Groundwater Risk Mapping Model Using GIS of Al-Khassa Upstream Sub- Basin, Kirkuk, Iraq

Received: 2 December 2022 Groundwater pollution is considered a serious threat to the environment and humanity in general. The presence of contaminated groundwater in wells allows us to identify risks, especially in the study area. Therefore, studies must be conducted using modern techniques to determine risks. The objective of this study is to produce a map show zones of groundwater at risk. The groundwater risk maps based on the combination of two criteria are groundwater vulnerability and land uses/land covers map using GIS and QGIS software. In addition, validation work for groundwater risk map with heavy metals pollution index. The results risk map are range between 94-202 (very low, low, medium, high, and very high) i.e. five zones. The study area has very low medium risk on the eastern and northeastern sides and some areas in the west; while the rest areas represent a high very high risk. Accepted: 18 January 2023 Published: 31 May 2023


Introduction
In general, Iraq has recently tended to exploit groundwater to meet all the necessary water needs; especially in the study area (Ali and Al-Timimi, 2019). Groundwater pollution is consider a serious threat to the environment and humanity in general (Ijlil et al., 2022). The reason for continued studies of water worldwide is water exploitation and degradation (Beg et al., 2021). The groundwater pollution risk depends on two parts the vulnerability of the aquifer (natural characteristics) and the pollution loads above the soil surface (Dimitriou et al., 2008). One of the major global problems is the provision of potable water due to the increasing population growth, and the problems expect to increase in the future until they reach dangerous levels . In the near future, some countries will start demanding to increase their water quotas from upstream countries; as these demands are considered the beginning of future wars (Al-Gburi, 2020). Good quality freshwater resources are getting limited during the last few decades, due to pollution pressures from anthropogenic activities (Matiatos, 2016). Agriculture has become an anthropogenic activity that has an impact on groundwater in recent years; some fertilizers like nitrates affect the groundwater and soil because nitrates contain physical and chemical properties (Jafari et al., 2016). The aquifer is very sensitive to pollutants, especially if the land consists of some industrial activities (Thirumalaivasan et al., 2003). The DRASTIC method enables us to know the extent of exposure to the specific location of the pollutants as the land is classified into several classes from very low to very high. So that it can be impossible to know the contamination of groundwater in a particular location by applying the DRASTIC method alone; but it is possible to link the DRASTIC method with other methods such as conducting the analysis of groundwater or land use land covers (Stempvoort et al.,1993). Various studies of groundwater risk have been conducted (Seconda et al., 1998;Al-Adamat et al., 2003;Al-Rawabdeh et al., 2014;Ouedraogo et al., 2016;Al-Gburi, 2020 and. The rapid urban changes in all countries in terms of rapid population growth are increasing human activities and thus showing their negative effects on land uses or the environment. Understanding the pollution risks of an aquifer is a necessary process to prevent contamination its and appropriate management (Li and Qian, 2020). groundwater at risk map provides scientific support and appropriate protection in the management of groundwater, especially of Al-Khassa upstream sub-basin. The research aims to produce a map show zones groundwater at risk.

Study Area
The Al-Khassa upstream is locate in northeastern Iraq, it is between coordinates (3952964 -3928476) and (451807 -483362) UTM, it covers 420 km 2 . The Al-Khassa upstream is far from the covernerate center Kirkuk 21 km. The Al-Khassa dam is located west of Al-Khassa upstream, which is in the same direction as the general drainage of Al-Khassa upstream. The Al-Khassa upstream includes twenty six villages and their elevations range from 441-906 m (a.s.l) (Fig. 1). The study area is bounded from the southwest Chamchamal basin and from the northwest Shwan sub-basin. The study area is one of the upper parts Al-Adhim river basin and which that originate from Iraqi lands. The Al-Khassa upstream consists four geological formations ranging age from upper Miocene-middle Holocene which are Injana, Mukdadiyah, Bai-Hassan formations, and Quaternary deposits (Buday and Jassim, 1987;Stevanovic and Markovic, 2003). Injana, Mukdadiyah, and Bai-Hassan formations which covers about 0.94 km 2 , 30.59 km 2 , and 354.74 km 2 respectively of Al-Khassa upstream; addition to presence of the Quaternary deposits covers 33.73 km 2 of the study area. (Fig. 2). According to structure the study area limit from the east side, its north Chamchamal anticline.   (Buday and Jassim, 1987;Stevanovic and Markovic, 2003).

Materials and Methods
The method involved preparing a risk map of Al-Khassa upstream sub-basin, which was implemented based on groundwater vulnerability and land use/land cover; i.e. combining the groundwater vulnerability map with the land use/land cover map. The groundwater vulnerability according to (Al-Gburi and AL-Timimi, 2020). The land use/land cover map, has been obtain from the Q GIS (V 3.12), BBBIKE software and field work. The land use/land cover map was processed by the Interactive Supervised Classification (ISC) in Arc GIS, to give specific values for each LULC category. After the value of each category of land use and the cover was given based on Tables 2, 3 and 4 (Seconda et al., 1998), (Shirazi et al., 2013) and (Zwalin, 2003). The value land use/land cover are represent values of the rating (Lr), by the spatial analysis tools in the Arc GIS software; multiply by weight (Lw =5) produces a map of land use/land cover, as in the following equation: LULC= Lr*Lw.
(1) The risk map was the produce of the Al-Khassa upstream sub-basin by combining the groundwater vulnerability and LULC maps. The diagram shows how to create a risk map (Fig. 3). In addition to, the groundwater vulnerability and groudwater risk maps were reclassified. At the end work, the groundwater risk map was compared with the heavy metals pollution index (HPI). Hydrochemical analysis of the groundwater of the study area (Ali, 2020).  (Aller,1985).

DRASTIC vulnerability index Vulnerability degree
Less than 100 Very low 100-125 Low 125-150 Medium

150-200 High
More than 200 Very high Table 2. Land use categories and the weight of this parameter were modified (Secunda et al.,1998).

Land use category Land use rating
Built up area 8 Irrigated field crops 8 Uncultivated land 5 Land use weight 5 Table 3. Land use categories and weight of this parameter (Shirazi., et al 2013).

Land use/land Covrers category Land use rating
Animal husbandry, horticulture, urban and Agricultural area 8 Palm trees and other permanent crops land 5

Water-body 3
Swamps and marsh land, grass and wetland and others 2 Forest land 1 Table 4. Land use categories and weight of this parameter (Zwahlen, 2003).

Land use/land Covers category Land use rating
Detached houses without sewer systems 9 Roads, unsecured 8 Water-body 3 Hazardous waste site 18 Open field 5

Vulnerability Map of the Study Area
A vulnerability map explain an ability to infiltrate and spread pollutants from the surface of the earth to the aquifer (Nassery and Nejad, 2012). The map shows the locations, where pollution occurred in, within certain levels; these levels only be determined after a careful scientific study The vulnerability map is useful economically for setting up any specific project and appropriate plans in the management of water resources, and taking precautions to be taken from the possibility of pollution, i.e. preventive measures. The result of the Groundwater vulnerability map ranged from (75-126), which was classified into three classes (very low, low, and medium). The moderate value in the center of the sub-basin of the study area occupies 2.53 km 2 (0.6%). Other wells are located within the range of very low and low vulnerability. The very low vulnerability zone represents 132.47 km 2 , approximately (31.4655%), while the low vulnerability zone represents 285 km 2 approximately (67.85%) (Fig. 4). This section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation as well as the experimental conclusions that can be drawn.

LULC Map
It is important to know the land use/land cover data due to usefulness in infiltration water and runoff . The LULC are represent anthropogenic activities such as (buildings, agricultural, and industrial); these activities considered negative impacts on groundwater that lead to pollution of the aquifer. The land use/land cover map of the study area, has been obtaining from the Q GIS (V 3.12) software as well as the use of the BBBIKE software and field-work. The study area contains detached houses (11.96 km 2 ) 2.84% and agricultural land between the houses. It also contains an open field land (390 km 2 ) 92.857%, a water body (lake) (4.14 km 2 ) 1.04%, roads (13.774 km 2 ) 3.271%, and industrial activities (0.116 km 2 ) 0.0275%. The study area has divided into five categories (Fig. 5). Each of these categories has specific values shown in (Fig. 6).

Groundwater Risk Map
Risk map is defined as the result of a combination of a vulnerability map and a potential impact map (Karaouzas et al., 2009). Contamination probability or vulnerability maps and potential impact maps or land use are combined by using spatial analysis in the Arc GIS. As in the following equation: Groundwater Risk map = Groundwater vulnerability map + Land uses of the study area (2) The results showed that the risk map values ranged from (94-202), from very low to very high; and the study area was divided into five zones as shown in (Fig. 7). Where the study area of each category show very low 0.887 km 2 (0.21%), low 126 km 2 (29.9287%), medium 282.7 km 2 (67.3%), high 9.48 km 2 (2.2517%), and very high 0.933 km 2 (0.221%). The risk map assessment of contamination of groundwater consists of two main parts: the first is the possibility of pollution (Vulnerability map) and the second is the potential impact (Baalousha, 2006). Generally, if the probability and pollutants impact of the high lead to high risk; While in the case of the pollution possibility is high and the pollutants impact very low; produce a low groundwater risk (Fig.8) (Baalousha, 2011). Where the groundwater vulnerability map has been reclassified according to the pollution possibility and the groundwater at risk map based on impact potential (Figs. 9 and 10).

Validation
The most serious health problems result from the contamination of groundwater with heavy metals due to its toxicity (Mthembu et al., 2022). Heavy metal contamination of groundwater is a serious threat to this natural resource (Brindha et al., 2020). The groundwater risk map of the current study is shows a very high match with the wells' heavy metal pollutions index (HPI).

Conclusions
The application of such studies is very important for understanding the risks affecting aquifers. The study depends on several parameters such as hydrogeology, geological backgraound and LULC. The use QGIS and Arc GIS software contribute to obtaining data for land use/land covers; in addtion to the preparation of the final map. Results show most of the Al-Khassa upstream is an open field, twenty six villages, and water bodies. In addition industrial use is in the southwest effects aquifer. The locations of pollution that affect groundwater wells are the west, northwest, southwest, southeastern part, and center of Al-Khassa upstream which value (high, very high). While the rest parts of the study area at the east and north i.e in Injana, Mukdadiyh and beginning of the appearance Bai-Hassn Formation which value from very low -medium; not affect groundwater. The groundwater risk sites that very high and high impacts at groundwater are within the Bai-Hassan Formation.