Groundwater is a valuable resource and it is one of the important freshwater sources for domestic use, agriculture, and industry . At present, nearly 34% of the world’s water resources belong to groundwater . Groundwater occurs in almost all landscapes , and all surface water features include streams, wetlands, lakes, reservoirs, and estuaries, which are usually hydraulically connected to groundwater . Moreover, the natural and climatic environment of the landscape determines the presence of groundwater. For instance, a stream in a humid climate may receive groundwater influx, but a stream in an identical physiographic environment in a dry climate may lose water to groundwater . Glacial or fluvial sediments, including basins, river valley alluvium, and fillings in the bedrock topography, are important groundwater reservoirs . One of the prerequisites for sustainable groundwater management is groundwater recharge . However, it is not always the amount of surface water that penetrates the moisture content of an aquifer .
Groundwater in Iraq, especially in the Erbil Basin has an important role in water supply, agriculture, health, and poverty eradication in rural areas . It is usually recharged through precipitation and occasional snowmelt. However, in some topographic places, it can also be recharged by leakage from rivers, lakes, or canals . The increasing demand for limited supplies in semi-arid and dry regions is reducing groundwater levels and leading to a critical state of groundwater recharge . Generally, groundwater depletion has occurred all over the world as a result of overexploitation of groundwater  and particularly in the EB, where groundwater depletion has reached a point where it is nearly impossible to restore the groundwater table . Therefore, the potential area’s approach to groundwater recharge focuses specifically on promoting groundwater conservation, applying an appropriate scientific plan, regulating domestic and industrial water conservation practices, and leading to sustainable groundwater policies .
Many scientists investigated potential groundwater recharge zonation in semi-arid and arid regions using GIS, RS, and analytical hierarchical process techniques. For instance, India , United Arab Emirates , Tunisia , Egypt , Jordan , Israel , Syria , Turkey , and western Saudi Arabia .
The analytical hierarchy process (AHP)-based Multi Criteria Decision Making (MCDM) described by Saaty  is a very common method and it has been applied in widespread areas, including planning, choosing the best alternative, allocating resources, and resolving conflict . This method calculates the weights of the criteria for selecting the most important criteria from among the alternative criteria and is therefore based on the order decision. Furthermore, MCDM is a sub-branch of operations research that reflects multiple criteria in decision-making environments . Numerous previous investigations have used MCDM tools and applications to solve area problems such as the environment, energy, as well as sustainability, according [13, 24–26], in their literature review.
Overall, the GIS-based AHP, which is a traditional method, is a suitable tool for considering multiple-criteria decision analysis problems and simultaneously being applicable areas for using fuzzy set theory . Fuzzy set theory was created to deal with the concept of partial truth values ranging from absolute right to absolute false . From the late 1980s to the present, fuzzy-AHP methodologies have advanced rapidly, and countless applications based on F-AHP have been implemented and published in a variety of fields, including the environment, engineering, economics, and finance . Moreover, the fuzzy-AHP is an extended method and was developed from the traditional AHP, which is used to solve MCDM problems . The fuzzy method has been around for several decades and solves a lot of issues dealing with inaccurate and uncertain data. This method has some advantages over AHP and other MCDM in imprecise and uncertain contexts .
Furthermore, numbers are used instead of weight values in the fuzzy-AHP method to produce more realistic and accurate results and a more confident decision. In fact, the Fuzzy-AHP is a method that quantifies the AHP scale in the fuzzy triangle scale to reach priority [31, 32]. To overcome inconsistencies that may arise at a certain level during the construction of a pairwise comparison matrix, Van Laarhoven and Pedrycz  proposed the F-AHP, which Chang  developed. The combination of GIS, RS, and F-AHP has been verified to be a powerful tool in groundwater investigations . Integrated GIS, RS, and F-AHP techniques aim to categorize and prioritize a set of alternatives that best meet a set of criteria .
This technique was used to create groundwater potential map zones of the EB using meteorological, hydrological, and hydrogeological characteristics in the current study because it is a faster, more precise, and cost-effective way to detect the various factors important to the groundwater potential zone [27, 30, 35, 37]. In addition, valuable and rapid background information can be obtained from several thematic layers such as rainfall, lithology, geology, LULC, slope, NDVI, DEM, drainage density, lineament density, and others through those factors that control the occurrence and movement of groundwater .
The main goal of this research is to use AHP-coupled MCDA, GIS, and RS, as well as Fuzzy-AHP approaches, to delineate groundwater potential zones for sustainable development and management.
1.1 Groundwater Hydrology in Erbil Basin
EB covers an area of 3145 km2, with a length of 75 km and a maximum width of 55 km. According to Al-Ansari, Essaid , the depth of EB wells in the 1980s was between 5 and 30 meters. In 1996, the depth of wells was increased by approximately 150 to 200 meters, stated Kznee , but by 2015, it had risen to between 300 and 600 meters. As a result, there is a significant and catastrophic depletion of groundwater, which is the worst-case scenario for the Erbil basin's aquifer system. However, since 2011, on the Greater Zab River, water treatment plants have been built to provide drinking water to a large portion of Erbil city. Accordingly, the city of Erbil's water supply relies on 45% of the groundwater through wells and surface water for 55% of the water treatment plant units through its needs .
The Greater Zab River surrounds the EB on the northwest and the Lesser Zab River on the southeast. They are the largest tributaries of the Tigris River and the region of Iraqi Kurdistan's primary source of surface water . Moreover, a semicircular depression that represents Erbil plain separates the Pirmam anticline to the northeast and the Kirkuk structure to the southwest, Figure 1. In general, Habib, Al-Saigh  divided the EB into three secondary sub-basins: the northern Kapran sub-basin, the central sub-basin, and the southern Bash Tepa sub-basin.
Normally, the recharge zones are determined by the geological, hydrogeological, and topographic characteristics of the area. Moreover, the spatial distribution and extensions of hydrogeological components in terms of aquifers and aquitards, as well as their hydrological characteristics, are governed by geological, structural, and lithological conditions . The presence of thick terrigenous sediments in the middle of the Erbil plain, which reach up to 850 m in thickness, makes the EB one of the most important promising areas for groundwater resources in the low folded zone .
From the hydrogeological point of view, the EB is a part of the low folded zone, which is strongly influenced by its geological setting. The majority of the study areas are characterized by a plain divided by river valleys and controlled by a broad synclinal structure with linear hilly belts and anticlines. Geologically, this area is mainly covered by the conglomerate aquifers in the Quaternary and Pliocene within the formation of Bai Hassan, and some part covers by sandstone aquifers within the Injana (Miocene-Pliocene) and Muqdadiyah (Pliocene) formations . Furthermore, there are numerous hills, which are usually folded strata and extend in a parallel pattern from NW to SE. These hills range in elevation from 200 meters in the south to 500 meters in the northeast. Typically, these hills are narrow, with extremely wide plains in between .
The amount of recharge of the aquifer storage in the recharge area, as well as the velocity of the porous media in the region, determine the increase in groundwater level . The major groundwater basins are formed by broad synclinal valleys that are filled with sedimentary sequences ranging in age from Late Miocene to Recent. The main groundwater divides, especially in the elevated parts of the Low Folded Zone, where groundwater discharge occurs along streams and rivers, coincide with surface water flow. The potential for groundwater development along these streams and rivers could be significant .
1.2 Study area
This research is being carried out in the EB, which includes Erbil City, the capital of Iraq's Kurdistan Region (KRI). The geographical setting for the EB is between latitudes 35° 46' N and 36° 34' N and longitudes 43° 34' and 44° 19' E. The GZR is the most important branch of the Tigris River, which springs from southeastern Turkey at an altitude of more than 4,000 m above sea level and flows into northern Iraq . The Lower Zab River, on the other hand, extends from northeast Iran to Iraq and is located south of the GZ. The normal temperature ranges from 1°C in December–February to 44°C in July–August. The elevation ranges between 171 and 1091 meters above sea level and consists of numerous hills and flat terrains as the most prominent morphological features of semi-arid climatic conditions with the potential for direct run-off, Figure 1. This area was chosen because it contains the largest groundwater reservoir in the Erbil Governorate and is one of the most important groundwater aquifers in the Middle East, with conglomerates, sandstones, sand, and gravel forming the majority of the aquifers .