Groundwater Movement Research Articles

Longitudinally and laterally trench-supported subsurface dam innovative design procedures

Abstract According to the Paris climate change agreement, temperature increases of around 1.5 or 2.0 °C by 2050 are bound to increase the amounts of evaporation and evapotranspiration, which are among the losses from surface water bodies, such as rivers, lakes, reservoirs and dams. In order to reduce these losses and support local water supply, subsurface dam construction projects are at the forefront in many countries, especially in arid and semi-arid regions, even in subtropical climate regions. In the literature, there are classical methodological explanations for underground dams with quite insufficient and restrictive interpretations. In this paper, two very similar but different new alternatives are proposed as longitudinally and laterally supported underground dams with inspirations from historical qanat groundwater subsurface structures. Both types are supported by artificial trenches with higher hydraulic conductivity than the surrounding Quaternary alluvial deposits to increase external and meanwhile to support internal areal recharge possibilities between the trenches and the surrounding natural porous, weathered and fractured layers. It is noticed that trench-supported subsurface dams are more effective, affordable, sustainable and manageable than classical alternatives available in the literature. It is recommended that a more refined subsurface groundwater movement mathematical formulation should be developed in the future.

Efficiency of innovative technologies in agriculture and water industry

Flooding of agricultural areas negatively affects soil fertility, phytomass formation regimes and productivity of natural phytocenoses. Due to the transition to the digitalization of agriculture, it became possible to model various natural processes, including the movement of water flows in soils. Various software options are used to model flooding processes, which solves local problems and is quite expensive. Spreadsheets are an affordable solution to this problem. When implementing computer modeling using the finite difference algorithm in spreadsheets, it is necessary to rely on physical modeling of groundwater movement processes. The distribution of flooding is simulated at the stand reflecting the plane-parallel nature of groundwater movement. The analysis of the calculation results given in the paper revealed errors in the obtained results. The reason for discrepancy in the study results was determined based on the obtained data.

Eight-year catalog of deep short-term slow slip events at the Nankai trough based on objective detection algorithm using strain and tilt records

In subduction zones, slip deficit monitoring along the plate interface is important for understanding the seismogenesis of megathrust earthquakes. In the last two decades, aseismic slip transients, such as slow slip events (SSEs), which are usually synchronized with tectonic tremors, have been detected in subduction zones worldwide. Frequent SSEs are particularly important for releasing slip deficits during the inter-seismic periods of megathrust earthquakes. In southwest Japan, deep short-term SSEs have been primarily monitored with strain and tilt records because the SSEs in this region are small. However, strain and tilt records are so sensitive that they record not only SSEs, but also rainfall and local groundwater movements, which temporally affect the quality of data making it difficult to apply an automated detection algorithm. Therefore, previously reported short-term SSE catalogs, based on strain and tilt records, were created by visual inspections, although they are not suitable for generating a long-term catalog. In this study, a quantitative detection algorithm was developed to detect short-term SSEs using strain and tilt records. The problem of temporally varying data quality was solved by introducing the prior probability of log-normal distributions in the fitting variance. This method was applied to an 8-year (2013–2020) dataset of strains and tilts from southwest Japan. A total of 96 events were detected, among which, 78 corresponded with SSEs previously reported by the Geological Survey of Japan (GSJ). Although the GSJ catalog contained more events with smaller magnitudes, such events were difficult to distinguish from noise using the developed method. Three of the remaining 18 events were considered SSEs that were not reported in the GSJ catalog. Others could be artifacts because there were no obvious signals in the global navigation satellite system records (with events of magnitude > 6.0). Previous studies have suggested the existence of aseismic transients deeper or shallower than regular short-term SSEs in southwest Japan. However, detection results from this study did not confirm such events.Graphical

Fuzzy Unsteady-State Drainage Solution for Land Reclamation

Very well-drained lands could have a positive impact in various soil health indicators such as soil erosion and soil texture. A drainage system is responsible for properly aerated soil. Until today, in order to design a drainage system, a big challenge remained to find the subsurface drain spacing because many of the soil and hydraulic parameters present significant uncertainties. This fact also creates uncertainties to the overall physical problem solution, which, if not included in the preliminary design studies and calculations, could have bad consequences for the cultivated lands and soils. Finding the drain spacing requires the knowledge of the unsteady groundwater movement, which is described by the linear Boussinesq equation (Glover-Dumm equation). In this paper, the Adomian solution to the second order unsteady linear fuzzy partial differential one-dimensional Boussinesq equation is presented. The physical problem concerns unsteady drain spacing in a semi-infinite unconfined aquifer. The boundary conditions, with an initially horizontal water table, are considered fuzzy and the overall problem is translated to a system of crisp boundary value problems. Consequently, the crisp problem is solved using an Adomian decomposition method (ADM) and useful practical results are presented. In addition, by application of the possibility theory, the fuzzy results are translated into a crisp space, enabling the decision maker to make correct decisions about both the drain spacing and the future soil health management practices, with a reliable degree of confidence.

Towards a Mineral Systems Model for Surficial Uranium Mineralization Based on Deposits in the Erongo District of Namibia

Surficial deposits in Namibia’s Erongo district contain substantial but low-grade resources of uranium and vanadium (nearly 500 Mlb U3O8), hosted in palaeochannels. This review attempts to develop a mineral systems model for the deposit type, but it is emphasised that research into this important class of deposit has been minimal since the nineteen eighties, largely as a result of a limited investment in uranium exploration. The deposits are the result of groundwater movement in aquifers developed within Cenozoic palaeochannels. The source of uranium was probably granitic rocks traversed by these palaeodrainages, particularly black-quartz rich pegmatites similar to those that make up the hard-rock alaskite deposits of the region. Transport of uranium is generally assumed to have occurred in aqueous uranium species after palaeochannels became filled with sediment. U-enriched clasts within the palaeochannels have yet to be investigated as a local source of uranium. The localised deposition of uranium occurred after regionally extensive carbonate cementation of the palaeochannel sediments, which was the result of climate change (aridification). Pre-uranium calcite may have acted as a chemical buffer (pH) and probably influenced palaeochannel hydrology, restricting groundwater flow to the deeper portions. Uranium is paragenetically related to Mg clays and dolomite, suggesting that the groundwater evolved to a more Mg-rich composition during uranium deposition, probably as a result of more extreme evaporation. The controls on the localisation of mineralisation remain unclear and unpredictable, as are the controls on uranium grade—the fundamental determinant of economic viability. There are few absolute age determinations for any of the deposits, but none occur in rocks likely to be older than the Miocene. This reflects low preservation potential. For example, the Langer Heinrich deposit is incised by active drainage with attendant erosion and probable removal of mineralised material.

Hybrid ANFIS models were used to calculate the capillary water absorption values of construction stones

The most significant parameter in groundwater movement in stones is capillary water absorption. Specifying the capillary water absorption (CWP) of rocks needs hard and laborious experimental work, while prediction models can reduce the cost and required time. To this aim, different rock specimens were gathered from various rocks. For the prediction processes, the hybrid adaptive neuro-fuzzy inference system (ANFIS) models also were proposed to determine the optimal value of two constituent parameters of the ANFIS, which the particle swarm optimization (PSO) and whale optimization algorithm (WOA) algorithm applied to the ANFIS for this aim. Results present that ANFIS processes have passable accomplishment in forecasting the CWA with R2 larger than 0.832 and 0.917 for the training and testing data, respectively, a good connection among actual and anticipated values. Considering developed models, the ANFIS model optimized with WOA performs better than another model in training and testing datasets. In the training dataset, the value of R2 and RRSE is 0.917 and 29.29% for the WOA-ANFIS model, while the PSO-ANFIS model is 0.911 and 30.50%, respectively. Overall, it is clear that WOA-ANFIS can be recognized as the proposed model, which shows its capability to find the optimal value of two constituent parameters of the ANFIS.

Geographic Information System for changing the level of soil salinity in Jizzakh province, Uzbekistan

The task of GIS is to receive, collect, analyze, store and transmit data in any format. Being able to access any of these data formats and accessing the program will further enhance GIS capabilities. The ability of GIS to conduct various statistical analyzes, mapping and creation of various databases ensures that it is more relevant and popularized in the area of land and water conservation. Therefore, the task of GIS is to receive, collect, analyze, store and transmit data in any format. Being able to access any of these data formats and accessing a meal program will further enhance GIS capabilities. In Uzbekistan, especially in the Jizzakh province, the reclamation state of irrigated lands and soil salinization is inextricably linked with the level of groundwater, their salinity and movement. The level of groundwater and its salinity depends largely on the technical condition of the drainage networks and the amount of atmospheric precipitation, the supply of fresh water during the vegetation period, and the movement of groundwater from outside. Discussed future of using GIS in different sphere. GIS gives possibilities to collect the data, renewing it or use new information in analysis. It requires quick change of GIS information about Earth because procedures in the Earth are dynamically changeable. Periodically changing information in GIS gives us possibility to get new information and analyse it. GIS technologies and techniques started using widely in all sphere of humanity. It is important to know its properties.

Simulation of Groundwater levels in River basin using MODFLOW

MODFLOW is a groundwater modelling program. It can be compiled according to the practical applications. Groundwater flow models are used to calculate the rate and direction of movement of groundwater through aquifers. The outputs from model simulation are the groundwater flow and hydraulic heads which are in equilibrium with the specified hydrogeological conditions (i.e. hydrologic boundaries, hydrogeological framework, initial and transient conditions, hydraulic properties and sources) demarcated for the modelled area. Groundwater models perform an important role in the management and development of groundwater resources. This paper presents the results of a mathematical groundwater model developed for the Banda districts which is part of Yamuna River basin. For this purpose, groundwater modelling software (GMS) MODFLOW was used. The model results display that the computed values are in goodfitness of the measure data, which indicate the model is reliable.

ИСПОЛЬЗОВАНИЕ ИСПАРЕНИЯ С ВОДНОЙ ПОВЕРХНОСТИ ПРИ РАСЧЕТЕ ВОДОПОТРЕБЛЕНИЯ МНОГОЛЕТНИХ ТРАВ В УСЛОВИЯХ НЕЧЕРНОЗЕМНОЙ ЗОНЫ РОССИИ

The subject of research is the development of a method for calculating the water consumption of perennial grasses using evaporation from the water surface, aimed at improving the accuracy of its determination and saving water resources, on the watersheds of the Non-Chernozem zone of Russia. The object of research on the total water consumption of perennial grasses are sod-podzolic soils and soil moisture of watershed areas, when growing forage crops. Experimental experiments were carried out on plots, in lysimeters and laboratories, in different meteorological conditions in years. Scientific research, processing and analysis of experimental data were based on the theory of groundwater movement, the method of water balance, physical modeling, and the theory of mathematical statistics. When conducting scientific research on the water regime of sod-podzolic soils during irrigation of perennial grasses, the methodology developed at the Department of "Agricultural Land Reclamation, Forestry and Land Management" of the K. A. Timiryazev Russian State Agricultural Academy of Agriculture was used. Experiments conducted in lysimeters and plots in 2012...2014 served as the basis for the development of a formula for determining the water consumption of perennial grasses using evaporation from the water surface in the watersheds of the Non-Chernozem zone of Russia.

Assessment of alluvial aquifer conditions during a construction phase for a deep excavation

The Var low valley and its unconfined alluvial aquifer is the main water resource for around 600,000 inhabitants who live in the French cities and towns near the river mouth, such as Nice and St Laurent du Var. Several commercial and residential complexes are planned to be built in the downstream floodplain areas of the Var River and close to the Nice airport. Some of these buildings may have an impact on the groundwater table and consequently on the supply of drinking water. In this study, the groundwater flow was simulated using MIKE FEFLOW numerical model to assess the impacts of new development projects by estimating the drawdown of groundwater table due to the planned pumping activities as well as tracing the trajectories of groundwater movements to make sure the salt intrusion will not happen. The study focuses on a planned building, near well line used for water supply. The building was initially designed with several underground floors as parking lots. The model is developed and validated using the available piezometric data of 2010-2012 for the study area. The model was able to simulate the hydraulic head with a good precision (the Nash Sutcliffe Efficiency coefficient of 0.7 and higher). As the local groundwater level is very high and only a few meters below the ground surface, during the construction period of the foundation, the site must be kept dry, and the water should be pumped out. It will normally last around six months. However, this construction period is the most critical stage and will have serious impacts on the groundwater table, but our simulation results suggest that even after the construction period, the groundwater table will be dropped and consequently the salt intrusion into the groundwater due to the short distance of the site to the sea will be continued. Therefore, different foundation levels were tested to find the best solution.

Investigation of groundwater flow direction using Geospatial technology: A case study in part of Port Harcourt, Rivers State, Nigeria

A geospatial technique was used in some parts of the Port Harcourt metropolis to establish the direction of groundwater movement. This method included the use of twelve carefully selected boreholes and a variety of cutting-edge tools, such as depth meters, handheld GPS, and measuring tape. The static water level in the boreholes and the ground surface elevation in relation to the average sea level of the region were two of the variables that were gathered. High-end software was used to analyze the data in order to create groundwater flow direction maps and 3D visualizations for displaying the whole research region based on the fluctuation in static water levels. This software included Microsoft Excel, ArcGIS 10.4, and ArcScene 10.4. Afterward, the main and minor flow directions were identified. The results showed that groundwater in the area moves from the north to the south, with group 4 having the largest hydraulic gradient and group 1 coming in second. On the other hand, groups 3 and 2 had the lowest hydraulic gradient. The main factors influencing groundwater flow were determined to be gravity and external pressure brought on by pumping. The research region's southern regions are more vulnerable to groundwater pollution, which may result from zones with higher hydraulic heads, according to the flow pattern in the aquifer system. As a result, it is advised that residential boreholes and municipal water wells be located on the study area's northern sides, whereas sanitary landfills and garbage sites should only be located in the southwest.

THE EMERGENCE AND DEVELOPMENT OF A CRACK IN THE CONCRETE OF THE ABUTMENT OF THE LOWER HEAD OF LOCK № 2 OF THE VOLGA-BALTIC WATERWAY

An analysis of the concrete structures state of the lower head of lock № 2 of the Belousovsky hydroelectric complex of the Volga-Baltic waterway is presented. In 1985, a crack was discovered in the concrete of the left abutment of the lock lower head. Observations for the dynamics of its development have showed that the crack size increases with time. To explain the causes of the crack occurrence and development, an analysis of concrete quality of the lower head structures is made according to the data of previous studies. Taking into account the technology of concreting during the construction process, as well as studies carried out during operation, the low quality of concrete and its heterogeneous structure have been stated. The analysis of the soils structure at the base of the lower head is carried out; the filtration regime of groundwater movement is considered. It is noted that the base soils are represented by fine-grained sands with an interlayer of loams. The presence of several aquifers in the basement soils, as well as the formation of the pressure front of the hydroelectric complex, led to significant gradients of the filtration flow. This contributed to the development of suffusion processes in the soils of the lower head base, which led to the formation of a decompacted layer in the roof of the rocks of the lower head base. The data of modern surveys of soil characteristics confirm that suffusion processes continue at the present time. This led to the occurrence of multidirectional settlement of the right and left abutments of the lower head, which, in turn, led to the development of the crack in the concrete mass. The measures taken to eliminate or stabilize the development of the crack, namely, pumping a cement-sand mixture into the soil, grouting the abutment concrete, anchoring the structure, injecting the concrete mass with a two-component synthetic resin, have not stopped the crack opening, because the main reasons such as the poor quality of concrete and the weak bearing capacity of the underlying soils of the base had not been eliminated.

M. King Hubbert and "The Theory of Ground-Water Motion".

M. King Hubbert and "The Theory of Ground-Water Motion".

Three-Dimensional Tetrahedron Network (3D TEN) and Volumetric Geo-Objects (VGO) Data Model for Groundwater Simulation in Bida Basin, Nigeria

The presence of complex ground soil structures limits the attempt for groundwater extraction for alternate water supply usage. Hydrologists and engineers have made many attempts to Model 3D groundwater flow and storage using digital elevation model (DEM) data structures but have resulted in limited success in terms of actual 3D subsurface geology representation. This study attempts to construct resistivity data in an actual 3D environment using volumetric geo-objects (VGOs) and 3D tetrahedron network (3D TEN) data structures. Subsurface data were collected using the vertical electrical sounding (VES) approach to analyse the geological structure of the study area. To determine the course and movement of groundwater, the 3D constant was applied from Darcy's law in the Lagrangian technique. A time frame of one hour, two hours, four hours and eight-hour intervals was tested to simulate the porosity and permeability of various soil types with complex geological structures. The findings validated the use of 3D visualisation to model resistivity data. The implemented volumetric geo-object (VGO) data model and the 3D TEN model show the volume of water over the topsoil to be 17,461,228.07 in an hour; clay soil was 870,614.04; clayey sand was 435,307.02; and sandy clays was 348,245.61 per kilometre cube (km3). The use of 3D TEN and VGO for groundwater simulation in this research offers an improved perspective in groundwater visualisation that will promote sustainable groundwater exploration for societal developments. The findings of this study will be beneficial to stakeholders, water resource managers and government agencies such as Ministry of Water Resources. Keywords: Data model, Groundwater simulation, Three-dimensional tetrahedron network (3D TEN), Vertical electrical sounding (VES), Visualisation, Volumetric geo-objects (VGOs)

Using Apparent Electrical Conductivity to Delineate Field Variation in an Agroforestry System in the Ozark Highlands

Greater adoption and better management of spatially complex, conservation systems such as agroforestry (AF) are dependent on determining methods suitable for delineating in-field variability. However, no work has been conducted using repeated electromagnetic induction (EMI) or apparent electrical conductivity (ECa) surveys in AF systems within the Ozark Highlands of northwest Arkansas. As a result, objectives were to (i) evaluate spatiotemporal ECa variability; (ii) identify ECa-derived soil management zones (SMZs); (iii) establish correlations among ECa survey data and in situ, soil-sensor volumetric water content, sentential site soil-sample EC, and gravimetric water content and pH; and (iv) determine the optimum frequency at which ECa surveys could be conducted to capture temporal changes in field variability. Monthly ECa surveys were conducted between August 2020 and July 2021 at a 4.25 ha AF site in Fayetteville, Arkansas. The overall mean perpendicular geometry (PRP) and horizontal coplanar geometry (HCP) ECa ranged from 1.8 to 18.0 and 3.1 to 25.8 mS m−1, respectively, and the overall mean HCP ECa was 67% greater than the mean PRP ECa. The largest measured ECa values occurred within the local drainage way or areas of potential groundwater movement, and the smallest measured ECa values occurred within areas with decreased effective soil depth and increased coarse fragments. The PRP and HCP mean ECa, standard deviation (SD), and coefficient of variation (CV) were unaffected (p > 0.05) by either the weather or growing/non-growing season. K-means clustering delineated three precision SMZs that were reflective of areas with similar ECa and ECa variability. Results from this study provided valuable information regarding the application of ECa surveys to quantify small-scale changes in soil properties and delineate SMZs in highly variable AF systems.

Visualization Method for Porous Groundwater Seepage Flow Field Based on Particle Flow: Case of Yancheng City in the East Coast of China

Porous groundwater seepage flow field reflects the spatiotemporal dynamic characteristics of porous groundwater movement. The geometric point and vector line methods are the traditionally used visualization methods for groundwater seepage flow field; however, they exhibit difficulty in describing the characteristics and attributes of a seepage flow field. Therefore, a new particle flow method in the field of computer graphics is introduced in this study to visualize seepage flow field, including the storage conditions, transport mechanism, and seepage field properties of porous groundwater. This visualization method is discussed from four aspects: the generation of seed points, the life cycle of particles, the movement velocity of particles, and the formation of particle trajectory and smooth processing. The seepage field of confined aquifer III groundwater expressed via particle flow and the contour of critical groundwater level are superimposed and analyzed in Yancheng City in the east coast of China. Results show that particle flow can be effectively applied to the visualization of groundwater seepage flow field and provide spatial auxiliary decision-making support for the sustainable exploitation of groundwater and the formulation of geological environment protection measures.

Attachment of Extracellular Metabolic Products of Lysinibacillus sp . DRG3 on Sand Surface under Variable Flow Velocities and Bioprocesses

The efficacy of microbially mediated stabilization of soil mass depends on soil aggregation and further depends on the complex interplay of environmental parameters, microbial extracellular metabolic products, and surface characteristics of soil particles. Failures of flood control dikes or similar structures often culminate from minor erosion of soil particles initiated by groundwater seepage. Although the introduction of microbial metabolic products in controlling soil erosion has been studied by researchers, the influence of slow fluvial activities on the composition, characteristics, and their impacts on attachment mechanisms of extracellular polymeric substances (EPS) on soil surfaces have remained unexplored. Impacts of slow fluvial activities on the amount and chemical composition of EPS produced by Lysinibacillus sp. DRG3, a nonpathogenic soil bacterium, and the attachment mechanisms of the EPS produced under noncalcifying, nonureolytic, and ureolytic calcifying bioprocesses on the sand surfaces were investigated. DRG3-inoculated specimens were incubated in the presence of steady circulation of aqueous media containing minimal concentrations of minerals and carbon and nitrogen sources to simulate groundwater movements through soil. Quantity, compactness, continuity, and viscosity of EPS and the amounts of carbohydrate, protein, lipid, DNA, and RNA found in EPS increased with circulation velocity and incubation duration. EPS were found to attach to sand through electrostatic interaction and hydrogen bonding. Internally, EPS components interacted with each other through electrostatic interaction, hydrogen bonding, and hydrophobic interaction. Electrostatic interaction appeared to weaken with increasing media circulation intensity and alkalinity. In contrast, EPS production and hydrogen bonding intensified under increased media circulation. Results of this investigation suggest microbe-mediated soil aggregation becomes stronger and more efficient under slow media circulation and are expected to have implications on microbially mediated soil stabilization, particularly in addressing soil erosion. This study provides useful insights for successful field implementation of biomediated soil stabilization. Work presented herein also demonstrates a role for microbial activities found in subterranean environments in strengthening an existing sand deposit.

Experimental study of the solitary wave induced groundwater hydrodynamics

Coastal groundwater hydrodynamics are affected by the swash uprush and backwash processes. In this study, laboratory experiments were carried out to investigate the solitary wave induced groundwater hydrodynamics over a coarse-grained sand beach. Pore water pressures at 27 cross-shore positions (covering both the subaqueous and subaerial areas) along 3 different beach depths were measured, and the synchronized shoreline position as well as the local water surface elevations (WSE) were also recorded. Temporal variation of the total water head (TWH) was found almost hydrostatically controlled by the instantaneous WSE in the subaqueous area. In the capillary truncated zone, the capillary effect contributes to the non-hysteresis phenomenon between the TWH and WSE. In other subaerial area, time-varying features of the TWH and WSE show clear differences in terms of their magnitudes and phases. Regarding the experimental observations, four representative regions could be identified along the cross-shore direction, i.e., Region I corresponding to the initially subaqueous area, Region II in between the still water shoreline and the top of capillary fringe (saturated beach), Region III in between the upper boundary of Region II and the maximum swash run-up, and Region IV landward beyond the Region III. With respect to the cross-shore distribution characteristics of the maximum TWH and the maximum WSE, as well as the time instants when the maximum TWH and the maximum WSE occur, different groundwater hydrodynamics were observed during the swash event in these four regions. In addition, spatiotemporal characteristics of the TWH were scrutinized and discussed. Both the vertical and horizontal TWH gradients in different regions were considered to reveal the sophisticated groundwater hydrodynamics. Finally, the groundwater movement pattern and its percolation circulation under the solitary wave swash were also specified. • Solitary wave induced groundwater hydrodynamics are investigated through detailed laboratory experiments. • Four regions are identified regarding the spatial characteristics of the maximum total water head and its occurrence time. • Hydrostatic effect, capillary effect and the wetting front are significant for the swash groundwater hydrodynamics. • Horizontal groundwater seepage flow is evident, even larger than the vertical one, during the entire swash process. • Two groundwater circulations are observed in the subaqueous and subaerial areas during the swash cycle.

Electrokinetic effect provided by long oceanic waves coming on shore

Electrokinetic effect (EK) caused by long oceanic waves in porous water-saturated rocks of seabed and shore is examined theoretically. One possible reason for this effect is the motion of groundwater due to the volume deformation of porous rocks by oceanic waves coming on shore. The same mechanism is responsible for seismoelectric effect observed during seismic waves passage through ground-recording station. In this study, we examine another mechanism in which the wave-produced variable pressure on the seabed plays a role of a piston pushing seawater through the seabed rocks into sandy or porous rocks of the seashore thereby exciting the EK effect. To estimate this effect, we first consider a long gravity wave and then solve 2D‑problem on the pressure variations produced by this wave on the bottom. This solution is used to describe groundwater filtration in porous rocks subjected to the variable pressure of seawater. The EK current and telluric electric field in a porous medium are derivable through the pressure gradient of porous fluid. The amplitude of telluric electric field in a porous medium has been shown to decrease almost exponentially with distance from a shoreline. A penetration depth of the telluric field as a function of wave frequency in the range of 10‑100 mHz was analyzed. A role played by EK effect in the generation of ULF natural electromagnetic noise in coastal zone was discussed.

Hydro-geochemical characterization and suitability analysis of spring water of the Mai Khola Watershed, Ilam, eastern Nepal

The interaction of different physical and chemical factors as well as anthropogenic activities influences the chemistry of groundwater. The hydro-geochemical assessment of the groundwater is the basic part of the water resources management and its assessment in regards to its usability is considered vital. The study involves the measurement of physicochemical parameters (pH, EC, EH, DO, TDS) of the observed 147 springs and the ionic concentration of the representative 32 springs along the Mai Khola Watershed using standard analytical procedure. The results of the physicochemical parameters and ionic concentration were analysed and interpreted using different indices and graphical methods. The physicochemical parameter suggests that spring water is weakly acidic to alkaline and the measured EC and TDS suggest low interaction of rocks and water therein. The piper diagram indicates Ca2+ and Mg2+ together (alkaline earth metals) dominate over combined Na+ and K+ (alkali metals) and Cl- and SO42- (strong acids) predominate over HCO3- (weak ones). The Gibbs plot also satisfies the movement of groundwater from the precipitation domain to the rock-water interaction domain. The groundwater in this area is derived from a shallow aquifer with low rock-water interaction and the water is good for drinking purpose and excellent to good for irrigation. The spring water in the study area possesses no threat to quality deterioration, however proper management and conservation plans are required to maintain the quality of the water.