نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی عمران، دانشکده عمران، آب ومحیطزیست، دانشگاه شهیدبهشتی، تهران، ایران.
2 گروه مهندسی عمران،دانشکده عمران، آب و محیط زیست دانشگاه شهید بهشتی
3 گروه مهندسی عمران، دانشکده عمران، آب و محیطزیست، دانشگاه شهیدبهشتی، تهران، ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Population growth and the limitations of freshwater resources have heightened the importance of assessing the quality of groundwater resources in arid and semi-arid regions. The Bahar Plain, located in the northwest of Hamadan Province and characterized by a cold semi-arid climate, is a major source of drinking water and agricultural supply for the region. The objective of this study is to evaluate the groundwater quality of the Hamadan–Bahar Plain for drinking purposes. For quality assessment, spatial and temporal variations of four indicators—pH, nitrate, bicarbonate (HCO₃⁻), and electrical conductivity (EC)—were examined over the period 2020–2024. Data were collected from 20 wells and spatially interpolated using the inverse distance weighting (IDW) method based on neighborhood power in a GIS environment. The results indicated that pH values ranged from 7.6 to 7.9, remaining within the desirable range (6.5–8.5) throughout the study period. Nitrate concentrations in some areas exceeded 50 mg/L, showing a gradual increasing trend over time. EC values in parts of the plain surpassed 1,000 µS/cm, indicating the onset of salinity conditions. Bicarbonate levels did not exceed 10 mg/L at any point, remaining within acceptable limits. To identify water quality patterns, hierarchical cluster analysis (HCA) was applied. Based on all indicators, the wells were classified into four main clusters, using Ward’s method with Euclidean distance applied to normalized data. These findings emphasize the necessity of focused management in the eastern and southern regions of the plain, along with continuous monitoring of groundwater quality changes.
کلیدواژهها [English]
Groundwater resources play a vital role as the main source of drinking water, agriculture, and industry in many arid and semi-arid regions of Iran. Limited surface water availability, population growth, agricultural and industrial expansion, and frequent droughts have significantly increased reliance on groundwater in recent decades. However, groundwater quality is under serious threat due to the overuse of chemical fertilizers and pesticides, discharge of municipal and industrial effluents, and excessive abstraction. The Hamedan–Bahar plain, located in the northwest of Hamedan Province with a cold semi-arid climate, covers about 880 km² and supplies over 80% of agricultural and nearly half of urban drinking water needs. Assessing its spatiotemporal variations in groundwater quality is therefore of critical importance. This study focuses on monitoring four key parameters—pH, nitrate, electrical conductivity (EC), and bicarbonate—during the period 2020–2024. The use of Geographic Information System (GIS) for spatial mapping of critical zones and Hierarchical Cluster Analysis (HCA) for classifying wells constitutes the main innovation of this research, providing a practical framework for groundwater management and strategic planning.
Data from 20 production wells in the Hamedan–Bahar plain were collected over a five-year period (2020–2024). The dataset included annual measurements of pH, nitrate (NO₃⁻), bicarbonate (HCO₃⁻), and electrical conductivity (EC), recorded by the Regional Water Authority of Hamedan Province. Sampling wells were selected from different land-use zones—agricultural, industrial, urban, and peripheral areas—to ensure adequate representation. All procedures followed national and international standards, and samples were analyzed in the laboratory. For spatial analysis, the Inverse Distance Weighting (IDW) interpolation method was applied in ArcGIS Pro to generate continuous maps of groundwater quality. For statistical analysis, five-year averages of each parameter were calculated and normalized, followed by Hierarchical Cluster Analysis (HCA) using Ward’s linkage and Euclidean distance to classify wells into groups with similar quality characteristics.
The five-year analysis revealed significant spatiotemporal variations in groundwater quality. The pH values ranged from 6.7 to 7.9 and remained within the national drinking water standard (6.5–8.5). Slightly lower values occurred in the eastern and southern regions, while higher values were found in the west and north. Nitrate concentrations showed a clear increasing trend, rising from 28 mg/L in 2020 to 51 mg/L in 2024. By the end of the monitoring period, about 30% of wells exceeded the permissible limit of 50 mg/L, with the highest concentrations in the southern and eastern zones where fertilizer use is more intensive. Electrical conductivity values in some wells surpassed 2400 µS/cm, indicating the onset of salinity. Although the maximum occurred in 2020 and the minimum in 2022, the overall trend showed gradual increases, especially in the eastern and northeastern sectors. In contrast, bicarbonate remained relatively stable, always below 10 mg/L across the plain. HCA grouped the wells into four categories: wells with good quality, wells with moderate pollution, wells with elevated nitrate and EC, and critically polluted wells concentrated in the south and east.
The findings demonstrate that groundwater quality in the Hamedan–Bahar plain is facing increasing pressure. Rising nitrate levels and gradual salinization, particularly in the southern and eastern parts of the plain, are mainly linked to excessive fertilizer application, infiltration of agricultural and industrial effluents, and over-abstraction. These trends pose significant risks to public health, agricultural productivity, and ecosystem sustainability. HCA proved effective in identifying critical zones and prioritizing management interventions. The results highlight the urgent need for continuous monitoring, reduced use of nitrogen fertilizers, improved wastewater management, and adoption of modern irrigation technologies in vulnerable areas. Integrating GIS-based spatial mapping with temporal monitoring provides a comprehensive and transferable framework for groundwater management that can also be applied to other aquifers. To ensure long-term sustainability, regular monitoring programs, stricter regulation of illegal withdrawals, better agricultural input management, development of wastewater treatment facilities, and the application of predictive models are recommended. When combined with community participation and stronger policy enforcement, these measures can safeguard the Hamedan–Bahar aquifer and serve as a model for sustainable groundwater management in similar regions.
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
Data available on request from the authors.
The authors would like to thank the reviewers and editor for their critical comments that helped to improve the paper.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
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