Hydraulic Transmissivity Research Articles

Estimation of main aquifer parameters using geoelectric measurements to select the suitable wells locations in Bahr Al-Najaf depression, Iraq

The aquifer parameters like hydraulic conductivity and transmissivity are extremely important for the management and development of groundwater resources. Vertical Electrical Sounding (VES) and 2D Electrical Resistivity Imaging (ERI) techniques were adopted for geophysical investigation in Fadaq plantation area within Bahr Al-Najaf depression, Iraq. A total of 22 VES point distributed as a grid along six profiles in the plantation with half-current electrode spacing (AB/2) is 400 m are used to evaluate the aquifer geoelectric and hydraulic parameters, where six 2D ERI profiles were conducted and concatenated as one 2D ERI profile with a total length of 4525 m to verify the results of VES. The average formation factor of the aquifer is 22.33 with porosity and water saturation average of 22.62% and 0.59% respectively. Geoelectric and hydraulic parameters estimated values are; apparent resistivity 2.17–2.92 Ω, formation factor 6.23–31.18, porosity 17.91–40.06%, water saturation 0.18–0.85, longitudinal conductance 1.60–10.06 Ω-1, transverse resistance 3258–27200 Ωm2, hydraulic conductivity 0.62–0.68 m2/day and transmissivity 70.68–198.05 m2/day. The thickness and bulk resistivity vary between 112 and 320 m and 18–85 Ωm respectively. About 26% of the aquifer in the study area has an intermediate designation, while 73.91% of the aquifer has high designation. There is a linear relationship between transmissivity and water saturation. Based on designation, protective capacity, and groundwater supply potential VES 6C, VES 7A, VES 4C and VES 2E were recommended for new drilling sites.

Quantitative and Qualitative Appraisals of Aquifer Properties in Kachia Area of Kaduna State, Nigeria

Kachia Local Government Area (LGA) is located at the southern part of Kaduna State, Nigeria. Quantitative and qualitative appraisals were carried out in order to have proper understanding of the aquifer system and ensure sustainable development by using geophysical, geological and pumping test data obtained from 32 producing boreholes across the entire LGA. Hydraulic conductivity, transmissivity and storativity values were computed, piezometric surface map and the basement relief map were prepared, geoelectric layer characteristics were delineated and two geological profile sections were constructed. The hydraulic conductivity values were found to range from 0.021 m/day at Walijo to 1.391 m/day at Iddah-Hanya with an average of 0.42 m/day. The transmissivity values ranged between 0.90 m²/day at Walijo to 25.37m²/day at Iddah-Hanya, with average value of 6.31 m²/day. Storativity values were lowest at Walijo with a value of 89.42 and highest at Iddah-Hanya having a value of 2877 with an average of 929.82. The lowest values of these three aquifer constants were observed to converge at Walijo at the extreme eastern part and they all peaked at Iddah Hanya on the western border of the study area. The piezometric surface contour map showed that static water level is generally deeper around the central part of the study area than at the southern and western parts. The basement relief map revealed that the depth to Basement rock is generally deeper at the central part than at the eastern, western and southern boundaries of the study area. Three-layer geoelectric horizons delineated agreed with the drilled sections. The two profile sections 1 and 2 suggested that the weathered layer constituted the major aquiferous unit, and it occurred within a depth of 1 m to as much as 35 m, except Kurmin-Sara with 80 m thickness. Groundwater prospecting can therefore be targeted to an approximately uniform regolith thickness across the entire study area.

Geohydraulic Study of Aquifer characteristics in Parts of Enugu North Local Government Area of Enugu State using electrical resistivity soundings

Geophysical survey employing Vertical Electrical Sounding (VES) was achieved in Enugu State College of Education (Technical). Schlumberger electrode configuration was used in acquiring the data which was interpreted using the WinrResist software. Four to five geoelectric layers were delineated from the interpreted results. The hydraulic parameters (hydraulic conductivity, porosity, formation factor, tortuosity and transmissivity) were estimated from the values of resistivity and thickness which are primary geoelectric parameters. The result shows the hydraulic conductivity varying from 2.71 to 70.45m/day, transmissivity: 49.2288 to1127.944 , porosity: 33.71 to 49.44%, formation factor: 0.0014 to 0.0026 and tortuosity: 0.2667 to 0.2935. The zones with high and low values of these parameters were delineated. The potentiality of the aquifer units show moderate to high, a reflection of the heterogeneity of the subsurface which is affected by the composition and geometry of the formation. The result from this study provides some important conclusions for future groundwater exploration and management.

A review on design, material selection, mechanism, and modelling of permeable reactive barrier for community-scale groundwater treatment

Over the last thirty years, several techniques of groundwater (GW) remediation based on the principles of physical (air sparging), biological (bioventing), and chemical (e.g., ion exchange) processes have proven to be effective; however, only a handful of them could successfully be implemented at a community or regional scale due to issues like longevity, a requirement of significant investment and operation cost, skilled labours, and others. Therefore, considering the scope of Permeable Reactive Barriers (PRBs) to be implemented on a regional scale and its capability to be a significant replacement for several existing GW treatment methods, this review was prepared with the following objectives: (i) to compare the PRB method with the conventional methods of groundwater treatment along with the possibility and problems associated with the PRB installation in pilot-scale; (ii) to enlist all the probable sets of adsorbents (reactive materials) that can be used for different types of organic and inorganic contaminants; (iii) to understand the key mechanisms of degradation/removal of contaminants involved in PRB design; and (iv) to put forward the future research perspectives of this domain. Review augments that PRBs certainly has a low maintenance cost and a longer life span of ̃30 years that requires very ordinary skills. PRBs promise to be effective in developing countries like India, Bangladesh, and Sri Lanka for the removal of geogenic contaminants like arsenic and fluoride given the appropriate aquifer depth and hydrogeological settings like hydraulic gradient and transmissivity. Furthermore, reactive fillers required in PRBs are readily available, have longer expected life, and operate with no surrounding disturbances. With the advent of several green nanomaterials based adsorbents, PRB’s performance can achieve another height, but it needs the experiences from several pilot and larger scale projects. Indeed PRBs are the need of the hour, but a more programming-based investigation would be expected for its superior comprehension.

Estimation of hydraulic parameters by using VES sounding and neural network techniques in the semi-arid Khanasser valley region, Syria

This paper discusses the in near–real time processing of Global Navigation Satellite An alternative approach based on using Vertical Electrical Sounding (VES) measurements and Artificial Neural Network (ANN) technique is newly proposed for computing the hydraulic conductivity K and the transmissivity T of an aquifer. VES measurements in the locations, where available water samples exist are required in such an approach, in order to train a neural network with fitting capability to evaluate both the hydraulic conductivity and transmissivity. The hydraulic conductivity and transmissivity are thereafter extrapolated by the use of trained neural network, even in the VES points where no water samples exist. This approach is practiced and tested in the Khanasser valley, Northern Syria, where the hydraulic conductivity and the transmissivity of the Quaternary aquifer is computed. We find an acceptable agreement between the hydraulic conductivity values obtained by the new approach and those obtained by the pumping test, which range between 0.864 and 8.64 m/day.

Fracture Flow Characterization with Low-Noise Spontaneous Potential Logging.

Geophysical well logging has been applied for fracture characterization in crystalline terrains by physical properties measurements and borehole wall imaging. Some of these methods can be applied to monitor pumping tests to identify fractures contributing to groundwater flow and, with this, determine hydraulic conductivity and transmissivity along the well. We present a procedure to identify fractures contributing to groundwater flow using spontaneous potential measurements generated by electrokinetic processes when the borehole water head is lowered and then monitored while recovering. The electrokinetic model for flow through a tabular gap is used to interpret the measured data and determine the water head difference that drives the flow through the fracture. We present preliminary results at a test site in crystalline rocks on the campus of the University of São Paulo.

Geohydraulic study of aquifer characteristics in parts of Enugu North Local Government Area of Enugu State using electrical resistivity soundings

Geophysical survey employing vertical electrical sounding (VES) was achieved in Enugu State College of Education (Technical). Schlumberger electrode configuration was used in acquiring the data which were interpreted using the WinResist software. Four to five geoelectric layers were delineated from the interpreted results. The hydraulic parameters (hydraulic conductivity, porosity, formation factor, tortuosity and transmissivity) were estimated from the values of resistivity and thickness which are primary geoelectric parameters. The result shows the hydraulic conductivity varying from 2.71 to 70.45 m/day, transmissivity: 49.2288–1127.944 m2/day, porosity: 33.71–49.44%, formation factor: 0.0014–0.0026 and tortuosity: 0.2667–0.2935. The zones with high and low values of these parameters were delineated. The potentiality of the aquifer units show moderate to high a reflection of the heterogeneity of the subsurface which is affected by the composition and geometry of the formation. The result from this study provides some important conclusions for future groundwater exploration and management.

GEOELECTRIC STUDY OF GROUNDWATER REPOSITORY IN PARTS OF AKWA IBOM STATE, SOUTHERN NIGERIA

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.

Determination of aquifer parameters from geosounding data in parts of Afikpo Sub-basin, southeastern Nigeria

Aquifer parameters (e.g. hydraulic conductivity and transmissivity) are routinely determined from pumping tests. Pumping tests are very expensive and researchers have continued to explore cheaper and reliable alternatives to determine these parameters at locations without producing wells. Electrical resistivity method was applied to determine hydraulic conductivity and transmissivity in areas without boreholes in the present study area. Fifteen (15) vertical electrical soundings with a maximum current electrode spacing of 300 m, in the Schlumberger configuration, were acquired. Seven (7) of the soundings were carried out near existing boreholes for comparative analysis between geologic and geoelectric sections. Modelling was done using the IPI2™ software. Cross-plot of hydraulic conductivity (K) obtained from pumping tests and aquifer resistivity (ρ) extracted from sounding interpretations was used to generate a linear relation of the form K = 0.0426ρ + 0.8584. A similar cross-plot between transmissivity (T) and transverse resistance (R) gave another linear relation of the form T = 31.92–0.0019R. These relations, which connects geoelectrical properties with aquifer hydraulic properties, were used to estimate aquifer properties in areas away from well locations. Results show that depth to water ranges from 11.5 m at Mgbom to 52.1 m at Immama Ozizza, while aquifer thickness varies from 14 m at Poperi Primary School, Amasiri (VES 1) to 47.6 m at Immama Ozizza (VES 11). Hydraulic conductivity values range from 1.344 m/day at Mgbom (VES 2) and 2.792 m/day at Okpotokun Primary School Amata-Akpoha (VES 15), with a mean of 2.068 m/day. Transmissivity on the other hand varies between 28.18m2/day at Immama Ozizza (VES 11) and 31.73 m2/day at Mgbom (VES 2) with a mean of 29.96 m2/day. The derived results correlates well with those obtained from pumping test analysis and have provided a cost-effective method for estimating aquifer hydraulic parameters in areas away from well locations.

Hydraulic properties determination from pumping test in Northern areas of Ondo state, South-western Nigeria for groundwater development

Groundwater potential evaluation of the Northern area of Ondo State using information obtained from hydrogeological measurements of hydraulic conductivity, transmissivity, and yield aquifer characteristics from 37 drilled boreholes. These data were analyzed alongside the information gathered during the pumping test at each site which includes drawdown values, static water level, and pumping rate. The average depth of the borehole and installation depth are 30.76 m and 28.9 m respectively. The static water level ranges from 2.7 m to 14.0 m with an average of 6.0 m. The drawdown recorded from the observation wells varies from 1.9 m and 15.1 m. The yield capacity of the boreholes ranges between 0.40 – 2.98 L/s, and an average of 25.5654 m3/d. The values of hydraulic conductivity conducted in the area vary from 0.37 to 23.29 m/d, and an average of 3.67 m/d. The calculated transmissivity for the study area ranges from 4.79 (gneiss) to 165.32m2/d (migmatite) and an average of 30.08m2/d. The values of specific capacity vary from 4.07 – 140.53, while storativity within the range of 0.0002 – 0.001 are the most dominant showing a corresponding low specific capacity values generally less than 10 m2/d. Consequently, specific yield, hydraulic conductivity, and transmissivity values were integrated to generate a groundwater potential map for Ondo Northern area.

Geoelectrical analysis for evaluating the aquifer hydraulic characteristics in Ain El-Soukhna area, West Gulf of Suez, Egypt

ABSTRACT Ain El-Soukhna area is an important industrial area for building and construction, so we used the subsurface shallow geophysical method, as represented by geoelectric resistivity measurements (Vertical Electric Sounding (VES)). These are processed and interpreted in the forms of a geologic model composed of five geoelectric layers of varying resistivities, lithologies, depthsand thicknesses. The thickness and true resistivity maps of the different layers and 2D geoelectric cross sections are generated for the represented layers to delineate their spatial distribution. The geoelectric Dar-Zarrouk parameters (Transverse Resistance and Longitudinal Conductance) were used to evaluate the electric anisotropy and aquifer hydraulic characteristics; such as hydraulic conductivity and transmissivity within the aquifer, as well as the groundwater quality (salinity of the aquifer) are estimated the true resistivity values acquired on the surface through the geoelectric resistivity survey.

Geoelectrical analysis for evaluating the groundwater characteristics of wadi El Madamud Area, Southeast Luxor, Egypt

In this work, the totally 31 Vertical Electric Soundings (VESes) were carried out at wadi El Madamud, Southeastern Luxor city. These are processed and interpreted the forms of geologic models composed of five geoelectric layers of varying resistivities, lithologies, depths and thicknesses. They are surfacial unconsolidated dry silts, sands and gravels, consolidated silts, sandy gravels, sandstone and clay saturated with water, clay with unsaturated sand intercalations and chalky limestone with chert bands. The surficial layer, dry silts, sands and gravels layer (Quaternary) is cropped out on the surface of the whole area with a very small thickness range (0.5-2.2 meter (m.)) and average thickness 1.1 meters. The surficial layer, Unconsolidated wadi deposits composed of silts, sands and gravels which show the highest resistivity range (3073-90,581 Ω.m.) with average value 27,968 Ω.m. throughout the whole study area. The consolidated silt, sandy and gravels is the second geoelectric layer, which has decreasing resistivity values than the first layer. Thickness of the second geoelectric layer ranges from 1–14 meter. The third geoelectric layer is sandstone and clay saturated with groundwater, which has resistivity range from 4 to1887 Ω.m. and average value 234 Ω.m. and thickness range from 18 to 41 meters with average 21.3 meters. The main target is the shallow aquifer which represented in third geoelectric layer. The clay with unsaturated sandstone intercalation is forth geoelectric layer and has resistivity range from 11 to 10,700 Ω.m. and thickness ranges from 44 to 83 m. The last geoelectric layer is the chalky limestone with chert band, having a wide resistivity range (264–37,045 Ω.m.) with non-defined thickness. The thickness and true resistivity maps of the different layers and 2D geoelectric cross sections are generated for the represented layers to delineate their spatial distribution. The aquifer hydraulic characteristics; such as hydraulic conductivity and transmissivity within the salty aquifer, as well as the groundwater quality (salinity) are estimated, utilizing the true resistivity values acquired on the surface through the geoelectric resistivity survey.

Empirical Relations Between Aquifer Geohydraulic–Geoelectric Properties Derived from Surficial Resistivity Measurements in Parts of Akwa Ibom State, Southern Nigeria

Aquifer geohydraulic properties such as hydraulic conductivity and transmissivity are very vital parameters in groundwater resource management and exploitation. In this study, electrical resistivity investigation was carried out using a SAS 4000 model of ABEM Terrameter and its accessories. Altogether, 13 locations were considered for vertical electrical soundings across the area of study using the Schlumberger array and a maximum current electrode separation AB of 400 m. The results of the sounding interpretation reveal that the study area comprises four geoelectric layers with their characteristic resistivities and thicknesses. The third layer interpreted as saturated coarse sand constitutes the major aquifer in the area with a resistivity range of 50.3–2088.9 Ωm and thickness of 14.9–81.7 m. The estimated aquifer transmissivity ranges from 10.5 to 178.7 m2/day, while the hydraulic conductivity ranges from 0.71 to 4.05 m/day. Least-squares regression analysis was utilized to establish empirical relations between the aquifer geoelectric and geohydraulic properties. The established relations show excellent correlations, showing that aquifer geohydraulic properties can be estimated with high degree of confidence from surface resistivity data at ease and less cost in the area and other areas with similar geology.

From the design of bottom landfill liner systems to the impact assessment of contaminants on underlying aquifers

The most recent advancements of the research activity that has been carried out at the Polytechnic University of Turin since the 1990s are presented, with a focus on the design approaches which can be adopted for the optimisation of the engineered clay barriers that are used as a part of the composite liners of solid waste landfills. A particular attention is devoted to the characterisation of the geosynthetic clay liners (GCLs) in terms of their microstructural features and semipermeable properties, which affect both the liquid and contaminant transport and the swelling–shrinking behaviour upon a variation in the chemical and mechanical boundary conditions. In the first part of the paper, novel analytical solutions are derived in order to account for the influence of the chemico-osmotic counter-flow on the leakage rate through a lining system that consists of a geomembrane (GM) overlying a GCL, as well as for the effect of a variation in the GCL swelling pressure on the hydraulic transmissivity of the GM–GCL interface. In the second part of the paper, a steady-state analysis approach is proposed with the aim to include all the aforementioned phenomena in the assessment of the impact of contaminant migration through the landfill bottom liners on the groundwater quality, taking into account the presence of a natural attenuation layer between the GCL and the underlying aquifer.

Characteristics and Productivity of Volcanic Rock Aquifers in the Upper Part of Blue Nile Basin, Ethiopia

This study was conducted in the upper parts of the Blue Nile Basin, Ethiopia, with the objective of characterizing the different volcanic rock aquifers and evaluating their respective productivity. Geological, structural and hydrogeological methods were utilized in this study. Quaternary vesicular basalt (27.33%) and Tertiary aphanitic basalts (72.67%) are the two geological formations in the basin. In both cases, the weathered and fractured zones are the water bearing zones. Confined aquifer, multilayer confined aquifer and multilayer unconfined–confined aquifer are the types of aquifers identified in the basin. The computed values of the hydraulic conductivity, transmissivity and specific capacity for the multilayer unconfined-confined aquifers ranges from 0.165 to 49 m/day, 11.30 to 3870 m2/day, and 0.164 to 30.968 l/sec/m, respectively. The computed hydraulic conductivity, transmissivity and specific capacity for the multilayer confined aquifer are 0.525 m/day, 10.9 m2/day and 0.190 l/sec/m, respectively. The hydraulic conductivity, transmissivity and specific capacity for the confined aquifer are 6.46 m/day, 148 m2/day and 1.363 l/sec/m, respectively. Based on the analyzed results of transmissivity and specific capacity, three aquifer potentiality groups were recognized: high potentiality aquifer, moderately potentiality aquifer and low potentiality aquifers. For sustainable groundwater management in the basin, development of groundwater should take place in the area covered by high potentiality aquifer by considering the whole thickness of the aquifers.

Hydraulic tomography in time-lapse mode for tracking the clogging effects associated with the colloid injection

Clogging due to transport and accumulation of the colloids in the pore space has been recognized as one of the most significant challenges in water management research and environmental engineering. This paper proposes an inversion algorithm in time-lapse mode to track that complex process through the assessment of alteration in the transmissivity field produced by the injection of colloids. The concept is based on a joint inversion of hydraulic head and colloidal particles concentration data acquired during the injection of colloids in the porous aquifer to reconstruct the spatial variability of the transmissivity field at different times. The inversion code is deterministic and was implemented in the time-lapse scheme by adding in the objective function a temporal geostatistical constraint to control changes of the hydraulic transmissivity. This algorithm is linked to a forward problem that consists of the groundwater flow and transport equations, which were solved numerically and jointly by considering the effect of particles deposition on the decrease of hydraulic properties. As the inverse problem is deterministic and underdetermined, we have opted to use the efficient adjoint state technique to derive the sensitivity matrices. The approach has been successfully applied to a theoretical case in which the hydraulic head responses have been used alone and jointly to assess the evolution of the clogging impact on hydraulic transmissivity.

Conceptual hydrological approach to a geologically complex basin with scarce data: the Hula Valley, Middle East

The Hula Valley in the Middle East is a cross-border hydrogeological system. A highly complex hydrogeological framework and the absence of production or even observation wells poses difficulties in modeling this hydrogeological basin. Various tools were used to overcome the scarcity of data and the hydrogeological complexity to create a reliable conceptual hydrological model. The isotopic δ18O ratio was used to distinguish between two hydrogeological units in the alluvium fill of the valley, which are recharged from the different regional and local aquifers surrounding it. Abundant gas boreholes that discharge a mixture of natural gas and groundwater were equipped, measured and sampled to obtain valuable hydrological data such as hydraulic head and transmissivity of the hydrogeological units in the valley. These findings were integrated with geological analyses of the subsurface flow domain to construct the first conceptual hydrological model of the unclear Hula Valley groundwater flow system. The described methodology to overcome lack of hydrogeological data might be relevant to complex hydrogeological basins worldwide with scarce hydrological information.

Effects of Drainage for Silviculture on Wetland Hydrology

Wetland silviculture on the Southeastern Coastal Plain attempts to balance competing objectives of draining topsoils sufficiently to provide access and promote tree growth while maintaining hydric soil characteristics in compliance with the Clean Water Act. This balancing act is dynamic as soil hydraulic properties, and thus water table regimes, change over the stand rotation cycle. Previous studies have defined threshold ditch spacings that would sustain wetland hydrology on a wide range of poorly drained coastal plain soils in US southeast. There is strong evidence that the hydraulic conductivity (K) and transmissivity (T) of the soil profile increase as trees mature. Such changes increase drainage rates, lower water tables, and potentially remove wetland hydrology from drained sites. Results from a long term forested watershed study showed that T of the profile decreased from 50 m2/d under a mature loblolly pine plantation to 5.5 m2/d after harvest and site preparation for regeneration, and then increased to 34 m2/d by 8 years after replanting. Based on these results, a modeling case study was conducted to determine the effects of changes in soil properties on wetland hydrology for a pine plantation. Results showed that 90 cm deep drainage ditches would have to be more than 62 m apart in a young plantation (YP) to sustain wetland hydrology on a site with 15 cm of surface storage. Increases in K and T as the plantation matures increased the predicted threshold spacing (LT) for wetland hydrology from 62 m for YP to 290 m for a mature plantation (MP). For ditch spacings greater than LT, wetland hydrology will be sustained in a broad center section midway between ditches, with the width of the wetland section dependent on ditch depth, spacing and soil properties. Methods developed to estimate the lateral effect of a single ditch on wetland hydrology were used to determine the width of a strip adjacent to the ditch where wetland hydrology is not sustained, and, thereby the percentage of wetland loss from the plantation. Depending on ditch depth, wetland hydrology will not be sustained on 14 to 27% of the land area for a 200 m ditch spacing on the young plantation of the case study. As the plantation matures (to MP), wetland hydrology will not be sustained for normal ditch spacings (100 to 200 m) on these soils. More research is needed to determine effects of stand age and production practices on hydraulic conductivity for a wide range of drained soils. Wetland hydrology can be enhanced by limiting depth and increasing spacing of drainage ditches, by use of control structures in some cases, and by allowing field ditches to fill naturally as plantations mature.

Landslide susceptibility mapping using sinmap method in a small hilly area: case study in Cibanteng Village, West Java

This paper presents the results of landslide susceptibility mapping in small hilly areas, Cibanteng village, Cianjur district, West Java. In this study. the physically-based model SINMAP (Stability Index Mapping) was applied in the GIS platform. The SINMAP model simulation requires data of physical properties of soil, such as cohesion value, internal friction angle, and soil hydrology to calculate the value of factor of safety (FS). The values of cohesion and fraction angel for the 10 sample points were obtained from the laboratory test results, while the value of soil hydrology, i.e hydraulic conductivity, transmissivity, effective rainfall and index wetness, referred to the literature source. The DEM (digital elevation model) was generated from the 1:25,000 digital topographic map, which produced the soil slopes and specific upstream contributing areas. The result of SINMAP model simulation shown that the regions with a high landslide susceptibility (FS <1, unstable) were spread unevenly with an area of 261ha (17,6% of the study area). The Landslide susceptibility map from the SINMAP model provided a satisfactory result with an accuracy of 62,5% against to the landslide events occurred during the period 2010-2017.

Geophysical and physicochemical investigation of groundwater repositories in Njaba LGA of Imo State, eastern Nigeria

Geoelectric survey integrated with physicochemical method of water analysis was used to investigate the aquifer repositories in Njaba, Imo State, eastern Nigeria. This was done in 15 locations using vertical electrical sounding (VES) employing Schlumberger electrode configuration, and water samples from four boreholes were analyzed in the laboratory. The resistivity data were interpreted using forward and iterative least square inversion modeling of WINRESIST software. Four to six geoelectric layers and the VES characteristic curve types were obtained. The resistivity values vary across the study area with their respective depths and thicknesses. The aquifer resistivities range from 402.50 to 16,484.40 Ωm. The hydraulic parameters estimated include: Dar Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The longitudinal conductance ranges between 0.0004 and 0.0763 Ω−1, and transverse resistance ranges between 6823.40 and 245,320.00 Ωm2. The range of hydraulic conductivity and transmissivity varies from 0.0450 to 1.4363 m day−1 and 0.3195 to 44.0944 m2 day−1, respectively. The contour maps generated using Surfer software package displayed the variations of these parameters across the study area. The results obtained indicate that the study area has low groundwater potential based on the transmissivity values and may be prone to surface contamination due to its poorly protected aquiferous units. The concentrations of the ions in the water samples measured were compared with the World Health Organization (WHO) standard for drinking water and were found to be below WHO standard. The sodium percentage and sodium absorption ratio were calculated in order to determine the suitability of the groundwater for agriculture.