1 Introduction

1.1 Background

Access to potable and sustainable water supply is a fundamental prerequisite for the survival of humans, animals and even plants. It is still a core necessity for the development of thriving communities. While surface water resources may be available, its availability and reliability are often limited, thus, underscoring the crucial role that groundwater plays in meeting the ever-growing water demands of the expanding population. Groundwater has proven over the years to be a dependable source of water for various purposes, including drinking, domestic activities, recreation, irrigation, and livestock farming. In fact, it is estimated that about 85% of total water demand in Nigeria is met by groundwater sources [1].

Shango is situated in a part of Minna, north-central Nigeria. This area is experiencing a surge in population growth and its attendant urbanization challenges. The demand for groundwater resources have been significantly driven by population. Other demands from industries located within the study have put a major strain on water demands. While surface water bodies, such as rivers and lakes, can contribute to the water supply, they often suffer from seasonal variations and are susceptible to pollution. Consequently, the local community in Shango heavily depends on groundwater as the primary source of potable water and for sustaining various economic activities. The sustainable management of groundwater resources in the study area encounters numerous challenges. There are issues of improper waste disposal and other land use practices that may contaminate aquifers, jeopardizing the quality of groundwater and rendering it unsuitable for consumption.

To address these challenges and ensure the sustainable utilization of groundwater resources in the study area, a comprehensive assessment of groundwater potential and aquifer protective capacity of underlying aquifers in the area are imperative. By understanding the hydrogeological characteristics and subsurface geologic structures of the region, effective management strategies can be developed to ensure the long-term availability and quality of groundwater resources. Geo-electric surveys have emerged as a valuable scientific tool for assessing groundwater potential and understanding aquifer characteristics [2,3,4,5].

Geo-electric survey methods involve measuring the electrical resistivity of subsurface materials and interpreting the data to infer the presence and characteristics of aquifers. The valuable information that may be extracted from these surveys include nature of the subsurface lithology, the depth and thickness of aquifers, potential sites for groundwater development. The implementation of effective groundwater development and aquifer protection strategies necessitates a multidisciplinary approach, integrating geological, hydrogeological, and geophysical techniques. By implementing these, a comprehensive understanding of groundwater potential of the area may be attained. Furthermore, this systematic assessment would lead to understanding aquifer characteristics, identification of vulnerable areas, and the formulation of protective measures, to ensure the sustainability and resilience of groundwater resources in the study area.

Several notable researchers, including [6,7,8], have conducted groundwater investigations in and around Minna. However, it is important to note that these hydro-geoscientific studies have not specifically focused on aquifer delineation in most parts of the study area. As a result, the challenge of accessing potable water persists for residents residing in these regions. To address this pressing issue, it is crucial to identify suitable locations for productive hand-dug wells and boreholes, while also characterizing the geological and geo-electrical attributes of existing productive boreholes and hand-dug well sites. Unfortunately, a comprehensive study addressing these aspects has not yet been undertaken in the Shango area.

Therefore, the objective of this research paper is to utilize geo-electric survey techniques and systematic interpretation methods as a scientific approach to assess groundwater potential and the aquifer protective capacity in the area. This will be archived through the provision of insights into the hydrogeological conditions and subsurface lithology of the area. This research also aims to contribute to the development of sustainable groundwater management strategies and promote the long-term availability of safe and reliable water resources for the inhabitants of area.

1.2 Study area

1.2.1 Geology and hydrogeology

The study area is located within the vicinity of Minna, the capital city of Niger State, north-central Nigeria. The coordinate is bounded between latitudes N9º33ʹ00″ to N9º35ʹ00″; and longitudes E6º33ʹ00″ to E6º35ʹ00″, on a topographic map Minna Sheet 164 SW (1:50,000) extending to parts of Shango and Numbupi. The total area coverage is about 15 km2 (Fig. 1).The study area can be easily accessed via a prominent road that runs through the city center. This road serves as a connection between the city gates, the western and eastern bypasses, as well as the minor roads that interconnect different areas within the city. Additionally, there are footpaths that link various houses in the vicinity. The geology of the area is part of the Nigerian Basement Complex and is characterized by rocks that have undergone polyphase deformation and metamorphism. Intruding upon these strata are granitic rocks of Pan-African age. Extensive field investigations within the Minna area have allowed for the identification of five distinct lithologic units: schist, granite, quartzite, granodiorite, and gneiss. Prominent outcrops of granite, schist, diorite, and amphibolites have been observed, indicating their geological significance (Fig. 2) and the presence of deformation features such as fractures, folds and faults facilitate the accumulation of groundwater.

Fig. 1
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Location map of the study area

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Fig. 2
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Geological map of the study area

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The Shango region is located within the crystalline hydrogeological province and comprises two interconnected aquifers: the weathered overburden aquifer and the fractured basement aquifer. According to [9], the overburden aquifer is typically characterized by a relatively unconsolidated material with an approximate thickness of 15 m in Minna and its surrounding areas. Boreholes drilled into this aquifer yield an average water discharge rate of 0.5 L per second. On the other hand, the fractured basement aquifer serves as a secondary and more reliable source of groundwater in the Minna area. Strategically positioned boreholes within the fractured zone can yield an average discharge rate of 1.5 L per second. However, by exploiting both aquifers, optimal yields of up to 5 L per second can be achieved. The replenishment of these aquifers primarily occurs through precipitation in the region, and groundwater extraction is primarily carried out through the utilization of hand-dug wells and boreholes [10].

2 Methodology

The research methodology employed in this study involves a comprehensive approach, beginning with an extensive review of relevant literature and the creation of a detailed map of the study area. Subsequently, a series of field activities were conducted, including a reconnaissance survey, geological mapping, hydro-geological mapping, geo-electric sounding, and the subsequent interpretation of these datasets.

2.1 Geographical and hydrogeological mapping

Geological research was completed by creating a base map from Minna sheet 164 SW and extending it to a scale of 1:10,000 with GPS support. This map was used for geographical and hydrogeological mapping. The inquiry included locating outcrops and categorizing rocks based on how they were formed. A compass clinometer was used to measure the strike and dip, and new rock samples were also obtained. Additionally, water levels in productive hand-dug wells were monitored with a deep meter, and the locations of boreholes and hand-dug wells were geo-referenced using GPS coordinates.

2.2 Geo-electrical sounding

Sixteen (16) Vertical Electrical Soundings (VES) were conducted using the Schlumberger array to identify optimal drilling locations for boreholes and hand-dug wells. The survey was executed in the southward direction, which aligns with the regional groundwater flow, employing a maximum half electrode spread AB/2 of 200 m. Several phases were involved in the survey procedure. Initially, to ensure precise measurements, traverses were established in open areas perpendicular to the NE/SW regional strike.

Following the traverse setup, current and voltage electrodes were positioned at specific locations, and resistance readings were recorded. Gradual extension of the survey layout and incremental increase in the spacing between potential electrodes were implemented to attain potential differences of sufficient magnitude for accurate measurements. For each current electrode spacing, the resistance value R was multiplied by the geometric factor K to determine the apparent resistivity at each survey station.

2.3 Data acquisition

The geophysical investigation employed the electrical resistivity soundings (VES) method utilizing the ABEM-Terrameter (SAS1000-Signal Averaging System) Electrical Resistivity equipment in Schlumberger configuration. The measurements were conducted with a maximum current electrode spread AB/2 of 200 m, ensuring adequate depth coverage. A distance of 200 m was traversed towards the right-hand side, while an equal distance of 200 m was covered on the left side. However, due to the presence of valleys, gullies, and residential buildings, offset VES measurements were necessary. All necessary precautions for precise geo-electric measurements were diligently implemented, taking advantage of favorable weather conditions. In all, sixteen VES stations were occupied in the study area.

Figure 3 provides a schematic illustration elucidating the operating principles of electrical resistivity. As the depth of current penetration, known as the depth of investigation, increases, the distance between current electrodes also expands. The A and B electrodes' separation exclusively determines the current penetration, while the depth of examination is governed by the geometric arrangement of all four electrodes (Fig. 3).

Fig. 3
figure 3

Schematic diagram of electrical resistivity operating principles

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The apparent resistivity (\({\rho }_{(a)}\)) of a Schlumberger array measured at a single point with systematically variable electrode spacing is given by:

$${\rho }_{a(s)}=R\pi \left(\frac{{a}^{2}}{b}- \frac{b}{4}\right)$$
(1)

a = (AB/2)—(half current electrode spacing).

b = MN—(spacing between potential electrodes).

The resistance (R) is derived from the current (I) and voltage (V) values using the equation below:

$$\text{R }=\frac{V}{I}$$
(2)

Equation (2) can be written as

$${\rho }_{a(s)}=K\times R$$
(3)

Geometric factor,

$$\text{K }=\pi \left(\frac{{a}^{2}}{b}- \frac{b}{4}\right)$$
(4)

K is a geometric factor that depends on the position of the electrodes in the ground and may be determined for any electrode configuration.

2.4 Date processing

The IPI2WIN software was used to process the vertical electrical sounding (VES) data that had been obtained. The program was used to enter the apparent resistivity in response with its AB/2 for additional modelling and iteration. Computer iteration between 1 and 29 was used to minimize mistakes to the desired limit and to increase goodness-of-fit. True resistivity layers were obtained by this procedure, together with the corresponding thicknesses and depths that were employed as Dar-Zarrouk parameters.

2.5 Hydraulic conductivity estimation

Hydraulic conductivity (k) is a crucial parameter in understanding groundwater flow and aquifer potential. In the absence of direct measurements through pumping tests, alternative methods are necessary for its estimation. This study utilizes the Dar Zarrouk parameters and the concept of "real resistivity" to indirectly assess hydraulic conductivity.

2.5.1 Dar-Zarrouk parameters

Dar-Zarrouk parameters can be used as a basis for evaluation of aquifer properties such as transmissivity and protective capacity of overburden rock material [11, 12]. The parameters can be obtained as:

$$H={\sum }_{i=1}^{n}hi$$
(5)

Longitudinal Conductance (S)

$$S=\frac{h1}{\rho 1}+\frac{h2}{\rho 2}+\frac{h3}{\rho 3}+\cdots \cdots \cdots \cdots \cdots \cdots \frac{hn}{\rho n}={\sum }_{i=1}^{n}\frac{hi}{\rho i}$$
(6)

Transverse Resistance (T)

$$T=\rho 1h1+\rho 2h2+\rho 3h3+\cdots \cdots \cdots \cdots \cdots \cdots \rho nhn={\sum }_{i=1}^{n}\rho ihi$$
(7)

Longitudinal Resistivity

$$Rs=\frac{H}{S}$$
(8)

Transverse Resistivity

$$Rt=H*S$$
(9)

where;ρi and hi are the layer resistivity and thickness respectively.

The aquifer transmissivity (Tr) is calculated by multiplying the hydraulic conductivity (k) by the layer thickness (h).

Thus;

$$T=kh$$
(10)

According to [13], in the absence of pumping test data, the true resistivity of an aquifer acquired through geoelectric study can be utilized as aquifer hydraulic conductivity (k).

$$T=kh=\rho h$$
(11)

The transmissivity T (the product of hydraulic conductivity and aquifer thickness) can be derived in terms of R and S as proposed by [14] in Eqs. 12 and 13:

$$T=k\sigma R$$
(12)
$$T=\left(\frac{k}{\sigma }\right)S$$
(13)

It has been observed by [15, 16] that either of the two propositions, \(k\sigma\)= constant or \(k/\sigma\) = constant could be true for an area under study, also valid for other areas with similar geological setting and water quality. As opined by [15], the overall resistivity of aquifer material can correlate with hydraulic conductivity (K) using the relation theorized by [14]

$$k \infty A$$
(14)

where

$$A=\sum {\rho }_{i}$$
(15)

In the context of this study, the variable i represents distinct layers within the aquifer. It is widely acknowledged that changes in resistivity result from the diverse compositions of geological formations and their characteristic variations. Previous researches have extensively explored the correlation between aquifer parameters and geo-electric properties across various geological configurations, as extensively detailed in the introduction section. In the current investigation, the correlation between transverse resistance and aquifer transmissivity, as well as the relationship between total resistivity and hydraulic conductivity, is examined to elucidate functional analogous connections specific to the study area.

2.6 Data interpretation

The relationship between apparent resistivity and electrode separation gives rise to various types of field curves. By considering the available geological information and borehole data, valuable insights into the subsurface conditions can often be inferred. The interpretation of Vertical Electrical Sounding (VES) data involved two stages: The first stage entailed qualitative interpretation, involving the examination of field curve types and their quality. Apparent resistivity profiles were constructed alongside pseudo-sections, enabling a visual and qualitative assessment of the successive geo-electrical zones. This preliminary evaluation aided in understanding the detected subsurface features. The second stage involved quantitative interpretation, which included determining the resistivities and thicknesses of the different subsurface zones. Geo-electrical sections were created, and these sections were then converted into geological sections by integrating lithological information from existing wells and other available sources. The absence of such data could present challenges, particularly when dealing with field curves associated with more than three layers [17].

Following the representation of observed field data as curve types, resistivity profiles, and litho-logs (Figs. 4 and 5), qualitative interpretation was performed. The goal of this interpretation was to conduct preliminary evaluation of the detected geo-electrical zones. By utilizing the entire field curves, resistivities, thicknesses, and depths of the respective geo-electrical zones were calculated. These results were further employed in constructing geo-electric sections. Ultimately, these findings were compared and correlated with available geological information pertaining to the study area, enabling a comprehensive understanding of the subsurface conditions. Manual interpretation outcomes could be complemented by computer software programs that employ forward calculation and inverse modelling techniques [18].

Fig. 4
figure 4

Typical computer modelled curve showing modelled curve, theoretical curve and litho-log

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Fig. 5
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Histogram of different curve types in the study area

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3 Results and discussion

3.1 Qualitative interpretation of field data

Qualitative interpretation can be achieved for all the types of field curves and the numbers of their layers. The types of the curves can give a general idea about the depths of different geo-electrical zones through their inflection points, but it should be considered that the inflection points may result from the lateral variations of the electric resistivity [19, 20].

3.2 Modelled curve interpretation

The characteristics of each VES location are revealed by curve matching and computer modelling, as shown in Fig. 4. The geologic and geo-electric layers provide the essential interpretation, whilst the quantity of layers and the curve's form define other properties, such as layer thickness, resistivity, and depth [15]. Quantitative analysis is provided by the identified curve types, which range from simple to sophisticated.

Each VES curve has five layers. The prevalent curve type is HH, which accounts for 33.33% of all VES done in the research area (Fig. 5). HK and KA curve types account for 11.11%, and AA, AH, HA, HQ, KH and QA account for 5.55%each.

3.3 Aquifer and Dar-Zarrouk parameters

Aquifer resistivity, conductivity, thickness, transmissivity, longitudinal conductance, transverse resistance, and hydraulic conductance are among the aquifer and Dar-Zarrouk properties. Their values are provided in Tables 1 and 2.

Table 1 Location, resistivity, depth and thickness of delineated aquifer in the study area
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Table 2 Dar-Zarrouk parameters for aquifers in the study area
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3.4 Aquifer resistivity

Aquifer resistivity is a fundamental parameter that provides valuable insights into the electrical resistance of subsurface materials. It is important to acknowledge that the resistivity of rocks and their constituents is directly proportional to their composition and characteristics [21]. Therefore, the aquifer resistivities are influenced by a combination of factors, including the VES data, model curve shapes, and the local geology. Lower resistivity values typically indicate the presence of more conductive and porous materials, such as sand, gravel, or fractured rocks, which facilitate the accumulation and movement of groundwater [22].

In the study area, the VES measurements revealed a range of aquifer resistivity values. Notably, VES 7 exhibited the lowest resistivity value of 182 Ωm, while VES 8 demonstrated the highest resistivity value of 288 Ωm, as depicted in Fig. 6. These findings suggest that the aquifer materials in the study area possess reasonably low resistivity, implying the presence of porous and permeable subsurface materials that promote the flow and accumulation of groundwater [23, 24]. These resistivity values align with the expectation that lower resistivity corresponds to higher conductivity. The porous and permeable nature of these subsurface materials enhances the connectivity and permeability of the aquifer system, enabling groundwater to accumulate and flow more readily. Understanding the resistivity characteristics of the aquifer provides crucial insights into the hydrogeological dynamics of the study area and aids in the development of effective groundwater management and extraction strategies.

Fig. 6
figure 6

2D color contour map of aquifer resistivity of the study area

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3.5 Aquifer thickness

Aquifer thickness played a critical role in characterizing the vertical extent of saturated zones within an aquifer. It serves as a controlling factor in determining the volume of water that can be stored within the aquifer, consequently influencing the potential amount of extractable groundwater [25]. The knowledge of this parameter is essential for comprehending an aquifer's vulnerability to contamination, thereby aiding in the development of appropriate measures for its protection and effective management. In this research, 2D contour map illustrating the aquifer thickness within the study region was produced (Fig. 7). Notably, the thickness of VES 1 exhibited the narrowest extent, measuring 20.10 m, while VES 2 portrayed the maximum thickness, spanning 52.20 m. Furthermore, the northwestern part of the study area showcased the highest values of aquifer thickness, with a notable increase observed from the central region towards the northwestern and south-eastern parts of the study area.

Fig. 7
figure 7

2D color contour map of aquifer thickness of the study area

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The substantial variation in the thickness of aquifers across the area underscores the heterogeneity of the subsurface hydrogeological conditions [26]. The greater thicknesses observed in the northwestern part indicate a potentially higher storage capacity for groundwater, which implies a greater potential for groundwater extraction in this area. These findings bear significant implications for groundwater resource management, as areas with thicker aquifers may offer favourable conditions for sustainable extraction practices. Furthermore, understanding the spatial distribution of aquifer thickness is crucial for identifying areas of potential vulnerability to contamination. Thicker aquifers generally provide a greater buffer against the intrusion of contaminants from the surface, thus exhibiting a higher degree of protection [27]. This knowledge can inform the design and implementation of appropriate measures to safeguard the aquifer and preserve the quality of the groundwater resource [28] (Gaaloul and Eslamian).

3.6 Aquifer depth

The aquifer depth represents the vertical distance between the saturation zone and the overlying zones of aeration, situated above the water table. During rainfall events, water infiltrates through fractures in the soil and rock, descending under the influence of gravity. Consequently, water accumulates and fills the lower region, known as the zone of saturation. Variations in precipitation patterns lead to fluctuations in the position of the water table, impacting the amount of water entering the saturation zone. As water is withdrawn or consumed from the saturation zone, the water table gradually rises, moving further away from the land surface [29].

To visualize the spatial distribution of aquifer depth within the research area, Fig. 8 presents a two-dimensional contour map. Among the VES points, VES 6 exhibited the shallowest depth, measuring 55.6 m, while VES 5 represented the deepest point with an aquifer depth of 68.9 m. These variations in aquifer depth highlighted the heterogeneity of subsurface conditions and the complex interaction between hydrological processes and geological formations [30].Understanding aquifer depth is critical for assessing groundwater availability, evaluating the vulnerability of the aquifer system, and devising effective management strategies. Shallow aquifer depths may indicate areas more susceptible to fluctuations in water table levels and have implications for sustainable groundwater utilization. Conversely, deeper aquifer depths signify greater potential for water storage and can offer more resilience to seasonal variations in precipitation [31].

Fig. 8
figure 8

2D color contour map of aquifer depth of the study area

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The contour map aided in identifying areas of varying aquifer depth, providing valuable information for groundwater resource planning and protection. By comprehending the spatial distribution of aquifer depth, stakeholders can make informed decisions regarding well placement, water extraction, and sustainable groundwater management practices.

3.7 Aquifer transverse resistance

Transverse resistance plays a crucial role in characterizing the resistance encountered by groundwater as it flows laterally within the aquifer. It provides insights into the level of hindrance faced by groundwater moving perpendicular to the hydraulic gradient [30, 32]. The values of the transverse resistance are obtained by multiplying the resistivity of the aquifer with its corresponding thickness across the study area, as illustrated in Fig. 9. Among the VES measurements, VES 16 exhibited the lowest aquifer transverse resistance at 5232.40 Ωm2, while VES 2 demonstrates the highest at 12,267.00 Ωm2. Analysis of the eastern portions of the study area revealed greater values of aquifer transverse resistance.

Fig. 9
figure 9

2D color contour map of aquifer transverse resistance of the study area

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A high transverse resistance indicates a good aquifer with well-defined boundaries and having limited potential for lateral water movement. This has been used to infer good groundwater potential as groundwater is efficiently stored and channeled within the aquifer, enhancing its overall water-holding capacity [33, 34]. Conversely, lower transverse resistance suggests a leaky aquifer without well-defined boundaries, hence, it has increased susceptibility to contaminants infiltrating from the sides. This poses a threat to aquifer protection, as pollutants can readily move and contaminate the available groundwater resources [30].Understanding aquifer transverse resistance is essential for evaluating groundwater flow dynamics, identifying areas of potential groundwater recharge or discharge, and assessing the vulnerability of the aquifer to contamination.

3.8 Aquifer longitudinal conductance

Longitudinal conductance serves as a measure of the ease with which water can flow parallel to the direction of current. It is estimated based on layer thickness and aquifer resistivity. Our study revealed a range of longitudinal conductance values from 4.502 to 13.383 Siemens (Fig. 10), indicating varying degrees of ease for horizontal groundwater flow within the aquifer system. Areas exhibiting higher longitudinal conductance values typically possess favorable conditions for groundwater flow, characterized by well-connected and permeable aquifer materials. These regions are likely to experience enhanced groundwater movement, potentially leading to higher yields. Conversely, lower longitudinal conductance values may suggest restricted or limited groundwater flow, which can be attributed to less permeable or discontinuous aquifer formations [35].

Fig. 10
figure 10

2D color contour map of aquifer longitudinal conductance of the study area

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In the context of aquifer protection and sustainable groundwater management, a thorough understanding of longitudinal conductance plays a crucial role. It helps identify areas with significant groundwater potential, aiding in the determination of appropriate well placement, extraction rates, and aquifer recharge strategies. By leveraging knowledge of longitudinal conductance, effective measures can be implemented to ensure the optimal utilization and protection of groundwater resources.

3.9 Aquifer hydraulic conductivity

Hydraulic conductivity stands as a pivotal parameter in the assessment of groundwater potential and aquifer protective capacity, playing a crucial role in understanding the ability of subsurface materials to transmit water. In this study, the hydraulic conductivity values were within a range of 0.465 m/day to 0.534 m/day, which effectively reflect the spatial variability of water flow through the subsurface (Fig. 11). Notably, higher hydraulic conductivity values signify increased permeability and improved connectivity, thereby facilitating efficient groundwater movement and, consequently, potentially yielding higher water extraction rates. Conversely, lower values indicate areas characterized by reduced permeability, effectively impeding groundwater flow [36].

Fig. 11
figure 11

2D contour map of aquifer hydraulic conductivity of the study area

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Gaining a profound understanding of the hydraulic conductivity patterns holds paramount importance in optimizing well placement strategies and devising sustainable groundwater extraction methods. Consequently, it enables us to make informed decisions regarding the preservation and management of precious groundwater resources. It is worth highlighting that the determination of hydraulic conductivity values through the utilization of Vertical Electrical Sounding (VES) measurements significantly contributes to unravelling the intricate dynamics of groundwater within the study area. This methodological approach provides invaluable insights into the subsurface’s capability to transmit water and, consequently, proved instrumental in assessing groundwater potential and safeguarding the integrity of aquifer systems. By employing the VES technique, we can acquire reliable data, thus fortifying the scientific foundation of our study and enhancing its credibility.

3.10 Aquifer transmissivity

Transmissivity is a crucial parameter that quantifies an aquifer’s ability to transmit groundwater across its saturated thickness. It represents the volume of water that can flow through a unit width of the aquifer under specific hydraulic gradient conditions. The transmissivity values range from 9.589 m2/day at VES 1 to 26.029 m2/day at VES 2, indicating variations in the groundwater flow capacity across the study area. Figure 12 offers valuable insights into the spatial patterns of aquifer transmissivity in the study area. Higher transmissivity values signify greater permeability and hydraulic connectivity, facilitating efficient groundwater movement and potentially higher yields. Conversely, lower transmissivity values suggest areas with reduced permeability, limiting the groundwater flow potential. This information aids in optimizing well placement and designing sustainable extraction strategies, considering the varying transmissivity characteristics across the study area. Understanding the distribution of aquifer transmissivity is crucial for assessing groundwater availability, optimizing resource utilization, and implementing effective management practices.

Fig. 12
figure 12

2D contour map of aquifer transmissivity of the study area

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The categorization of aquifers according to their transmissivity rating is illustrated in Table 3 and Fig. 13.

Table 3 Classification of transmissivity magnitude and variation in the study area [37]
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Fig. 13
figure 13

Histogram for groundwater supply potential and designation of aquifers in the study area

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The findings indicated that most aquifers in the study area are classified as intermediate in terms of their designation and withdrawal potential for local water supply, including small communities and plants. However, VES 1 stands out with a low designation and smaller water extraction potential for local water supply, primarily for private consumption (Table 4). These results provided valuable insights into the groundwater supply potential across the study area, enabling stakeholders to make informed decisions regarding water resource management and sustainable utilization for different purposes.

Table 4 Classification of Aquifer Based on Transmissivity (Modified after [38]
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3.11 Soil corrosivity and protective capacity

Aquifer protective capacityrefers to an aquifer's capacity to slow and filter contaminated groundwater that percolates from the surface. An aquifer’s vulnerability to pollution intrusion depends on the properties of the materials or layers that make up its overburden. Oladapo and Akintorinwa in [39] asserted that an aquifer's capacity to provide protection is directly related to the longitudinal conductance of the units above the aquifer. Table 5 and Fig. 14 presents the protective capacity and soil corrosivity of aquifers in the research region, providing valuable information for evaluating the potential corrosiveness of the soil at shallow depths. This assessment is particularly relevant when considering the installation of metal pipes or buried utilities for groundwater development and other engineering purposes. Corrosive regions are characterized by lower resistivity values, while non-corrosive areas exhibit higher resistivity values [40]. The protective capacity of a soil medium is determined by its ability to attenuate and filter percolating fluids [41].

Table 5 Rating of protective capacity and soil corrosivity
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Fig. 14
figure 14

Histogram for soil corrosivity and aquifer protective capacity aquifers in the study area

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As argued by [42], the effectiveness of an overburden layer in protecting against seeping contaminants is inversely related to its hydraulic conductivity and is influenced by its thickness. Clayey materials generally exhibit characteristics of low permeability, resistivity, hydraulic conductivity, and longitudinal unit conductance [43]. Consequently, there exists a linear relationship between protective capacity and longitudinal conductance, with the protective capacity increasing in proportion to the overburden’s longitudinal conductance. Electrical resistivity, as highlighted by Braga in [44], is a crucial property for characterizing various geological materials, providing insights into their alteration, fracture, and water saturation levels. This property enables the identification of different lithologies without the need for expensive excavation or time-consuming drilling.

The VES Schlumberger array provided valuable outputs, including electrical resistivity, groundwater level depth, and the Dar Zarrouk parameter longitudinal conductance. These outputs hold significant importance, especially in the initial phases of environmental studies. By utilizing the Dar Zarrouk method, it became possible to establish correlations between electrical resistivity and hydrogeological properties such as porosity, permeability, transmissivity, and hydraulic conductivity. This methodology greatly aided in estimating these parameters. These connections were based on analogies between the equations governing electric current in a conductive medium and groundwater flow through a permeable medium. Geo-electric data collected at the surface can thus be utilized to determine the hydrodynamic characteristics of an aquifer [45, 46].

4 Conclusion

This research presents a comprehensive assessment of groundwater potential and aquifer protective capacity using geo-electric survey techniques and systematic interpretation methods. The trend of lithology in the study area is complex, as indicated by the absence of a specific trend in resistivity values. This complexity arises due to the presence of varying lithology underlying the study area [47]. However, the research successfully delineated lithologic units and provides valuable aquifer characterization parameters, contributing to a thorough understanding of the aquifer in the study area. The study area exhibits a wide range of aquifer resistivity values, where lower values indicate the presence of more conductive and porous materials that facilitate groundwater movement. The thickness of aquifers varies across the region, with thicker aquifers found in a small pocket in the northern part, suggesting a higher storage capacity and potential for groundwater extraction [48]. An analysis of aquifer depth reveals variations in the vertical extent of saturated zones, which directly impact groundwater availability and vulnerability to fluctuations in water table levels [49]. Aquifer transverse resistance measures the hindrance faced by groundwater as it flows laterally, while longitudinal conductance evaluates the ease of horizontal groundwater flow [50]. These parameters play a crucial role in assessing groundwater flow dynamics, identifying areas of recharge or discharge, and evaluating vulnerability to contamination. Hydraulic conductivity, an indicator of the subsurface materials' ability to transmit water, is used to assess permeability and connectivity. Higher values of hydraulic conductivity indicate improved groundwater movement. Additionally, aquifer transmissivity quantifies the groundwater flow capacity across the study area, with higher values indicating greater yields. The protective capacity of aquifers is influenced by longitudinal conductance and soil corrosivity, which provide insights into potential soil corrosiveness and the aquifer's ability to resist contamination.

Based on the geo-electrical characteristics of the underlying lithologies, the study area has been divided into low, medium, and high groundwater potential zones, as shown in Fig. 15. This zoning provides valuable information for groundwater resource management and sustainable development. The high groundwater potential zones are characterized by low resistivity values, indicating the presence of more conductive and porous materials that facilitate groundwater movement. These zones are also characterized by high aquifer thickness, transmissivity, and hydraulic conductivity, suggesting a high storage capacity and potential for groundwater extraction. The medium groundwater potential zones exhibit moderate values of geo-electrical and aquifer parameters, while the low groundwater potential zones are characterized by high resistivity values, low aquifer thickness, and transmissivity, indicating limited groundwater availability and storage capacity.

Fig. 15
figure 15

Groundwater potential map of the study area

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Many VES point fall into the low potential zone, followed by the medium potential zone. Few of the zones fall into high groundwater potential zones. This indicates the need for careful planning and sustainable extraction practices to ensure the long-term availability of groundwater resources. Further investigations, such as drilling and pumping tests, are recommended to refine the assessment and identify specific high-yielding locations within the moderate and high potential zones. This would aid in designing sustainable groundwater extraction schemes and may be used to assess the vulnerability of aquifers to contamination and develop appropriate mitigation measures.