Mapping of Groundwater Potential Zone Using GIS and Remote Sensing of Shwan Sub-Basin, Kirkuk, NE Iraq

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Introduction
Groundwater is considered one of the resources that cannot be neglected and drained in an unplanned way due to its usefulness in life sustainability in all countries of the world (Al-Gburi et al., 2022).The general, water is one of the precious and valuable resources of life for sustainable development (Benjmel et al., 2020).The groundwater is the third source after rainwater and surface water in the world (Abdul-Hameed and Hatem, 2021).The groundwater is an economically vital resource in all urban and rural areas (Magesh et al., 2012).The groundwater is a renewable resource and is also considered a guaranteed resource at any time compared to surface water (Chowdhury et al., 2009).The water must be sufficiently available for the various requirements of life, including groundwater, which supports human health and represents economic development (Berhanu and Hatiye, 2020).The population increase at present has led to an increase in industrial development, increasing the use of groundwater in conjunction with climatic changes and the lack of precipitation (Awadh, and Ahmad, 2012).The study area contains some industrial, commercial and, agricultural activities that need groundwater (Al-Hayali et al., 2021).The increase in population and industrial and agricultural activities in and of itself is a problem that requires a groundwater resource due to the scarcity of surface water resources, thus leading to the depletion and pollution of groundwater through untreated extracted waste (Srinivasa and Jugran, 2003).The current increase in agriculture is a result of population increase, and therefore an increase in the use and depletion of groundwater (Al-Gburi and Al-Tamimi, 2020).The excessive and increasing exploitation of groundwater has led to a decrease in levels of groundwater in most countries of the world because of the great development that the whole world is witnessing (Priyan, 2021).The description of aquifers scientific way is necessary to understand the sits of groundwater potential zones (Fashae et al., 2014).Surface water is decreasing due to lack of rainfall and evaporation in arid and semi-arid areas (Heyns, 2009).The Middle East region was considered the region that suffers the most from water shortage, as most of its countries are within the water poverty index (Scott, 2019).Recently, the management of water resources has become of a global importance, being a valuable resource for all creatures (Mohammed, 2021).At present, the need for water began to increase daily.Iraq is currently exposed to a water shortage after reducing Iraq's water imports through the construction of dams to neighboring countries, which are considered a source of water.Groundwater potential zones are an ideal way to know information for various phenomena on the ground such as soil, slope and geomorphology based on the spectral reflection of the ground surface (Avtar et al., 2010).The drilling methods are one of the classic and effective ways to determine groundwater potential zones, but it is considered a cost method and takes a long time.Therefore, modern methods were used through GIS as an alternative way to identify the groundwater potential (Anbazhagan et al., 2016).The study of water and the possibility of its presence is considered one of the most important studies, especially with the availability of space and field data (Sahar et al., 2021).The importance of geographic information systems and remote sensing is an important role in the management and development of water resources (Kumar et al., 2014).The water crisis in Iraq, especially in recent times, is stimulating the conduct of applied studies for the areas that retain groundwater, so producing groundwater potential zone maps has become very important based on GIS and remote sensing.Modern technologies such as geographic information systems, remote sensing, and AHP found groundwater zones, in addition to its contribution to the development and planning of watersheds (Pande et al., 2020).Every year billions of dollars are waste by drinking water.In recent years, the use of groundwater has increasingly begun to meet the population's need for water, so it is very important to determine the potential of groundwater (Al-Djazouli et al., 2021).Determining groundwater areas is necessary to obtain the ideal use of water to meet various needs, whether human or other (Etikala et al., 2019).The protection of water resources in Iraq is important, so the government began to monitor the groundwater for its proper management.Hydrogeological maps are an important tool in managing water resources (Al-Ozeer, 2021).Groundwater potential zones depend on geological, land use, and hydrological surveys.The groundwater conditions depend on the nature of slopes, fractures, water bodies, and depth of weathering (Ganapuram et al., 2009).It is possible to analyze these factors and obtain good results using remote sensing and GIS (Jain, 1998).The problems related to groundwater are many.The pressure on groundwater can be observed in areas characterized by low rainfall, population increase, industrial and agricultural development (Arulbalaji et al., 2019).The reduced discharge of water to most of the watersheds of the Tigris and Euphrates rivers causes the search for groundwater as an alternative resource (Al-Tamimi and Al-Shwani, 2019).Especially, the area is completely dependent on groundwater in their daily lives, as it includes nearly sixty villages; which means that the population is large.It is possible to invest the sub-basin agriculturally, especially in non-rugged sites or on flat land.Through the reconnaissance tour of the area, some simple agricultural sites were noted.Climate change poses a strong threat to the world; especially in Iraq is considering one of the arid and semi-arid regions.The climatic changes are lead to an increase in the demand for groundwater, especially with low rainfall and an increase in the population of the sub-basin.It is very important to establish the potential of the groundwater model for sub-basin, especially with the low rainfall seen in Iraq and the sub-basin region in particular.The main objective of the research is to identify groundwater potential zone.

Study Area
The study area is located in the Northeast part of Iraq, within Kirkuk governorate.It occupies an area of 765 km 2 .The boundaries of the study area are from the eastern and southeastern parts Al-Khassa sub-basin, but from the western and northwestern parts of the Lesser Zap River (Fig. 1).The Shwan sub-basin is located depending on tectonics in the unstable zone, but structurally the sub-basin was bounded in the northeastern part of the Chamchamal anticline and the southwest part of Kirkuk structure -Baba Dome (Jassim and Goff, 2006).The sub-basin of the study area consists of three geological formations (Mukdadiyah Formation, Bai-Hassan Formation and Quaternary sediments), their ages from the Upper Miocene to Holocene ( Stevanovic and Markovic, 2003).

Materials and Methods
The work included an accurate description of the factors maps adopted in this study to produce a map showing the groundwater potential zone.The Digital Elevation Model (DEM) was obtained from the USGS website.Three factors are the elevations, slope, and drainage density of the sub-basin were extracted by DEM 30 meter.The values of the geological map were obtained based on the contents of the geological formations of the sub-basin ( Stevanovic and Markovic, 2003).Harmonized Global Soil Database (HWSD) created a soil map for the sub-basin.Land use and Land covers (LULC) were prepared through an exploratory tour of the sub-basin, based on data from the Esri website (10) meters to obtain land uses and land covers.Based on the Analytical Hierarchy Process (AHP) put forward by the scientist (Saaty, 1980) (Table 1).Weight has to be given to all factors according to the strength of each factor's influence on the region (Table 2).For each specific topic within the map, a specific rating was assigned from 1 to 5 (very low to very high) according to its impact on the groundwater potential zone table.Used an overlay tool in spatial analysis within the GIS software, a groundwater potential map was created by the following equation: Groundwater potential map = WG*RG + WE*RE + WS* RS + WD*RD +WSO*RSO + WLULC*RLULC (1) Where: Weight Geological (WG) and Rating Geological (RG).Weight Elevation (WE) and Rating Elevation (RE).Weight Slope (WS) and Rating Slope (RS).Weight Drainage density (WD) and Rating Drainage density (RD).Weight Soil (WSO) and Rating Soil (RSO).Weight LULC (W LULC) and Rating LULC (R LULC).The flowchart shows how to create the groundwater potential map (Fig. 2).

Geology
The geology of any area plays a major role in the groundwater recharge (Bhattacharya et al., 2021).Depending on the geology of the study area, three types of geological formations are observed (Mukdadiyah Formation, Bai-Hassan Formation, and Quaternary sediments) (Fig. 3A) (Stevanovic and Markovic, 2003).The middle and late Pliocene (Bai-Hassan Formation) composed of conglomerates, sandstones, and claystone dominate about 60% of the sub-basin.The remaining 40% are from the rocks of the Mukdadiyah Formation occupy 7% consisting of pebbly sandstone, sandstone, claystone in the west part of the sub-basin while Quaternary sediments cover 33% consisting of conglomerates, sandstone, clay, siltstone, silt, and rock fragments.The proportion of rocks from sandstone and sand especially in the Bai-Hassan Formation and Quaternary sediments is greater than of clays in Mukdadiyah Formation.For this reason, water can penetrate layers of land and reach the aquifer.Based on the above, the rating of the geological map has given a value of 3 for Mukdadiyah Formation and 4 for Bai-Hassan Formations and Quaternary sediments (Fig. 3B).

Elevation
Elevations have a dominant and sensitive role in most hydrological or hydrogeological studies.Elevation plays a major role as it was used as a source for the map Drainage Density and slop.The elevations of the sub-basin ranged 245-839 meters above sea level.From the DEM (Fig. 4A), the elevation map was derived, as it was categorized into five zones by the Natural Breaks method in the Arc GIS software; the value 5 represents the highest groundwater potential, while the value (1) represents the lowest groundwater potential (Fig 4B).According to this map, the groundwater potential decreases in areas with high elevations.However, the area with lower elevations has an increased groundwater potential.

Slope
Slope plays an important role in knowing the groundwater potential.Slope can be described as the rate of change in elevations (Ibrahim and Ahmed, 2016).An increase in slope leads to velocity runoff and, as a result, no water infiltration, as well as an increase in soil erosion.The slope map of the sub-basin was generated through DEM using Arc GIS software.The result shows the varies in the slope angle of the sub-basin from 0 to 23 degrees, consisting of five zones (Fig. 5A).The highest value (1) indicates a high slope (low groundwater potential); while the value (5) indicates the low slope, which represents the highest groundwater potential (Fig. 5B).

Drainage Density
Drainage density is the total length of the streams segment of all orders per unit area.A drainage density map was created using the spatial analysis tools in the Arc GIS software.Drainage density is inversely proportional to the water infiltration capacity in the soil.The result of the drainage density map appears, consisting of five zones; the value ranged from 0 to 8.7 (Fig. 6A).The lowest rating value (1) was given for the high-density drainage, while the highest rating value (5) was given for the lowdensity drainage (Fig. 6B).Depending on the drainage density map of the sub-basin, it is clear that the groundwater potential is low in most of the region except for some parts.

Soil
Soil texture is one of the main factors of agricultural production and recharge of groundwater (Kumar and Krishna, 2018).Soil has a major role in the infiltration of water to the aquifer or its run-off on the surface of the earth.It is necessary to know the texture of the soil in the study area for agricultural importance as well as for water sustainability.The soil of the sub-basin reveals two main soil categories, loam and sandy loam (Fig. 7A).Soil rating was determined based on its infiltration rate, the value of rating was (2) for loam and (3) for sandy loam (Fig. 7B).The loam soil texture covers most of the subbasin, except the eastern and western parts of the sandy loam soil texture.The sandy loam soil texture has better groundwater potential than the loam soil texture.

Land Use and Land covers
The land use and land cover map provide the necessary data on surface water runoff and infiltration capacity.The result appeared for the map of land uses and ground cover for the sub-basin, consisting of water land, bare land, built area, crops or open filed, forest, scrubland, and grassland (Fig. 8A).The rating value is given to the factors crops or open field, forest, scrubland, and grassland (4), while the rating value is given for water land (5), built lands (1), and bare land (2) (Fig. 8B).The rating value (4) covers most of the sub-basin.

Groundwater Potential Map
The groundwater potential map was prepared by overly weight for all six layers.The sub-basin was classified into five groundwater potential zones as, very good (162.1 km 2 ) good (193.833km 2 ), moderate (171.649km 2 ), low (145.798km 2 ) and very low (91.68 km 2 ) of the study area (Fig 9).The result shows for study area that the groundwater potential zone is in the area concentrated western and northwestern part due to the nature of the flat terrain and the open field in addition to the coarse sediments.

Conclusions
The application of groundwater potential study is very important.It was considered one of the modern applications in understanding and tracking the groundwater potential zone.This application depends on several factors (geology, elevations, slopes, drainage density, soil, and land uses/land cover).The highest elevations are located in the eastern and northeastern parts, while the lowest elevations are located in the western and northwestern parts of the sub-basin.The results show groundwater potential of the Shwan sub-basin consists of five divisions, ranging from very low to very high.The eastern, northeastern and southeastern parts range in values from very low to low, due to the influence of the strength of the slopes and elevations in this part.The values of the western and southwestern parts adjacent to the sub-basin boundary range from low to medium as a result of the geological impact of the Mukdadiyah Formation, which contains a high percentage of clay; which leads to low -medium groundwater potential.The high and very high values of groundwater potential cover most of the center of the sub-basin in addition to the western, northwestern, and southern parts because of the geology (Bai-Hassan Formation and Quaternary sediments) which contains a high percentage of coarse sand and the nature of the flat land in these sites.

Table 2 .
Weight of groundwater potential zone factors for Shwan sub-basin