Geo-Spatial Assessment of Groundwater Potential Zones in Birnin-Kudu Local Government Area Jigawa State, Nigeria

ABSTRACT


INTRODUCTION
Water is a chemical substance with a chemical formula H 2 O which can exist in different states as; solid, liquid and gaseous forms.Water covers 70.9% of the earth's surface and it is vital for all known forms of life.On earth, water is found mostly in oceans, rivers, lakes, ponds and other surface water bodies (Rilwanu and Haruna, 2014).Groundwater is the water beneath the surface of the ground.In other words, it is the water that flows or collects beneath the earth's surface.Groundwater originates from rainfall, melting snow and ice which infiltrates into the ground, percolates through porous rocks and stored in aquifers.Groundwater, being a hidden natural resource is not amenable to direct observations and hence, exploration or assessment of this vital resource plays a pivotal role in determining locations of water supply, monitoring wells and in controlling groundwater pollutions (Pandian and Jeyachandran, 2014).Aquifers, springs and wells are recharged by the flow of groundwater.Groundwater is regarded as a finite resource which is very essential for agriculture, industrial activities and human consumptions since its supply has a profound impact on the quality of life.Nowadays, about 34% of the world's water resources belong to groundwater and is an important source of drinking water (Zeinolabedin and Esmaeily, 2015).Groundwater potentials in an area is controlled by many factors such as geology, geomorphology, climate, drainage, slope, depth of weathering, presence of fractures, surface water bodies, canals and irrigated fields amongst others (Stanley, 2017).Slope for example is one of the factors that control the rate of infiltration of rainwater into the subsurface and could therefore be used as an index of groundwater potential evaluation.On a gentle slope area the run-off is slow allowing more time for rain water to percolate, whereas steep slope areas facilitate high run-off allowing less residence time for rain water to percolate, hence comparatively less infiltrations (Stanley, 2017).Consequences of unsustainable and improper groundwater exploration are increasingly evident in several parts of the world due to ever-increasing population, urbanization, industrialization and intensified human activities (Pandian, and Jayachandran 2014).The main concern for groundwater assessment is to maintain groundwater supply on a long-term basis for a sustainable growth and development.The major sources of water in several parts of the developing worlds are taps, boreholes, hand pumps, open wells, streams and rivers.In the absence of available good and safe water sources, people begin to use unsafe sources and this resulted in some health problems.Increasing population and water scarcity have raised the importance of groundwater zones, as they are a major source of freshwater.Integrated remote sensing and GIS are widely used in groundwater mapping.Locating potential groundwater targets is becoming more convenient and cost effective with the advent of a number of satellite imageries.Remotely sensed based groundwater exploration has made it feasible to explore the areas with limited human access, for the wide visual range, short time cycle, and increasing spatial resolution (Huajie, et al 2016).
Geographic information systems (GIS) have emerged as powerful tools for handling spatial data and decision-making in several areas including engineering and environmental fields.Since the delineation of groundwater prospect zones involve a large volume of multidisciplinary data, an integrated application of RS and GIS techniques has become a valuable tool.Moreover, GIS has the ability to process multiple of data, which may reveal certain relationships and visualize different types of information simultaneously.In contrast, remote sensing (RS) technology, with its advantages of spatial, spectral and temporal availability of data covering large and inaccessible areas within a short time.GIS has been a very useful tool for the assessment, monitoring and management of groundwater resources in different parts of the world (Engman andGurney 1991, Jha et al 2007).

MATERIALS AND METHOD Study aim and Objectives
The aim of this study is to assess the spatial variation of groundwater potential zones in Birnin Kudu Local Government Area of Jigawa State, Nigeria.The specific objectives are to: • Characterize the factors contributing to groundwater potentials in the study area; • Identify and map the groundwater potential zones in the study area, and • Analyze the spatial extent of groundwater potentials in the study area.

Study Area
The study area Birnin Kudu Local Government is located between Latitudes 11º 20′N to 11º39′ North of the equator and Longitudes 09º 10′E to 09º 40′ East of the Greenwich meridian.It covers area of about 2,073 square Kilometers.The main elevation of the plain surface of the area is between 400 -420m above mean sea level.The total annual rainfall received ranges between 500-600mm in the region (Olofin 2008).The area is characterized by a long dry season which lasts on average of 8 months from October to April or May.The mean monthly temperature in the area ranges between 30°C and 35°C.The wet season mean annual temperature is about 25°C and diurnal range of about 10°C to 13°C.Relative humidity ranges from 80% in August to 23% between the month of January and March.The major rivers of the area are River Birnin Kudu, River Masaya and Kiyako (Murtala and Yazid, 2019).

Data Processing Characterization of Factors Contributing to Groundwater Potential
The Analytic Hierarchy Process (AHP) introduced by Saaty (1980) was used to determine the weight of groundwater parameters by integrating the various thematic maps (layers) of the factors contributing to groundwater potentials in the study area.AHP is an effective tool for dealing with complex decision making and may help the decision maker to set priorities and make the best decision without being biased.The AHP was used to characterize the zones into very good, good, moderate, low and very low.These zones were characterized based on the aquifer properties, soil type, geology and topography.Table 3.1 shows the processes involved in weight assignment using AHP and Table 3.2 shows weight for the factors according to Solomon (2003).

Groundwater Potentials Zones Mapping
Integration of the thematic maps of Rainfall, lineament, geology, slope, DEM, soil, Drainage density and LULC) was carried out in ArcGIS environment.The prediction model of groundwater potentials formulated by Hopkins (1977) for generating suitability maps was adopted.It is given as: GwP = DDw + Gw + Tw + SStw + Rw + SCw + LDw…Ow (1) Where; GwP = Groundwater potentials, DD = drainage density, Gw = Geology, T = Topography SS = Slope steepness, R = Rainfall, SC = soil and clay ratio, LD = Lineament density, w = weightage, O = other parameters.This was modified for the study as adopted by Mogaji, Aboyeji and Omosuyi (2011), Mary (2016)

Estimating Spatial Extent of Groundwater Potential Zones in the Study Area
Each prospect zone from the groundwater potential zones map was converted individually to shape file in ArcGIS environment.Geometry calculator tool was used in calculating the areal extent of the various potentiality of the groundwater in the study area.The result is presented in a table.

RESULTS AND DISCUSSIONS
The result from the Weights of the factors influencing groundwater prospects zones in the study area shows that rainfall is the major contributor, and weighed as the highest contributor with (34%) followed by lineament (24%) and geology was weighed (14%).The least groundwater contributor in the study area is the land use land cover with (2%).The study showed that the very high groundwater potential areas occupy 59.92 sq.km (2.89%) of the area, the high potential zones constitute about 527.52 sq.km (25.45%) of the study area and the moderate potential area has the highest area of 602.69 sq.km (29.07%).The low and very low potentials occupy an area of about 528.13 sq.km (25.48%) and 354.75 sq.km (17.11%) respectively.The very high and high groundwater potentiality are observed in Sundumina,

Figure 1 :
Figure 1: The Study Area (Birnin Kudu LGA) Source: Modified from Administrative Map of Nigeria.Data and Software Used Data used include remotely sensed data like Landsat 7 (ETM + 30m) image of Birnin Kudu and ASTER Global Digital Elevation Model (DEM); other maps are geology, lineament, drainage density, soil map of the study area; and the rainfall data.Software used include ArcGIS 10.8, PCI Geomatica and Google Earth Pro.

Figure 9 :
Figure 9: Land use Land cover Map Source: GIS Analysis, 2023

Table 1 :
Procedure for Assigning Weightages in Analytical Hierarchy Process (AHP)

Table 3 :
Spatial Extent of Groundwater Potentials in the Study Area Groundwater

Table 4 :
Weights of all the Groundwater Controlling Factors