Document Type : Original Article

Authors

• Hosein Atashgaran ¹
• Massumeh Rostamabadi ²
• Saeed Kazemi Mohsenabadi ³

¹ MSc student of water and hydraulic structures engineering, Islamic Azad University, Buin Zahra Branch, Buin Zahra

² Department of Civil Engineering, BuZ. C., Islamic Azad University, BuinZahra , Iran.

³ Department of Civil Engineering, BuZ. C. Islamic Azad University, BuinZahra, Iran

Abstract

Introduction
     Groundwater resources, as the main supplier of agricultural, drinking and industrial uses, are affected by polluting factors such as irrigation return water, urban and rural wastewater, and industrial effluents. Alborz County, one of the important agricultural and industrial regions of Qazvin Province, is at risk of groundwater pollution due to its increasing development and population. Due to the lack of implementation of appropriate wastewater disposal systems, a large volume of pollutants, including nitrate, enter the aquifer of this plain. The aim of this study is to investigate the vulnerability of the Alborz County aquifer using the DRASTIC method and to utilize the Geographic Information System (GIS) to determine areas susceptible to pollution and to provide management solutions to maintain the quality of groundwater resources.
 Materials and Methods
Geographical Location
     Alborz County is located in the northeast of Qazvin Province with an area of about 428 square kilometers. The county borders Qazvin County to the north, Abyeq County to the east, Abyek and Buin Zahra County to the south, and Qazvin County to the west. This region is heavily affected by environmental pressures due to industrial and agricultural development.
 DRASTIC Model
     The DRASTIC method, introduced by the US Environmental Protection Agency, focuses on assessing groundwater vulnerability using seven key parameters: depth of groundwater (D), net recharge (R), aquifer media (A), soil media (S), topography (T), Impact of vadoes zone (I), Hydraulic conductivity of the aquifer (C). A rate value and a weight were determined for each of these parameters based on table (1), and then these data were processed in ARCGIS software to prepare a vulnerability map of the region.
Table 1- Drastic parameter weight and rate table for Alborz County




C


I


T


S


A


R


D


Parameter




3


5


1


2


3


4


5


Weight




1--4


5--6


8--10


4--7


6--8


6--9


1--2


Rate




  The vulnerability index (DI) was calculated based on the combination of these factors according to equation (1) and levels of vulnerability were identified.
     Based on the analysis, the vulnerability index of the Alborz County plain varies between 87 and 136. According to the Drastic classification, the study area is divided into two zones of low vulnerability (31 percent) and medium vulnerability (69 percent). The western and central areas of the aquifer have the highest vulnerability potential due to the high groundwater level and low land slope and require more monitoring.
     To examine the accuracy of the vulnerability zoning map, the nitrate level of groundwater in the area was examined. The results showed that areas with higher vulnerability have higher nitrate concentrations, indicating a direct relationship between the vulnerability index and groundwater quality. The most important polluting factor in this area is the excessive use of chemical fertilizers and the lack of urban wastewater treatment systems.
     In order to assess the effect of different parameters on the vulnerability index, a sensitivity analysis of layer removal was performed. The results showed that the most important parameters affecting vulnerability are Impact of vadoes zone (I) and net recharge (R). Removing these factors caused significant changes in the vulnerability index, indicating their critical role in the transfer of contaminants to groundwater.
 Conclusion
     This research, by providing vulnerability maps, provides an important tool for planning and managing groundwater resources in Alborz County and will assist officials in major environmental and executive decisions. The results showed that Alborz County has areas with a moderate level of vulnerability, and the western and central parts of the aquifer should be considered as critical areas. Accordingly, the following suggestions are made:
     Management of chemical fertilizer use: Modifying the cropping pattern and monitoring the use of nitrate fertilizers in order to reduce the transfer of contaminants to groundwater.
Implementation of urban and rural wastewater treatment projects: To prevent the entry of contaminated wastewater into groundwater resources.
      Monitoring well drilling in vulnerable areas: Preventing hydraulic communication between contaminated and uncontaminated aquifers.
     Accurate monitoring of groundwater quality: Implementing continuous monitoring systems to control and manage groundwater pollution.

Keywords

• Vulnerability
• Alborz Plain
• DRASTIC
• GIS

Main Subjects

• Water Resources and Consumption