*Article* **Delineating Groundwater Recharge Potential through Remote Sensing and Geographical Information Systems**

**Ahsen Maqsoom 1,\* , Bilal Aslam <sup>2</sup> , Nauman Khalid <sup>1</sup> , Fahim Ullah <sup>3</sup> , Hubert Anysz 4,\* , Abdulrazak H. Almaliki <sup>5</sup> , Abdulrhman A. Almaliki <sup>6</sup> and Enas E. Hussein <sup>7</sup>**


**Abstract:** Owing to the extensive global dependency on groundwater and associated increasing water demand, the global groundwater level is declining rapidly. In the case of Islamabad, Pakistan, the groundwater level has lowered five times over the past five years due to extensive pumping by various departments and residents to meet the local water requirements. To address this, water reservoirs and sources need to be delineated, and potential recharge zones are highlighted to assess the recharge potential. Therefore, the current study utilizes an integrated approach based on remote sensing (RS) and GIS using the influence factor (IF) technique to delineate potential groundwater recharge zones in Islamabad, Pakistan. Soil map of Pakistan, Landsat 8TM satellite data, digital elevation model (ASTER DEM), and local geological map were used in the study for the preparation of thematic maps of 15 key contributing factors considered in this study. To generate a combined groundwater recharge map, rate and weightage values were assigned to each factor representing their mutual influence and recharge capabilities. To analyze the final combined recharge map, five different assessment analogies were used in the study: poor, low, medium, high, and best. The final recharge potential map for Islamabad classifies 15% (136.8 km<sup>2</sup> ) of the region as the "best" zone for extracting groundwater. Furthermore, high, medium, low, and poor ranks were assigned to 21%, 24%, 27%, and 13% of the region with respective areas of 191.52 km<sup>2</sup> , 218.88 km<sup>2</sup> , 246.24 km<sup>2</sup> , and 118.56 km<sup>2</sup> . Overall, this research outlines the best to least favorable zones in Islamabad regarding groundwater recharge potentials. This can help the authorities devise mitigation strategies and preserve the natural terrain in the regions with the best groundwater recharge potential. This is aligned with the aims of the interior ministry of Pakistan for constructing small reservoirs and ponds in the existing natural streams and installing recharging wells to maintain the groundwater level in cities. Other countries can expand upon and adapt this study to delineate local groundwater recharge potentials.

**Keywords:** geographical information systems; groundwater assessment; groundwater recharge; remote sensing; Islamabad

#### **1. Introduction and Background**

Groundwater is necessary to sustain various forms of life [1]. It is defined as a form of water occupying all the voids within a geological stratum [2]. It is one of the important water sources for agriculture, industry, and domestic use worldwide [3]. The groundwater

**Citation:** Maqsoom, A.; Aslam, B.; Khalid, N.; Ullah, F.; Anysz, H.; Almaliki, A.H.; Almaliki, A.A.; Hussein, E.E. Delineating Groundwater Recharge Potential through Remote Sensing and Geographical Information Systems. *Water* **2022**, *14*, 1824. https:// doi.org/10.3390/w14111824

Academic Editors: Dengfeng Liu, Hui Liu and Xianmeng Meng

Received: 19 April 2022 Accepted: 2 June 2022 Published: 6 June 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

level is naturally maintained through precipitation that balances the water cycle, which is crucial for all multicellular life forms. The occurrence of groundwater in a geological formation and the scope for its exploitation primarily depend on the formation porosity [2]. The aquifers rely upon soil and fissured rocks as the medium of pores for the consistent flow between them [4]. In these complex networks of interconnected pores, fractures, cracks, joints, crushed zones (such as faults zones or shear zones), or solution cavities, rainwater can easily percolate through them and maintain groundwater tables [5].

In the past few decades, the greater reliance on groundwater has decreased groundwater table levels. Globally, more than 60% of agricultural practices depend on groundwater as a water source [6]. In developing countries in Asia, groundwater-based irrigation has grown up to 500% [7]. Moreover, due to the rapid increase in population, the demand for groundwater resources increases due to the inadequate availability of useable surface water resources. Furthermore, increased industrial and agricultural activities pollute water resources by directly releasing untreated waste into channels [8]. This eventually results in the unavailability of clean surface water, causing extreme dependency on the groundwater table. Therefore, the recharge of groundwater is of extreme importance to meet the global population's needs.

Groundwater/aquifer recharge is defined as water entry from the unsaturated zone to the saturated zone [9]. The degree of the recharge by natural means primarily depends on the amount of rainfall in a region that is considered a prime element for groundwater recharge [4]. The relationship between rainfall and the natural groundwater recharge is mainly governed by the region's topography, soil moisture content, rock structures, geology, the extent of fractures, elevation, slope, drainage patterns and density, landform, and landuse/land-cover and climatic conditions [3,4,10]. As a result of climate change, the overall global precipitation has decreased, resulting in a decrease in groundwater recharge [11,12]. Furthermore, the rapid worldwide urbanization also results in transforming once natural landscapes into urban water-impervious lands [12]. This limits the availability of freshwater resources but also causes hindrance in the recharge of the available water resources [13]. This puts tremendous pressure on the groundwater table considering the continuous use of groundwater to sustain essential life forms [10].

The aforementioned factors are resulting in water scarcity around the globe and are emerging as a major concern globally [14]. To temporarily maintain the groundwater levels and meet the ever-increasing water demand, artificial methods for recharging the aquifers have been employed. These methods are considered a prerequisite for sustainable groundwater management [3,15]. For this purpose, a new technique called managed aquifer recharge (MAR) has been gaining popularity lately. It is an efficient means of recycling storm water or treated sewage effluent for non-potable and indirect potable reuse in urban and rural areas [16]. Despite these artificial methods, a more sustainable approach must be adopted, and focus must be put on the natural means of groundwater recharge in line with the United Nations Sustainable Development Goals (UNSDGs).

In the case of Pakistan, the agriculture sector is the prime contributor to the country's GDP, with an overall contribution of 21% [17]. The surface water supplies are sufficient to irrigate 27% of the cultivable area, whereas the remaining 73% is directly or indirectly irrigated using groundwater. This is evident since out of Pakistan's total estimated annual groundwater extraction of 60 billion cubic meters [18,19], more than 85% is used for agricultural purposes compared to 40% in the rest of the world [20,21]. This makes Pakistan the third-largest user of groundwater for irrigation in the world [17]. Irrigation and agricultural usage have caused excessive groundwater abstraction in Pakistan, leading to water scarcity [7]. This growing deficiency of groundwater and ever-widening consumption for food production could weaken agriculture-dependent economies such as Pakistan [22,23]. In addition to the great agricultural and industrial demand for water, the increased urbanization [12] and overpopulation in Pakistan have also led to the overexploitation of ground and underground water. This, in turn, affects the water level/table and thus its availability [13].

Furthermore, the reduction of natural water pervious landscapes due to urbanization [13] and the natural reduction of precipitation due to climate change also prevent proper groundwater recharge [12]. Due to these facts, Pakistan is affected by acute groundwater shortages similarly to most developing countries [24,25]. As a result, the local groundwater levels are falling, increasing pumping costs and deteriorating groundwater quality. Thus, it is high time to carry out studies to delineate potential groundwater recharge zones in the country to use the resulting data to devise mitigation strategies [8].

Researchers have used different criteria for delineating potential groundwater zones in previous studies. Examples include the use of lineament and hydro geomorphology [26], geophysical data with geospatial information [27–33], delineation of artificial recharges sites using the use of remote sensing (RS) and geographic information system (GIS) [28,34,35], and the use of RS and GIS for geomorphic features and lineaments [36–42]. These techniques are important tools for enabling the appropriate management of crucial groundwater resources [43]. They are used to integrate various data to delineate potential groundwater zone and solve associated groundwater problems. Furthermore, these technologies are rapid and cost-effective in producing valuable data on geology, geomorphology, lineaments, slope, etc., which are important parameters for groundwater exploration, exploitation, and devising management strategy. Therefore, recent studies have used RS, satellite imagery, and GIS for hydrogeological and hydro-geomorphological investigations.

Several studies have also applied RS and GIS applications to delineate groundwater resources and potential recharge zones [8,34,44–58]. Some specific examples include a study by Saraf et al. [59], which used GIS technology to process and interpret groundwater quality data. In other studies, GIS and RS integrated with multi-criteria decision making (MCDM) have been successfully used to uncover potential recharge zones [60]. Such integration has also been used for district groundwater modeling [61], identification of water zones [62], climatic analysis for groundwater recharge [63], and aquifer analysis for recharge [64]. Selvam et al. [65] used similar techniques to decipher the groundwater recharge potential zones in a coastal area of India, which is geographically closer to our case study area. Other relevant studies using GIS have been described in Table 1 along with their respective limitations.


**Table 1.** Studies outlining techniques for groundwater recharge.

Table 1 shows various factors considered in respective studies for delineating groundwater resources. In this respect, a more accurate predicting model can be devised by increasing the number of influencing factors used and improving the data collection procedures. The current study uses an integrated RS and GIS technologies approach to delineate the potential recharge zones and categorize the study area into regions with high, moderate, low, and very low recharge potential. These techniques were employed in combination with the influencing factor (IF) technique, which has been previously used for studies related to semi-arid areas [10] and coastal areas [65]. However, it has not been employed in a noncoastal terrain such as the study area in the current research.

Moreover, compared to the previous studies, more factors have been introduced to increase the accuracy of the predicted results in the current study. The key assessment factors are overlaid with the spatial analysis tool of ArcGIS 9.3 to produce a combined thematic map uncovering the zones with their potential recharge. To further improve the model efficiency, more data were taken for the factors affected by temporal variations such as rainfall, etc. For other factors, data from a decade were taken and averaged before being used in the model development to nullify the effect of temporal variations. Further, thematic maps of larger spatial scales and the digital elevation model (DEM) data of a smaller resolution were used to study the targeted area comprehensively and accurately.

This study has practical applications for water management in developing and developed countries. For example, the groundwater delineation process paves the way for the relevant authorities to develop infrastructure and devise critical policies and committees to better manage the local groundwater sources. Furthermore, it can help policymakers, town planners, and construction stakeholders to plan future cities with a focus on sustainability and preserving the natural landscape required for proper groundwater recharge. Moreover, artificial structures could also be constructed to meet the associated groundwater demand and enable groundwater flow towards the region of lower concentration systematically. Such planned groundwater management will help meet the ever-increasing and widespread water demand among the country's residential, commercial, and agricultural zones. Moreover, sophisticated systems such as the one proposed in this study have lower costs and can easily interpret data to identify and suggest water contributing zones and factors. Accordingly, the applications in developing countries are numerous, which are usually concerned about the budgets of such projects. This provides incentives for developing countries such as Pakistan to use these sophisticated and integrated systems for groundwater delineation.

Further, this research contributes to the existing literature by providing an efficient integrated approach of RS and GIS coupled with the IF technique to identify the potential groundwater zones in a non-coastal study area. A similar approach was used to identify groundwater recharge zones in the coastal areas [73] and near the watershed [66]. However, such a study has not been conducted in non-coastal areas in a developing country. This presents a research gap that has been targeted in the current study. Moreover, a distinguishing element of this study is the introduction of more factors coupled with the use of more data (of a decade) for the temporal affected factors to nullify the temporal influence and variations. This was reported as a limitation in multiple similar studies. This study considers a larger spatial scale and finer resolution compared to other published works. This study can be extended to other non-coastal cities around the globe.

The main objective of this research is to identify the potential influencing factors that may impact groundwater recharge. Further, the potential groundwater recharge zones are determined by incorporating all influencing factors using the IF weightage technique. This will help the policymakers manage the groundwater resources and help researchers understand the utilization of remote sensing and GIS for groundwater analysis.
