Study of water salinity in the Chtouka plain (Morocco) using TEM geophysical method, chemical and isotopes tracers

2021 ◽  
Author(s):  
Henrik Schreiber ◽  
Saadou Oumarou Danni ◽  
Amine Touab ◽  
Fatima Abourig ◽  
Nelly Montcoudiol ◽  
...  
Keyword(s):  
Seawater Intrusion ◽  
Monitoring Network ◽  
Water Salinity ◽  
Geophysical Method ◽  
Transient Electromagnetic ◽  
Rock Water Interaction ◽  
Groundwater Overexploitation ◽  
Local Water ◽  
Stable Isotopes Of Water ◽  
Tem Method

<p>The Chtouka plain in Morocco suffers from groundwater overexploitation and a significant increase in water salinity. In this study, a multidisciplinary approach combining water chemistry, stable isotopes of water (18O, 2H) and Transient Electromagnetic (TEM) method was used. The main objective was to identify the water salinity sources and the extension of the marine intrusion. Water samples were collected from wells and boreholes, springs, the Massa river and the main source of freshwater in the region, the Youssef Ibn Tachfine Dam. Geophysical (TEM) measurements (12 profiles comprising 83 measurement points) were carried out along the coastal zone and around the northern bank of the Massa river. The results show a spatial variability of water salinity, indicating rock-water interaction, seawater intrusion and anthropogenic influence. The interpretation of the TEM soundings allow to draw the front line of the marine intrusion in the aquifer. The results, compared to previous numerical simulations, show a significant progress of the marine intrusion into the coastal aquifer. The intrusion indeed reaches a distance of 2.5 km from the coast, far beyond models’ predictions. The local water authorities can use these results to improve their monitoring network and better assess the progress of the seawater intrusion.<br>Keywords: Water salinity, TEM geophysical method, chemical and isotopes tracers, marine intrusion</p>

scholarly journals A Transient ElectroMagnetic (TEM) Method Survey in North-Central Coast of Crete, Greece: Evidence of Seawater Intrusion

Geosciences ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 107 ◽  
Author(s):  
Despina Kalisperi ◽  
Maria Kouli ◽  
Filippos Vallianatos ◽  
Pantelis Soupios ◽  
Stephen Kershaw ◽  
...  
Keyword(s):  
Seawater Intrusion ◽  
Central Coast ◽  
North Central ◽  
Transient Electromagnetic ◽  
Tem Method

scholarly journals MINERAL NUTRITION OF CRISPHEAD LETTUCE GROWN IN A HYDROPONIC SYSTEM WITH BRACKISH WATER

2016 ◽  
Vol 29 (3) ◽  
pp. 656-664 ◽  
Author(s):  
HAMMADY RAMALHO E SOARES ◽  
ÊNIO FARIAS DE FRANÇA E SILVA ◽  
GERÔNIMO FERREIRA DA SILVA ◽  
RAQUELE MENDES DE LIRA ◽  
RAPHAELA REVORÊDO BEZERRA
Keyword(s):  
Nutrient Solution ◽  
Mineral Nutrition ◽  
Brackish Water ◽  
Water Source ◽  
Water Salinity ◽  
Hydroponic System ◽  
Foliar Phosphorus ◽  
Solution Preparation ◽  
Phosphorus And Potassium ◽  
Local Water

ABSTRACT Water availability in the Brazilian semiarid is restricted and often the only water source available has high salt concentrations. Hydroponics allows using these waters for production of various crops, including vegetables, however, the water salinity can cause nutritional disorders. Thus, two experiments were conducted in a greenhouse at the Department of Agricultural Engineering of the Federal Rural University of Pernambuco, to evaluate the effects of salinity on the mineral nutrition of crisphead lettuce, cultivar Taina, in a hydroponic system (Nutrient Film Technique), using brackish water in the nutrient solution, which was prepared by adding NaCl to the local water (0.2 dS m-1). A randomized blocks experimental design was used in both experiments. The treatments consisted of water of different salinity levels (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1) with four replications, totaling 24 plots for each experiment. The water added to compensate for the water - depth loss due to evapotranspiration (WCET) was the brackish water of each treatment in Experiment I and the local water without modifications in Experiment II. The increase in the salinity of the water used for the nutrient solution preparation reduced the foliar phosphorus and potassium contents and increased the chloride and sodium contents, regardless of the WCET. Foliar nitrogen, calcium, magnesium and sulfur contents were not affected by increasing the water salinity used for the nutrient solution preparation.

The use and misuse of apparent resistivity in electromagnetic methods

Geophysics ◽  
1986 ◽  
Vol 51 (7) ◽  
pp. 1462-1471 ◽  
Author(s):  
Brian R. Spies ◽  
Dwight E. Eggers
Keyword(s):  
Apparent Resistivity ◽  
Early Time ◽  
Asymptotic Formulas ◽  
Voltage Response ◽  
Late Time ◽  
Induced Voltage ◽  
Resistivity Curve ◽  
Transient Electromagnetic ◽  
Electromagnetic Methods ◽  
Tem Method

Problems and misunderstandings arise with the concept of apparent resistivity when the analogy between an apparent resistivity computed from geophysical observations and the true resistivity structure of the subsurface is drawn too tightly. Several definitions of apparent resistivity are available for use in electromagnetic methods; however, those most commonly used do not always exhibit the best behavior. Many of the features of the apparent resistivity curve which have been interpreted as physically significant with one definition disappear when alternative definitions are used. It is misleading to compare the detection or resolution capabilities of different field systems or configurations solely on the basis of the apparent resistivity curve. For the in‐loop transient electromagnetic (TEM) method, apparent resistivity computed from the magnetic field response displays much better behavior than that computed from the induced voltage response. A comparison of “exact” and “asymptotic” formulas for the TEM method reveals that automated schemes for distinguishing early‐time and late‐time branches are at best tenuous, and those schemes are doomed to failure for a certain class of resistivity structures (e.g., the loop size is large compared to the layer thickness). For the magnetotelluric (MT) method, apparent resistivity curves defined from the real part of the impedance exhibit much better behavior than curves based on the conventional definition that uses the magnitude of the impedance. Results of using this new definition have characteristics similar to apparent resistivity obtained from time‐domain processing.

Influences of the Earth’s Magnetic Field on the Transient Electromagnetic Process in the Geoelectric Field: an Experimental Study

2021 ◽  
Vol 62 (12) ◽  
pp. 1430-1439
Author(s):  
V.S. Mogilatov ◽  
V.V. Potapov ◽  
A.N. Shein ◽  
V.A. Gur’ev
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Field Experiments ◽  
Geoelectric Field ◽  
Earth’S Magnetic Field ◽  
Electromagnetic Process ◽  
Transient Electromagnetic ◽  
Schematic Layout ◽  
Earth's Magnetic Field ◽  
Tem Method

Abstract —A mathematical model of the influence of the Earth’s magnetic field (the Hall effect) on results of the controlled source transient electromagnetic (TEM) method has been elaborated. For identification of this effect, we propose a schematic layout of the experimental grounded system with a pulsed loop source and signals recording by radial receive lines equally spaced relative to the loop. The 2018–2019 special field experiments were conducted in the Tatar region of the West Siberian Lowland with an aim to estimate the Hall effect contributions to the TEM method. To detect the Hall effect, transient electromagnetic responses were measured mainly by four receive lines radiating from a 500×500 m square loop. Analysis of the TEM results processing aimed at improving the signal quality and reducing the interference revealed a great similarity in signals from the radial lines, which is theoretically possible only under the Hall effect. Comparison of the field signals with the theoretical ones enabled estimation of the components caused by the Hall effect, in particular, conductivity at ~0.002 S/m.

scholarly journals Application of TEM sounding method on riverbank filtration site subsurface suitability

2019 ◽  
Vol 19 (8) ◽  
pp. 2206-2213
Author(s):  
Mohd Firdaus Abdul Razak ◽  
Md Azlin Md Said ◽  
Ismail Abustan ◽  
Mohd Hanis Mohamad
Keyword(s):  
Cross Section ◽  
Riverbank Filtration ◽  
Loop Area ◽  
Transient Electromagnetic ◽  
M 10 ◽  
Tem Method ◽  
Sand And Gravel ◽  
Geological Units ◽  
Future Work ◽  
Data Acquisition Process

Abstract Transient electromagnetic (TEM) sounding technology is known for its capability in detecting resistive zones, especially those associated with fresh water. Nevertheless, to date, there have been no available studies that have employed TEM for riverbank filtration (RBF) application. Therefore, this study was conducted to investigate the capability of TEM technology in profiling the subsurface of RBF areas adjacent to Sungai Perak, Kota Lama Kiri, Kuala Kangsar. A total of 27 survey points of simple rectangular loop configuration with loop area of 100 m2 (10 m × 10 m) were executed in the study area. A suite of TerraTEM equipment was used for the data acquisition process. The inversion and interpretation processes were then conducted by using the modeling program of ‘TDEM Geomodel’ and Surfer 13. The results showed four 2-D resistivity cross-section (depth–distance) profiles with their corresponding geological units. The interpretation results indicated that the subsurfaces of the study area were identified as alluvial-type soils (with a range of 10 to 40 Ωm) up to 8 m due to the presence of silt, sand and gravel. Based on the good quality results produced as well as its convenience, it is recommended that the TEM method is used for RBF exploration in future work.

scholarly journals An Express Algorithm for Transient Electromagnetic Data Interpretation

Electronics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 354 ◽  
Author(s):  
Roman Kaminskyj ◽  
Nataliya Shakhovska ◽  
Gregus Michal ◽  
Borys Ladanivskyy ◽  
Lidia Savkiv
Keyword(s):  
Experimental Data ◽  
Spline Approximation ◽  
Numerical Differentiation ◽  
Data Interpretation ◽  
Continuous Functions ◽  
Electromagnetic Data ◽  
Polynomial Coefficients ◽  
Transient Electromagnetic ◽  
1D Model ◽  
Tem Method

The transient electromagnetic (TEM) method is a time-domain, controlled source, electromagnetic (EM) geophysical technique which is often applied to image the subsurface conductivity distributions of shallow layers due to its effectiveness and adaptability to complex site working conditions. The means for an express analysis of such experimental data in several practical cases have advantages and are suitable for use. We developed our approach for determining the approximate one-dimensional (1D) model of background conductivity based on the formal transformation of the TEM experimental data and the mathematical analysis of continuous functions. Our algorithm, which allows the 1D model’s parameters to be obtained in terms of a layer’s thickness and resistivity, widely utilizes the numerical differentiation of experimental curves as well as of transformed ones. Since the noise level increases with time in the attenuating TEM signals and differentiation even enhances it, special procedures are required to calculate the derivative values. We applied the piecewise cubic spline approximation to solve this problem. In that case, the derivatives are obtained using polynomial coefficients which are available for each node. The application of the created facilities is demonstrated using real experimental data of the TEM soundings.

scholarly journals Modelling Actual and Future Seawater Intrusion in the Variconi Coastal Wetland (Italy) Due to Climate and Landscape Changes

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1502 ◽  
Author(s):  
Mastrocicco ◽  
Busico ◽  
Colombani ◽  
Vigliotti ◽  
Ruberti
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Seawater Intrusion ◽  
Coastal Wetland ◽  
Coastal Lagoons ◽  
Three Dimensional ◽  
Climate Data ◽  
Climate Change Effects ◽  
Modelling Framework ◽  
Groundwater Overexploitation

Coastal freshwater resources are commonly under high risk of being contaminated from seawater. The main processes that affect seawater intrusion are groundwater overexploitation, land use change, and climate change effects. In this context coastal lagoons represent the more sensitive environments prone to seawater intrusion. Numerical modelling is a useful tool to understand and predict seawater intrusion. In this study, a three-dimensional SEAWAT model is employed to simulate the seawater intrusion to coastal aquifers of Variconi Oasis (Italy). The present simulation was divided into a calibration and a validation model, then the model was used to predict the salinization trend up to 2050. Results show the role of the sea in salinizing the beach front, while the retrodunal environment is characterized by transitional environments. Future seawater intrusion scenarios considering only climate data showed no significative differences in respect to the actual situation. The same happens considering also a low sea level rise prediction. On the contrary, the worst scenario (high sea level rise prediction), depicts a quite different situation, with a saline intrusion in the Variconi oasis that will severely affect the fragile transitional ecosystem. This modelling framework can be used to quantify the effects of climate changes in similar coastal environments.

The borehole transient electromagnetic response of a three‐dimensional fracture zone in a conductive half‐space

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1469-1478 ◽  
Author(s):  
Richard C. West ◽  
Stanley H. Ward
Keyword(s):  
Half Space ◽  
Fracture Zone ◽  
Geophysical Methods ◽  
Practical Interest ◽  
The Body ◽  
Secondary Response ◽  
Direct Integral ◽  
Transient Electromagnetic ◽  
Integral Equation Formulation ◽  
Tem Method

Borehole geophysical methods can be useful in detecting subsurface fracture zones and mineral deposits which are nearby, but not intersected by boreholes. One electrical borehole technique which can be applied to this problem is the surface‐to‐borehole transient electromagnetic (TEM) method. In this method a transmitting loop is deployed on the surface while a receiving coil is moved down a borehole. A conductive, horizontal, tabular body in a homogeneous half space was chosen to simulate a 3-D fracture zone or mineral deposit within the earth. Theoretical borehole TEM responses for several models of practical interest were computed using a direct integral‐equation formulation. The anomalous TEM response (secondary response) is the result of a complex interaction between vortex and galvanic currents within the body. Distortion of the secondary response by the conductive host does not affect the estimate of the depth to the horizontal body but it does lead to erroneous estimates of the conductivity and size of the body. Increasing the resistivity of the host decreases the host effects and increases the peak response of the body. Decreasing the separation between the body and borehole or decreasing the depth of the body increases the secondary response. The decrease in the vortex response due to the decreased coupling when a transmitting loop is offset from the body is nearly countered by an increase in the galvanic response at late times; however, this phenomenon is model‐dependent. This study indicates promise for the borehole TEM method, but the application of the technique is limited by the hardware and modest modeling capabilities presently available.

scholarly journals Mapping Saltwater Intrusion using Transient ElectroMagnetic Data in Maopa, Central Province, Papua New Guinea

2021 ◽  
Author(s):  
◽  
Ronald Verave
Keyword(s):  
Papua New Guinea ◽  
Saltwater Intrusion ◽  
Groundwater Resources ◽  
Cost Effective ◽  
New Guinea ◽  
Small Island ◽  
Mixing Zone ◽  
Low Resistivity ◽  
Transient Electromagnetic ◽  
Tem Method

<p>Saltwater intrusion studies in coastal Papua New Guinea (PNG) are a rarity despite recognized vulnerabilities to salination of coastal groundwater resources. For many seaside communities such as Maopa the threat of salination is exacerbated by high extraction rates by a growing population and the likelihood of the effects of climate change. Saltwater intrusion can be addressed using various methods, including direct water sampling from wells and electrical resistivity measurements. This study advances knowledge of a previous assessment of saltwater intrusion and groundwater in this region that used DC Schlumberger resistivity soundings, through an extensive and cost-effective Transient ElectroMagnetic (TEM) survey. The study aims to map the lateral and vertical extent of salination and the characterization of groundwater in the landward direction over seven lines of TEM soundings along Keakalo Bay. The TEM method proved successful in identifying four main geoelectric layers. The top layer has a highly variable resistivity (range of 5 to 355 Ωm) inferred as the vadose zone. Beneath this layer is a layer of intermediate resistivity (100 Ωm > p ≥ 20 Ωm) characterizing a perched freshwater aquifer with a thickness range of 3.2 to 15 m. An intermediate layer of low resistivity (20 Ωm > p ≥ 3 Ωm) was detected at the boundary separating the freshwater aquifer from the inferred saltwater intrusion. This layer is typically thicker than the freshwater aquifer and is referred to as the mixing zone. The deepest layer constituting the salination zone has a very low resistivity (3 Ωm > p ≥ 0.4 Ωm), occurring at depths of up to 42 m. The depth to the salination zone varied from deep in the middle of the survey area to shallow in the fringes of the survey. This pattern is reflective of surface seawater infiltration marked by mangrove forest in the interior and subsurface infiltration from the coast. Similar depth trends but at shallower depths were also observed for the mixing zone, and the freshwater region. In some cases the mixing area overwhelms the freshwater regions. Layering confirmed groundwater resource and salination patterns as those of basic models reflective of small island hydrology, except that salination and the freshwater boundary were less distinctive due to the relatively high thickness of the dispersion zone. The use of different sounding parameters in line 7 provided useful information about the nature of the deep basement unit and thickness of the overlying unconsolidated quaternary sediment.</p>

Sign in / Sign up

Export Citation Format

Share Document