Delineation of Groundwater Potential Using GIS, RS and AHP Techniques of the Chia Sur Sub-basin in Sulaymaniyah-Kirkuk, Northeastern Iraq

Abstract


Introduction
Groundwater is one of the most essential natural resource stored in geological formations (Fitts, 2002).Water is considered an essential source for organisms of life.Water must be sufficiently available for all humans and animal's needs.The management of groundwater resources is a significant resource for all organisms in the world (Mohammed, 2021).Groundwater is considered an essential resource in the field of investments for any country in the world.In the Chia Sur sub-basin, villages depend on groundwater only, so that the demand for groundwater increases.The increase in population and agricultural activities need the groundwater continuously (Al-Gburi and Al-Tamimi, 2020).Currently, the use of groundwater is increasing due to the climatic changes and lack of rain (Awadh and Ahmad, 2012).Due to the increasing demand in the various uses for groundwater at Chia Sur sub-basin, it is very important to understand the groundwater potential in this area.The problem of unsustainable use of groundwater has become very worrying for various countries of the world.There is a lack of understanding or determination of the potential of groundwater, especially at present time, because of the lack of rain and climatic changes.There are two ways to detect groundwater; the surface water is the least expensive but the subsurface water is the more expensive and needs more efforts (Berhanu and Hatiye, 2020).Nowadays, with the increase in scientific development, it is become possible to obtain and process data to explore the groundwater potential by collecting maps, such as geological, geomorphological, elevations, slopes, soil, drainage density and land use/land cover.Geographic information systems and remote sensing have a positive role in the development and management of water resources (Kumar et al., 2014).Remote sensing and Geographic information systems techniques have become important techniques in identifying or mapping potential groundwater (Moore et al., 1991;Andualem and Demeke, 2019).The increase of population growth and expansion in the field of agriculture leads to the daily use of groundwater, especially in arid and semi-arid areas.Aim of the study is to draw a map that identifies groundwater potential zones by using RS and GIS techniques of Chia Sur sub-basin.

Study Area
The most part of the Chia Sur sub-basin is located at the west of Sulaymaniyah Governorate and a small part is located at the northeast of Kirkuk Governorate.The sub-basin lies between 3956572-3938750 latitude and 471022-500623 longitude.The Ghia Sur sub-basin occupies an area of 276 km2.The boundaries of the Chia Sur sub-basin are Al-Khassa sub-basin from the west, Shewasoor sub-basin from the northwestern, Basara basin from the southeast, Agjler sub-basin from the northeast and Chamchamal basin from the south (Fig. 1).Depending on tectonics, the Chia Sur sub-basin is located at the West of Zagros Thrust fold belt within (High folded and Low folded zones) (Sissakian et al., 2017).Structurally, the borders of the sub-basin at the western side are Chamchamal North Anticline, from the north Dara Quota Anticline and from the eastern side by Darbandi-Bazian-Sagram-Qaradagh Anticline (Sissakian, 2013).The sub-basin consists of six geological formations (Gercus -Pila Spi, Fatha, Injana, Muqdadiyah and Bai Hassan) from the middle Eocene to late Pliocene age (Stevanovic and Marcovic, 2003).

Materials and Methods
The work includes an accurate description of eight factors adoptted in this search to produce a map of the groundwater potential.The four factors are the elevations, lineament, slope, and drainage density of the Chia Sur sub-basin which were derived by (DEM STRM 30 meter).The geological map of the Chia Sur sub-basin was obtained based on (Stevanovic and Marcovic, 2003).The geomorphology map the Chia Sur sub-basin were obtained from (Sissakian, 2013).The soil data were obtained from Harmonized Global Soil Database (HWSD).The LULC map was derived from the Esri website height of 10 m, on 21/04/2021.By using the GIS and RS, a groundwater potential map was created.In addition to using Analytical Hierarchy Process (AHP) which was established by Saaty (1980) (Table 1).Weight was given for eight factors according to the strength of each factor influence on the area (Table 2).A rating has been established for each of the categories of factors according to the effect of these categories on the groundwater potential, represented by values from 1 to 5, e.g., from very low to very high (Table 3).By using the overlay process, within the tool's spatial analysis in GIS software, a groundwater potential was derived from the following equation: Weight Geology (WGE) and Rating (RGE).Weight Geomophologyl (WGEOM) and Rating Geological (RGEom).Weight Elevation (WE) and Rating (RE).Weight Slope (WSLO) and Rating (RSLO).Weight Lineament (WLI) and Rating (RLI).Weight Drainage Density (WDD) and Rating (RDD).Weight Soil (WSO) and Rating (RSO).Weight LULC (W LULC) and Rating (R LULC).
The flowchart and procedures to create the groundwater potential map for the Chia Sur sub-basin are shown in Fig. 2. Table 1.The scale of relative importance according (Saaty, 1980).

Geomorphology
Geomorphology is very important for any region as it gives information about the description of the terrain, therefore, it depends on the structural evolution of geological formations (Gupta, 2003).Geomorphology plays a major role in the storage and movement of groundwater (Thomas et al., 2009).In the Ghia Sur sub-basin, five geomorphological features have appeared (Valleys, Hogbacks -Questas, Ridges -small valleys, dissected slopes and Bad land) (Fig. 4a) (Sissakian and Jabbar, 2013).The value of the rating of groundwater potential has been given for (valleys 5, Hogbacks -Questas 4, Ridgesvalleys small 3, dissected slopes 2, and bad land 1) in five categories (Fig. 4b).The value 5 was considered a high groundwater potential.The value 1 is regarded a low groundwater potential.

Elevations
The elevations in hydrological and hydrogeological studies are important factors which impact on the drainage density or surface runoff (Al-Gburi et al., 2022).The elevations of the Chia Sur sub-basin ranged from 495-1430 m (a.s.l) (Fig. 5a).The elevation map of the Chia Sur sub-basin was categorized into five zones the value 5 represents the high groundwater potential, as the 1 represents the low groundwater potential (Fig. 5b).The groundwater potential decreases in areas with high elevations and vice versa.

Slope
There is an inverse relationship between the high degree of slope and recharge groundwater.The high degree of gradient leads to an increase in the velocity of the run-off, as result, the groundwater potential is feeble (Magesh et al., 2011a) (Magesh et al., 2011b).Reveal the result of the slope map divided into five categories (Fig. 6a).Rating values show a slope map of the Chia Sur sub-basin was divided into five categories (very low 1very high 5) (Fig. 6b).The Chia Sur sub-basin was located within the slope degree from 0 to 1 area of very high groundwater potential.The areas within slope degrees 1 to 2 represent areas of high groundwater potential.The areas within the slope degree from 2 to 3 are considered to be of medium groundwater potential.The areas that fall within the slope degree from 3 to 4 are areas with low groundwater potential.Where area within slope degrees 4 to 5 was considered very low groundwater potential.

Lineament
Satellite imagery is very useful in determining the lineament.Lineament is an important factor in terms of groundwater (Pradhan, 2009).Lineament represents fracture areas that lead to an increase in permeability and porosity, meaning paths or ways for groundwater (Magesh et al., 2012).The result of the lineament density of the Chia Sur sub-basin reveals the lineament density high value in the north of the area with a value ranging from 0 to 1.78 km/ km 2 (Fig. 7a).The lineament map of the Chia Sur subbasin is categorized into five zones (Fig. 7b).The rating value 5 represents the high groundwater potential.

Drainage Density
The increase in of the drainage density leads to a decrease in the penetration of water into the soil.Therefore, the drainage density has an inverse relationship with the groundwater potential, i.e., the high drainage density value, is the low value of the groundwater potential.The high drainage density leads to an increase of in the surface runoff, thus, it reduces the amount of groundwater nutrition (Bera et al., 2019).The drainage density of the Chia Sur sub-basin includes five zones, valuing from 0 to 13 (Fig. 8a).The rating values successively are (very low 1, low 2, medium 3, high 4 and very high 5) (Fig. 8b).The high drainage density in the most central parts means that the groundwater potential is low at the Chia Sur sub-basin.

Soil
One of the most important factors for agriculture and recharge of groundwater is the soil texture (Kumar and Krishna, 2018).The soil that is found on the upper surface of the earth due to its location acts as a medium for water infiltration (Patel et al., 2022).The soil texture is important for groundwater sustainability (Al-Gburi et al., 2022).The soil of the Chia Sur sub-basin reveals one main soil category, which is loam (Fig. 9a).The value of rating soil is (2) for loam (Fig. 9b).The loam soil texture is a low groundwater potential.

LULC
Forests, water bodies, and grass are good for groundwater potential, but the areas that contain buildings are not good for groundwater potential (Chowdary et al., 2008).It is very important to know data about land uses/ land cover due to its usefulness in runoff and infiltration water.The result appears on the map LULC for the Chia Sur sub-basin, consisting of (water, tree, grassland, crops, forest, scrubland, built area, and bare land) (Fig. 10a).The rating value for crops land, forest, scrubland, and grassland is (4), while for water land (5), bare land (2) built land (1) (Fig. 10b).Some of the parts of the southwest and southeast Chia Sur sub-basin represent the lowest groundwater potential.

Groundwater Potential
The groundwater potential map is produced by overlay weighted analysis of the eight factors.The groundwater potential map of Chia Sur sub-basin appears that it is divided into five categories, from very low category to very high category (Fig. 11).The very high groundwater potential occupies (19.3 km 2 ) i.e. (6.992%) of the study area, the high (73.2km 2 ) i.e. (26.523%), the moderate (80.5 km 2 ) i.e. (29.167%), the low (81.1 km 2 ) i.e. (29.381%) and the very low (21.9 km 2 ) i.e. (7.939%).The result shows that the groundwater potential of Chia Sur sub-basin was concentrated in the north, center and southern parts, as well as some northeastern parts.

Conclusions
Hydrogeological studies are regarded as one of the applied studies.The development taking place at the present time of using some applications such as (GIS and RS) leads to the discovery of the groundwater potential.These applications, which is used in the current study, depending on several variables such as (geology, geomorphology, elevations, slopes, lineament, drainage density, soil, and LULC).The high elevations are located at the eastern and southeastern parts of the Chia Sur sub-basin, but the lower elevations are located at the center and northern parts of the Chia Sur sub-basin.The results showed that the groundwater potential of Chia Sur sub-basin from the very low to the very high, i.e. five categories.Groundwater potential is found in the eastern, southeastern, western and southwestern parts from very low value to low value, due to the influence of geomorphology, low lineament and some slopes in these parts.Groundwater potential is located at the northern, southern parts and the center of the sub-basin of Chia Sur, as well as some small eastern and western parts due to geological formations, such as (Pila Spi, Gercus, Fatha and Bai Hassan Formations); which contains a high percentage of limestone, gypsum, pebbly sandstone and conglomerate.Also, the effect of geomorphology on the northern, southern and the middle parts of Chia Sur sub-basin indicates the very high value and high value of groundwater potential.

Fig. 2 .
Fig.2.Flow chart for determine groundwater potential zone map in Chia Sur sub-basin.

Fig. 9 .
Fig.9.(a) Soil map and (b) soil rating of the Chia Sur sub-basin.

Table 2 .
Weight groundwater potential factors for Chia Sur sub-basin.

Table 3 .
Groundwater potential index