American Journal of Earth Sciences 2015; 2(6): 242-246 Published online January 10, 2016 (http://www.openscienceonline.com/journal/ajes) ISSN: 2381-4624 (Print); ISSN: 2381-4632 (Online) Application of Remote Sensing and Geo-Electrical Method for Groundwater Exploration in Khor Al Alabyad, North Kordofan State, Sudan Elhag A. B. Department of Civil Engineering, College of Engineering, King Khalid University, Abha, Saudi Arabia Email address ahmedhydro@gmail.com, abalhaj@kku.edu.sa To cite this article Elhag A. B. Application of Remote Sensing and Geo-Electrical Method for Groundwater Exploration in Khor Al Alabyad, North Kordofan State, Sudan. American Journal of Earth Sciences. Vol. 2, No. 6, 2015, pp. 242-246. Abstract Remote Sensing technology in this century is widely used in survey and very effective in identification of potential zones for groundwater exploration. In the study area the main rock types are schist, gneisses and quartzite Precambrian terrain of Khor Al Alabyad, Sudan. The main landform units in this area are valley fills lower and upper relief. Occurrence of groundwater in hard rock terrain is mainly controlled by structures, landforms, lithology and recharge conditions. The subsurface column consists of three resistivity layers, which obtained from upper to lower are composed of very dry superficial deposits, followed by an intercalation layer of weathered and fractured basement, then an impermeable hard basement complex respectively. Spectral resolution and geo-electrical resistivity survey has the potential to infer structures as well as lineaments and faults in this hard rock area. It's essential to identify the location of interconnected lineaments below buried channel plains in the hard rock area for targeting subsurface groundwater occurrence is more dependent on fractures. Generally groundwater potential is good in the valley fills and poor in the upper relief, but specifically the target zones are indicated by overlap of the highintensity lineament contours and low-intensity drainage contours. Therefore, the lineaments can be very helpful in sitting successful wells at zones (C and B) which exhibited a higher lineament density and frequency compared to the other zones. Keywords Remote Sensing, Fractured Basement, Groundwater, Khor Al Alabyad, North Kordofan, Sudan 1. Introduction Continuous development of society and even the very existence of life in different forms depend upon the availability of water. Human beings need adequate amount of fresh water for daily necessities as well as for agricultural, industrial and cultural uses. Groundwater plays a crucial role in arid and semi-arid regions in most parts of the world especially in Africa, especially in areas covered by crystalline complex rock and frequent water shortages are being faced annually due to unreliable surface water supplies. This research work focuses on developing the remote sensing and geophysical survey methodology for regional groundwater potential evaluation. The area under study is situated on a low relief hill, southern part of El Obeid city in North Kordofan State, Sudan (Fig. 1). Satellite data products inferred Land use, Geological and morphological information. The satellite imageries covering the area were analyzed digitally to prepare geomorphologic features. On the other hand, the target area is underlain by crystalline basement rocks and groundwater development is complicated by the high variability of geological and hydrogeological settings of the basement aquifers. Gustafson (1993) used GIS for the analysis of lineament data derived from SPOT imagery for groundwater potential mapping. The objective of this study to produce a regional structural lineament map of Khor Al Alabyad from remotely sensed data, topographic, geological inference and geo-electrical data; (i) assessment of the hydrogeological implication of the lineaments by integrating them with the available ancillary data especially geo-electrical resistivity method (ii) analyses the lineament trend distribution of the study area using lineament density, lineament intersection and drainage pattern maps.
American Journal of Earth Sciences 2015; 2(6): 242-246 243 1.1. Geology of the Area The surface geology of the study area is formations the first is described from the geological map of Sudan, performed by (GRAS, 2004) and is shown in (Fig. 1). The area is covered by different geologic formations for different geologic ages, where Superficial deposits which covered most Wadis and distribute through the most area. The second Formation is the basement rocks of Precambrian age which is composed mainly of different types of the metamorphic rocks. In the target area the geological formation exposed in the eastern part belongs to the J. Kordofan of the Precambrian age. They are predominantly massive, compact, Grey colored. Therefore, the formation of the study area ridge along N-S side indicating isoclinals folds also the satellite images show a series of lineaments in some part of the area. The metamorphic rocks as schist, gneiss and quartzite are characterized by several sets of borehole-developed fractures and joints. Of these, the following sets are more prominent in the study area. Vein quartz and pegmatite have been emplaced along fractures and joints in quartzite. Pegmatite contains feldspars, muscovite, quartz and tourmaline. Clay derived from weathering of mica is extensively in the area east of the Khor Al Alabyad. The compact, white quartzites are highly resistant to weathering and they stand out as jointed, blocky or sub rounded boulders as a result of intersecting joints. In October 1966 and 1973, Kordofan State was shaken by strong earthquakes that have great attention to hydrology due to a few of groundwater wells in the aquifer are dry (Elhag, A. B. and Elzien, S. M., 2013). In the 1966 J. Dumbeir earthquake occurred in an area characterized by moderate lineament density and a few number of faults. This area is occupied by basement rocks, and the epicenter of the 1993 Khartoum earthquake is located in an area characterized by high lineament density and considerable number of faults (Khalid A. et al. 2014). 1.2. Hydrogeology During the rainy season, there is a great increase in water flow volume in the major rivers while there is hardly water in some of the streams during the dry season, as well as, surface water percolates down through the fractures and the process of chemical weathering proceeds. Rainfall is the dominant factor that determines the occurrences of groundwater. In the study area groundwater occurs and restricted in a typical basement complex either in the weathered or in the deepseated fracture zones only high-resolution satellite data has the potential to infer buried pediment plains and interconnected fracture zones for the selection of groundwater exploration and artificial recharge sites. According to (Ahmed, et al 1984), lineaments (dykes silicified or shear fracture zones, open faults or joint systems) constitute more reliable sources for groundwater in crystalline rocks. The main target of this paper is to exploration of surface and subsurface features by integrating the remote sensing data and geo-electrical survey techniques proved to be an essential in identifying aquifer zones for potential groundwater exploitation because the topography and landforms have strong influence on groundwater prospect of an area as they influence the thickness of weathered zone especially in the Khor Al Alabyad crystalline basement rock. Figure 1. Location and geological units of the study area (Modified after GRAS, 2004). 2. Materials and Methods Image processing includes directional filtering, color composite and linear that was employed to enhance the image spatially and spectrally for lineaments extraction. ArcGIS 9.3 and ERDAS Imaging processing software were used to perform all the operations. The extracted lineaments were classified by drawing which discerned the orientation and frequency of occurrence of the extracted lineaments. The information from the satellite imageries of the study are presented in form of structural lineaments and analyzed using the lineament intersection, lineament density (LD), lineament intersection density maps and lineaments frequency (LF), also the processed remote sensing data were analysis and presented in the form of drainage pattern which including two parameters, the drainage-length density (Dd), and drainage frequency (Df). Geophysical prospecting of groundwater is one of the electrical methods is Schlumberger array of electrical resistivity method (Fig. 2). The Schlumberger array was adopted to ensure deep penetration and for logistics of limited manpower in the field. Evidence has shown that geophysical methods are the most reliable and the most accurate means of all surveying method of subsurface structural investigations and rock variation (Carruthers, 1985; Emenike, 2001). Karuppannan (2015) announce resistivity of rock formations varies over a wide range, depending mainly
244 Elhag A. B.: Application of Remote Sensing and Geo-Electrical Method for Groundwater Exploration in Khor Al Alabyad, North Kordofan State, Sudan on the material, density, porosity, pore size and shape, water content and quality, and temperature. On the other hand, Telford et al, (1990) announce that the different factors affect the resistivity in the subsurface. Both the survey procedures resistivity profiling and resistivity sounding (VES) have been carried out. Interpretation and analysis of geo-electrical data have been done by qualitative and quantitative analyzed and interpreted; - Using IPI2 WIN software packages is useful for delineate and to prepare the VES curves. - To obtain the geo-electrical parameters. - To delineate the subsurface geology and the groundwater resources. The interpretation of resistivity data is done in two stages as follow: 1. Processing of the quantitative data to get the geo-electric parameters i.e., the true resistivity, depth/thickness etc. 2. These parameters are used to infer the nature of subsurface lithology on the basis of the local geological knowledge and correlation studies. The measurements of resistivity are made by increasing the electrode spacing (AB/2) in a fixed point along a tract and this method of vertical exploration in known as resistivity sounding or VES. In the study area, VES have been conducted using Schlumberger configuration (Fig. 2). The electrode spacing AB/2 of 100 meters as the maximum was employed to delineate the subsurface lithology and groundwater potentials. The resistivity meter displays resistance (R), apparent resistivity (ρ a ) and true resistivity for each AB/2 setting. VES have been carried out at the target area (Fig. 4) and for comparison and correlation some VES have been conducted outside of the study area. After the completion of fieldwork, the resistivity data stored in memory have been downloaded to the computer for further interpretation. Figure 2. Schlumberger configuration. All the VES have been carried out in the study area, are made into three profiles covering the entire study area (Fig. 3) with certain orientations, traversing different geological formations to project a two dimensional subsurface geoelectrical section along that profile. The resistivity sections only reflect the interpreted subsurface lithology. The ordinate X axis represent the distance of traverse and the abscissa Y axis represent the depth in meters below ground level. Figure 3. The acquired field data (VES # 1). 3. Results and Discussion Lineaments provide the pathways for groundwater movement in hard rock areas. The movement and occurrence of groundwater depends mainly on the secondary porosity and permeability resulting from faulting and fracturing etc. These structural features appear on remote sensing imagery as lineaments. The remote sensing data offer synoptic view of large area and helps in understanding and mapping of the lineaments both on regional and local scale. Figure (4) shows the generalized lineaments map of the study area. The map shows that there are different orientation predominant sets of lineament which are closely related to tectonic activities such as fractures, faults and joints in the study area. The lineaments extend from several directions and the majority of this class has the N-S general trend and the other lineaments appeared to be shorter and extend from E-W direction (Fig. 4). The map shows that the southern part is characterized by very high frequency lineaments (high number of lineament per unit area), but the northern part of the study area is characterized by moderate lineament while the east and west parts have low to very low lineaments. In the study area the highlights are importance of lineaments, geology and drainage pattern. The maximum number of lineaments restricted in zone A and minimum number of lineaments observed in zone C, and the lineament range in length from several tens of kilometers to more than hundred meters respectively. Therefore, more length density areas are expected to have a high lineament frequency and high lineament intersection, as well as, the well production increases with increasing lineament density (Edet, A. E., 1993). These differences in lineament intensity probably reflect differences in the geology. The analysis of drainage patterns including two parameters, the drainage-length density (Dd), and drainage frequency (Df) which were carried out based on lineament length density survey (Fig. 4). The interpretation of the VES with regional structures that associated with the data of borehole was calibrated. The interpretation of the VES revealed by geo-electrical units that the upper layer called superficial deposits (Wadis) until average depth of 7 m according to data of boreholes. The second layer which represented by the weathering and fractures aquifer which have average depth of 50 m. The third layer of interpretation indicated that the depth reached the upper surface of the hard basement complex.
American Journal of Earth Sciences 2015; 2(6): 242-246 245 Figure 4. Lineament map shows directional filter applied by using Land-sat image and drainage pattern of Khor Al Alabyad. The study area occurrence of a major fracture zone at depth of about 80 m delineated from the interpretation of the VES data along this profile closely correlates with the profile anomaly pattern. A total of three subsurface layers are recognized in the geo-electric cross sections and controlled by a drilled borehole as follows: 1. A surface layer composed of very dry superficial deposits (sand or clayey sand). It has a resistivity more than 250 Ωm and a thickness ranging between 3-15 m. 2. Weathered and fractured basement layer of gneiss and schist with resistivity ranging between 25-150 Ωm and thickness ranging between 30-80 m. 3. Hard basement complex shows increase in the resistivity value attains 1200 Ωm (Fig. 5). and 1200 Ωm and majority of the VES curves are combination of A and H type curves. - The crystalline rocks formation of borehole depth 90 m and average yield about 1000 Liter per minute (lpm) which is concentrated in valley fills. References [1] Ahmed, F.; Andrawis, A. S.; and Hagaz, Y. A. (1984) Land sat Model for Groundwater Exploration in Nuba Mountains, Department of Geology, University of Khartoum, Sudan. Remote Sensing Institute. Brookings, SD, U.S.A. [2] Carruthers, R.M., 1985, Review of geophysical techniques for groundwater exploration in crystalline basement terrain: British Geological Survey, Regional Geophysics Research Group, Report 85/3, 30 p. [3] Edet, A. E. (1993). Hydrogeology of parts of Cross River State, Nigeria: Evidence from aero-geological and surface resistivity studies. Unpublished Ph. D Thesis of the Department of Geology, University of Calabar, 350p. [4] Elhag, A. B. and Elzien, S. M. (2013): Structures Controls on Groundwater Occurrence and Flow in Crystalline Bedrocks: a case study of the El Obeid area, Western Sudan. Global Advanced Research Journal of Environmental Science and Toxicology (ISSN: 2315-5140) Vol. 2(2) pp. 037-046. Available online http://garj.org/garjest/index.htm. Figure 5. Generalized subsurface geo-electric cross-sections for delineation of stratigraphic. 4. Conclusion Based on the integration of geological, remote sensing and geo-electrical investigations of the study area the following are inferred: - The drainage pattern is dendritic to sub-dendritic and two sets of lineaments are found. In the majority of lineaments are north- south oriented and the other west-east orientation. - The black soils are dominant in the bottom of Khor and the red soils are dominant in the bank river. - The litho units of basement rocks formations are consist mainly of metamorphic rocks as schist, gneiss and quartzite. - The minimum and maximum apparent resistivity is 3Ωm [5] Emenike, E.A. (2001): Geophysical exploration for groundwater in a Sedimentary Environment: A case study from Nanka over Nanka Formation in Anambra Basin, Southeastern Nigeria: Global Journal of Pure and Applied Sciences, v. 7/1, p. 1-11. [6] Gustafson, P. (1993): High resolution satellite data and GIS as a tool for assessment of groundwater potential of semi-arid area. IX thematic conference on geologic, remote sensing, Pasadena. Calefornia, USA 8 11. [7] GRAS, (2004): The Geological Research Authority of the Sudan (GRAS), URL: http://www.gras-sd.com. [8] Karuppannan S. (2015): Delineation of Groundwater Potential Zone by Using Geophysical Electrical Resistivity Inverse Slope Method in the Kadayampatty Panchayat Union, Salem District, Tamil Nndu. International Journal of Recent Scientific Research Vol. 6, Issue, 7, pp.5013 5017, July, 2015. www.recentscientific.com.
246 Elhag A. B.: Application of Remote Sensing and Geo-Electrical Method for Groundwater Exploration in Khor Al Alabyad, North Kordofan State, Sudan [9] Khalid, A. E. Z., Eiman A. M., Elsheikh M. A. (2014): Detection of possible causes of earthquakes in central Sudan: An integrated GIS approach. International Journal of Geomantic and Geosciences Volume 4, No. 3, 2014. [10] Telford, W.M., L.P. Geldart, R.E. Sheriff, and D.A. Keys, (1990): Applied Geophysics (Second Edition: Cambridge University Press, p. 344-536. Wilson, A.F., 1922, Geology of the Western Railway: Geological Survey of Nigeria Bulletin, No. 2.