining, respectively. Water-table changes caused by rainfall events controlled flow paths between riparian zones and the stream, affecting spatiotemporal variation in the redox and pH conditions of the aquatic environment. Subsequently, the fate and transport of As in GW–SW mixing zones was responsive to variations in redox and pH conditions. Through the oxidative dissolution of As-bearing sulfide minerals and the reductive dissolution of iron (Fe) oxides with adsorbed As, As was released into the groundwater in the riparian zones and transported to the stream and streambed along the baseflow discharge. However, As was also immobilized in the sediment through adsorption onto Fe-oxides and coprecipitation with calcium (Ca) and zinc (Zn), suggesting that the sediment acts as a sink-and-source of As in aquatic environments. Therefore, water-table changes and GW–SW interactions could play an important role in the fate and transport of As in aquatic environments, specifically groundwater–riparian–streambed–stream systems. The findings of this study will provide scientific insights into the mechanisms of As in aquatic environments, aiding in improved decision–making to ensure safe and sustainable water management in response to future climate change.

Spatial modeling of the water table and its historical variations in Northeastern Italy via a geostatistical approach

Groundwater resources are the most important freshwater source for any human use and its preservation in the context of climatic variability is of crucial importance. So far, no systematic spatial estimation of the water table in Northeastern Italy has ever been made available, whereas the Veneto Region (North-Eastern Italy) provides a free database with recorded water table measurements between 1999 and 2022. These starting data have been cleaned, leading to a final database of 53 yearly water table data. The lack of knowledge about the spatial estimation of the water table within the historical period is overcome through the well-known geostatistical technique of cokriging. The latter is the most suitable approach for reproducing water table elevations upon local terrain elevation as an auxiliary variable. Results underline modest decrements between 1999 and 2022, which are more pronounced in the Prealps area and in general in sedimentary soils, and less in the Fontanili belt, a crucial freshwater source area. Moreover, the estimated water table change is highly non-linear in time from year to year and highly varying in space. The results seem particularly interesting in the plain areas and within the Fontanili belt, where the management of groundwater resources is becoming crucial. However, the spatial estimation in the Prealps area needs to be improved for a better assessment and future reliable predictions.

Multi-sensor satellite imagery reveals spatiotemporal changes in peatland water table after restoration

Remote sensing (RS) has been suggested as a tool to spatially monitor the status of peatland ecosystem functioning after restoration. However, there have been only a few studies in which post-restoration hydrological changes have been quantified with RS-based modelling. To address this gap, we developed an approach to assess post-restoration spatiotemporal changes in the peatland water table (WT) with optical (Sentinel-2 and Landsat 7–9) and radar (Sentinel-1) imagery. We tested the approach in eleven northern boreal peatlands (six restored, and five control sites) impacted by forestry drainage in northern Finland using Google Earth Engine cloud computing capabilities. We constructed a random forest regression model with spatiotemporal field-measured WT data as a dependent variable and satellite imagery features as independent variables. To assess the spatiotemporal changes, we constructed representative maps for situations before and after restoration, separately for early summer high-water and midsummer low-water conditions. To further quantify temporal changes during 2015–2023 and to test their statistical significance, we conducted a bootstrap hypothesis test for the areas near the restoration measures and similar areas in the control sites. The regression model had a relatively good fit and explanatory capacity (overall R2 = 0.71, RMSE = 6.01 cm), while there were notable site-specific variations. The WT maps showed that the post-restoration changes were not uniform and concentrated near the restoration measures. The bootstrap test showed that the WT increased more in the restored areas (4.7–8.8 cm) than in the control areas (0.1–5.2 cm). Our results indicate that restoration impact on surface hydrology can be quantified with multi-sensor satellite imagery and a machine learning approach in treeless peatlands.

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.

PLAXIS 3D numerical analysis of complex geotechnical problems of colossal built heritage

The paper aims to contribute to the preservation of high valuable historic masonry structures and historic urban landscapes through the combination of geotechnical, structural engineering. The main objective of the study is to conduct finite element analysis (FEA) of bearing saturated soft clay soil problems and induced structural failure mechanisms. This analysis is based on experimental and numerical studies using coupled PLAXIS 3D FE models. The paper presents a geotechnical analytical model for the measurement of stresses, deformations, and differential settlement of saturated clay soils under colossal stone/brick masonry structures. The study also discusses the behavior of soft clay soils under Qasr Yashbak through numerical analysis, which helps in understanding the studied behavior and the loss of soil-bearing capacity due to moisture content or ground water table (G.W.T) changes. The paper presents valuable insights into the behavior of soft clay soils under colossal stone/ brick masonry structures. The present study summarized specific details about the limitations and potential sources of error in Finite Element Modeling (FEM). Further field research and experimental analysis may be required to address these limitations and enhance the understanding of the studied soft clay soil behavior. The geotechnical problems in historic monuments and structures such as differential settlement are indeed important issues for their conservation since it may induce serious damages. It deserves more in-depth researches.

Silvicultural Practices and Water Table Dynamics of Coastal Forested Wetlands

HighlightsForested wetland hydrology (WH) is characterized by changes in daily water table (WT) depth over time.Silvicultural operations (harvesting, thinning, bedding, and minor drainage and intensity) affect WT dynamics.Both WT dynamics and WH are also affected by tree stand age/growth and soil types, besides the climate.Knowledge gaps and future research using modeling, including machine learning methods are discussed.Abstract. Sustainable management of forested wetlands requires an understanding of water table (WT) dynamics affected by rainfall and evapotranspiration (ET) as well as management practices to sustain water quality, quantity, and ecosystem services. The hydrology, the most important factor influencing productivity of forested wetlands, may be characterized by measuring changes in WT depth over time. The hydrology of U.S. Southeastern Coastal Plain forested wetlands, particularly wet pine flats and pocosins, where drainage has been commonly used to improve tree growth, is relatively well understood. However, uncertainties remain regarding the effects of some silvicultural practices on WT dynamics of varying soil and drainage types and the role of climatic trends, including extreme events (precipitation and droughts), on WT dynamics of these forested lands. In this paper, we use information from long-term monitoring and modeling studies conducted at sites in the Southeastern Atlantic Coastal Plain to review the current state of research on potential effects of harvesting, thinning, bedding, and minor drainage on changes to WT dynamics in coastal non-riverine forested wetlands. We also briefly illustrate current gaps in knowledge and outline future potential research in this area. Keywords: Pine forest, Bedding, Harvesting, Minor drainage, Water table, Wetland hydrology, Hydrology models.

Climate Change Impact on the Trigger of Natural Disasters over South-Eastern Himalayas Foothill Region of Myanmar: Extreme Rainfall Analysis

The study examines the characteristics and variability of monsoon rainfall in Myanmar, focusing on the relationship between heavy rainfall, floods, and earthquakes, which impact agriculture, hydrology, and the environment. Generally, heavy rainfall can cause flooding, economic losses, and water table changes. Northern Myanmar floods occur mainly during the monsoon season from June to October and can be classified into widespread floods along major rivers like Ayeyarwady, Thanlwin, Chindwin, and Sittoung and flash floods in small streams and rivers. Climate change is expected to increase the frequency and intensity of extreme weather events, including heavy rainfall, which can trigger floods or landslides, which also can in turn cause earthquakes. Heavy rainfall over northern Myanmar and the Sagaing faults, which are the main triggers of earthquakes, has been the subject of several studies. The study uses the Copernicus 5 database of global climate model (GCM) simulations with two scenario analyses on climate change detection and indices (ETCCDI) to study changes in climatic extremes. Results show high intensity in the northern region and monsoon core regions, while the central region shows less intensity. The study also uses intensity-duration-frequency (IDF) curves to analyze the relationship between rainfall duration, intensity, and return time in major risk zones. The study finds that as short duration lengthens, rainfall intensity increases for future rainfall patterns. This information is expected to be convenient for local authorities and flood protection projects in rural and urban basins.

A New Highly Parameterized Linear Inversion of Water Table Change and Groundwater Depletion Rate Tested With the High Plains Aquifer, U.S.A.

AbstractUnderstanding groundwater resource dynamics is limited by the sparsity of observations of water levels, pumping rates, and hydraulic properties relative to their spatiotemporal heterogeneity. To address some of this complexity, we proposed a new highly parameterized linear inverse method to quantify water table change and groundwater depletion rate in unconfined aquifers that does not require initial or boundary conditions. The method requires linearization, and we tested the performance of six proposed water table functions with three coordinate systems with synthetic models, finding that water table functions by the dimensionless method achieve the lowest errors. Our inverted water table changes and depletion rates remained stable and accurate with head measurement error of 5%. However, inversions became less accurate when head observations contained large temporal gaps. Next, we applied the inversion for water table changes and depletion rates in the Texas High Plains Aquifer (HPA) and the HPA during 2000–2015. To address sparse water levels and uncertain hydraulic conductivity measurements, two modifications were made to improve data constraints for inversion: (a) calculating winter‐time water levels for wells with >1 head observation by linear interpolation and (b) using hydraulic conductivity geostatistical realizations. The inverted water table change and depletion rate expected mean values and uncertainties were reasonable compared to the known pumping records of the Texas HPA. With relatively minor data curation, the new inverse method can quantify spatiotemporally continuous water table change, depletion rates, and their uncertainty for heterogeneous aquifers with temporally sparse and noisy water level observations.

Dynamic Monitoring of In-situ Chemical Oxidation for Remediation of Hydrocarbon Contamination with Electrical Resistivity Tomography

In situ chemical oxidation (ISCO) using persulfate, a conductive oxidant, provides a powerful signal for non-invasive geophysical techniques to characterize the remediation process of hydrocarbon contaminants. This study used ISCO for remediation in a laboratory sandbox and at an on-site contaminated site to evaluate the ability of resistivity chromatography (ERT) to monitor the process of alkali-activated persulfate remediation of hydrocarbon-contaminated soils. The experimental results show that the persulfate plume migrates mainly vertically due to density-driven flow. The relationship between resistivity and pollutant metrics further showed that pollutant depletion contributed 25.6% to the resistivity change in polluted source regions, while this contribution was less than 16% in low or non-polluted regions. In addition, field monitoring results indicate that the resistivity response is consistent with changes in water chemistry, water table, contaminant concentration and temperature. In conclusion, geophysical methods are excellent for dynamic monitoring of in situ remediation processes for hydrocarbon contamination.

Holocene vegetation dynamics in southern Ukraine under changing land use and climate

The Holocene vegetation dynamics of the Eurasian steppe are underinvestigated despite its vast extension, chiefly because of the scarcity of suitable sites for palaeoecological research. Here, we present a palaeoecological reinvestigation from Kardashynskyi mire (southern Ukraine), approximately 4 km from a previously cored site. Using pollen, spores and microscopic charcoal, we have reconstructed vegetation dynamics, fire history and land use for the past c. 8300 years. Regionally, steppe vegetation with Poaceae, Chenopodiaceae and Artemisia was always dominant. However, pollen assemblages also reflect the presence of floodplain and upland tree stands. At the beginning of the sequence, c. 8300 years ago, Pinus stands were growing on the sandy terraces of the Dnipro dry upland sites. Later, at c. 7950 cal yr BP, diverse stands with Quercus, Ulmus, Fraxinus, Tilia and Alnus established along the riverbanks, where moisture availability was sufficient. Around 6100 cal yr BP, those deciduous broadleaved stands experienced a severe decline, likely in response to changing water table levels. Cultural indicators suggest land use activities after c. 7900 cal yr BP. During the Bronze Age, human impact intensified. Overall, both climate and humans drove vegetation dynamics in the Pontic steppe for millennia. Nowadays, this once extensive biome has almost completely been converted to cropland. Similarly, the wetland vegetation, the riparian forests and, above all, the pine forests growing on the sandy terraces were strongly reduced by millennial-long land use. Under the current conditions, even the last remnants of these special vegetation types are severely threatened.

Sources and transformation of nitrogen in shallow aquifers with progressive water table recovery using geochemical and isotopic approaches.

Groundwater level recovery has a significant effect on the sources and transformation of nitrogen in groundwater, but there are still few studies on the influences of the water table on the sources and transformation of nitrogen in groundwater using field data. In this study, the changes in groundwater level, geochemical composition, and isotopic signatures of NO3- and NH4+ during a period of groundwater level recovery at a pilot site were analyzed in detail. The water table underwent progressive recovery of almost 1.6 m in 16 months. At a depth of 5.5 m below the surface, both low NH4+ and high NO3- appeared in the groundwater, whereas below that depth, both high NH4+ and low NO3- simultaneously appeared in the groundwater. The main sources of NO3- were manure and septic waste, and NH4+ fertilizers. The main sources of NH4+ were mineral fertilizers. The main transformation process were nitrification and denitrification at a depth of 5.5 m below the surface; below that depth, the main transformation processes were denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This study provides a theoretical understanding of the relationship between the changing water table and nitrogen in groundwater level recovery areas.

Using InSAR and GPR Techniques to Detect Subsidence: Application to the Coastal Area of “A Xunqueira” (NW Spain)

Climate change represents an important cause of subsidence, especially in coastal cities affected by changes in surface water level and water table. This paper presents a complementary study of Interferometric Synthetic Aperture Radar (InSAR) and Ground Penetrating Radar (GPR) for the early detection of subsidence and sinkhole phenomena. The methodology was applied to a coastal urban area in Galicia, northwest Spain (humid region), showing apparent signs of subsidence and building settlement during the last two years. Two different InSAR methods are compared for the period from June 2021 to March 2022: PSI (Persistent Scatterer Interferometry) and SBAS (Small Baseline Subsets), and the average deformation velocities obtained resulted in −3.0 mm/yr and −4.1 mm/yr, respectively. Additional GPR data were collected in January 2022 to validate the InSAR results, which detected subsidence in agreement with the persistent scatters obtained from the PSI method. This is crucial information to plan preventive maintenance.

A feasibility study on time-lapse transient electromagnetics for monitoring groundwater dynamics

Time-lapse geophysical studies have been used as noninvasive tools to study subsurface processes. However, compared to direct current resistivity methods, the transient electromagnetic (TEM) method has not been explored in much detail for time-lapse investigations. Here, we introduce the use of a monitoring TEM (mTEM) system and methodology for long-term groundwater monitoring purposes. The system can run measurements automatically and the modeling approach uses a time-constrained inversion (TCI) scheme based on an existing laterally constrained inversion scheme. Instead of lateral constraints that traditionally ensure lateral coherency between measurements, temporal constraints are used to control the temporal coherency between measurements. Synthetic analysis demonstrates that very tight time constraints on resistivities and a time constraint on the depth to the water table fixed at a fraction of the expected annual water table variation is needed to track water table changes at the decimeter level. Furthermore, the synthetic analysis indicates that the mTEM method can track annual variations in the water table with amplitudes as low as 0.6 m with a mean absolute error of 0.2 at depths between 16 m and 30 m. A field example consisting of 233 1D TEM measurements acquired over 10 months using the mTEM instrument supports the synthetic results. The estimated water table depth from the TCI scheme reproduces the variation in the water table accurately, as confirmed by measurements from a water level data logger in a nearby well. The differences between the results from the TEM monitoring system and the diver measurements are in the range of ±0.1 m with an average absolute difference of 0.05 m. This study demonstrates the potential to monitor changes in the groundwater level noninvasively.

Mycorrhizal colonization had little effect on growth of Carex thunbergii but inhibited its nitrogen uptake under deficit water supply.

Plant nitrogen (N) acquisition via arbuscular mycorrhizal fungi (AMF) serves as a dominant pathway in the N nutrition of many plants, but the functional impact of AMF in acquisition of N by wetland plants has not been well quantified. Subtropical lake-wetland ecosystems are characterized by seasonal changes in the water table and low N availability in soil. Yet, it is unclear whether and how AMF alters the N acquisition pattern of plants for various forms of N and how this process is influenced by soil water conditions. We performed a pot study with Carex thunbergii that were either colonized by AMF or un-colonized and also subjected to different water conditions. We used 15N labelling to track plant N uptake. AMF colonization had little effect on the biomass components of C. thunbergii but did significantly affect the plant functional traits and N acquisition in ways that were dependent on the soil water conditions. The N uptake rate of AMF-colonized plants was significantly lower than that of the non-colonize plants under low soil water conditions. Decreased NO3 - uptake rate in AMF-colonized plants reduced the plants' N/P ratio. Even though C. thunbergii predominantly took up N in the form of NO3 -, higher water availability increased the proportion of N taken up as NH4 +, irrespective of the inoculation status. These results emphasize the importance of AMF colonization in controlling the plant's N uptake strategies and can improve predictions of N budget under the changing water table conditions in this subtropical wetland ecosystem.

Water Table and Permeability Estimation From Multi‐Channel Seismoelectric Spectral Ratios

AbstractRecent developments in predicting and interpreting seismoelectric (SE) signals suggest a great potential for studying near‐surface hydrogeological properties, particularly in the vadose zone. Previous studies have revealed that the SE spectral ratios obtained from earthquake‐triggered SE data contain valuable hydrogeological information concerning porous media (e.g., permeability, porosity, fluid viscosity, and salinity). This study introduces Multi‐Channel SeismoElectric Spectral Ratios (MC‐SESRs) by considering an active seismic source acting on the ground surface. The frequency‐ and saturation‐dependent excess charge density is adopted to calculate the cross‐coupling coefficients. Applying a supervised learning task based on a flat neural network, the so‐called “broad learning (BL)” model, to map and extract the features of MC‐SESRs data, we seek to determine the permeability and the water table depth. Our results indicate that (a) MC‐SESRs are sensitive to the water table depth and permeability; (b) using more traces of SESRs data for inversion can increase accuracy; and (c) the changing water table can be rapidly determined by the MC‐SESRs by resorting to the BL inverse model, and it can attain an excellent accuracy while disturbed by data noise and misspecified model parameters (e.g., porosity and permeability) with errors of up to 20%. The proposed MC‐SESRs inversion has potential applications for non‐invasive monitoring in shallow porous media (e.g., frost thawing and geothermal upwelling).