A GIS-based DRASTIC Model and an Adjusted DRASTIC Model (DRASTICA) for Groundwater Susceptibility Assessment along the China–Pakistan Economic Corridor (CPEC) Route

Abstract

Land use types and anthropogenic activities represent considerable threats to groundwater pollution. To effectively monitor the groundwater quality, it is vital to measure pollution levels before they become severe. In our research area, located in Gilgit Baltistan in northern Pakistan, groundwater supplies are diminishing due to urban sprawl. In this study, we used a GIS-based DRASTIC model (Depth to water, Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone, Hydraulic conductivity) to analyze the area’s hydrological attributes to assess the groundwater susceptibility to pollution. Considering the importance of anthropogenic activities, this research primarily utilizes an adjusted DRASTIC model called DRASTICA, which incorporates anthropogenic impact as a parameter in the model. The resulting map, which depicts vulnerability to groundwater contamination, reveals that 19% of the study area is classed as having high vulnerability, 42% has moderate vulnerability, 37% has low vulnerability, and 2% has very low vulnerability to groundwater contamination. The adopted validation process (nitrate parameter of water quality) revealed that the suggested DRASTICA model achieved better results than the established DRASTIC model in a built-up environment. We used the nitrate concentration in groundwater to verify the formulated results, and the single parameter sensitivity analysis and map removal sensitivity analysis to analyze the model sensitivity. The sensitivity analysis indicated that the groundwater vulnerability to pollution is largely influenced by anthropogenic impact and depth to the water table, thereby suggesting that anthropogenic impact must be explicitly tackled in such studies. The groundwater zones exposed to anthropogenic pollution can be better classified with the help of the proposed DRASTICA model, particularly in and around built-up environments. The responsible authorities can use this groundwater contamination data as an early warning sign, so they can take practical actions to avoid extra pressure on this vital resource.

Anthropic Pollution Impacts on Groundwater Vulnerability Based on Modified DRASTIC-FAHP

“…For this purpose, the land use parameter was added to the original DRASTIC model. The rating and weight of the anthropogenic impact map were determined according to the land use class contracts (Al-Adamat et al, 2003;Maqsoom et al, 2020) to produce a vulnerability map of MDRASTIC (Fig.6B). The parameters that had the least impact on groundwater pollution include soil media, aquifer media, and topography while water depth table, land use, and hydraulic conductivity had the greatest impact among the parameters.…”

“…Simple linear regression analysis (SLRA) was used to comparethe results of the four DRASTIC methods to nitrate concentration parameter to evaluate the correlation. Pearson, Spearman correlation coefficients (Panagopoulos et al,2006;Kumar and Pramod Krishna, 2019;Maqsoom et al, 2020) were also used to evaluate the degree of correlation between models and nitrate concentration parameter to select the best method. Pearson's correlation coefficient (r) determines the correlation between two variables with distance and relative scales, assuming a normal distributionand varies between +1 and -1 (Chok, 2010).…”

“…The DRASTIC model calculates a vulnerability index that is used to study groundwater pollution by hydrogeological parameters in different regions.The DRASTIC model results are calculated analytically and then processed using GIS. In the past few years, the DRASTIC model has been modified according to the characteristics of specificstudy areasby adding or removing various parameters (Lee, 2003;Wang et al, 2007;Simsek et al, 2006;Umar et al, 2009;Awawdeh and Jaradat, 2010;Martinez-Bastida et al, 2010;Şener and Şener, 2015;Jesiya and Gopinath, 2019;Maqsoom et al, 2020).The classification range for each parameter-between 1 and 10-indicates the impact of each parameter on aquifer vulnerability. Weights from 1 to 5 are then assigned to the seven DRASTIC parameters toindicate their relative importance (Table 1).…”

“…All communities need a clean and plentiful source of water for drinking, health, agriculture, industry, and energy production (Maqsoom et al, 2020). In arid and semi-arid areas where surface water is less available, groundwater can be the main source of water supply due to its large volume and less vulnerabilityto pollution.…”

“…Modified DRASTIC factors were rated using FAHP and finally the information was integrated by GIS tool and areas with high to very high vulnerabilities were identified. Maqsoom et al (2020) studied the vulnerability of groundwater in the Gilgit area of Baltistan in northern Pakistan. Due to urban sprawl, groundwater resources in this area are declining.…”